Browse Category School

The Salvage of Abu Simb

by LUCIA ALLAIS

In 1965, British architectural historian and technology enthusiast Reyner Banham wrote a letter to a preservationist who had asked him to intervene against the demolition of the Reliance Building in Chicago. “The day you find me speaking up for the preservation of any building whatsoever,” Banham wrote, “send flowers, the next stage will be the general paralysis of the insane.” Banham refused to engage in what he called “idiotic preservationist panics” for fear of being subjected to similar requests from “every crackpot period group and broken-down country-house owner in England.” But he could also have aimed his sarcasm at preservationists with much more cos mopolitan tastes. In 1965, after all, Le Corbusier’s Villa Savoye was declared a national historic monument in France, thanks in part to an international advocacy campaign by modernist architects and historians, including Siegfried Giedion. The mid-1960s constitutes something of a historical turn ing point, when a wave of fervor swept up architects and architectural histo rians of every allegiance across Europe and North America, and transformed architectural preservation from a fringe movement into a mainstream political cause. A few dates serve to evidence this shift. In 1963, architects (including Philip Johnson) joined urban activists (including Jane Jacobs) to protest the demolition of New York’s Penn Station. In 1964, a group of architects and archaeologists from sixteen countries coauthored the Venice Charter, the first international document to call for the protection of both monuments and historic sites. At the 1965 White House conference where the phrase “world heritage” was coined, visionaries R. Buckminster Fuller and John McHale joined architectural historian Vincent Scully to recommend that “the cultural diversity of the earth” be conserved as a resource, akin to oil or gas. This three-year period is bracketed by major acts of legislation that extended the legal protection of historic buildings to entire urban districts: the 1962 Loi Malraux in France and the 1966 National Historic Preservation Act in the United States. In 1972, the World Heritage Convention was signed by the United Nations’ cultural agency, Unesco, establishing mechanisms for protecting sites of natural and cultural heritage worldwide.

So where Banham saw “idiotic panics,” others saw political empowerment. The timeline I have sketched out is rapidly being historicized as the start of a dramatic rise in the political power of preservationists, coincident with a global shift from conserving individual monuments to preserving entire environments. According to this new historiography, the 1960s saw an enlarge ment of preservation’s domain and a concurrent expansion of its political effectiveness worldwide. The preservationist Alan Powers even identifies 1965-1985 as a “heroic period of conservation,” when the “parallel progress of voluntary association and legislative and administrative action, combined with media pressure,” triggered a politics of expansion that aimed to establish “the place of conservation in life as a whole.” Powers’s use of the preferred British term conservation gives away his geographic specificity. But like many other national narratives, his story has international implications, whereby local “heroism” helped to ignite a global movement, which, in turn, followed the political example of national groups to bring pressure onto international organizations. Thus, in an accumulating number of national histories, the globalization of preservation politics is ascribed to a convergence of political will along four axes: an alliance between modern architects and historic preservationists; a shift of media attention from object-buildings to urban ensembles and vernacular milieus; a joining of forces between nature conservationists and architectural activists; and a concerted effort by scholars to diversify the architectural canon and the demand for its protection. And so (the narrative goes) the protective boundary of preservation was progressively enlarged, by sheer force of activism, to include ever-larger sectors of the built environment.

The trouble with this narrative of progressive enlargement lies in its conception of architectural history; specifically, the notion that architectural monuments stayed the same while around them mentalities changed. If a new politics of expansion arose from a synchronous wave of activist practices, how was this politics enacted at the architectural scale? What values and criteria had to be invented for historic architecture to sustain its expanded political charge? Perhaps most importantly, how did preservation, once conceived as a historical accumulation of buildings in time, become a spatial practice that lays a claim to entire environments?

Some historians have pointed to the social, legal, and technological forms of mediation that intervened to accomplish this enlargement. In the 1970s, the German art historian Willibald Sauerländer commented on the growing consensus that an “extension of heritage” had occurred, but he expressed skepticism that the process had been purely additive. “To conserve is not only to preserve historical evidence but also to mediate it,” he wrote. Instead he hypothesized a shift from quantity to quality—from art-historical “accumulation” to a populist “cult of monuments”—and hinted that public demand for expanding the boundary of protection did not necessarily empower the people who found themselves inside that boundary. International activists tracking this expansion on the global stage soon detected another layer of mediation, pointing out that case-by-case activism had been accompanied by a dissemination of norms. Piero Gazzola, founder of the International Council on Monuments and Sites (ICOMOS, the first nongovernmental organization devoted to architecture), remarked that preservationists turned their attention to urban spaces and vernacular typologies all over the world at the same time. “In the span of ten years,” he wrote in 1978, “we have gone from punctual protection to global protection.” But he also warned against thinking that this “diffusion of criteria” had created a blanket of control. “Total protection,” he wrote, “can lead to non-protection.”

Over the next two decades, talk of heritage expansion turned to concern for heritage inflation. The French historian Françoise Choay, for instance, concluded her authoritative 1992 history of patrimony with a chapter on new technologies—of mass communication and transportation—which she blamed for turning heritage into an instrument of “hidden mediation” that fueled a “cult of passive self-contemplation” worldwide. Appealing to Sigmund Freud, she detected in the diffuse globalization of heritage a strain of narcissism. “Heritage today,” she wrote, “seems to play the role of a vast mirror in which we . . . contemplate our own image.” More recently, the architect Rem Koolhaas has analyzed what he calls “the onward march of preservation” and confirmed Choay’s diagnosis of passivity, concluding that “preservation is overtaking us.” In this formulation, preservation is a spatiotemporal mechanism that compresses historical values and disseminates them in order to control the built environment.

Together, Sauerländer, Gazzola, Choay, and Koolhaas provide the seeds for a critique of the heroic narrative of preservation history because they point out that the expansion of preservation has been accompanied by a fundamental shift in how historical and political agency operate through architecture. If historic preservation entered a new phase in the mid-1960s, it did so not only because preservationists acquired more political power but because power found new ways to circulate through the built environment. Architectural agency took on new norms, new forms, new techniques.

This article addresses the radical change that occurred in preservation’s modus operandi beginning in the mid-1960s by telling the story of one episode when the expansion of preservation’s domain “from the punctual to the global” was the subject of an international engineering competition. The objects of the competition were the temples of Abu Simbel: two massive pharaonic shrines, fronted by eight colossal figures that were carved out of a sandstone cliff on the banks of the Nile during the rule of Rameses II in the twelfth century BCE. From 1960 to 1968, the temple complex was saved from drowning, moved 208 meters over and 65 meters up from its original site in a highly publicized international campaign led by Unesco. The salvage remains a world-historical event and an important marker in the history of preservation. The monuments were so large and monolithic that they blurred the boundaries between an architectural object and its site, and their salvage was part of a regional plan that exemplified preservation’s expanded scale of operation. Furthermore, because the temples were so remote and had no “local” constituency advocating on their behalf, the question of what kind of technical and political mediation was required for their salvage was brought into particular relief.10 They also offer a unique case study of the role technology has played in making historic preservation a global field of expertise. The salvage of Abu Simbel exemplifies the new model of monumentality that was catalyzed when new approaches to preservation mixed with geopoliti cal ambitions and experimental engineering.

In this article I focus on technology not only because the international preservation movement coalesced in reaction to a perceived acceleration of technological progress—although it is true that the proliferation of public works and engineering projects throughout the 1960s served as a rallying cry for both environmental and architectural activists. Nor is it simply that technological obsolescence became, in this period, the dominant criterion for determining what qualifies as historic architecture to be preserved— although many of the buildings that turned modernists into preservationists, such as Penn Station and the Euston Arch, had been built around industrial technologies, now newly old.11 More generally, architects’ attitudes toward technology were crucial in determining where they stood in the debates about the historical self-image of modernism and the fate of its most famous buildings. No doubt Banham’s real objection to preservation was technological: for him, to be modern was “to keep pace with a technological situation,” not to conserve and memorialize past architectural technologies.12 Yet, like many other architectural practitioners during this period, preservationists tried to “keep pace” with history by adopting and adapting the technologies against which they were fighting. I focus on technology, then, because chang ing conceptions of history, including architectural history, must be thought in relation to changing technologies, particularly those building technologies that translated notions of historical progress, of development, of teleology— of time—into space.

Monument and/as Infrastructure

On May 14, 1964, the New York Times published a photograph of Soviet president Nikita Khrushchev and Egyptian president Gamal Abdel Nasser “hurling rocks” into the Nile to inaugurate the construction of the Aswan High Dam. Originally designed in 1946 by an international consortium led by a German-American engineer, the dam was to be one of the largest rock fill dams ever built, its size commensurate with its impressive multipurpose task: to retain water in a gigantic reservoir lake, generating enough energy to electrify the Nile Valley all the way to the delta and permanently irrigate much of Egypt along the way. The dam was also to become the object of an intense and prolonged geopolitical tug-of-war. As soon as Nasser came to power in 1952, he made the project central to his plan for jump-starting the country’s development and achieving agricultural self-sufficiency. Large infrastructural projects were frequently used by nonaligned leaders like Nasser to leverage their strategic position with both sides of the Cold War’s East-West divide, and in 1956 Nasser approached the West, receiving an immediate offer to fund the dam from the World Bank, the United States, and the United Kingdom. But after realizing that this economic debt would not dictate Egypt’s political allegiance, the Western consortium withdrew its offer. Defiant, Nasser nationalized the Suez Canal to raise funds for the dam— sparking a crisis that would shake up the Middle East for decades—and turned to the Eastern bloc for further support. By 1964, the dam was being built largely with Soviet money and expertise.13 In this context, Khrushchev and Nasser’s act of “hurling rocks” stands out as a raw and triumphant demonstration of technopolitics: a delegation, by sheer force of gravity, of an immense amount of political power to an enormous machine.

The inaugural photograph was disseminated in the West as a cautionary tale. Suspended in midair, the stones of the Aswan High Dam were carriers of a political force that could divert not only the flow of the Nile but also Western channels of influence in the Middle East. There was no shortage of infrastructural metaphors to make the point: Khrushchev used his Egyptian trip to declare his intentions to “drown capitalism on the African continent,” and another photo opportunity the next day showed the leaders pushing a button, in unison, to detonate the first explosion that would demolish temporary construction digs. Western com mentators witnessing this political theater responded by attacking the monumental qualities of the dam, calling it “Nasser’s pyramid” and an “Egyptian monopolization of the Nile.”14 Not to be outdone in monumental rhetoric, Nasser’s Ministry of Information spent much of the early 1960s comparing the Aswan High Dam to the monuments of pharaonic Egypt. One pamphlet, aptly titled “Aswan: The City with Public Works More Grandiose Than Obelisks and Pyramids,” computed that the dam would require “enough stone to build 26 ancient pyramids,” a comparison made easier by the fact that the dam was itself “in the form of a collapsed pyra mid.”15 But the ministry also emphasized the dam’s absolute modernity. Whereas the pyramids were “monstrous architectural conceptions” that had wasted material and exploited labor for the memory of only a “few powerful men,” the Aswan High Dam was a new kind of monument, “larger and more human” because it would remain active, in the service of all Egyptians, in hydrological perpetuity.16

The contest between two kinds of monumentality (the one ancient and static, the other modern and dynamic) was no mere metaphor. The six-trillion cubic-foot lake created by the dam was projected to flood dozens of ancient temples and archaeological sites in Nubia that sat along the banks of the Nile. By 1964 the dam had become a veritable iron curtain neatly dividing the Nile Valley between Eastern and Western blocks, each side running a large scale engineering project. Downstream, more than 800 Russian engineers built the dam and its associated power stations. Upstream, Nubia was crowded with Western archaeologists and engineers brought by Unesco to survey and salvage hundreds of monuments and sites.

The temples of Abu Simbel were the largest and most impressive of the temples, and they were understood from the start of the project as counter monuments to the dam. Like the dam, they represented engineering projects of massive scale. Also like the dam, their salvage would require unprecedented international cooperation. But unlike the dam, which gen era ted power, the colossi of Abu Simbel appeared to absorb the immense effort that was invested in them. For instance, in 1960, Unesco publicized its appeal to “Save the Treasures of Nubia” on the cover of the Courier with an image of the tem ples sitting impassibly, facing the Nile. Four years later, the temples appeared again on a Courier cover, which proclaimed this time that “Victory in Nubia” had been achieved.17 Nowhere was the human agency required to achieve this victory in evidence: the temples sat unchanged, still facing the Nile impassibly. In contrast, Soviet publications commemorating Khrushchev’s visit to Aswan depicted hydroelectricity as a source of political empowerment, proudly claiming that “Russian-Egyptian friendship” had built the dam. Against this political specificity, Unesco made use of what Bruno Latour has called its “sociological Esperanto” to describe the work of preservation: according to the organization’s publicity material, “the world saved Abu Simbel.”18

What does this mean? One place to start decoding Unesco’s abstract language is the final engineering report for the salvage of the temples, whose preface breaks down “the world” into six collective nouns:

The EGYPTIAN PEOPLE, through their GOVERNMENT, have shoul dered the greatest part of the burden of this noble enterprise.

UNESCO called on nations and people all over the world and urged them to make generous contributions.

The ARCHAEOLOGIST, represented by specialists from Egypt as well as from other countries, outlined the fundamental conditions for the Salvage Operation.

The CONTRACTOR, in the form of a Joint Venture composed of companies from Egypt, Italy, France, Germany and Sweden, executed the gigantic works involved.

The CONSULTING ENGINEER planned and prepared the whole project and supervised the works. He also submitted this Report.19

This disembodied chain of human agency actually describes a specific set of actors who participated not only in saving Abu Simbel but also in the entire campaign to salvage the twenty-four other temples of Nubia. Each plural noun represents a human network whose presence in Nubia was care fully orchestrated: from Egyptian workers to foreign archaeologists and engineers to international bureaucrats. Elsewhere, I have described how this delicate orchestration can be understood as a design project that reconfigured the Nubian Desert into a new, massive exhibition space. Here it might suffice to note that this project was tacitly regulated by a logic of concentration and dissemination.20 The design began in 1959, when Unesco assigned a priority to each temple, designating some as of “first” or “second importance,” deeming the rest unsalvageable, and vetting proposals for new sites. Over the next twenty years, some temples were consolidated in four oases along the new lake, while others were dispersed individually as “ambassadors of Egyptian culture” in Western museums. To legitimate this work, Unesco invented an entirely new legal and bureaucratic framework for cul tural exchange. But despite Unesco’s guarantee of scientific and political neutrality, the overall effect of the temple movement was to optimize the number of tourists to the temples. In a sense, this redesign of the desert literalized what Gazzola called the passage “from the punctual to the global.”21 Once a sequence of points on a map, the monuments of Nubia became part of a global network wherein they retained their Nubian identity despite being dispersed across temporal and spatial discontinuities. So although the Abu Simbel temples were technically salvaged in situ (i.e., they were note, conceptually, relocated), they were fundamentally transformed by their movement, becoming the crowning moment of this new experiential complex—a new monumental infrastructure for a new nation-state.

Integrities

The task of salvaging Abu Simbel was never declared an international com petition, but it unfolded as a series of alternative schemes proposed by national delegations and assessed by Unesco. For the organization’s cultural officers, the project offered an opportunity to codify emerging international criteria for preservation, especially the concept of “integrity.” Borrowed from ecological discourse, the idea of integrity appeared especially promising to conservationists eager to expand their activities beyond the walls of individual monuments because it implied that a matrix of relationships exists between all the elements of a given site.22 But as in ecological thinking, the notion of integrity also provoked a constant slippage between ethical and scientific discourses. When applied to the moving of monuments, the term integrity alternately designated the morphology of a site, the material properties of an object to be moved, and the moral fiber of the person (or entity) doing the moving.

Unesco’s judging committees were composed of a variety of disciplinary representatives, and each national team making proposals was also an exper iment in collaboration. Most teams were led by engineers (who likely under stood integrity as a structural notion) but also included architects (for whom integrity was a site-planning strat egy) and sometimes preservation ists (who focused on the material integrity of objects). This intricate division of tasks—among engi neers and architects, individuals and institutions, nation-states and international organizations—was further complicated by an under lying debate over whether any modern human gesture should be legible in the desert. Here integrity, as a term applicable to environ mental systems, became entwined with integration, an aesthetic notion that had been developed by European art and architectural conservators since 1945.23 And while each team’s proposal can be read for its contribution to the new international discourse on integrity and integration, the rhetoric surrounding each scheme also reveals a preservation mentality strongly influenced by national traditions. These national discourses must be recalled along with the various salvage schemes proposed by each team— not in order to caricature them, but, on the contrary, to show how invisible these intellectual legacies had become in their home countries and how incon gruous and incompatible they suddenly appeared when forced to compete on an international stage. One irony of preservation history is that although preservation discourse became properly international as early as the mid nineteenth century, many of its practices and values remained nationally bounded well into the twentieth century, in part because the profession of preservation is largely administered by national state institutions.24

Damming, Lifting, Flooding, Floating

The first scheme to salvage Abu Simbel was proposed by the French engineering firm of Coyne et Bellier in summer 1960: to preserve the temple in situ by building a rock-fill dam—in some ways a copy of the Aswan High Dam—in front of the temples.25 This scheme would reintegrate the monu ments into the desert using the same technologies that had radically trans formed it. Coyne et Bellier were specialists in thin-shell concrete dams, but they left the design of the dam to French architect Albert Laprade, who sought to maintain what he called “the extraordinary harmony between the elements of this unique site.”26 Laprade devised an intricate choreography where visitors arrived by water at the level of the lake, descended along a sinuous scenic route to circumvent a shallow pool in front of the temples, and finally found themselves aligned with an axis that corresponded with the angle taken by the rising sun during a once-a-year illumination with the innermost shrine of the large temple.

Laprade felt no qualms about leaving a legible human gesture in the sand—so long as he deemed the gesture to be aesthetically continuous with the original setting. In this sense, he engaged in the French practice of “restoration” as it had been pioneered by Viollet-le-Duc and had continued to be fol lowed, in spirit, well into twentieth-century France: that is, the act of “re-instating a monument in a condition of completeness which could never have existed at any given time.”27 This “condition of completeness” had long been the French answer to the question of integrity, and Laprade evoked it when he called the site a “timeless landscape.” Yet completeness did not mean ideality. Having spent much of his career drawing and designing neo-orientalist buildings in an explicit rebellion against classicism, Laprade rejected circular geometry as “too majestic,” favoring instead an elliptical gesture that, he argued, created “a jewel-case” around the temples, “fusing” his work “into the landscape.” Found nature took the place of past architecture in this redefinition of restoration, as the new site was now described as having an “almost natural appearance.”28

Opposite: Twenty-four temples were relocated to four oases along the Nile and five Western museums during Unesco’s Campaign to Salvage the Temples of Nubia, 1960—1980. Diagram by Lucia Allais. Left: Coyne et Bellier with Albert Laprade. “Dam” scheme to pro tect the temples of Abu Simbel, 1960. Plan and rendering.

But the architectural legibility of this “dam” scheme only concealed its weakness as an engineering proposal. As Unesco’s chief archaeologist soon realized, “unfortunately, dams are made to go across streams not to protect something on the side of the stream.”29 A pumping station, located far from view behind the temples, would perform most of the work of preservation. Financing this pumping would have been prohibitively expensive. Faced with the prospect of indefinite maintenance, within a few months Unesco decided to pursue an alternative plan that Piero Gazzola—the same Italian preservationist mentioned at the beginning of this article—had proposed during Unesco’s first fact-finding mission in October 1959.30

Gazzola was the first to propose “liberating” the temples of Abu Simbel from the mountain in order to “preserve the integrity of the temple by lifting it whole.”31 Influenced by an Italian tradition of painting restoration that distinguished between the epiderme and the struttura (the skin and the structure) of any work of art, Gazzola transformed the monolithic site into a building with a façade, a structure, and a site—or, as he put it, “the rock, the block and the box.”32 This preliminary sketch was further developed and officially presented to Unesco in October 1960: the temples would be severed from the cliff with three extended cuts into the rock, then encased in a gigantic concrete box and lifted about sixty meters, one centimeter at a time, by a grid of hydraulic jacks. This, too, implied a certain notion of integrity, similar to the one theorized by Cesare Brandi in his 1963 Theory of Restoration: the idea of preserving “the material wholeness of the work of art.” The difference between Italian wholeness and French completeness was that while Laprade had posited a timeless environment, Brandi identified a precise moment in time: restoration occurred at “the methodological moment in which the work of art is appreciated in its material form.”33 Restoration was a reenactment of aesthetic value.

One advantage of the theory of reenactment is that it allows for modern technology to be exposed in preservation. Riccardo Morandi, the structural engineer who joined the Italian team, often contributed to preservation projects by designing modern structures for ancient monuments. For example, in his entry to the 1965 competition for the Tower of Pisa he proposed to build a scaffold around the tower, giving the medieval monument a visible modern crutch against which to lean. Similarly, Morandi proposed to reenact in Nubia the “wholeness” of Abu Simbel through the design of the concrete box to be poured around the temples to secure them during lifting. The box was designed in collaboration with the mathematician Gustavo Colonnetti so that the elasticity of the concrete—its ability to absorb mechanical forces— would be continuous with that of the sandstone.34 The elegance of the scheme lay in this momentary replacement of integrity with a calculated continuity between old and new materials. After all, this was the first scheme to propose a violation of integrity, a cut along three planes that would effec tively sever the relationships between the temples and their site.

One cannot overstate the technological heroism that permeated both the Italian team’s rhetoric and the publicity that Unesco derived from this scheme. Every component was experimental. Morandi drew dramatic sketches of the salvage that were circulated worldwide for fund-raising. But these renderings did surprisingly little to dramatize the process of lifting. In the most famous view, the hydraulic jacks are barely visible—the concrete box dwarfs them. Enframing the seated figures, the box appears to be a brutalist monument in its own right, similar to Morandi’s own concrete architecture. The only other perspective view Morandi submitted does not even show the temples, instead featuring the “tunnels” dug below the monument and occupied, in the architectural drawing, by two Nubian children. Undoubtedly they were drawn to demonstrate the monumental scale of the hydraulic jacks, but, as the only human beings in the whole scheme, they also serve an allegorical purpose of inhabiting “the cut” between the old and the new. Despite—or perhaps because of—the Utopian resonances of these drawings, the scheme never attracted enough funds for Unesco to begin con struction. By the middle of 1963, as the flooding grew near and fund-raising stalled, other nations volunteered their schemes.35

Of these, the most fantastic was a British proposal to leave the temples underwater. Based on the assumption that it was not water per se that would disintegrate the temples but the chemical composition of Nile water in particular, the British team proposed to build a concrete dam not to retain water but to purify it. The scheme was designed by the young structural engineer Ted Happold, later to become one of the best-known members of the postwar engineering avant-garde, then still working for Ove Arup. Architects Jane Drew and Max Fry, who had worked with Le Corbusier and Pierre Jeanneret in Chandigarh, joined him. They proposed to delegate the work of maintaining the integrity of the site to one architectural element: a single, thin, reinforced concrete membrane. In their plan, the membrane appears as a rigid curtain, folded for stability.36 The ingenuity of this solution lay in the thinness of the interface between object, subject, and site. Instead of the monument, it was the visitor who was encased: in bubbles, tunnels, and shafts that left undisturbed the harmonious continuum of elements. Visitors were shown casually strolling the underwater realm in their leisure suits—as if the ordinary city dweller or museum-goer had been transposed into this nomadic underwater environment.

Here, too, the scheme can be seen as a critical take on a long-standing (in this case, British) tradition of conservation—although much had changed since John Ruskin famously defined restoration in negative terms as “the most total destruction which a building can suffer.”37 Ruskin preferred that buildings be left to the forces of “universal decay,” and his follower William Morris later founded Britain’s first Preservation Society, devoted to ensuring that British monuments would be subjected only to minimal intervention, leaving visible only traces of what Ruskin had called “parasitical sublimity.” In the twentieth century, this Morrisian tradition developed into a careful technical practice, one that maintained old buildings through a combination of materials science and picturesque planning. The British scheme at Abu Simbel echoes this tradition and its contradictions by apparently combining willful ruination, minimal intervention, high-tech chemistry, and picturesque enjoyment. Certainly the circulation route around this fantastical underwater scheme was episodic: from a restaurant at the top of the dam, visitors proceeded down an elevator to access three levels of curved pathways where circular windows and bubbles of glass offered glimpses of the colossi, or a worm’s-eye view of the inner shrine.

Architecturally, this scheme was the most eclectic. The folded surface recalls contemporaneous structural experiments at Ove Arup, the bubbles of glass echo the plug-in sensibilities of the British neo-avant-garde, while the nautical windows are a throwback to the first machine age. This eclecticism might be explained by the fact that the original idea had been proposed not by an architect but by a film producer, William MacQuitty, who sold the scheme as “a cool modern miracle at a relatively low cost.” An avid scuba diver with a theory of underwater perception, MacQuitty intended his visitor to swim around the monuments. He also added an environmentalist’s prediction: that nuclear power would replace hydroelectricity, that the dam would become obsolete, the reservoir drained, and the temples rediscovered.38 Perhaps it goes without saying that although this underwater scheme captured the pub lic imagination, it was far more radical than anything Unesco was willing to imagine. In her memoir, Jane Drew commented that Egypt would probably have refused any plan proposed by Britain anyway.39

In contrast to the British scheme’s notoriety, a second French scheme was officially proposed in April 1963, but it never gained publicity. Designed by the French military engineer Albert Caquot, the proposal was to “float” the temples to a new site in synchronicity with the rising of the Nile. Caquot had invented various aeronautical devices for military and civilian uses, and the circular steel floaters he designed for Abu Simbel were inspired by ship building technology, “the only procedure being practically used today to lift vertically, and transfer horizontally, any mass weighing thousands of tons.”40 Modern hydraulics were therefore combined with an appeal to the ancient Egyptian tradition of Nile water transport. But the elegance of this solution did not compensate for its incompletion or for the awkwardness of some of its architectural choices—such as cutting the temples in a triangular shape to maintain their horizontality. The question of water infiltration during lifting was also left unaddressed. In fact, this scheme was proposed as a last minute attempt at a “wet” scheme before “dry” thinking was brought to its dreaded logical conclusion.

Not one of these four schemes was implemented. Instead, the temples were cut into blocks—7,047 blocks sawed by hand, numbered, removed to a storage area, and then reconstituted on a hill about 200 meters behind the original site.

Hand-Sand-Lens

The “cutting” scheme was developed by the Swedish geological engineering firm Vattenbyggnadsbyrân (VBB), which became involved in the project in September 1962 at the request of the Egyptian government. VBB’s scheme was three times cheaper than the other proposals and was adopted in extremisin June 1963 after it became evident that cutting was the only alternative to flooding and after the United States secretly offered a guarantee of funding.41 The cutting was violently opposed by some of Unesco’s own experts. As late as May 1963, a panel of experts wrote that they were “immensely repulsed at the thought of recommending a project that leads to the cutting or fragmenting of these precious monuments in any way possible, even if they can be reconstituted in another site.”42 Yet by June this fragmentation was approved, and by October publicized as a victory. In a complete reversal of the rhetoric of integrity that had been building momentum around the French, Italian, and British schemes, a political logic ultimately seemed to take precedence over any coherent preservation theory.

Yet we should be careful not to equate the failure of the four architectural schemes with a failure of integrity. Instead we should ask what definition of integrity was validated by the salvage method that eventually unfolded. Integrity stands as an accepted norm today, and nobody—not preservationists, not heritage historians, and least of all Unesco—dares to speak of the Abu Simbel temples as if they had not remained authentically themselves.43 I would like to suggest that a theory of integrity lies latent in the Swedish cutting scheme, a theory found not in the doctrinal pronouncements of conservationists but in the salvage apparatus they were forced to use—the technologies for surveying, cutting, moving, and reconstructing the temples, which formed a complicated assemblage of humans and nonhumans, ancient materials and modern machines.

We can begin to locate this assemblage in the film version of The World Saves Abu Simbel, an hour-long publicity film produced by Unesco in 1967.44 Set against a free-jazz sound track, the film documents the cutting process with frightening bluntness. Unlike most films in this genre, it does not open with a dramatization of the drowning of Nubia. Instead, the title sequence shows a rapid montage of men at work, cutting away at the face of Rameses against the rhythms of an upbeat xylophone. Men at work dominate the rest of the documentary. Despite the many machines in play, the human hand emerges as the most salient architectural technology. The film features an overwhelming display of human labor. The camera cuts to different workers performing individual parts of this vast enterprise, zooming in on their hands as if to certify the monument’s tactility. In the voice-over commentary, much is made of the fact that the most delicate parts of the temples were sawed continuously through the night, so changes in temperature would not affect the size of the seams. Everywhere the human hand is seen, we also see a lot of sand. Any cutting is followed by the pouring of sand. Any hole is filled with sand. Any block is stored on a bed of sand. Sand is ubiquitous, and this alliance between the hand, the sand, and the camera lens produces more than just a propagandistic montage. These three technologies also bind together the three aspects of the salvage scheme that made it politically real izable: calculability, aggregation, and spectacularization.

Calculability

By calculability, I mean the potential of an architectural project to be incor porated into a project of economic development.45 From the point of view of calculability, cutting had one advantage over all other salvage methods: it required a lot of labor, which could be paid in local currency—Egyptian pounds—and local currency was what the United States wanted to spend in Egypt. The United States held large amounts of Egyptian pounds, derived from the sale to Egypt of agricultural surpluses such as wheat and cotton under the terms of the “Food for Peace” program established in 1955. The idea that one country gives its excess food to feed the hungry of another might seem simple, almost philanthropic, but this “gift” was twice mediated by economic transactions: the U.S. government bought wheat from its farmers, then sold that wheat to the Egyptian government, earning local purchasing power. The “aid” consisted in the discount that made an American com modity affordable to a poorer nation, but this affordability came with obliga tions for both sides: a crucial component of the program’s “peaceful” ideology was that funds should be spent on projects of national economic develop ment agreed upon by both governments. This kind of aid, known to Congress as Public Law (PL) 480 funds, allowed the U.S. government to transform surplus production at home into increased political power abroad.46 But as diplomatic tensions with Nasser rose in the early 1960s, negotiations over how to spend PL 480 funds lagged. By the time Unesco’s fund-raising cam paign for Abu Simbel got underway, U.S.-owned Egyptian pounds were accu mulating in Cairo, unspent, under threat of devaluation. A cultural project like the salvage seemed an expedient and, in the words of one cultural attaché, “non-controversial” way to expend these funds.47 Thus the Egyptian food-for-peace program became, for a few years in the mid-1960s, a program of monuments-for-peace.

The choice of the cutting scheme was thus a direct result of American foreign policy: cutting is labor-intensive, and laborers could be paid in Egyptian pounds, whereas more-experimental technologies (such as the hydraulic jacks, floaters, and pumping stations of the schemes proposed ear lier) had to be imported with convertible dollars. Against the unmistakably Western character of the other schemes, the image of so many Egyptian laborers in direct contact with the monuments of Nubia suggested cutting was a native building method. Yet even as local labor appeared to lend cultural authenticity to architecture, the real function of thousands of Egyptian laborers was to grant the monuments their international value, to act as a technological bridge between two countries at a time when their diplomatic ties were strained.

The particular economic structure of the Food for Peace program gave American officials the power to dictate not only how but also whether the sal vage of Abu Simbel would be performed. When John F. Kennedy committed to covering about 30 percent of the total cost of the salvage (in accordance with a long-standing policy that the United States contribute no more than a third of all expenses in any given international project), calculability became the deciding factor in determining whether the temples would be saved at all.48

Cutting was not just cheaper. Calculability also introduced a qualitative logic, by subjecting architecture to a procedure where incommensurable values—such as agricultural commodities and temples—were somehow made commensurate. However quantifiable engineering and its technologies were at one end of the equation, an intangible value had to emerge at the other end. The importance of this intangible, “surplus” cultural value for all the nations involved can be detected in the way the Egyptian government tabulated the “International Fund to Salvage Abu Simbel.” Whereas Unesco tallied the financial contributions of every nation in dollars in a single chart, Egypt’s official records devoted two columns to the fund, one to pounds, the other to dollars, separating out the few nations who were able to make local contributions.40 Those few nations comprised the United States and the four other Western nations that eventually received a small temple as a “grant-in-return.” Despite the complicated financial procedure that rendered these buildings exportable, the temples were conceived essentially as architectural gifts, surplus objects bearing a properly cultural value. A gifting rhetoric also per meated Unesco’s language, where temples were described informally as “bonus” (incentives for nations to contribute to the campaign) and legally as “surplus” (not unique enough to warrant remaining on national territory).50

How then did the logic of calculability map onto the architecture of the temples? Clearly the concept of integrity that emerged from the cutting scheme had less to do with the temples as architectural objects and more with their ability to absorb and redistribute economic value. The financial feasibility of the salvage provoked a complete rethinking of the notion of objecthood, not only for Abu Simbel but for the other Nubian temples. For instance, American officials originally hoped to devote American aid exclusively to rescuing the island of Philae—the so-called Pearl of Egypt, whose eclectic collection of temples the officials felt could become a symbol of America’s own cultural pluralism.51 But a different link between architecture and finance was realized instead. First, Egypt used the American aid to dismantle as many temples as possible, storing them on the island of Elephantine. This act of mass disaggregation had the double effect of distributing funds across the twenty-four temples and disseminating architectural matter across the desert. Then, Egypt encouraged individual nations to pay for individual reconstructions and required that any nation hoping to receive the “gift” of a temple contribute to the salvage of one or both of the “big temples,” Philae and Abu Simbel. Thus, from a financial perspective, the Unesco campaign was an elaborate procedure for investing value in two sites (the big temples) in order to redistribute that value and create a cultural “surplus” in several others (at each Nubian oasis, and in foreign museums). The specificity of Nubia’s pharaonic architecture—the fact that individual temples could be disaggregated from the desert and reconstituted in heterogeneous museum environments—made possible this translation from money to matter.

As the value of Abu Simbel became calculable and its stone divisible, geological engineering became the project’s dominant techno scientific discourse. VBB was a large engineering firm with a portfolio of international projects, including a new electric power plant built at Aswan in 1959 to harness the power that would be created by the new dam/’2 As managing director Nils Berg later recalled, the firm became involved in the Abu Simbel project through its direct contacts with the Egyptian government. In 1961 an Egyptian official casually mentioned to Berg that a geological consultant was needed for the Italian lifting scheme.53 VBB was hired as a subcontractor to Italconsult, an Italian consortium that was heading the lifting project. Only after it engineered the three “cuts” required for the lifting was VBB asked to develop an alternate scheme where the “cut” became systematic. In other words, calculability travels in expert networks—in this case, through the hydrogeological specialization of Swedish engineers—that are not necessarily bound by the rise and fall of diplomatic alliances. More to the point, VBB’s changed position from supporting role to center stage in the salvage operation indexes a shift of attention provoked by the cutting scheme: from the architecture of the temples to their aggregability.

Aggregation

As specialists in soil mechanics, VBB redefined “integrity” in geological terms, replacing an architectural notion based on the legibility of a “block” with a geological notion based on the mechanics of sand, soil, and stone. This process began when VBB was still acting as a consultant to the Italian scheme. Describing the monuments scientifically as an aggregate system, the firm’s engineers drew detailed elevations of the fissures in the temple rock, shaded the plan along the likely fault lines that ran across the temples, and constructed a Plexiglas model that abstracted these fault lines as diagonal planes.54 Next the firm developed plans for cutting, which mandated differ ent saws and a sliding scale of stone sizes. Here, too, prescription arose directly from description: the same nomenclature used to illustrate the results of stress tests became the design tool for a temple reconstruction that would occur in three, sometimes four, layers of aggregate. Eventually, once the cutting was adopted, no less than three surface “treatments” were prescribed to replicate different types of rock finish. The cliff would be roughly cut into large blocks, whereas sculptures and reliefs would be cut with fine saws and in pieces calibrated so that seams would least disturb their figuration.

That the integrity of the temples lay in their nature as a stone aggregate is perhaps best evidenced in VBB’s final report, which concludes with the triumphant claim that “Every piece of stone sculptured in the rock more than 3,200 years ago still does exist!”55 What this phrase cleverly avoids mention ing is that the stone was not originally in pieces. Most of VBB’s energies were devoted to precisely designing, then filling, the space between the stones, at both the architectural and molecular level. First, a new building material— a mortar made of Nubian sand—had to be invented and added to join blocks together after they were reassembled. Second, copious volumes of epoxy were injected into the temples to “consolidate” the outer sculptural layer that soon came to be called the “façade” of the temples. If mortar joined together the stone blocks to dissimulate the cuts, epoxy performed a much more per vasive role, intervening in the space between stone granules to ensure that the stone did not crumble during cutting, moving, and reassembly. Epoxy was injected three times: before the temples were cut, as the blocks were fastened to their moving anchors, and after the entire complex was reassembled. VBB was familiar with epoxy as a waterproofing agent in hydrological works, but here they retooled the substance so that it worked as a glue. In structural terms, the epoxy glue, not the “pieces of stone,” performed the “integrity” of the temples.

But soil mechanics is a science fundamentally unconcerned with outward form. Geologists and soil engineers deal with a certain amount of aggregate and ask how tightly this aggregate is packed, in order to compute the amount of pressure that any pile, including a sculpted one, can withstand. From this molecular perspective, the claim that “every piece of stone” of Abu Simbel remained is indeed true; what was dramatically transformed was the voids between the pieces.

VBB’s geological analysis redefined the concept of material integrity at an infinitely small scale. As a result, the sand of the Nubian Desert became the smallest element in a family of related building materials. VBB made extensive use of sand: as a building material, as protective coating, for shock absorption, to buffer direct contact between metal and stone, and to prevent the collapse of cavities old and new. Every time a stone was severed from the monoliths, it was placed in direct contact with matter drawn from around the site. By inscribing monument movement in an intricate system of sand displacement, VBB maintained Abu Simbel’s image as a monolith while cut ting it into increasingly smaller pieces. In the hands of the Swedish engineers, the sandstone of Nubia was a chameleonic architectural substance: sometimes a solid mass susceptible to stereometry, sometimes a loose substance that could be molded, and, throughout the salvage, a building technology akin to the crane and the saw.

By focusing on sand, VBB also created a direct connection with archaeology. Most memorably, the temple fronts were covered with a gigantic pile of sand to minimize damage to the sculpted figures, creating an image of a half-buried Rameses that became for a time iconic of the entire salvage, even appearing on the cover of Life magazine.56 A clever engineering solution, the pile of sand was intended to shield the temples from rocks that might detach and fall while the “mountain” above them was dismantled. The new plateau created by the pile also served as an elevated ground for the cranes to reach the rocks above, and, eventually, as a scaffolding for the archaeologists cutting the temple faces. This piling technique was inspired by ancient Egyptian artists and engravers, who filled temples with sand in order to work on the upper portions of their walls, then gradually removed the sand in layers as they worked their way down the surfaces.57 Yet there was more to this striking image of a buried Rameses than the revival of an archaic building technique. The sand cover also rehearsed the modern act of archaeological discovery. After its rediscovery under a mountain of sand by a Swiss explorer in 1813, Abu Simbel spent much of the nineteenth century being repeatedly dug in and out of sand (including by such famous tourists as Gustave Flaubert and Maxime du Camp). This history of repeated uncovering had even earned the temples a place above the couch in the office of Sigmund Freud, where a David Roberts rendering of the temples was hung to trigger a patient’s psycho archaeological introspection. By capitalizing on this history of excavation, the Swedish scheme highlighted the modern nature of the temples as dis covered, rather than their ancient nature as sculpted.

The aesthetic potential of this archaeo-geological viewpoint was not lost on VBB, especially on its in-house architects, Sune Lindström and Alf Bydén. In January 1962—while still working as consultants to the Italian scheme and entrusted only with the “reconstruction of the site”—they made proposals that took striking formal liberties with the design of the site. The architects offered three options to Unesco. At one extreme, they proposed to “preserve the setting and appearance of the temples as closely as possible” by recon structing the rock exactly as in the original site. At the other extreme, they proposed to mold the rock around the temples into a “characteristic silhouette in an otherwise featureless landscape,” thereby creating a “new work.” The mountain around the seated figures would be sculpted into a chain of reinforced concrete splines faced with sandstone and dramatically extruded to a point of absolute thinness. VBB justified this elastic geometry by talking of “a synthesis of the original conditions and the new” and a need to create “a monument with fresh values, still in the spirit of the ancient Egyptians” but “embodying present day technology and philosophy.”58 The horizontal plane of approach in front of the temples would also be “shaped,” and Lindström and Bydén again offered several options: geometricize the optimal angles for arrival by boat; or create a floating pier that could rise and recede with the tide. Both options, however, expanded the futuristic idiom of the elevations, using convex geometry to redesign the new site.

The architects of VBB were motivated by the same impulse as Laprade, who wanted to inscribe a new elliptical dam in the desert. Within a decade, Lindström and Bydén produced iconic buildings in the Middle East that took up Laprade’s orientalizing legacy and brought it to new heights of postmodern regionalism—one famous example being their water towers for Kuwait City. Already in their 1962 proposal for the Abu Simbel site this direction can be glimpsed in their unsolicited design for a “floating hotel” shaped as an oval peninsula. Striped so as to disappear into the desert, the hotel would dock itself to the floating platform in front of the temples, offering tourists direct access from the water to the shrine.

Unesco reacted to these bold sculptural proposals by promptly instituting a rule that “architectural shapes should be avoided” in the reconstruction of the site.59 Evidently VBB had mistaken building for site and vice versa. In the final instance, the rock face and water approach were made to look exactly like the original site. Yet a closer look at a section through the temples as built shows that, even without sculptural bravura, the plastic “synthesis” VBB advocated ultimately prevailed in the architectonic logic of the new whole. But rather than being outwardly expressed, this synthesis was turned inward. A massive concrete dome was built to support the artificial hill in back of the seated figures—a dome whose futuristic interior, worthy of James Bond, is usually excluded from the definition of the monument as such. In fact, this domed space is but the largest void created by a thin layer of reinforced concrete that lines the whole monumental complex. Concrete is the main shaping agent of the work: it supports the interior walls of the shrine, pro vides a backing for the reconstructed sculptural fronts, and supports a new rear façade with a gentle pyramidal form.60 From an architectural standpoint, the Swedish scheme transformed the temples into a new kind of building.

Once a shrine with a single, thick façade, each temple became a façade system wrapped around two inhabitable spaces: a shrine and a dome. Yet, because the scheme was only ever described in geological terms, no such architectural overview was ever provided. Instead, modern architectural technologies were hidden from view, a gesture that brings us to the last aspect of the hand sand-lens alliance: visibility and its instrument, the eye.

Spectacularization

There is a distinct continuity between the reconceptualization of the Abu Simbel temples as geological and financial aggregates and the spectacularization of their movement. This awkward word, spectacularization, helps to thematize a pattern whereby every aspect of the temples’ movement was not only visually recorded but enhanced, annotated, presented and re-presented, narrated, edited, and dramatized in order to be showcased across the world. The intense effort to publicize an event taking place deep in the desert of Nubia confirms Guy Debord’s 1967 pronouncement that “modern society has invested the surface of every continent—even where the material basis of economic exploitation is still lacking—by spectacular means.”61 In the case of Abu Simbel, spectacularization also means something more specific: the incorporation of optical technologies into the apparatus that certified and reproduced the integrity of the temples. In order to be saved, the temples had to be validated by experts, technically described by engineers, and popular ized to a worldwide public. A crucial component of each of these tasks was performed not by strictly architectural technologies but by media of visualization than focused on imaging elements of the temples up close (and in pieces), rather than depicting the monumental complex as a whole. In other words, new modes of seeing came to the rescue of the monument as well.

Throughout the salvage, camera crews recorded the movement of every stone. The ever-present lens attested to the integrity of the work by showing that salvage workers were behaving ethically and that architectural matter was being treated authentically. Filming the movement of stones became standard practice in Nubian salvage work (photographs of the most recent temple reassemblies show blocks being lifted while surmounted by an engineer and a cameraman).62 But aside from documenting the work, the filming process also contributed its own mechanics of cutting and editing to the staging of the sal vage. In The World Saves Abu Simbel, optical montage (of film) and physical assemblage (of blocks) are conjoined so that cutting between film shots helps to hide the fundamental violence of cutting the stone into blocks.

Another type of mechanical vision became instrumental at the other end of the process, where reconstruction was aided by the use of a sophisticated apparatus of photogrammetry. The French National Geographic Institute originally used photogrammetry to record the temples as a set of topographic elevations in 1959. Indeed the word salvage originally designated only this process of recording temples before they disappeared—when it was assumed that the Abu Simbel temples would inevitably be flooded and all that could be “preserved” was the three-dimensional information of photogrammetry.63 Once the temple movement began, however, these topographic drawings became guarantors of originality, used to check the reconstructed profile. The institute also produced a film, Nubie 64 (Nubia ’64), that showcases pho togrammetric technology as a modern wonder, pausing on every component of the machinery as if it were the product of an evolution in visual accuracy.64 Dne particular sequence proceeds through a chain of specialized viewing agents: beginning with archaeologists hunched over Egyptian reliefs, con tinuing with geographers standing upright pointing their cameras at the temples, and culminating with a prolonged sequence about a “machine oper ator” who is prosthetically attached to a stereometric vision machine through eyes, hands, and feet. The film decomposes the act of seeing into discreet actions, so that the eye is focused on individual lines and points rather than on the monument as a whole. Conversely, each point on the visible surface of the temples is subjected to intense and close-up examination by the stere ometric camera. The eye and the body of the machine operator perform a reenactment of these reference points, and the task of reconstituting the visual whole is then delegated to a “plotting machine.”

These optical technologies reconstructed a new image for the temples of Abu Simbel in the same way experimental building technologies reconsti tuted a new architecture for the temples. Just as cutting and injecting were two ways to intervene directly into the fabric of the stone, so filming and pho togrammetry allowed a mechanical reenactment of the visual experience of the monument even after it could no longer be apprehended as an aesthetic whole. In this manner the perceiving eye was subjected to a logic of disas sembly, placing the temples in what Walter Benjamin called the “age of mechanical reproducibility.” Indeed, the pairing of architectural and visual technologies at Abu Simbel recalls Benjamin’s famous analogy between scalpel and camera—the idea that “the camera operator is like a surgeon, in that he intervenes mechanically in the assemblage of the work of art.”65 Taking Benjamin’s cue, we can further specify the hand-sand-lens alliance by imagining that technologies that “penetrated” the stone and those that “scanned” its surface were paired off: the eye and the blade, the syringe and the camera, the block of stone and the reel of film.

The significance of this pairing of visual and surgical technologies is that it was systematically used to perform a delicate balancing act between truth fully rendering the features of Egyptian architecture and giving them a newly modern aesthetic meaning. Consider the three characteristics of Egyptian art that were theorized by art historians in the twentieth century: first, its nature as an art form “conceived for strictly near viewing,” to use Alois Riegl’s words; second, the shallowness of Egyptian representation, its strict adher ence to the rules of what Adolf Hildebrand called “relief space”; and third, the representation of body parts as disconnected components, what Erwin Panofsky called its “mechanical” rather than “organic” arrangement of parts.60 Each of these formal properties was enhanced and manipulated in the cutting performance. Because Egyptian art is an art with no built-in fore shortening, the documentarians could film pieces of the temple in extreme close-up without exposing optical distortions. Because the three salvage techniques—cutting, injecting, and photogrammetry—required an extreme proximity of the eye to the sculpted form, they reenacted Riegl’s near view. Similarly, because the planarity of Egyptian art bears the memory of the block from which the art was carved, seeing blocks with elements of relief being carried away from the site was not shocking—they looked like the unfinished Egyptian sculptures that were known from museum collections throughout the world. Finally, because Egyptian artists proportioned each part of the body independently—rather than modifying their shape and size in relation to the whole body—parts of the temple could lay exposed in amputated form (as happened with the legs famously photographed truncated from Rameses’s torso) without provoking in the viewer repulsion at human dismemberment, producing instead a mild longing for the other limbs, each of which retained their own idealized proportions. Perhaps the most important part of the cut ting apparatus to aid in the visual reconstruction of the temples as a properly Egyptian whole was the cutting grid itself. Again Panofsky provides a clue in his description of “the Egyptian theory of proportions” as a theory that made no difference between viewing and producing. Panofsky emphasized that Egyptian artists worked “not by prospectus (view) but in geometric plan,” using a finely meshed grid to subdivide the block of stone and lay out the position of each part.67 For Panofsky, the use of this grid meant that Egyptian art was an art of reconstruction not imitation. In light of this, the imposition of a cutting grid onto the temple fronts of Abu Simbel appears no longer as a gesture of deconstruction but of re-construction, a reenactment of the grid that must have been a part of the temples’ original making.

Whereas the original artists of Abu Simbel needed only a grid to convey a normative proportional system to the ancient Egyptian beholder, in reconsti tuting Abu Simbel as a modern work of art the cutting grid was comple mented by a proliferation of media. All the views, renderings, drawings, films, and photographs that were produced around the salvage give the mod ern viewer a simultaneous and separate rendering of multiple projections, narrativizing them over time into a story of “preservation.” Consider, for instance, the most dramatic sequence of The World Saves Abu Simbel, when the “face” of Rameses is severed from the body. The camera begins with a wide shot from below (the modern monumentalizing view par excellence) that shows the block of one of Rameses’s heads, the crane lifting it, and the men around it. As soon as the face is detached and begins to rise, the camera zooms in on the hands of the archaeologists who take hold of the block to keep it from rotating off axis, inserting their fingers into a hole that has been bored in the face. After this moment of tactility, the camera adopts and main tains the normal view—an axis perpendicular to the surface—following the face of Rameses in a full-frontal close-up as it is carried to its new site and cutting to a countershot of what Rameses sees as the voice-over narrates: “King Rameses gives one last majestic look” toward his former abode.

This careful reimaging of the formal qualities of the temples was integral to their material salvage. To modernize the temples was to integrate contem porary spectacular values into Egyptian form, and “integrity” was redefined as an alignment, across millennia, of ancient modes of construction with mod ern modes of perception. More than an added propaganda dimension, this intense effort of spectacularization was aimed at granting the temples their eventual status as international objects—a status that was far from guaranteed.

“Rameses Had Himself Sculpted in Quadriplicate”

From the moment its survival was in doubt, the legitimacy of the Abu Simbel complex as a suitable international monument became a matter of con tention, especially in the American and international press. Because PL 480 funds were “public” and had to be appropriated by Congress, the temples became the object of a sustained debate, from 1960 to 1963, both in Congress and in a constant stream of op-eds, feature articles, firsthand reports, travel ogues, radio specials, and museum exhibitions. These debates amount to a debased form of criticism, derivative of more sophisticated discourses. (In one notorious episode, a presiding congressman reacted to an archaeologist’s presentation by “asking the prize question, who is Abu Simbel?” His mistake was quickly rectified: “Mr. Chairman, Abu Simbel refers to a geographical location.”)68 But in this discourse, and especially in the words of detractors who argued against any salvage, we find a cohesive new definition of preser vation as a practice of mediation.

The first argument put forth against saving the temples was that the sculpted figures were crudely made, that they were not particularly fine examples of Egyptian architecture—not unique enough to be saved. “Look at the thick knees,” one critic wrote.69 This critique echoed the judgment of many architectural historians, among them Giedion, who visited Abu Simbel in 1958 and found the temples’ sculptures too small to be monumental and too gigantic to be refined. For Giedion, and a whole generation of architects fascinated with pyramids as “space-emanating objects,” the Abu Simbel tem ples were merely “colossal”—and therefore symptoms of decline and man nerism in Egyptian art.70 A related argument developed by art critics was that by drawing attention to Abu Simbel as a “unique work of art” Unesco had encouraged the confusion of spectacle and art. The temples were valuable only as part of a unique sequence of sun, sand, and Nile, and Unesco used film and photography to artificially inflate this scenographic value, effec tively fabricating a tourist attraction in advance. Certainly the involvement of André Malraux rendered the entire enterprise suspect in some scholarly circles. In 1959 Malraux had taken part in Unesco’s inaugural ceremony, comparing Nubia in a famous speech to his “museum without walls,” where sculpture is given new life by photographic reproduction.71 According to Malraux, ancient art could be reinvigorated by modern media, which granted even secondary works a “spurious” (though positive) “modernism” by blow ing up their details to colossal scale.72 It was through Malraux’s rhetoric that many readers of Unesco’s literature first heard of the temples of Abu Simbel, and when Malraux visited the temples in 1966 he was photographed staring down one of Rameses’s delaminated faces, undoubtedly testing this “spuriousness” firsthand. But more traditional art scholars found spuriousness not in the temples themselves but in the motivation of popularizers such as Malraux and Unesco, who tried to replace their exacting value judgments (that Abu Simbel was a secondary work) with the seductive value of modern spectacle (that Abu Simbel was photogenic).

Yet the blindness of American cultural officials to these critiques only fed the controversy, especially abroad. For many British Egyptologists, America cared less about Egyptian monumentality than about its own, and the entire project was simply a way for the United States to achieve a colossal presence in the world. The European intelligentsia, well-versed in arguments made by art historians such as Wilhelm Wörringer about the “Americanist immoder ation” of Egyptian art, came to consider Abu Simbel cynically as a fitting emblem of American arrogance.73 Even in the United States, some skeptical prehistorians and politicians were quick to point out that Rameses was not a particularly important pharaoh but a megalomaniac, a “fanatical builder” obsessed with reproducing himself.74 To preserve Abu Simbel meant to pre serve a monument to a despot, and a not particularly good one. Rameses II’s only historical achievement was the creation of an arts industry for the mass production of effigies, reliefs, and statues.75 Ironically, increased quantity led to a decline in quality, and this repetition rendered any sculpture Rameses commissioned less valuable, including those at Abu Simbel. So at worst the temples of Abu Simbel were emblems of a hollow, narcissistic, imperial power. At best they were simply a site where, as one journalist put it, “Rameses fore sightedly had himself sculpted in quadriplicate [sic].”76

Crude execution, cheap spectacle, questionable politics, showy repeti tion—none of these attacks put a stop to the salvage effort because they merely pointed out that the temples of Abu Simbel were already mass-produced objects. In a sense the lack of originality in their making only facilitated their ability to be reproduced as a modern monument. In light of these debates, the salvage of Abu Simbel appears as a solution not to the problem of preserving existing cultural value but to the problem of creating a new one. Ultimately the temples of Abu Simbel were saved not in spite of the fact that they were cut into blocks but because they could be cut into blocks while becoming more or less authentic modern versions of themselves.

History at Two Speeds: Preservation as a Medium

What does this episode tell us about the expansion of preservation’s domain in the 1960s, pithily expressed by Gazzola as “we have gone from punctual to global protection”?77 To reiterate, the phrase is usually interpreted to mean that monuments in this period became smaller and more vernacular, while the protective boundary around them became larger. But in the case of Abu Simbel, a monolith literally injected with boundaries, as protective norms and forms became increasingly finer, more “punctual,” the monument emerged as more “global.” Also clear is the fact that, although the project offered preservationists unprecedented access to political power, the architectural object itself eventually appeared to take on more power than any of the human actors, none of whom could claim to control the project entirely. While the story is undoubtedly “heroic,” we cannot speak, with Powers, of a narrative of local empowerment. Yet, to say, as Choay might, that Abu Simbel is therefore a narcissistic mirage, a symptom of human passivity in the face of tourist machinery, is not enough. If we are to take seriously the claim that preservation’s “expansion” diffuses architectural values to the point that they mediate social bonds, for good and for ill, then preservation must be retheorized as a historically variable, space-making practice.

Paying closer attention to technologies of preservation alerts us to the fact that the debate about agency and passivity that has animated preservation circles since the 1960s is really a debate about the emergence of a new archi tectural medium. With this phrase I do not mean only that preservationists experimented with new materials, such as sand and epoxy, or new crafts, such as cutting and reassembling. Nor do I mean that architectural heritage is a kind of machine for producing images, akin to a camera or a television, although this argument has been convincingly made.78 Rather, I mean medium in the expanded sense: a sociotechnical apparatus whose emergence Raymond Williams recounted in 1972 when he talked about the reification, ongoing since the nineteenth century, of the “properties of the medium” and the “material consciousness” of artistic makers into a set of social, aesthetic, and often commercial institutions.79

The apparatus I have been describing—the hand-sand-lens alliance, its associated financing and engineering structures, and all the networks that made them possible—placed architecture under a logic of media. The logic of moving monuments was allied with the logic of moving images. The logic of storing stones was allied with the logic of storing photographs. And the logic of repeated hand-cutting was allied with the logic of image reproduc tion. Throughout these repetitions and translations, the object of preserva tion was fundamentally transformed. In this sense preservation functioned as a mode of cultural production and communication that incorporated the characteristics of another mode of production, architecture. Could we not, then, see architectural preservation as a medium whose content is another medium, namely architecture?

This proposition seems particularly promising for dealing with the historical asynchronies of the history of preservation-—the fact that preservation is always a theory of history at two speeds. “Advances” in preservation tech nology subject architecture to a double axis of progress, and preservationists take seriously the task of mediating between these two tempos. Sometimes they achieve perfect alignment; sometimes syncopation is all they can manage. But even when two speeds of history align, something is always rendered invisible—as in films where the spokes of a rotating wheel appear to us stand still because the frame rate of the camera has conspired with the rhythm of the wheel’s revolution to fool the eye. For the historian trying to make sense of this mediating act, consulting media theorists may prove helpful. Consider, for instance, a central axiom of Marshall McLuhan’s theory of media: that when new media emerge they manifest themselves in new environments that are invisible, serving instead to “make visible the preceding environment” that is their content.80 Without endorsing McLuhan’s teleological history, we can learn from his insight, especially in his spatialized “environmental” ver sion of the argument, wherein historical causality seems less important than spatial replacement. What should ultimately strike us about the architectural technologies that were used to dismantle Abu Simbel is how unremarkable, how “invisible,” they were. Cranes, jackhammers, steel bars, flatbed trucks, bulldozers, and thousands of workers—these same machines appeared in development and modernization projects across the world. Their use to cut apart an ancient temple may shock us today, but they were effectively invis ible to the international citizen of the 1960s. In contrast, the features of Ramesside architecture, the “content,” with its camera-friendly gigantism, were rendered newly visible and subjected to intense aesthetic judgment.

One way to approach the history of preservation, then, is to look for places where technologies have aged, rendering visible mediations that were previ ously invisible. At Abu Simbel, counterintuitively, the “cuts” have withstood the test of time and remain more or less invisible, thanks in part to a mainte nance crew that regularly fills them with mortar. As for the very technology that once threatened the temple’s existence—electricity—-it was soon used to incorporate the temples into established touristic norms. Within a decade the temples were plugged into the power grid that was brought up from Aswan, and lit up with an extensive system of light and sound. The technology that has aged most is the injected epoxy. Once invisible, it has over time darkened the overall appearance of the temple front by changing the way light pene trates its internal structure. Stone derives its usual color from the light absorption in the space around each particle, but in a phenomenon appro priately called “increase in specular, or mirror-like, reflection,” the epoxy has saturated the aggregate, impeding the ability of internal stone granules to absorb light and making the external granules act increasingly as minuscule mirrors.61 Thus, the Rameses we see today is a hyperreflective Rameses— a stiffer, puffier version of his old self.

This material connection between saturation and visuality should help to dispel the idealist misconception that preservation today always operates through nested frames of historicity, or through two images of architecture, one contemporary and framing, the other historic and enframed. The “envi ronmental” turn in preservation practices is also sometimes mistaken to mean that spatial scale now corresponds to historical distance—that the more modern the viewer, the better his or her perspective. Chemical saturation connotes a different idea: that images appear and disappear through subtle changes in the material composition between the adjoining spaces and sur faces that make up architecture. Rather than considering the imageability of architecture as an external product of its material presence, we can think saturation to mean that images produced through preservation cannot help but return to, and reside in, the architecture itself, and we can imagine that a semimagical, perhaps electrochemical process causes a constant toggling between all of these accumulated images, depending upon the discursive environment that comes to pass. Lastly, the notion of saturation hints that a historical tipping point has been reached: if architectural preservation has long been a social and political medium, around the 1960s it became a medium tout court.

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Recent Work – Rem Koolhaas

“We are living in an incredibly exciting and slightly absurd moment, namely that preservation is overtaking us.”

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Rem Koolhaas at Columbia University Graduate School of Architecture, Planning and Preservation. September 17, 2004. Courtesy of Columbia University GSAPP.

I want to start with a project in China because the current context there is paradoxically both one inviting gross financial abuse and a potential laboratory for other investigations.

If you chart the distribution of architects per thousand people in the world, you will find that European countries have many architects, America has about two-thirds the number of Europe, and China has very few. Yet if you look at how much these architects are building, European architects are building very little, American architects a lot, and Chinese architects exceed all of us extensively.

In addition, by comparing various rates of urbanization from different regions of the world, you see that urbanization in America and Europe slowed down in the 1970s while in East Asia, and China in particular, the rate began to substantially increase. Coinciding with urbanization, if you plot architectural publications, you will see a timeline that suggests Europeans and Americans were incredibly active in terms of producing architectural manifestos and architectural thinking, but that our thinking stopped in the 1970s when we stopped urbanizing. Books like Learning from Las Vegas, published in 1972, is one of the books near the end. And if you look carefully at what we’ve produced since then, it’s mostly reactionary tracts against the city and against modern architecture.

This is an interesting situation because it means that China, at the moment of its greatest need, cannot in any way benefit from any thinking or Western doctrine for the creation of the city. It means that almost anything that is architecturally important in China is entering both an absolute ideological void and a completely defenseless situation.

The projects we are working on are an attempt to think about the Chinese situation and see what its potentials are. It is very clear that it’s a politically fraught situation because it imposes and raises the inevitable question, to what extent one can collaborate or not with a regime such as the Chinese. And clearly all of our work at the moment is based on a certain assumption about what is happening in China and where China is going under its new president and leadership.

By comparing aerial images of Beijing from 1976 and the early 1990s, you can see an incredible explosion in the scale of construction. The Central Square, with the Forbidden City more or less in the middle, is in the center of Beijing. In the 1990s you can still recognize the Forbidden City and its system of lakes, and around it, more or less intact, is traditional Beijing, the “hutongs,” that have become a very critical issue in terms of the perception of China’s development and the destructiveness of China’s modernization, both inside and outside the country.

It is undeniably true that the hutong is an unbelievably beautiful and seductive way of inhabiting the metropolis in a way that is still delicate, intimate, and, I would say, old-fashioned. It is also true that in the past Beijing has not always been treated kindly by the Chinese. But it’s also true that through UNESCO and other political pressures, the “destruction” of Beijing has become a very political issue. Just like human rights, preservation is now becoming a hot-button issue that enables different political sides to either sound the alarm of preservation or not.

What we found interesting in the hutongs is that there is not only interest in preserving them from the outside—from America and Europe (which is perhaps rather hypocritical because we destroyed our cities with impunity before anyone could warn us against it)—but also an enormous interest inside China for the specific qualities, the specific urban conditions, that are still present in such enormous numbers in the cores of its cities.

We were lucky in 2002 to receive a commission from the Beijing government that enabled us to investigate and define for China a specific form of preservation. This is one of those unique moments in which we come closer—and maybe I should say in this case that I come closer—to one of my most intimate utopian dreams, which is to find an architecture that does nothing. I’ve always been appalled that abstinence is the one part of the architectural repertoire that is never considered. Perhaps in architecture, a profession that fundamentally is supposed to change things it encounters (usually before reflection), there ought to be an equally important arm of it that is concerned with not doing anything.

What we started to do was look at preservation in general and look a little bit at the history of preservation. Now, the first law of preservation ever defined was in 1790, just a few years after the French Revolution. That is already an interesting idea, that at the moment in France when the past was basically being prepared for the rubbish dump, the issue of preserving monuments was raised for the first time. Another equally important moment was in 1877, when, in Victorian England, in the most intense moment of civilization, there was the second preservation proposition. If you look at inventions that were taking place between these two moments—cement, the spinning frame, the stethoscope, anesthesia, photography, blueprints, etc.—you suddenly realize that preservation is not the enemy of modernity but actually one of its inventions. That makes perfect sense because clearly the whole idea of modernization raises, whether latently or overtly, the issue of what to keep.

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Historic preservation as a modern technological innovation. Courtesy of OMA. We then looked at the history of preservation in terms of what was being preserved, and it started logically enough with ancient monuments, then religious buildings, etc. Later, structures with more and more (and also less and less) sacred substance and more and more sociological substance were preserved, to the point that we now preserve concentration camps, department stores, factories, and amusement rides. In other words, everything we inhabit is potentially susceptible to preservation. That was another important discovery: The scale of preservation escalates relentlessly to include entire landscapes, and there is now even a campaign to preserve part of the moon as an important site.

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Historically, each new preservation law has moved the date for considering preservation-worthy architecture closer to the present. Courtesy of OMA. Then we started looking at the interval or the distance between the present and what was preserved. In 1818, it was 2,000 years. In 1900, it was only 200 years. And near the 1960s, it became 20 years. We are living in an incredibly exciting and slightly absurd moment, namely that preservation is overtaking us. Maybe we can be the first to actually experience the moment that preservation is no longer a retroactive activity but becomes a prospective activity. This makes perfect sense because it is clear that we built so much mediocrity that it is literally threatening our lives. Therefore, we will have to decide in advance what we are going to build for posterity sooner or later. Actually, this seems an absurd hypothesis, but it has happened, for instance, in the cases of some houses that were preserved at the moment they were finished, putting the inhabitants in a very complex conundrum.

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“Barcode” preservation scheme for Beijing where different preservation scenarios can be implemented in horizontal bands. Courtesy of OMA. We then started to look at how to apply this thinking to the issue of preservation. Of course, preservation is also dominated by the lobby of authenticity, ancientness, and beauty, but that is, of course, a very limited conception of preservation. We started to conceive and imagine that you could perhaps impose upon the entire center of Beijing a kind of barcode and declare that the bands in the barcode could either be preserved forever or systematically scraped. In such a case, you would have the certainty that you preserved everything in a very democratic, dispassionate way—highways, Chinese monuments, bad things, good things, ugly things, mediocre things—and therefore really maintained an authentic condition. Also you could begin to plan the city in terms of phasing. In all the cities that now are almost suffocatingly stable in the center and alarmingly unstable at the periphery, you could introduce a new condition of phasing in which, sooner or later, any part of the city would be eliminated to be replaced by other development. You could project and plan over almost millennia to generate a situation in which each part of the city would always confront its opposite in a kind of complementary condition.

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IBC Chapter 16

STRUCTURAL DESIGN

User note: Code change proposals to this chapter will be considered by the IBC – Structural Code
Development Committee during the 2016 (Group B) Code Development Cycle. See explanation on page iv.

SECTION1601
GENERAL

1601.1 Scope.

The provisions of this chapter shall govern the structural design of buildings, structures and portions thereof regulated by this code.

SECTION1602
DEFINITIONS AND NOTATIONS

1602.1 Definitions.

The following terms are defined in Chapter 2:

ALLOWABLE STRESS DESIGN.

DEAD LOADS.

DESIGN STRENGTH.

DIAPHRAGM.

ESSENTIAL FACILITIES.

FABRIC PARTITION.

FACTORED LOAD.

HELIPAD.

ICE-SENSITIVE STRUCTURE.

IMPACT LOAD.

LIMIT STATE.

LIVE LOAD.

LIVE LOAD (ROOF).

LOAD AND RESISTANCE FACTOR DESIGN (LRFD).

LOAD EFFECTS.

LOAD FACTOR.

LOADS.

NOMINAL LOADS.

OTHER STRUCTURES.

PANEL (PART OF A STRUCTURE).

RESISTANCE FACTOR.

RISK CATEGORY.

STRENGTH, NOMINAL.

STRENGTH, REQUIRED.

STRENGTH DESIGN.

SUSCEPTIBLE BAY.

VEHICLE BARRIER.

NOTATIONS.

D=Dead load.
Di=Weight of ice in accordance with Chapter 10 of ASCE 7.
E=Combined effect of horizontal and vertical earthquake induced forces as defined in Section 12.4.2 of ASCE 7.
F=Load due to fluids with well-defined pressures and maximum heights.
Fa=Flood load in accordance with Chapter 5 of ASCE 7.
H=Load due to lateral earth pressures, ground water pressure or pressure of bulk materials.
L=Roof live load greater than 20 psf (0.96 kN/m2) and floor live load.
Lr=Roof live load of 20 psf (0.96 kN/m2) or less.
R=Rain load.
S=Snow load.
T=Self-straining load.
Vasd=Nominal design wind speed (3-second gust), miles per hour (mph) (km/hr) where applicable.
Vult=Ultimate design wind speeds (3-second gust), miles per hour (mph) (km/hr) determined from Figure 1609.3(1), 1609.3(2), 1609.3(3) or ASCE 7.
W=Load due to wind pressure.
Wi=Wind-on-ice in accordance with Chapter 10 of ASCE 7.

SECTION1603
CONSTRUCTION DOCUMENTS

1603.1 General.

Construction documents shall show the size, section and relative locations of structural members with floor levels, column centers and offsets dimensioned. The design loads and other information pertinent to the structural design required by Sections 1603.1.1 through 1603.1.8 shall be indicated on the construction documents.

Exception: Construction documents for buildings constructed in accordance with the conventional light-frame construction provisions of Section 2308 shall indicate the following structural design information:

  1. 1.Floor and roof live loads.
  2. 2.Ground snow load, Pg.
  3. 3.Ultimate design wind speed, Vult, (3-second gust), miles per hour (mph) (km/hr) and nominal design wind speed, Vasd, as determined in accordance with Section 1609.3.1 and wind exposure.
  4. 4.Seismic design category and site class.
  5. 5.Flood design data, if located in flood hazard areas established in Section 1612.3.
  6. 6.Design load-bearing values of soils.

1603.1.1 Floor live load.

The uniformly distributed, concentrated and impact floor live load used in the design shall be indicated for floor areas. Use of live load reduction in accordance with Section 1607.10 shall be indicated for each type of live load used in the design.

1603.1.2 Roof live load.

The roof live load used in the design shall be indicated for roof areas (Section 1607.12).

1603.1.3 Roof snow load data.

The ground snow load, Pg, shall be indicated. In areas where the ground snow load, Pg, exceeds 10 pounds per square foot (psf) (0.479 kN/m2), the following additional information shall also be provided, regardless of whether snow loads govern the design of the roof:

  1. 1.Flat-roof snow load, Pf.
  2. 2.Snow exposure factor, Ce.
  3. 3.Snow load importance factor, Is.
  4. 4.Thermal factor, Ct.
  5. 5.Drift surcharge load(s), Pd, where the sum of Pd and Pf exceeds 20 psf (0.96 kN/m2).
  6. 6.Width of snow drift(s), w.

1603.1.4 Wind design data.

The following information related to wind loads shall be shown, regardless of whether wind loads govern the design of the lateral force-resisting system of the structure:

  1. 1.Ultimate design wind speed, Vult, (3-second gust), miles per hour (km/hr) and nominal design wind speed, Vasd, as determined in accordance with Section 1609.3.1.
  2. 2.Risk category.
  3. 3.Wind exposure. Applicable wind direction if more than one wind exposure is utilized.
  4. 4.Applicable internal pressure coefficient.
  5. 5.Design wind pressures to be used for exterior component and cladding materials not specifically designed by the registered design professional responsible for the design of the structure, psf (kN/m2).

1603.1.5 Earthquake design data.

The following information related to seismic loads shall be shown, regardless of whether seismic loads govern the design of the lateral force-resisting system of the structure:

  1. 1.Risk category.
  2. 2.Seismic importance factor, Ie.
  3. 3.Mapped spectral response acceleration parameters, SS and S1.
  4. 4.Site class.
  5. 5.Design spectral response acceleration parameters, SDS and SD1.
  6. 6.Seismic design category.
  7. 7.Basic seismic force-resisting system(s).
  8. 8.Design base shear(s).
  9. 9.Seismic response coefficient(s), CS.
  10. 10.Response modification coefficient(s), R.
  11. 11.Analysis procedure used.

1603.1.6 Geotechnical information.

The design load-bearing values of soils shall be shown on the construction documents.

1603.1.7 Flood design data.

For buildings located in whole or in part in flood hazard areas as established in Section 1612.3, the documentation pertaining to design, if required in Section 1612.5, shall be included and the following information, referenced to the datum on the community’s Flood Insurance Rate Map (FIRM), shall be shown, regardless of whether flood loads govern the design of the building:

  1. 1.Flood design class assigned according to ASCE 24.
  2. 2.In flood hazard areas other than coastal high hazard areas or coastal A zones, the elevation of the proposed lowest floor, including the basement.
  3. 3.In flood hazard areas other than coastal high hazard areas or coastal A zones, the elevation to which any nonresidential building will be dry floodproofed.
  4. 4.In coastal high hazard areas and coastal A zones, the proposed elevation of the bottom of the lowest horizontal structural member of the lowest floor, including the basement.

1603.1.8 Special loads.

Special loads that are applicable to the design of the building, structure or portions thereof shall be indicated along with the specified section of this code that addresses the special loading condition.

1603.1.8.1 Photovoltaic panel systems.

The dead load of rooftop-mounted photovoltaic panel systems, including rack support systems, shall be indicated on the construction documents.

SECTION1604
GENERAL DESIGN REQUIREMENTS

1604.1 General.

Building, structures and parts thereof shall be designed and constructed in accordance with strength design, load and resistance factor design, allowable stress design, empirical design or conventional construction methods, as permitted by the applicable material chapters.

1604.2 Strength.

Buildings and other structures, and parts thereof, shall be designed and constructed to support safely the factored loads in load combinations defined in this code without exceeding the appropriate strength limit states for the materials of construction. Alternatively, buildings and other structures, and parts thereof, shall be designed and constructed to support safely the nominal loads in load combinations defined in this code without exceeding the appropriate specified allowable stresses for the materials of construction.

Loads and forces for occupancies or uses not covered in this chapter shall be subject to the approval of the building official.

1604.3 Serviceability.

Structural systems and members thereof shall be designed to have adequate stiffness to limit deflections and lateral drift. See Section 12.12.1 of ASCE 7 for drift limits applicable to earthquake loading.

TABLE 1604.3

DEFLECTION LIMITSa, b, c, h, i

CONSTRUCTIONLS or W fD + Ld, g
Roof members:e
Supporting plaster or stucco ceilingl/360l/360l/240
Supporting nonplaster ceilingl/240l/240l/180
Not supporting ceilingl/180l/180l/120
Floor membersl/360l/240
Exterior walls:
With plaster or stucco finishesl/360
With other brittle finishesl/240
With flexible finishesl/120
Interior partitions:b
With plaster or stucco finishesl/360
With other brittle finishesl/240
With flexible finishesl/120
Farm buildingsl/180
Greenhousesl/120

For SI: 1 foot = 304.8 mm.

  1. a.For structural roofing and siding made of formed metal sheets, the total load deflection shall not exceed l/60. For secondary roof structural members supporting formed metal roofing, the live load deflection shall not exceed l/150. For secondary wall members supporting formed metal siding, the design wind load deflection shall not exceed l/90. For roofs, this exception only applies when the metal sheets have no roof covering.
  2. b.Flexible, folding and portable partitions are not governed by the provisions of this section. The deflection criterion for interior partitions is based on the horizontal load defined in Section 1607.14.
  3. c.See Section 2403 for glass supports.
  4. d.The deflection limit for the D+L load combination only applies to the deflection due to the creep component of long-term dead load deflection plus the short-term live load deflection. For wood structural members that are dry at time of installation and used under dry conditions in accordance with the ANSI/AWC NDS, the creep component of the long-term deflection shall be permitted to be estimated as the immediate dead load deflection resulting from 0.5D. For wood structural members at all other moisture conditions, the creep component of the long-term deflection is permitted to be estimated as the immediate dead load deflection resulting from D. The value of 0.5D shall not be used in combination with ANSI/AWC NDS provisions for long-term loading.
  5. e.The above deflections do not ensure against ponding. Roofs that do not have sufficient slope or camber to ensure adequate drainage shall be investigated for ponding. See Section 1611 for rain and ponding requirements and Section 1503.4 for roof drainage requirements.
  6. f.The wind load is permitted to be taken as 0.42 times the “component and cladding” loads for the purpose of determining deflection limits herein. Where members support glass in accordance with Section 2403 using the deflection limit therein, the wind load shall be no less than 0.6 times the “component and cladding” loads for the purpose of determining deflection.
  7. g.For steel structural members, the dead load shall be taken as zero.
  8. h.For aluminum structural members or aluminum panels used in skylights and sloped glazing framing, roofs or walls of sunroom additions or patio covers not supporting edge of glass or aluminum sandwich panels, the total load deflection shall not exceed l/60. For continuous aluminum structural members supporting edge of glass, the total load deflection shall not exceed l/175 for each glass lite or l/60 for the entire length of the member, whichever is more stringent. For aluminum sandwich panels used in roofs or walls of sunroom additions or patio covers, the total load deflection shall not exceed 1/120.
  9. i.For cantilever members, l shall be taken as twice the length of the cantilever.

1604.3.1 Deflections.

The deflections of structural members shall not exceed the more restrictive of the limitations of Sections 1604.3.2 through 1604.3.5 or that permitted by Table 1604.3.

1604.3.2 Reinforced concrete.

The deflection of reinforced concrete structural members shall not exceed that permitted by ACI 318.

1604.3.3 Steel.

The deflection of steel structural members shall not exceed that permitted by AISC 360, AISI S100, ASCE 8, SJI CJ, SJI JG, SJI K or SJI LH/DLH, as applicable.

1604.3.4 Masonry.

The deflection of masonry structural members shall not exceed that permitted by TMS 402/ACI 530/ASCE 5.

1604.3.5 Aluminum.

The deflection of aluminum structural members shall not exceed that permitted by AA ADM1.

1604.3.6 Limits.

The deflection limits of Section 1604.3.1 shall be used unless more restrictive deflection limits are required by a referenced standard for the element or finish material.

1604.4 Analysis.

Load effects on structural members and their connections shall be determined by methods of structural analysis that take into account equilibrium, general stability, geometric compatibility and both short- and long-term material properties.

Members that tend to accumulate residual deformations under repeated service loads shall have included in their analysis the added eccentricities expected to occur during their service life.

Any system or method of construction to be used shall be based on a rational analysis in accordance with well-established principles of mechanics. Such analysis shall result in a system that provides a complete load path capable of transferring loads from their point of origin to the load-resisting elements.

The total lateral force shall be distributed to the various vertical elements of the lateral force-resisting system in proportion to their rigidities, considering the rigidity of the horizontal bracing system or diaphragm. Rigid elements assumed not to be a part of the lateral force-resisting system are permitted to be incorporated into buildings provided their effect on the action of the system is considered and provided for in the design. A diaphragm is rigid for the purpose of distribution of story shear and torsional moment when the lateral deformation of the diaphragm is less than or equal to two times the average story drift. Where required by ASCE 7, provisions shall be made for the increased forces induced on resisting elements of the structural system resulting from torsion due to eccentricity between the center of application of the lateral forces and the center of rigidity of the lateral force-resisting system.

Every structure shall be designed to resist the overturning effects caused by the lateral forces specified in this chapter. See Section 1609 for wind loads, Section 1610 for lateral soil loads and Section 1613 for earthquake loads.

1604.5 Risk category.

Each building and structure shall be assigned a risk category in accordance with Table 1604.5. Where a referenced standard specifies an occupancy category, the risk category shall not be taken as lower than the occupancy category specified therein. Where a referenced standard specifies that the assignment of a risk category be in accordance with ASCE 7, Table 1.5-1, Table 1604.5 shall be used in lieu of ASCE 7, Table 1.5-1.

TABLE 1604.5

RISK CATEGORY OF BUILDINGS AND OTHER STRUCTURES

RISK CATEGORYNATURE OF OCCUPANCY
IBuildings and other structures that represent a low hazard to human life in the event of failure, including but not limited to: •Agricultural facilities.•Certain temporary facilities.•Minor storage facilities.
IIBuildings and other structures except those listed in Risk Categories I, III and IV.
IIIBuildings and other structures that represent a substantial hazard to human life in the event of failure, including but not limited to: •Buildings and other structures whose primary occupancy is public assembly with an occupant load greater than 300.•Buildings and other structures containing Group E occupancies with an occupant load greater than 250.•Buildings and other structures containing educational occupancies for students above the 12th grade with an occupant load greater than 500.•Group I-2 occupancies with an occupant load of 50 or more resident care recipients but not having surgery or emergency treatment facilities.•Group I-3 occupancies.•Any other occupancy with an occupant load greater than 5,000.a•Power-generating stations, water treatment facilities for potable water, wastewater treatment facilities and other public utility facilities not included in Risk Category IV.•Buildings and other structures not included in Risk Category IV containing quantities of toxic or explosive materials that:Exceed maximum allowable quantities per control area as given in Table 307.1(1) or 307.1(2) or per outdoor control area in accordance with the International Fire Code; andAre sufficient to pose a threat to the public if released.b
IVBuildings and other structures designated as essential facilities, including but not limited to: •Group I-2 occupancies having surgery or emergency treatment facilities.•Fire, rescue, ambulance and police stations and emergency vehicle garages.•Designated earthquake, hurricane or other emergency shelters.•Designated emergency preparedness, communications and operations centers and other facilities required for emergency response.•Power-generating stations and other public utility facilities required as emergency backup facilities for Risk Category IV structures.•Buildings and other structures containing quantities of highly toxic materials that:Exceed maximum allowable quantities per control area as given in Table 307.1(2) or per outdoor control area in accordance with the International Fire Code; andAre sufficient to pose a threat to the public if released.b•Aviation control towers, air traffic control centers and emergency aircraft hangars.•Buildings and other structures having critical national defense functions.•Water storage facilities and pump structures required to maintain water pressure for fire suppression.
  1. a.For purposes of occupant load calculation, occupancies required by Table 1004.1.2 to use gross floor area calculations shall be permitted to use net floor areas to determine the total occupant load.
  2. b.Where approved by the building official, the classification of buildings and other structures as Risk Category III or IV based on their quantities of toxic, highly toxic or explosive materials is permitted to be reduced to Risk Category II, provided it can be demonstrated by a hazard assessment in accordance with Section 1.5.3 of ASCE 7 that a release of the toxic, highly toxic or explosive materials is not sufficient to pose a threat to the public.

1604.5.1 Multiple occupancies.

Where a building or structure is occupied by two or more occupancies not included in the same risk category, it shall be assigned the classification of the highest risk category corresponding to the various occupancies. Where buildings or structures have two or more portions that are structurally separated, each portion shall be separately classified. Where a separated portion of a building or structure provides required access to, required egress from or shares life safety components with another portion having a higher risk category, both portions shall be assigned to the higher risk category.

1604.6 In-situ load tests.

The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708.

1604.7 Preconstruction load tests.

Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707, shall be load tested in accordance with Section 1719.

1604.8 Anchorage.

Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604.8.1 through 1604.8.3, as applicable.

1604.8.1 General.

Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads.

1604.8.2 Structural walls.

Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall. The connections shall be capable of resisting the horizontal forces specified in Section 1.4.5 of ASCE 7 for walls of structures assigned to Seismic Design Category A and to Section 12.11 of ASCE 7 for walls of structures assigned to all other seismic design categories. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 for earthquake design requirements.

1604.8.3 Decks.

Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:

  1. 1.The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on all portions of the deck.
  2. 2.The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck.

1604.9 Counteracting structural actions.

Structural members, systems, components and cladding shall be designed to resist forces due to earthquakes and wind, with consideration of overturning, sliding and uplift. Continuous load paths shall be provided for transmitting these forces to the foundation. Where sliding is used to isolate the elements, the effects of friction between sliding elements shall be included as a force.

1604.10 Wind and seismic detailing.

Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7, excluding Chapter 14 and Appendix 11A, even when wind load effects are greater than seismic load effects.

SECTION1605
LOAD COMBINATIONS

1605.1 General.

Buildings and other structures and portions thereof shall be designed to resist:

  1. 1.The load combinations specified in Section 1605.2, 1605.3.1 or 1605.3.2;
  2. 2.The load combinations specified in Chapters 18 through 23; and
  3. 3.The seismic load effects including overstrength factor in accordance with Section 12.4.3 of ASCE 7 where required by Section 12.2.5.2, 12.3.3.3 or 12.10.2.1 of ASCE 7. With the simplified procedure of ASCE 7 Section 12.14, the seismic load effects including overstrength factor in accordance with Section 12.14.3.2 of ASCE 7 shall be used.

Applicable loads shall be considered, including both earthquake and wind, in accordance with the specified load combinations. Each load combination shall also be investigated with one or more of the variable loads set to zero.

Where the load combinations with overstrength factor in Section 12.4.3.2 of ASCE 7 apply, they shall be used as follows:

  1. 1.The basic combinations for strength design with overstrength factor in lieu of Equations 16-5 and 16-7 in Section 1605.2.
  2. 2.The basic combinations for allowable stress design with overstrength factor in lieu of Equations 16-12, 16-14 and 16-16 in Section 1605.3.1.
  3. 3.The basic combinations for allowable stress design with overstrength factor in lieu of Equations 16-21 and 16-22 in Section 1605.3.2.

1605.1.1 Stability.

Regardless of which load combinations are used to design for strength, where overall structure stability (such as stability against overturning, sliding, or buoyancy) is being verified, use of the load combinations specified in Section 1605.2 or 1605.3 shall be permitted. Where the load combinations specified in Section 1605.2 are used, strength reduction factors applicable to soil resistance shall be provided by a registered design professional. The stability of retaining walls shall be verified in accordance with Section 1807.2.3.

1605.2 Load combinations using strength design or load and resistance factor design.

Where strength design or load and resistance factor design is used, buildings and other structures, and portions thereof, shall be designed to resist the most critical effects resulting from the following combinations of factored loads:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0029.jpg(Equation 16-1)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0030.jpg(Equation 16-2)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0031.jpg(Equation 16-3)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0032.jpg(Equation 16-4)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0033.jpg(Equation 16-5)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0034.jpg(Equation 16-6)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0035.jpg(Equation 16-7)

where:

f1=1 for places of public assembly live loads in excess of 100 pounds per square foot (4.79 kN/m2), and parking garages; and 0.5 for other live loads.
f2=0.7 for roof configurations (such as saw tooth) that do not shed snow off the structure, and 0.2 for other roof configurations.

Exceptions:

  1. 1.Where other factored load combinations are specifically required by other provisions of this code, such combinations shall take precedence.
  2. 2.Where the effect of H resists the primary variable load effect, a load factor of 0.9 shall be included with H where H is permanent and H shall be set to zero for all other conditions.

1605.2.1 Other loads.

Where flood loads, Fa, are to be considered in the design, the load combinations of Section 2.3.3 of ASCE 7 shall be used. Where self-straining loads, T, are considered in design, their structural effects in combination with other loads shall be determined in accordance with Section 2.3.5 of ASCE 7. Where an ice-sensitive structure is subjected to loads due to atmospheric icing, the load combinations of Section 2.3.4 of ASCE 7 shall be considered.

1605.3 Load combinations using allowable stress design.

1605.3.1 Basic load combinations.

Where allowable stress design (working stress design), as permitted by this code, is used, structures and portions thereof shall resist the most critical effects resulting from the following combinations of loads:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0036.jpg(Equation 16-8)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0037.jpg(Equation 16-9)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0038.jpg(Equation 16-10)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0039.jpg(Equation 16-11)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0040.jpg(Equation 16-12)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0041.jpg(Equation 16-13)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0042.jpg(Equation 16-14)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0043.jpg(Equation 16-15)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0044.jpg(Equation 16-16)

Exceptions:

  1. 1.Crane hook loads need not be combined with roof live load or with more than three-fourths of the snow load or one-half of the wind load.
  2. 2.Flat roof snow loads of 30 psf (1.44 kN/m2) or less and roof live loads of 30 psf (1.44 kN/m2) or less need not be combined with seismic loads. Where flat roof snow loads exceed 30 psf (1.44 kN/m2), 20 percent shall be combined with seismic loads.
  3. 3.Where the effect of H resists the primary variable load effect, a load factor of 0.6 shall be included with H where H is permanent and H shall be set to zero for all other conditions.
  4. 4.In Equation 16-15, the wind load, W, is permitted to be reduced in accordance with Exception 2 of Section 2.4.1 of ASCE 7.
  5. 5.In Equation 16-16, 0.6 D is permitted to be increased to 0.9 D for the design of special reinforced masonry shear walls complying with Chapter 21.

1605.3.1.1 Stress increases.

Increases in allowable stresses specified in the appropriate material chapter or the referenced standards shall not be used with the load combinations of Section 1605.3.1, except that increases shall be permitted in accordance with Chapter 23.

1605.3.1.2 Other loads.

Where flood loads, Fa, are to be considered in design, the load combinations of Section 2.4.2 of ASCE 7 shall be used. Where self-straining loads, T, are considered in design, their structural effects in combination with other loads shall be determined in accordance with Section 2.4.4 of ASCE 7. Where an ice-sensitive structure is subjected to loads due to atmospheric icing, the load combinations of Section 2.4.3 of ASCE 7 shall be considered.

1605.3.2 Alternative basic load combinations.

In lieu of the basic load combinations specified in Section 1605.3.1, structures and portions thereof shall be permitted to be designed for the most critical effects resulting from the following combinations. When using these alternative basic load combinations that include wind or seismic loads, allowable stresses are permitted to be increased or load combinations reduced where permitted by the material chapter of this code or the referenced standards. For load combinations that include the counteracting effects of dead and wind loads, only two-thirds of the minimum dead load likely to be in place during a design wind event shall be used. When using allowable stresses that have been increased or load combinations that have been reduced as permitted by the material chapter of this code or the referenced standards, where wind loads are calculated in accordance with Chapters 26 through 31 of ASCE 7, the coefficient (ω) in the following equations shall be taken as 1.3. For other wind loads, (ω) shall be taken as 1. When allowable stresses have not been increased or load combinations have not been reduced as permitted by the material chapter of this code or the referenced standards, (ω) shall be taken as 1. When using these alternative load combinations to evaluate sliding, overturning and soil bearing at the soil-structure interface, the reduction of foundation overturning from Section 12.13.4 in ASCE 7 shall not be used. When using these alternative basic load combinations for proportioning foundations for loadings, which include seismic loads, the vertical seismic load effect, Ev, in Equation 12.4-4 of ASCE 7 is permitted to be taken equal to zero.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0045.jpg(Equation 16-17)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0046.jpg(Equation 16-18)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0047.jpg(Equation 16-19)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0048.jpg(Equation 16-20)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0049.jpg(Equation 16-21)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0050.jpg(Equation 16-22)

Exceptions:

  1. 1.Crane hook loads need not be combined with roof live loads or with more than three-fourths of the snow load or one-half of the wind load.
  2. 2.Flat roof snow loads of 30 psf (1.44 kN/m2) or less and roof live loads of 30 psf (1.44 kN/m2) or less need not be combined with seismic loads. Where flat roof snow loads exceed 30 psf (1.44 kN/m2), 20 percent shall be combined with seismic loads.

1605.3.2.1 Other loads.

Where F, H or T are to be considered in the design, each applicable load shall be added to the combinations specified in Section 1605.3.2. Where self-straining loads, T, are considered in design, their structural effects in combination with other loads shall be determined in accordance with Section 2.4.4 of ASCE 7.

SECTION1606
DEAD LOADS

1606.1 General.

Dead loads are those loads defined in Chapter 2 of this code. Dead loads shall be considered permanent loads.

1606.2 Design dead load.

For purposes of design, the actual weights of materials of construction and fixed service equipment shall be used. In the absence of definite information, values used shall be subject to the approval of the building official.

SECTION1607
LIVE LOADS

1607.1 General.

Live loads are those loads defined in Chapter 2 of this code.

TABLE 1607.1

MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS, L0, AND MINIMUM CONCENTRATED LIVE LOADSg

OCCUPANCY OR USEUNIFORM (psf)CONCENTRATED (pounds)
1. Apartments (see residential)
2. Access floor systems
Office use502,000
Computer use1002,000
3. Armories and drill rooms150m
4. Assembly areas
Fixed seats (fastened to floor)60m
Follow spot, projections and control rooms50
Lobbies100m
Movable seats100m
Stage floors150m
Platforms (assembly)100m
Other assembly areas100m
5. Balconies and deckshSame as occupancy served
6. Catwalks40300
7. Cornices60
8. Corridors
First floor100
Other floorsSame as occupancy served except as indicated
9. Dining rooms and restaurants100m
10. Dwellings (see residential)
11. Elevator machine room and control room grating (on area of 2 inches by 2 inches)300
12. Finish light floor plate construction (on area of 1 inch by 1 inch)200
13. Fire escapes100
On single-family dwellings only40
14. Garages (passenger vehicles only)40mNote a
Trucks and busesSee Section 1607.7
15. Handrails, guards and grab barsSee Section 1607.8
16. HelipadsSee Section 1607.6
17. Hospitals
Corridors above first floor801,000
Operating rooms, laboratories601,000
Patient rooms401,000
18. Hotels (see residential)
19. Libraries
Corridors above first floor801,000
Reading rooms601,000
Stack rooms150b, m1,000
20. Manufacturing
Heavy250m3,000
Light125m2,000
21. Marquees, except one-and two-family dwellings75
22. Office buildings
Corridors above first floor802,000
File and computer rooms shall be designed for heavier loads based on anticipated occupancy
Lobbies and first-floor corridors1002,000
Offices502,000
23. Penal institutions
Cell blocks40
Corridors100
24. Recreational uses:
Bowling alleys, poolrooms and similar uses75m
Dance halls and ballrooms100m
Gymnasiums100m
Ice skating rink250m
Reviewing stands, grandstands and bleachers100c, m
Roller skating rink100m
Stadiums and arenas with fixed seats (fastened to floor)60c, m
25. Residential
One- and two-family dwellings
Uninhabitable attics without storagei10
Uninhabitable attics with storagei, j, k20
Habitable attics and sleeping areask30
Canopies, including marquees20
All other areas40
Hotels and multifamily dwellings
Private rooms and corridors serving them40
Public roomsm and corridors serving them100
26. Roofs
All roof surfaces subject to maintenance workers300
Awnings and canopies:
Fabric construction supported by a skeleton structure5 Nonreducible
All other construction, except one-and two-family dwellings20
Ordinary flat, pitched, and curved roofs (that are not occupiable)20
Primary roof members exposed to a work floor
Single panel point of lower chord of roof trusses or any point along primary structural members supporting roofs over manufacturing, storage warehouses, and repair garages2,000
All other primary roof members300
Occupiable roofs:
Roof gardens100
Assembly areas100m
All other similar areasNote 1Note 1
27. Schools
Classrooms401,000
Corridors above first floor801,000
First-floor corridors1001,000
28. Scuttles, skylight ribs and accessible ceilings200
29. Sidewalks, vehicular driveways and yards, subject to trucking250d, m8,000e
30. Stairs and exits
One- and two-family dwellings40300f
All other100300f
31. Storage warehouses (shall be designed for heavier loads if required for anticipated storage)
Heavy250m
Light125m
32. Stores
Retail
First floor1001,000
Upper floors751,000
Wholesale, all floors125m1,000
33. Vehicle barriersSee Section 1607.8.3
34. Walkways and elevated platforms (other than exitways)60
35. Yards and terraces, pedestrians100m

For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2,

1 square foot = 0.0929 m2,

1 pound per square foot = 0.0479 kN/m2, 1 pound = 0.004448 kN,

1 pound per cubic foot = 16 kg/m3.

  1. a.Floors in garages or portions of buildings used for the storage of motor vehicles shall be designed for the uniformly distributed live loads of this Table or the following concentrated loads: (1) for garages restricted to passenger vehicles accommodating not more than nine passengers, 3,000 pounds acting on an area of 41/2 inches by 41/2 inches; (2) for mechanical parking structures without slab or deck that are used for storing passenger vehicles only, 2,250 pounds per wheel.
  2. b.The loading applies to stack room floors that support nonmobile, double-faced library book stacks, subject to the following limitations:
    1. 1.The nominal book stack unit height shall not exceed 90 inches;
    2. 2.The nominal shelf depth shall not exceed 12 inches for each face; and
    3. 3.Parallel rows of double-faced book stacks shall be separated by aisles not less than 36 inches wide.
  3. c.Design in accordance with ICC 300.
  4. d.Other uniform loads in accordance with an approved method containing provisions for truck loadings shall be considered where appropriate.
  5. e.The concentrated wheel load shall be applied on an area of 4.5 inches by 4.5 inches.
  6. f.The minimum concentrated load on stair treads shall be applied on an area of 2 inches by 2 inches. This load need not be assumed to act concurrently with the uniform load.
  7. g.Where snow loads occur that are in excess of the design conditions, the structure shall be designed to support the loads due to the increased loads caused by drift buildup or a greater snow design determined by the building official (see Section 1608).
  8. h.See Section 1604.8.3 for decks attached to exterior walls.
  9. i.Uninhabitable attics without storage are those where the maximum clear height between the joists and rafters is less than 42 inches, or where there are not two or more adjacent trusses with web configurations capable of accommodating an assumed rectangle 42 inches in height by 24 inches in width, or greater, within the plane of the trusses. This live load need not be assumed to act concurrently with any other live load requirements.
  10. j.Uninhabitable attics with storage are those where the maximum clear height between the joists and rafters is 42 inches or greater, or where there are two or more adjacent trusses with web configurations capable of accommodating an assumed rectangle 42 inches in height by 24 inches in width, or greater, within the plane of the trusses.The live load need only be applied to those portions of the joists or truss bottom chords where both of the following conditions are met:
    1. i.The attic area is accessible from an opening not less than 20 inches in width by 30 inches in length that is located where the clear height in the attic is a minimum of 30 inches; and
    2. ii.The slopes of the joists or truss bottom chords are no greater than two units vertical in 12 units horizontal.
    The remaining portions of the joists or truss bottom chords shall be designed for a uniformly distributed concurrent live load of not less than 10 pounds per square foot.
  11. k.Attic spaces served by stairways other than the pull-down type shall be designed to support the minimum live load specified for habitable attics and sleeping rooms.
  12. l.Areas of occupiable roofs, other than roof gardens and assembly areas, shall be designed for appropriate loads as approved by the building official. Unoccupied landscaped areas of roofs shall be designed in accordance with Section 1607.12.3.
  13. m.Live load reduction is not permitted unless specific exceptions of Section 1607.10 apply.

1607.2 Loads not specified.

For occupancies or uses not designated in Table 1607.1, the live load shall be determined in accordance with a method approved by the building official.

1607.3 Uniform live loads.

The live loads used in the design of buildings and other structures shall be the maximum loads expected by the intended use or occupancy but shall in no case be less than the minimum uniformly distributed live loads given in Table 1607.1.

1607.4 Concentrated live loads.

Floors and other similar surfaces shall be designed to support the uniformly distributed live loads prescribed in Section 1607.3 or the concentrated live loads, given in Table 1607.1, whichever produces the greater load effects. Unless otherwise specified, the indicated concentration shall be assumed to be uniformly distributed over an area of 21/2 feet by 21/2 feet (762 mm by 762 mm) and shall be located so as to produce the maximum load effects in the structural members.

1607.5 Partition loads.

In office buildings and in other buildings where partition locations are subject to change, provisions for partition weight shall be made, whether or not partitions are shown on the construction documents, unless the specified live load is 80 psf (3.83 kN/m2) or greater. The partition load shall be not less than a uniformly distributed live load of 15 psf (0.72 kN/m2).

1607.6 Helipads.

Helipads shall be designed for the following live loads:

  1. 1.A uniform live load, L, as specified below. This load shall not be reduced.
    1. 1.1.40 psf (1.92 kN/m2) where the design basis helicopter has a maximum take-off weight of 3,000 pounds (13.35 kN) or less.
    2. 1.2.60 psf (2.87 kN/m2) where the design basis helicopter has a maximum take-off weight greater than 3,000 pounds (13.35 kN).
  2. 2.A single concentrated live load, L, of 3,000 pounds (13.35 kN) applied over an area of 4.5 inches by 4.5 inches (114 mm by 114 mm) and located so as to produce the maximum load effects on the structural elements under consideration. The concentrated load is not required to act concurrently with other uniform or concentrated live loads.
  3. 3.Two single concentrated live loads, L, 8 feet (2438 mm) apart applied on the landing pad (representing the helicopter’s two main landing gear, whether skid type or wheeled type), each having a magnitude of 0.75 times the maximum take-off weight of the helicopter, and located so as to produce the maximum load effects on the structural elements under consideration. The concentrated loads shall be applied over an area of 8 inches by 8 inches (203 mm by 203 mm) and are not required to act concurrently with other uniform or concentrated live loads.

Landing areas designed for a design basis helicopter with maximum take-off weight of 3,000-pounds (13.35 kN) shall be identified with a 3,000 pound (13.34 kN) weight limitation. The landing area weight limitation shall be indicated by the numeral “3” (kips) located in the bottom right corner of the landing area as viewed from the primary approach path. The indication for the landing area weight limitation shall be a minimum 5 feet (1524 mm) in height.

1607.7 Heavy vehicle loads.

Floors and other surfaces that are intended to support vehicle loads greater than a 10,000-pound (4536 kg) gross vehicle weight rating shall comply with Sections 1607.7.1 through 1607.7.5.

1607.7.1 Loads.

Where any structure does not restrict access for vehicles that exceed a 10,000-pound (4536 kg) gross vehicle weight rating, those portions of the structure subject to such loads shall be designed using the vehicular live loads, including consideration of impact and fatigue, in accordance with the codes and specifications required by the jurisdiction having authority for the design and construction of the roadways and bridges in the same location of the structure.

1607.7.2 Fire truck and emergency vehicles.

Where a structure or portions of a structure are accessed and loaded by fire department access vehicles and other similar emergency vehicles, the structure shall be designed for the greater of the following loads:

  1. 1.The actual operational loads, including outrigger reactions and contact areas of the vehicles as stipulated and approved by the building official; or
  2. 2.The live loading specified in Section 1607.7.1.

1607.7.3 Heavy vehicle garages.

Garages designed to accommodate vehicles that exceed a 10,000-pound (4536 kg) gross vehicle weight rating, shall be designed using the live loading specified by Section 1607.7.1. For garages the design for impact and fatigue is not required.

Exception: The vehicular live loads and load placement are allowed to be determined using the actual vehicle weights for the vehicles allowed onto the garage floors, provided such loads and placement are based on rational engineering principles and are approved by the building official, but shall not be less than 50 psf (2.9 kN/m2). This live load shall not be reduced.

1607.7.4 Forklifts and movable equipment.

Where a structure is intended to have forklifts or other movable equipment present, the structure shall be designed for the total vehicle or equipment load and the individual wheel loads for the anticipated vehicles as specified by the owner of the facility. These loads shall be posted in accordance with Section 1607.7.5.

1607.7.4.1 Impact and fatigue.

Impact loads and fatigue loading shall be considered in the design of the supporting structure. For the purposes of design, the vehicle and wheel loads shall be increased by 30 percent to account for impact.

1607.7.5 Posting.

The maximum weight of vehicles allowed into or on a garage or other structure shall be posted by the owner or the owner’s authorized agent in accordance with Section 106.1.

1607.8 Loads on handrails, guards, grab bars, seats and vehicle barriers.

Handrails, guards, grab bars, accessible seats, accessible benches and vehicle barriers shall be designed and constructed for the structural loading conditions set forth in this section.

1607.8.1 Handrails and guards.

Handrails and guards shall be designed to resist a linear load of 50 pounds per linear foot (plf) (0.73 kN/m) in accordance with Section 4.5.1 of ASCE 7. Glass handrail assemblies and guards shall also comply with Section 2407.

Exceptions:

  1. 1.For one- and two-family dwellings, only the single concentrated load required by Section 1607.8.1.1 shall be applied.
  2. 2.In Group I-3, F, H and S occupancies, for areas that are not accessible to the general public and that have an occupant load less than 50, the minimum load shall be 20 pounds per foot (0.29 kN/m).

1607.8.1.1 Concentrated load.

Handrails and guards shall be designed to resist a concentrated load of 200 pounds (0.89 kN) in accordance with Section 4.5.1 of ASCE 7.

1607.8.1.2 Intermediate rails.

Intermediate rails (all those except the handrail), balusters and panel fillers shall be designed to resist a concentrated load of 50 pounds (0.22 kN) in accordance with Section 4.5.1 of ASCE 7.

1607.8.2 Grab bars, shower seats and dressing room bench seats.

Grab bars, shower seats and dressing room bench seats shall be designed to resist a single concentrated load of 250 pounds (1.11 kN) applied in any direction at any point on the grab bar or seat so as to produce the maximum load effects.

1607.8.3 Vehicle barriers.

Vehicle barriers for passenger vehicles shall be designed to resist a concentrated load of 6,000 pounds (26.70 kN) in accordance with Section 4.5.3 of ASCE 7. Garages accommodating trucks and buses shall be designed in accordance with an approved method that contains provisions for traffic railings.

1607.9 Impact loads.

The live loads specified in Sections 1607.3 through 1607.8 shall be assumed to include adequate allowance for ordinary impact conditions. Provisions shall be made in the structural design for uses and loads that involve unusual vibration and impact forces.

1607.9.1 Elevators.

Members, elements and components subject to dynamic loads from elevators shall be designed for impact loads and deflection limits prescribed by ASME A17.1/CSA B44.

1607.9.2 Machinery.

For the purpose of design, the weight of machinery and moving loads shall be increased as follows to allow for impact: (1) light machinery, shaft- or motor-driven, 20 percent; and (2) reciprocating machinery or power-driven units, 50 percent. Percentages shall be increased where specified by the manufacturer.

1607.9.3 Elements supporting hoists for façade access equipment.

In addition to any other applicable live loads, structural elements that support hoists for façade access equipment shall be designed for a live load consisting of the larger of the rated load of the hoist times 2.5 and the stall load of the hoist.

1607.9.4 Lifeline anchorages for façade access equipment.

In addition to any other applicable live loads, lifeline anchorages and structural elements that support lifeline anchorages shall be designed for a live load of at least 3,100 pounds (13.8 kN) for each attached lifeline, in every direction that a fall arrest load may be applied.

1607.10 Reduction in uniform live loads.

Except for uniform live loads at roofs, all other minimum uniformly distributed live loads, Lo, in Table 1607.1 are permitted to be reduced in accordance with Section 1607.10.1 or 1607.10.2. Uniform live loads at roofs are permitted to be reduced in accordance with Section 1607.12.2.

1607.10.1 Basic uniform live load reduction.

Subject to the limitations of Sections 1607.10.1.1 through 1607.10.1.3 and Table 1607.1, members for which a value of KLLAT is 400 square feet (37.16 m2) or more are permitted to be designed for a reduced uniformly distributed live load, L, in accordance with the following equation:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0051.jpg(Equation 16-23)

For SI:https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0052.jpg

where:

L=Reduced design live load per square foot (m2) of area supported by the member.
Lo=Unreduced design live load per square foot (m2) of area supported by the member (see Table 1607.1).
KLL=Live load element factor (see Table 1607.10.1).
AT=Tributary area, in square feet (m2).

L shall be not less than 0.50Lo for members supporting one floor and L shall be not less than 0.40Lo for members supporting two or more floors.

TABLE 1607.10.1

LIVE LOAD ELEMENT FACTOR, KLL

ELEMENTKLL
Interior columns4
Exterior columns without cantilever slabs4
Edge columns with cantilever slabs3
Corner columns with cantilever slabs2
Edge beams without cantilever slabs2
Interior beams2
All other members not identified above including:1
Edge beams with cantilever slabs
Cantilever beams
One-way slabs
Two-way slabs
Members without provisions for continuous shear transfer normal to their span

1607.10.1.1 One-way slabs.

The tributary area, AT, for use in Equation 16-23 for one-way slabs shall not exceed an area defined by the slab span times a width normal to the span of 1.5 times the slab span.

1607.10.1.2 Heavy live loads.

Live loads that exceed 100 psf (4.79 kN/m2) shall not be reduced.

Exceptions:

  1. 1.The live loads for members supporting two or more floors are permitted to be reduced by a maximum of 20 percent, but the live load shall be not less than L as calculated in Section 1607.10.1.
  2. 2.For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted.

1607.10.1.3 Passenger vehicle garages.

The live loads shall not be reduced in passenger vehicle garages.

Exception: The live loads for members supporting two or more floors are permitted to be reduced by a maximum of 20 percent, but the live load shall not be less than L as calculated in Section 1607.10.1.

1607.10.2 Alternative uniform live load reduction.

As an alternative to Section 1607.10.1 and subject to the limitations of Table 1607.1, uniformly distributed live loads are permitted to be reduced in accordance with the following provisions. Such reductions shall apply to slab systems, beams, girders, columns, piers, walls and foundations.

  1. 1.A reduction shall not be permitted where the live load exceeds 100 psf (4.79 kN/m2) except that the design live load for members supporting two or more floors is permitted to be reduced by a maximum of 20 percent.Exception: For uses other than storage, where approved, additional live load reductions shall be permitted where shown by the registered design professional that a rational approach has been used and that such reductions are warranted.
  2. 2.A reduction shall not be permitted in passenger vehicle parking garages except that the live loads for members supporting two or more floors are permitted to be reduced by a maximum of 20 percent.
  3. 3.For live loads not exceeding 100 psf (4.79 kN/m2), the design live load for any structural member supporting 150 square feet (13.94 m2) or more is permitted to be reduced in accordance with Equation 16-24.
  4. 4.For one-way slabs, the area, A, for use in Equation 16-24 shall not exceed the product of the slab span and a width normal to the span of 0.5 times the slab span.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0053.jpg(Equation 16-24)

For SI:https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0054.jpg

Such reduction shall not exceed the smallest of:

  1. 1.40 percent for members supporting one floor.
  2. 2.60 percent for members supporting two or more floors.
  3. 3.R as determined by the following equation:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0055.jpg(Equation 16-25)

where:

A=Area of floor supported by the member, square feet (m2).
D=Dead load per square foot (m2) of area supported.
Lo=Unreduced live load per square foot (m2) of area supported.
R=Reduction in percent.

1607.11 Distribution of floor loads.

Where uniform floor live loads are involved in the design of structural members arranged so as to create continuity, the minimum applied loads shall be the full dead loads on all spans in combination with the floor live loads on spans selected to produce the greatest load effect at each location under consideration. Floor live loads are permitted to be reduced in accordance with Section 1607.10.

1607.12 Roof loads.

The structural supports of roofs and marquees shall be designed to resist wind and, where applicable, snow and earthquake loads, in addition to the dead load of construction and the appropriate live loads as prescribed in this section, or as set forth in Table 1607.1. The live loads acting on a sloping surface shall be assumed to act vertically on the horizontal projection of that surface.

1607.12.1 Distribution of roof loads.

Where uniform roof live loads are reduced to less than 20 psf (0.96 kN/m2) in accordance with Section 1607.12.2.1 and are applied to the design of structural members arranged so as to create continuity, the reduced roof live load shall be applied to adjacent spans or to alternate spans, whichever produces the most unfavorable load effect. See Section 1607.12.2 for reductions in minimum roof live loads and Section 7.5 of ASCE 7 for partial snow loading.

1607.12.2 General.

The minimum uniformly distributed live loads of roofs and marquees, Lo, in Table 1607.1 are permitted to be reduced in accordance with Section 1607.12.2.1.

1607.12.2.1 Ordinary roofs, awnings and canopies.

Ordinary flat, pitched and curved roofs, and awnings and canopies other than of fabric construction supported by a skeleton structure, are permitted to be designed for a reduced uniformly distributed roof live load, Lr, as specified in the following equations or other controlling combinations of loads as specified in Section 1605, whichever produces the greater load effect.

In structures such as greenhouses, where special scaffolding is used as a work surface for workers and materials during maintenance and repair operations, a lower roof load than specified in the following equations shall not be used unless approved by the building official. Such structures shall be designed for a minimum roof live load of 12 psf (0.58 kN/m2).

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0056.jpg(Equation 16-26)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0057.jpg

For SI:https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0058.jpg

where:https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0059.jpg

Lo=Unreduced roof live load per square foot (m2) of horizontal projection supported by the member (see Table 1607.1).
Lr=Reduced roof live load per square foot (m2) of horizontal projection supported by the member.

The reduction factors R1 and R2 shall be determined as follows:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0060.jpg(Equation 16-27)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0061.jpg(Equation 16-28)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0062.jpg

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0063.jpg(Equation 16-29)

where:

At=Tributary area (span length multiplied by effective width) in square feet (m2) supported by the member, and

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0064.jpg(Equation 16-30)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0065.jpg(Equation 16-31)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0066.jpg(Equation 16-32)

where:

F=For a sloped roof, the number of inches of rise per foot (for SI: F = 0.12 × slope, with slope expressed as a percentage), or for an arch or dome, the rise-to-span ratio multiplied by 32.

1607.12.3 Occupiable roofs.

Areas of roofs that are occupiable, such as vegetative roofs, roof gardens or for assembly or other similar purposes, and marquees are permitted to have their uniformly distributed live loads reduced in accordance with Section 1607.10.

1607.12.3.1 Vegetative and landscaped roofs.

The weight of all landscaping materials shall be considered as dead load and shall be computed on the basis of saturation of the soil as determined in accordance with ASTM E2397. The uniform design live load in unoccupied landscaped areas on roofs shall be 20 psf (0.958 kN/m2). The uniform design live load for occupied landscaped areas on roofs shall be determined in accordance with Table 1607.1.

1607.12.4 Awnings and canopies.

Awnings and canopies shall be designed for uniform live loads as required in Table 1607.1 as well as for snow loads and wind loads as specified in Sections 1608 and 1609.

1607.12.5 Photovoltaic panel systems.

Roof structures that provide support for photovoltaic panel systems shall be designed in accordance with Sections 1607.12.5.1 through 1607.12.5.4, as applicable.

1607.12.5.1 Roof live load.

Roof surfaces to be covered by solar photovoltaic panels or modules shall be designed for the roof live load, Lr, assuming that the photovoltaic panels or modules are not present. The roof photovoltaic live load in areas covered by solar photovoltaic panels or modules shall be in addition to the panel loading unless the area covered by each solar photovoltaic panel or module is inaccessible. Areas where the clear space between the panels and the rooftop is not more than 24 inches (610 mm) shall be considered inaccessible. Roof surfaces not covered by photovoltaic panels shall be designed for the roof live load.

1607.12.5.2 Photovoltaic panels or modules.

The structure of a roof that supports solar photovoltaic panels or modules shall be designed to accommodate the full solar photovoltaic panels or modules and ballast dead load, including concentrated loads from support frames in combination with the loads from Section 1607.12.5.1 and other applicable loads. Where applicable, snow drift loads created by the photovoltaic panels or modules shall be included.

1607.12.5.3 Photovoltaic panels or modules installed as an independent structure.

Solar photovoltaic panels or modules that are independent structures and do not have accessible/occupied space underneath are not required to accommodate a roof photovoltaic live load, provided the area under the structure is restricted to keep the public away. All other loads and combinations in accordance with Section 1605 shall be accommodated.

Solar photovoltaic panels or modules that are designed to be the roof, span to structural supports and have accessible/occupied space underneath shall have the panels or modules and all supporting structures designed to support a roof photovoltaic live load, as defined in Section 1607.12.5.1 in combination with other applicable loads. Solar photovoltaic panels or modules in this application are not permitted to be classified as “not accessible” in accordance with Section 1607.12.5.1.

1607.12.5.4 Ballasted photovoltaic panel systems.

Roof structures that provide support for ballasted photovoltaic panel systems shall be designed, or analyzed, in accordance with Section 1604.4; checked in accordance with Section 1604.3.6 for deflections; and checked in accordance with Section 1611 for ponding.

1607.13 Crane loads.

The crane live load shall be the rated capacity of the crane. Design loads for the runway beams, including connections and support brackets, of moving bridge cranes and monorail cranes shall include the maximum wheel loads of the crane and the vertical impact, lateral and longitudinal forces induced by the moving crane.

1607.13.1 Maximum wheel load.

The maximum wheel loads shall be the wheel loads produced by the weight of the bridge, as applicable, plus the sum of the rated capacity and the weight of the trolley with the trolley positioned on its runway at the location where the resulting load effect is maximum.

1607.13.2 Vertical impact force.

The maximum wheel loads of the crane shall be increased by the percentages shown below to determine the induced vertical impact or vibration force:

Monorail cranes (powered)25 percent
Cab-operated or remotely operated bridge cranes (powered)25 percent
Pendant-operated bridge cranes (powered)10 percent
Bridge cranes or monorail cranes with hand-geared bridge, trolley and hoist0 percent

1607.13.3 Lateral force.

The lateral force on crane runway beams with electrically powered trolleys shall be calculated as 20 percent of the sum of the rated capacity of the crane and the weight of the hoist and trolley. The lateral force shall be assumed to act horizontally at the traction surface of a runway beam, in either direction perpendicular to the beam, and shall be distributed with due regard to the lateral stiffness of the runway beam and supporting structure.

1607.13.4 Longitudinal force.

The longitudinal force on crane runway beams, except for bridge cranes with hand-geared bridges, shall be calculated as 10 percent of the maximum wheel loads of the crane. The longitudinal force shall be assumed to act horizontally at the traction surface of a runway beam, in either direction parallel to the beam.

1607.14 Interior walls and partitions.

Interior walls and partitions that exceed 6 feet (1829 mm) in height, including their finish materials, shall have adequate strength and stiffness to resist the loads to which they are subjected but not less than a horizontal load of 5 psf (0.240 kN/m2).

1607.14.1 Fabric partitions.

Fabric partitions that exceed 6 feet (1829 mm) in height, including their finish materials, shall have adequate strength and stiffness to resist the following load conditions:

  1. 1.The horizontal distributed load need only be applied to the partition framing. The total area used to determine the distributed load shall be the area of the fabric face between the framing members to which the fabric is attached. The total distributed load shall be uniformly applied to such framing members in proportion to the length of each member.
  2. 2.A concentrated load of 40 pounds (0.176 kN) applied to an 8-inch-diameter (203 mm) area [50.3 square inches (32 452 mm2)] of the fabric face at a height of 54 inches (1372 mm) above the floor.

SECTION1608
SNOW LOADS

1608.1 General.

Design snow loads shall be determined in accordance with Chapter 7 of ASCE 7, but the design roof load shall not be less than that determined by Section 1607.

1608.2 Ground snow loads.

The ground snow loads to be used in determining the design snow loads for roofs shall be determined in accordance with ASCE 7 or Figure 1608.2 for the contiguous United States and Table 1608.2 for Alaska. Site-specific case studies shall be made in areas designated “CS” in Figure 1608.2. Ground snow loads for sites at elevations above the limits indicated in Figure 1608.2 and for all sites within the CS areas shall be approved. Ground snow load determination for such sites shall be based on an extreme value statistical analysis of data available in the vicinity of the site using a value with a 2-percent annual probability of being exceeded (50-year mean recurrence interval). Snow loads are zero for Hawaii, except in mountainous regions as approved by the building official.

TABLE 1608.2

GROUND SNOW LOADS, pg, FOR ALASKAN LOCATIONS

LOCATIONPOUNDS PER SQUARE FOOTLOCATIONPOUNDS PER SQUARE FOOTLOCATIONPOUNDS PER SQUARE FOOT
Adak30Galena60Petersburg150
Anchorage50Gulkana70St. Paul Islands40
Angoon70Homer40Seward50
Barrow25Juneau60Shemya25
Barter Island35Kenai70Sitka50
Bethel40Kodiak30Talkeetna120
Big Delta50Kotzebue60Unalakleet50
Cold Bay25McGrath70Valdez160
Cordova100Nenana80Whittier300
Fairbanks60Nome70Wrangell60
Fort Yukon60Palmer50Yakutat150

For SI: 1 pound per square foot = 0.0479 kN/m2.

FIGURE 1608.2GROUND SNOW LOADS, pg, FOR THE UNITED STATES (psf)

1608.3 Ponding instability.

Susceptible bays of roofs shall be evaluated for ponding instability in accordance with Section 7.11 of ASCE 7.

SECTION1609
WIND LOADS

1609.1 Applications.

Buildings, structures and parts thereof shall be designed to withstand the minimum wind loads prescribed herein. Decreases in wind loads shall not be made for the effect of shielding by other structures.

1609.1.1 Determination of wind loads.

Wind loads on every building or structure shall be determined in accordance with Chapters 26 to 30 of ASCE 7 or provisions of the alternate all-heights method in Section 1609.6. The type of opening protection required, the ultimate design wind speed, Vult, and the exposure category for a site is permitted to be determined in accordance with Section 1609 or ASCE 7. Wind shall be assumed to come from any horizontal direction and wind pressures shall be assumed to act normal to the surface considered.

Exceptions:

  1. 1.Subject to the limitations of Section 1609.1.1.1, the provisions of ICC 600 shall be permitted for applicable Group R-2 and R-3 buildings.
  2. 2.Subject to the limitations of Section 1609.1.1.1, residential structures using the provisions of AWC WFCM.
  3. 3.Subject to the limitations of Section 1609.1.1.1, residential structures using the provisions of AISI S230.
  4. 4.Designs using NAAMM FP 1001.
  5. 5.Designs using TIA-222 for antenna-supporting structures and antennas, provided the horizontal extent of Topographic Category 2 escarpments in Section 2.6.6.2 of TIA-222 shall be 16 times the height of the escarpment.
  6. 6.Wind tunnel tests in accordance with ASCE 49 and Sections 31.4 and 31.5 of ASCE 7.

The wind speeds in Figures 1609.3(1), 1609.3(2) and 1609.3(3) are ultimate design wind speeds, Vult, and shall be converted in accordance with Section 1609.3.1 to nominal design wind speeds, Vasd, when the provisions of the standards referenced in Exceptions 4 and 5 are used.

1609.1.1.1 Applicability.

The provisions of ICC 600 are applicable only to buildings located within Exposure B or C as defined in Section 1609.4. The provisions of ICC 600, AWC WFCM and AISI S230 shall not apply to buildings sited on the upper half of an isolated hill, ridge or escarpment meeting the following conditions:

  1. 1.The hill, ridge or escarpment is 60 feet (18 288 mm) or higher if located in Exposure B or 30 feet (9144 mm) or higher if located in Exposure C;
  2. 2.The maximum average slope of the hill exceeds 10 percent; and
  3. 3.The hill, ridge or escarpment is unobstructed upwind by other such topographic features for a distance from the high point of 50 times the height of the hill or 1 mile (1.61 km), whichever is greater.

1609.1.2 Protection of openings.

In wind-borne debris regions, glazing in buildings shall be impact resistant or protected with an impact-resistant covering meeting the requirements of an approved impact-resistant standard or ASTM E1996 and ASTM E1886 referenced herein as follows:

  1. 1.Glazed openings located within 30 feet (9144 mm) of grade shall meet the requirements of the large missile test of ASTM E1996.
  2. 2.Glazed openings located more than 30 feet (9144 mm) above grade shall meet the provisions of the small missile test of ASTM E1996.

Exceptions:

  1. 1.Wood structural panels with a minimum thickness of 7/16 inch (11.1 mm) and maximum panel span of 8 feet (2438 mm) shall be permitted for opening protection in buildings with a mean roof height of 33 feet (10 058 mm) or less that are classified as a Group R-3 or R-4 occupancy. Panels shall be precut so that they shall be attached to the framing surrounding the opening containing the product with the glazed opening. Panels shall be predrilled as required for the anchorage method and shall be secured with the attachment hardware provided. Attachments shall be designed to resist the components and cladding loads determined in accordance with the provisions of ASCE 7, with corrosion-resistant attachment hardware provided and anchors permanently installed on the building. Attachment in accordance with Table 1609.1.2 with corrosion-resistant attachment hardware provided and anchors permanently installed on the building is permitted for buildings with a mean roof height of 45 feet (13 716 mm) or less where Vasd determined in accordance with Section 1609.3.1 does not exceed 140 mph (63 m/s).
  2. 2.Glazing in Risk Category I buildings, including greenhouses that are occupied for growing plants on a production or research basis, without public access shall be permitted to be unprotected.
  3. 3.Glazing in Risk Category II, III or IV buildings located over 60 feet (18 288 mm) above the ground and over 30 feet (9144 mm) above aggregate surface roofs located within 1,500 feet (458 m) of the building shall be permitted to be unprotected.

TABLE 1609.1.2

WIND-BORNE DEBRIS PROTECTION FASTENING SCHEDULE FOR WOOD STRUCTURAL PANELSa, b, c, d

FASTENER TYPEFASTENER SPACING (inches)
Panel Span ≤ 4 feet4 feet < Panel Span ≤ 6 feet6 feet < Panel Span ≤ 8 feet
No. 8 wood-screw-based anchor with 2-inch embedment length16108
No. 10 wood-screw-based anchor with 2-inch embedment length16129
1/4-inch diameter lag-screw-based anchor with 2-inch embedment length161616

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound = 4.448 N, 1 mile per hour = 0.447 m/s.

  1. a.This table is based on 140 mph wind speeds and a 45-foot mean roof height.
  2. b.Fasteners shall be installed at opposing ends of the wood structural panel. Fasteners shall be located a minimum of 1 inch from the edge of the panel.
  3. c.Anchors shall penetrate through the exterior wall covering with an embedment length of 2 inches minimum into the building frame. Fasteners shall be located a minimum of 21/2 inches from the edge of concrete block or concrete.
  4. d.Where panels are attached to masonry or masonry/stucco, they shall be attached using vibration-resistant anchors having a minimum ultimate withdrawal capacity of 1,500 pounds.

1609.1.2.1 Louvers.

Louvers protecting intake and exhaust ventilation ducts not assumed to be open that are located within 30 feet (9144 mm) of grade shall meet the requirements of AMCA 540.

1609.1.2.2.Application of ASTM E1996.

The text of Section 6.2.2 of ASTM E1996 shall be substituted as follows:

  1. 6.2.2 Unless otherwise specified, select the wind zone based on the strength design wind speed, Vult, as follows:
    1. 6.2.2.1Wind Zone 1—130 mph ≤ ultimate design wind speed, Vult < 140 mph.
    2. 6.2.2.2Wind Zone 2—140 mph ≤ ultimate design wind speed, Vult < 150 mph at greater than one mile (1.6 km) from the coastline. The coastline shall be measured from the mean high water mark.
    3. 6.2.2.3Wind Zone 3—150 mph (58 m/s) ≤ ultimate design wind speed, Vult ≤ 160 mph (63 m/s), or 140 mph (54 m/s) ≤ ultimate design wind speed, Vult ≤ 160 mph (63 m/s) and within one mile (1.6 km) of the coastline. The coastline shall be measured from the mean high water mark.
    4. 6.2.2.4Wind Zone 4— ultimate design wind speed, Vult >160 mph (63 m/s).

1609.1.2.3 Garage doors.

Garage door glazed opening protection for wind-borne debris shall meet the requirements of an approved impact-resisting standard or ANSI/DASMA 115.

1609.2 Definitions.

For the purposes of Section 1609 and as used elsewhere in this code, the following terms are defined in Chapter 2.

HURRICANE-PRONE REGIONS.

WIND-BORNE DEBRIS REGION.

WIND SPEED, Vult.

WIND SPEED, Vasd.

1609.3 Ultimate design wind speed.

The ultimate design wind speed, Vult, in mph, for the determination of the wind loads shall be determined by Figures 1609.3(1), 1609.3(2) and 1609.3(3). The ultimate design wind speed, Vult, for use in the design of Risk Category II buildings and structures shall be obtained from Figure 1609.3(1). The ultimate design wind speed, Vult, for use in the design of Risk Category III and IV buildings and structures shall be obtained from Figure 1609.3(2). The ultimate design wind speed, Vult, for use in the design of Risk Category I buildings and structures shall be obtained from Figure 1609.3(3). The ultimate design wind speed, Vult, for the special wind regions indicated near mountainous terrain and near gorges shall be in accordance with local jurisdiction requirements. The ultimate design wind speeds, Vult, determined by the local jurisdiction shall be in accordance with Section 26.5.1 of ASCE 7.

In nonhurricane-prone regions, when the ultimate design wind speed, Vult, is estimated from regional climatic data, the ultimate design wind speed, Vult, shall be determined in accordance with Section 26.5.3 of ASCE 7.

Notes:1.Values are nominal design 3-second gust wind speeds in miles per hour (m/s) at 33 ft (10m) above ground for Exposure C Category.2.Linear interpolation between contours is permitted.3.Islands and coastal areas outside the last contour shall use the last wind speed contour of coastal area.4.Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind conditions.5.Wind speeds correspond to approximately a 7% probability of exceedance in 50 years (Annual Exceedance Probability = 0.00143, MRI = 700 Years).FIGURE 1609.3(1)ULTIMATE DESIGN WIND SPEEDS, vult, FOR RISK CATEGORY II BUILDINGS AND OTHER STRUCTURES
Notes:1.Values are nominal design 3-second gust wind speeds in miles per hour (m/s) at 33 ft (10m) above ground for Exposure C Category.2.Linear interpolation between contours is permitted.3.Islands and coastal areas outside the last contour shall use the last wind speed contour of coastal area.4.Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind conditions.5.Wind speeds correspond to approximately a 3% probability of exceedance in 50 years (Annual Exceedance Probability = 0.000588, MRI = 1700 Years).FIGURE 1609.3(2)ULTIMATE DESIGN WIND SPEEDS, vult, FOR RISK CATEGORY III AND IV BUILDINGS AND OTHER STRUCTURES
Notes:1.Values are nominal design 3-second gust wind speeds in miles per hour (m/s) at 33 ft (10m) above ground for Exposure C Category.2.Linear interpolation between contours is permitted.3.Islands and coastal areas outside the last contour shall use the last wind speed contour of coastal area.4.Mountainous terrain, gorges, ocean promontories, and special wind regions shall be examined for unusual wind conditions.5.Wind speeds correspond to approximately a 15% probability of exceedance in 50 years (Annual Exceedance Probability = 0.00333, MRI = 300 Years).FIGURE 1609.3(3)ULTIMATE DESIGN WIND SPEEDS, vult, FOR RISK CATEGORY I BUILDINGS AND OTHER STRUCTURES

1609.3.1 Wind speed conversion.

When required, the ultimate design wind speeds of Figures 1609.3(1), 1609.3(2) and 1609.3(3) shall be converted to nominal design wind speeds, Vasd, using Table 1609.3.1 or Equation 16-33.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0067.jpg(Equation 16-33)

where:

Vasd=Nominal design wind speed applicable to methods specified in Exceptions 4 and 5 of Section 1609.1.1.
Vult=Ultimate design wind speeds determined from Figures 1609.3(1), 1609.3(2) or 1609.3(3).

TABLE 1609.3.1

WIND SPEED CONVERSIONSa, b, c

Vult100110120130140150160170180190200
Vasd788593101108116124132139147155

For SI: 1 mile per hour = 0.44 m/s.

  1. a.Linear interpolation is permitted.
  2. b.Vasd = nominal design wind speed applicable to methods specified in Exceptions 1 through 5 of Section 1609.1.1.
  3. c.Vult = ultimate design wind speeds determined from Figure 1609.3(1), 1609.3(2) or 1609.3(3).

1609.4 Exposure category.

For each wind direction considered, an exposure category that adequately reflects the characteristics of ground surface irregularities shall be determined for the site at which the building or structure is to be constructed. Account shall be taken of variations in ground surface roughness that arise from natural topography and vegetation as well as from constructed features.

1609.4.1 Wind directions and sectors.

For each selected wind direction at which the wind loads are to be evaluated, the exposure of the building or structure shall be determined for the two upwind sectors extending 45 degrees (0.79 rad) either side of the selected wind direction. The exposures in these two sectors shall be determined in accordance with Sections 1609.4.2 and 1609.4.3 and the exposure resulting in the highest wind loads shall be used to represent winds from that direction.

1609.4.2 Surface roughness categories.

A ground surface roughness within each 45-degree (0.79 rad) sector shall be determined for a distance upwind of the site as defined in Section 1609.4.3 from the categories defined below, for the purpose of assigning an exposure category as defined in Section 1609.4.3.

Surface Roughness B. Urban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger.

Surface Roughness C. Open terrain with scattered obstructions having heights generally less than 30 feet (9144 mm). This category includes flat open country, and grasslands.

Surface Roughness D. Flat, unobstructed areas and water surfaces. This category includes smooth mud flats, salt flats and unbroken ice.

1609.4.3 Exposure categories.

An exposure category shall be determined in accordance with the following:

Exposure B. For buildings with a mean roof height of less than or equal to 30 feet (9144 mm), Exposure B shall apply where the ground surface roughness, as defined by Surface Roughness B, prevails in the upwind direction for a distance of at least 1,500 feet (457 m). For buildings with a mean roof height greater than 30 feet (9144 mm), Exposure B shall apply where Surface Roughness B prevails in the upwind direction for a distance of at least 2,600 feet (792 m) or 20 times the height of the building, whichever is greater.

Exposure C. Exposure C shall apply for all cases where Exposure B or D does not apply.

Exposure D. Exposure D shall apply where the ground surface roughness, as defined by Surface Roughness D, prevails in the upwind direction for a distance of at least 5,000 feet (1524 m) or 20 times the height of the building, whichever is greater. Exposure D shall also apply where the ground surface roughness immediately upwind of the site is B or C, and the site is within a distance of 600 feet (183 m) or 20 times the building height, whichever is greater, from an Exposure D condition as defined in the previous sentence.

1609.5 Roof systems.

Roof systems shall be designed and constructed in accordance with Sections 1609.5.1 through 1609.5.3, as applicable.

1609.5.1 Roof deck.

The roof deck shall be designed to withstand the wind pressures determined in accordance with ASCE 7.

1609.5.2 Roof coverings.

Roof coverings shall comply with Section 1609.5.1.

Exception: Rigid tile roof coverings that are air permeable and installed over a roof deck complying with Section 1609.5.1 are permitted to be designed in accordance with Section 1609.5.3.

Asphalt shingles installed over a roof deck complying with Section 1609.5.1 shall comply with the wind-resistance requirements of Section 1504.1.1.

1609.5.3 Rigid tile.

Wind loads on rigid tile roof coverings shall be determined in accordance with the following equation:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0068.jpg(Equation 16-34)

For SI:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0069.jpg

where:

b=Exposed width, feet (mm) of the roof tile.
CL=Lift coefficient. The lift coefficient for concrete and clay tile shall be 0.2 or shall be determined by test in accordance with Section 1504.2.1.
GCp=Roof pressure coefficient for each applicable roof zone determined from Chapter 30 of ASCE 7. Roof coefficients shall not be adjusted for internal pressure.
L=Length, feet (mm) of the roof tile.
La=Moment arm, feet (mm) from the axis of rotation to the point of uplift on the roof tile. The point of uplift shall be taken at 0.76L from the head of the tile and the middle of the exposed width. For roof tiles with nails or screws (with or without a tail clip), the axis of rotation shall be taken as the head of the tile for direct deck application or as the top edge of the batten for battened applications. For roof tiles fastened only by a nail or screw along the side of the tile, the axis of rotation shall be determined by testing. For roof tiles installed with battens and fastened only by a clip near the tail of the tile, the moment arm shall be determined about the top edge of the batten with consideration given for the point of rotation of the tiles based on straight bond or broken bond and the tile profile.
Ma=Aerodynamic uplift moment, feet-pounds (N-mm) acting to raise the tail of the tile.
qh=Wind velocity pressure, psf (kN/m2) determined from Section 27.3.2 of ASCE 7.

Concrete and clay roof tiles complying with the following limitations shall be designed to withstand the aerodynamic uplift moment as determined by this section.

  1. 1.The roof tiles shall be either loose laid on battens, mechanically fastened, mortar set or adhesive set.
  2. 2.The roof tiles shall be installed on solid sheathing that has been designed as components and cladding.
  3. 3.An underlayment shall be installed in accordance with Chapter 15.
  4. 4.The tile shall be single lapped interlocking with a minimum head lap of not less than 2 inches (51 mm).
  5. 5.The length of the tile shall be between 1.0 and 1.75 feet (305 mm and 533 mm).
  6. 6.The exposed width of the tile shall be between 0.67 and 1.25 feet (204 mm and 381 mm).
  7. 7.The maximum thickness of the tail of the tile shall not exceed 1.3 inches (33 mm).
  8. 8.Roof tiles using mortar set or adhesive set systems shall have at least two-thirds of the tile’s area free of mortar or adhesive contact.

1609.6 Alternate all-heights method.

The alternate wind design provisions in this section are simplifications of the ASCE 7 Directional Procedure.

1609.6.1 Scope.

As an alternative to ASCE 7 Chapters 27 and 30, the following provisions are permitted to be used to determine the wind effects on regularly shaped buildings, or other structures that are regularly shaped, that meet all of the following conditions:

  1. 1.The building or other structure is less than or equal to 75 feet (22 860 mm) in height with a height-to-least-width ratio of 4 or less, or the building or other structure has a fundamental frequency greater than or equal to 1 hertz.
  2. 2.The building or other structure is not sensitive to dynamic effects.
  3. 3.The building or other structure is not located on a site for which channeling effects or buffeting in the wake of upwind obstructions warrant special consideration.
  4. 4.The building shall meet the requirements of a simple diaphragm building as defined in ASCE 7 Section 26.2, where wind loads are only transmitted to the main windforce-resisting system (MWFRS) at the diaphragms.
  5. 5.For open buildings, multispan gable roofs, stepped roofs, sawtooth roofs, domed roofs, roofs with slopes greater than 45 degrees (0.79 rad), solid free-standing walls and solid signs, and rooftop equipment, apply ASCE 7 provisions.

1609.6.1.1 Modifications.

The following modifications shall be made to certain subsections in ASCE 7: in Section 1609.6.2, symbols and notations that are specific to this section are used in conjunction with the symbols and notations in ASCE 7 Section 26.3.

1609.6.2 Symbols and notations.

Coefficients and variables used in the alternative all-heights method equations are as follows:

Cnet=Net-pressure coefficient based on Kd [(G) (Cp) – (GCpi)], in accordance with Table 1609.6.2.
G=Gust effect factor for rigid structures in accordance with ASCE 7 Section 26.9.1.
Kd=Wind directionality factor in accordance with ASCE 7 Table 26-6.
Pnet=Design wind pressure to be used in determination of wind loads on buildings or other structures or their components and cladding, in psf (kN/m2).

TABLE 1609.6.2

NET PRESSURE COEFFICIENTS, Cneta, b

STRUCTURE OR PART THEREOFDESCRIPTIONCnet FACTOR
1. Main windforce-resisting frames and systemsWalls:EnclosedPartially enclosed
+ Internal pressure– Internal pressure+ Internal pressure– Internal pressure
Windward wall0.430.730.111.05
Leeward wall-0.51-0.21-0.830.11
Sidewall-0.66-0.35-0.97-0.04
Parapet wallWindward1.281.28
Leeward-0.85-0.85
Roofs:EnclosedPartially enclosed
Wind perpendicular to ridge+ Internal pressure– Internal pressure+ Internal pressure– Internal pressure
Leeward roof or flat roof-0.66-0.35-0.97-0.04
Windward roof slopes:
Slope < 2:12 (10°)Condition 1-1.09-0.79-1.41-0.47
Condition 2-0.280.02-0.600.34
Slope = 4:12 (18°)Condition 1-0.73-0.42-1.04-0.11
Condition 2-0.050.25-0.370.57
Slope = 5:12 (23°)Condition 1-0.58-0.28-0.900.04
Condition 20.030.34-0.290.65
Slope = 6:12 (27°)Condition 1-0.47-0.16-0.780.15
Condition 20.060.37-0.250.68
Slope = 7:12 (30°)Condition 1-0.37-0.06-0.680.25
Condition 20.070.37-0.250.69
Slope = 9:12 (37°)Condition 1-0.270.04-0.580.35
Condition 20.140.44-0.180.76
Slope = 12:12 (45°)0.140.44-0.180.76
Wind parallel to ridge and flat roofs-1.09-0.79-1.41-0.47
Nonbuilding Structures: Chimneys, Tanks and Similar Structures:
h/D
1725
Square (Wind normal to face)0.991.071.53
Square (Wind on diagonal)0.770.841.15
Hexagonal or octagonal0.810.971.13
Round0.650.810.97
Open signs and lattice frameworksRatio of solid to gross area
< 0.10.1 to 0.290.3 to 0.7
Flat1.451.301.16
Round0.870.941.08
2. Components and cladding not in areas of discontinuity—roofs and overhangsRoof elements and slopesEnclosedPartially enclosed
Gable of hipped configurations (Zone 1)
Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 1
Positive10 square feet or less0.580.89
100 square feet or more0.410.72
Negative10 square feet or less-1.00-1.32
100 square feet or more-0.92-1.23
Overhang: Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2A Zone 1
Negative10 square feet or less-1.45
100 square feet or more-1.36
500 square feet or more-0.94
6:12 (27°) < Slope < 12:12 (45°) See ASCE 7 Figure 30.4-2C Zone 1
Positive10 square feet or less0.921.23
100 square feet or more0.831.15
Negative10 square feet or less-1.00-1.32
100 square feet or more-0.83-1.15
Monosloped configurations (Zone 1)EnclosedPartially enclosed
Flat < Slope < 7:12 (30°) See ASCE 7 Figure 30.4-5B Zone 1
Positive10 square feet or less0.490.81
100 square feet or more0.410.72
Negative10 square feet or less-1.26-1.57
100 square feet or more-1.09-1.40
Tall flat-topped roofs h > 60 feetEnclosedPartially enclosed
Flat < Slope < 2:12 (10°) (Zone 1) See ASCE 7 Figure 30.8-1 Zone 1
Negative10 square feet or less-1.34-1.66
500 square feet or more-0.92-1.23
3. Components and cladding in areas of discontinuity—roofs and overhangs (continued)Gable or hipped configurations at ridges, eaves and rakes (Zone 2)
Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 2
Positive10 square feet or less0.580.89
100 square feet or more0.410.72
Negative10 square feet or less-1.68-2.00
100 square feet or more-1.17-1.49
Overhang for Slope Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 2
Negative10 square feet or less-1.87
100 square feet or more-1.87
6:12 (27°) < Slope < 12:12 (45°) Figure 30.4-2CEnclosedPartially enclosed
Positive10 square feet or less0.921.23
100 square feet or more0.831.15
Negative10 square feet or less-1.17-1.49
100 square feet or more-1.00-1.32
Overhang for 6:12 (27°) < Slope < 12:12 (45°) See ASCE 7 Figure 30.4-2C Zone 2
Negative10 square feet or less-1.70
500 square feet or more-1.53
3. Components and cladding in areas of discontinuity—roofs and overhangsRoof elements and slopesEnclosedPartially enclosed
Monosloped configurations at ridges, eaves and rakes (Zone 2)
Flat < Slope < 7:12 (30°) See ASCE 7 Figure 30.4-5B Zone 2
Positive10 square feet or less0.490.81
100 square feet or more0.410.72
Negative10 square feet or less-1.51-1.83
100 square feet or more-1.43-1.74
Tall flat topped roofs h > 60 feetEnclosedPartially enclosed
Flat < Slope < 2:12 (10°) (Zone 2) See ASCE 7 Figure 30.8-1 Zone 2
Negative10 square feet or less-2.11-2.42
500 square feet or more-1.51-1.83
Gable or hipped configurations at corners (Zone 3) See ASCE 7 Figure 30.4-2B Zone 3
Flat < Slope < 6:12 (27°)EnclosedPartially enclosed
Positive10 square feet or less0.580.89
100 square feet or more0.410.72
Negative10 square feet or less-2.53-2.85
100 square feet or more-1.85-2.17
Overhang for Slope Flat < Slope < 6:12 (27°) See ASCE 7 Figure 30.4-2B Zone 3
Negative10 square feet or less-3.15
100 square feet or more-2.13
6:12 (27°) < 12:12 (45°) See ASCE 7 Figure 30.4-2C Zone 3
Positive10 square feet or less0.921.23
100 square feet or more0.831.15
Negative10 square feet or less-1.17-1.49
100 square feet or more-1.00-1.32
Overhang for 6:12 (27°) < Slope < 12:12 (45°)EnclosedPartially enclosed
Negative10 square feet or less-1.70
100 square feet or more-1.53
Monosloped Configurations at corners (Zone 3) See ASCE 7 Figure 30.4-5B Zone 3
Flat < Slope < 7:12 (30°)
Positive10 square feet or less0.490.81
100 square feet or more0.410.72
Negative10 square feet or less-2.62-2.93
100 square feet or more-1.85-2.17
Tall flat topped roofs h > 60 feetEnclosedPartially enclosed
Flat < Slope < 2:12 (10°) (Zone 3) See ASCE 7 Figure 30.8-1 Zone 3
Negative10 square feet or less-2.87-3.19
500 square feet or more-2.11-2.42
4. Components and cladding not in areas of discontinuity—walls and parapetsWall Elements: h ≤ 60 feet (Zone 4) ASCE 7 Figure 30.4-1EnclosedPartially enclosed
Positive10 square feet or less1.001.32
500 square feet or more0.751.06
Negative10 square feet or less-1.09-1.40
500 square feet or more-0.83-1.15
Wall Elements: h > 60 feet (Zone 4) See ASCE 7 Figure 30.6-1 Zone 4
Positive20 square feet or less0.921.23
500 square feet or more0.660.98
Negative20 square feet or less-0.92-1.23
500 square feet or more-0.75-1.06
Parapet Walls
Positive2.873.19
Negative-1.68-2.00
5. Components and cladding in areas of discontinuity—walls and parapetsWall elements: h ≤ 60 feet (Zone 5) ASCE 7 Figure 30.4-1EnclosedPartially enclosed
Positive10 square feet or less1.001.32
500 square feet or more0.751.06
Negative10 square feet or less-1.34-1.66
500 square feet or more-0.83-1.15
Wall elements: h > 60 feet (Zone 5) See ASCE 7 Figure 30.6-1 Zone 4
Positive20 square feet or less0.921.23
500 square feet or more0.660.98
Negative20 square feet or less-1.68-2.00
500 square feet or more-1.00-1.32
Parapet walls
Positive3.643.95
Negative-2.45-2.76

For SI: 1 foot = 304.8 mm, 1 square foot = 0.0929m2, 1 degree = 0.0175 rad.

  1. a.Linear interpolation between values in the table is permitted.
  2. b.Some Cnet values have been grouped together. Less conservative results may be obtained by applying ASCE 7 provisions.

1609.6.3 Design equations.

When using the alternative all-heights method, the MWFRS, and components and cladding of every structure shall be designed to resist the effects of wind pressures on the building envelope in accordance with Equation 16-35.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0070.jpg(Equation 16-35)

Design wind forces for the MWFRS shall be not less than 16 psf (0.77 kN/m2) multiplied by the area of the structure projected on a plane normal to the assumed wind direction (see ASCE 7 Section 27.4.7 for criteria). Design net wind pressure for components and cladding shall be not less than 16 psf (0.77 kN/m2) acting in either direction normal to the surface.

1609.6.4 Design procedure.

The MWFRS and the components and cladding of every building or other structure shall be designed for the pressures calculated using Equation 16-35.

1609.6.4.1 Main windforce-resisting systems.

The MWFRS shall be investigated for the torsional effects identified in ASCE 7 Figure 27.4-8.

1609.6.4.2 Determination of Kz and Kzt.

Velocity pressure exposure coefficient, Kz, shall be determined in accordance with ASCE 7 Section 27.3.1 and the topographic factor, Kzt, shall be determined in accordance with ASCE 7 Section 26.8.

  1. 1.For the windward side of a structure, Kzt and Kz shall be based on height z.
  2. 2.For leeward and sidewalls, and for windward and leeward roofs, Kzt and Kz shall be based on mean roof height h.

1609.6.4.3 Determination of net pressure coefficients, Cnet.

For the design of the MWFRS and for components and cladding, the sum of the internal and external net pressure shall be based on the net pressure coefficient, Cnet.

  1. 1.The pressure coefficient, Cnet, for walls and roofs shall be determined from Table 1609.6.2.
  2. 2.Where Cnet has more than one value, the more severe wind load condition shall be used for design.

1609.6.4.4 Application of wind pressures.

When using the alternative all-heights method, wind pressures shall be applied simultaneously on, and in a direction normal to, all building envelope wall and roof surfaces.

1609.6.4.4.1 Components and cladding.

Wind pressure for each component or cladding element is applied as follows using Cnet values based on the effective wind area, A, contained within the zones in areas of discontinuity of width and/or length “a,” “2a” or “4a” at: corners of roofs and walls; edge strips for ridges, rakes and eaves; or field areas on walls or roofs as indicated in figures in tables in ASCE 7 as referenced in Table 1609.6.2 in accordance with the following:

  1. 1.Calculated pressures at local discontinuities acting over specific edge strips or corner boundary areas.
  2. 2.Include “field” (Zone 1, 2 or 4, as applicable) pressures applied to areas beyond the boundaries of the areas of discontinuity.
  3. 3.Where applicable, the calculated pressures at discontinuities (Zone 2 or 3) shall be combined with design pressures that apply specifically on rakes or eave overhangs.

SECTION1610
SOIL LATERAL LOADS

1610.1 General.

Foundation walls and retaining walls shall be designed to resist lateral soil loads. Soil loads specified in Table 1610.1 shall be used as the minimum design lateral soil loads unless determined otherwise by a geotechnical investigation in accordance with Section 1803. Foundation walls and other walls in which horizontal movement is restricted at the top shall be designed for at-rest pressure. Retaining walls free to move and rotate at the top shall be permitted to be designed for active pressure. Design lateral pressure from surcharge loads shall be added to the lateral earth pressure load. Design lateral pressure shall be increased if soils at the site are expansive. Foundation walls shall be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed in accordance with Sections 1805.4.2 and 1805.4.3.

Exception: Foundation walls extending not more than 8 feet (2438 mm) below grade and laterally supported at the top by flexible diaphragms shall be permitted to be designed for active pressure.

TABLE 1610.1

LATERAL SOIL LOAD

DESCRIPTION OF BACKFILL MATERIALcUNIFIED SOIL CLASSIFICATIONDESIGN LATERAL SOIL LOADa (pound per square foot per foot of depth)
Active pressureAt-rest pressure
Well-graded, clean gravels; gravel-sand mixesGW3060
Poorly graded clean gravels; gravel-sand mixesGP3060
Silty gravels, poorly graded gravel-sand mixesGM4060
Clayey gravels, poorly graded gravel-and-clay mixesGC4560
Well-graded, clean sands; gravelly sand mixesSW3060
Poorly graded clean sands; sand-gravel mixesSP3060
Silty sands, poorly graded sand-silt mixesSM4560
Sand-silt clay mix with plastic finesSM-SC45100
Clayey sands, poorly graded sand-clay mixesSC60100
Inorganic silts and clayey siltsML45100
Mixture of inorganic silt and clayML-CL60100
Inorganic clays of low to medium plasticityCL60100
Organic silts and silt clays, low plasticityOLNote bNote b
Inorganic clayey silts, elastic siltsMHNote bNote b
Inorganic clays of high plasticityCHNote bNote b
Organic clays and silty claysOHNote bNote b

For SI: 1 pound per square foot per foot of depth = 0.157 kPa/m, 1 foot = 304.8 mm.

  1. a.Design lateral soil loads are given for moist conditions for the specified soils at their optimum densities. Actual field conditions shall govern. Submerged or saturated soil pressures shall include the weight of the buoyant soil plus the hydrostatic loads.
  2. b.Unsuitable as backfill material.
  3. c.The definition and classification of soil materials shall be in accordance with ASTM D2487.

SECTION1611
RAIN LOADS

1611.1 Design rain loads.

Each portion of a roof shall be designed to sustain the load of rainwater that will accumulate on it if the primary drainage system for that portion is blocked plus the uniform load caused by water that rises above the inlet of the secondary drainage system at its design flow. The design rainfall shall be based on the 100-year hourly rainfall rate indicated in Figure 1611.1 or on other rainfall rates determined from approved local weather data.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0071.jpg(Equation 16-36)

For SI:https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0072.jpg

where:

dh=Additional depth of water on the undeflected roof above the inlet of secondary drainage system at its design flow (i.e., the hydraulic head), in inches (mm).
ds=Depth of water on the undeflected roof up to the inlet of secondary drainage system when the primary drainage system is blocked (i.e., the static head), in inches (mm).
R=Rain load on the undeflected roof, in psf (kN/m2). When the phrase “undeflected roof” is used, deflections from loads (including dead loads) shall not be considered when determining the amount of rain on the roof.
[P] FIGURE 1611.1100-YEAR, 1-HOUR RAINFALL (INCHES) WESTERN UNITED STATESFor SI: 1 inch = 25.4 mm.Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington, DC.

1611.2 Ponding instability.

Susceptible bays of roofs shall be evaluated for ponding instability in accordance with Section 8.4 of ASCE 7.

1611.3 Controlled drainage.

Roofs equipped with hardware to control the rate of drainage shall be equipped with a secondary drainage system at a higher elevation that limits accumulation of water on the roof above that elevation. Such roofs shall be designed to sustain the load of rainwater that will accumulate on them to the elevation of the secondary drainage system plus the uniform load caused by water that rises above the inlet of the secondary drainage system at its design flow determined from Section 1611.1. Such roofs shall also be checked for ponding instability in accordance with Section 1611.2.

SECTION1612
FLOOD LOADS

1612.1 General.

Within flood hazard areas as established in Section 1612.3, all new construction of buildings, structures and portions of buildings and structures, including substantial improvement and restoration of substantial damage to buildings and structures, shall be designed and constructed to resist the effects of flood hazards and flood loads. For buildings that are located in more than one flood hazard area, the provisions associated with the most restrictive flood hazard area shall apply.

1612.2 Definitions.

The following terms are defined in Chapter 2:

BASE FLOOD.

BASE FLOOD ELEVATION.

BASEMENT.

COASTAL A ZONE.

COASTAL HIGH HAZARD AREA.

DESIGN FLOOD.

DESIGN FLOOD ELEVATION.

DRY FLOODPROOFING.

EXISTING STRUCTURE.

FLOOD or FLOODING.

FLOOD DAMAGE-RESISTANT MATERIALS.

FLOOD HAZARD AREA.

FLOOD INSURANCE RATE MAP (FIRM).

FLOOD INSURANCE STUDY.

FLOODWAY.

LOWEST FLOOR.

SPECIAL FLOOD HAZARD AREA.

START OF CONSTRUCTION.

SUBSTANTIAL DAMAGE.

SUBSTANTIAL IMPROVEMENT.

1612.3 Establishment of flood hazard areas.

To establish flood hazard areas, the applicable governing authority shall adopt a flood hazard map and supporting data. The flood hazard map shall include, at a minimum, areas of special flood hazard as identified by the Federal Emergency Management Agency in an engineering report entitled “The Flood Insurance Study for [INSERT NAME OF JURISDICTION],” dated [INSERT DATE OF ISSUANCE], as amended or revised with the accompanying Flood Insurance Rate Map (FIRM) and Flood Boundary and Floodway Map (FBFM) and related supporting data along with any revisions thereto. The adopted flood hazard map and supporting data are hereby adopted by reference and declared to be part of this section.

1612.3.1 Design flood elevations.

Where design flood elevations are not included in the flood hazard areas established in Section 1612.3, or where floodways are not designated, the building official is authorized to require the applicant to:

  1. 1.Obtain and reasonably utilize any design flood elevation and floodway data available from a federal, state or other source; or
  2. 2.Determine the design flood elevation and/or floodway in accordance with accepted hydrologic and hydraulic engineering practices used to define special flood hazard areas. Determinations shall be undertaken by a registered design professional who shall document that the technical methods used reflect currently accepted engineering practice.

1612.3.2 Determination of impacts.

In riverine flood hazard areas where design flood elevations are specified but floodways have not been designated, the applicant shall provide a floodway analysis that demonstrates that the proposed work will not increase the design flood elevation more than 1 foot (305 mm) at any point within the jurisdiction of the applicable governing authority.

1612.4 Design and construction.

The design and construction of buildings and structures located in flood hazard areas, including coastal high hazard areas and coastal A zones, shall be in accordance with Chapter 5 of ASCE 7 and ASCE 24.

1612.5 Flood hazard documentation.

The following documentation shall be prepared and sealed by a registered design professional and submitted to the building official:

  1. 1.For construction in flood hazard areas other than coastal high hazard areas or coastal A zones:
    1. 1.1. The elevation of the lowest floor, including the basement, as required by the lowest floor elevation inspection in Section 110.3.3 and for the final inspection in Section 110.3.10.1.
    2. 1.2. For fully enclosed areas below the design flood elevation where provisions to allow for the automatic entry and exit of floodwaters do not meet the minimum requirements in Section 2.7.2.1 of ASCE 24, construction documents shall include a statement that the design will provide for equalization of hydrostatic flood forces in accordance with Section 2.7.2.2 of ASCE 24.
    3. 1.3. For dry floodproofed nonresidential buildings, construction documents shall include a statement that the dry floodproofing is designed in accordance with ASCE 24.
  2. 2.For construction in coastal high hazard areas and coastal A zones:
    1. 2.1. The elevation of the bottom of the lowest horizontal structural member as required by the lowest floor elevation inspection in Section 110.3.3 and for the final inspection in Section 110.3.10.1.
    2. 2.2. Construction documents shall include a statement that the building is designed in accordance with ASCE 24, including that the pile or column foundation and building or structure to be attached thereto is designed to be anchored to resist flotation, collapse and lateral movement due to the effects of wind and flood loads acting simultaneously on all building components, and other load requirements of Chapter 16.
    3. 2.3. For breakaway walls designed to have a resistance of more than 20 psf (0.96 kN/m2) determined using allowable stress design, construction documents shall include a statement that the breakaway wall is designed in accordance with ASCE 24.

SECTION1613
EARTHQUAKE LOADS

1613.1 Scope.

Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with ASCE 7, excluding Chapter 14 and Appendix 11A. The seismic design category for a structure is permitted to be determined in accordance with Section 1613 or ASCE 7.

Exceptions:

  1. 1.Detached one- and two-family dwellings, assigned to Seismic Design Category A, B or C, or located where the mapped short-period spectral response acceleration, SS, is less than 0.4 g.
  2. 2.The seismic force-resisting system of wood-frame buildings that conform to the provisions of Section 2308 are not required to be analyzed as specified in this section.
  3. 3.Agricultural storage structures intended only for incidental human occupancy.
  4. 4.Structures that require special consideration of their response characteristics and environment that are not addressed by this code or ASCE 7 and for which other regulations provide seismic criteria, such as vehicular bridges, electrical transmission towers, hydraulic structures, buried utility lines and their appurtenances and nuclear reactors.

1613.2 Definitions.

The following terms are defined in Chapter 2:

DESIGN EARTHQUAKE GROUND MOTION.

ORTHOGONAL.

RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATION.

SEISMIC DESIGN CATEGORY.

SEISMIC FORCE-RESISTING SYSTEM.

SITE CLASS.

SITE COEFFICIENTS.

1613.3 Seismic ground motion values.

Seismic ground motion values shall be determined in accordance with this section.

1613.3.1 Mapped acceleration parameters.

The parameters SS and S1 shall be determined from the 0.2 and 1-second spectral response accelerations shown on Figures 1613.3.1(1) through 1613.3.1(8). Where S1 is less than or equal to 0.04 and SS is less than or equal to 0.15, the structure is permitted to be assigned Seismic Design Category A.

FIGURE 1613.3.1(1)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR THE CONTERMINOUS UNITED STATES OF 0.2-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(2)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR THE CONTERMINOUS UNITED STATES OF 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(3)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR HAWAII OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(4)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR ALASKA OF 0.2-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(5)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR ALASKA OF 1.0-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(6)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR PUERTO RICO AND THE UNITED STATES VIRGIN ISLANDS OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(7)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR GUAM AND THE NORTHERN MARIANA ISLANDS OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B
FIGURE 1613.3.1(8)RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS FOR AMERICAN SAMOA OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B

1613.3.2 Site class definitions.

Based on the site soil properties, the site shall be classified as Site Class A, B, C, D, E or F in accordance with Chapter 20 of ASCE 7.

Where the soil properties are not known in sufficient detail to determine the site class, Site Class D shall be used unless the building official or geotechnical data determines Site Class E or F soils are present at the site.

1613.3.3 Site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters.

The maximum considered earthquake spectral response acceleration for short periods, SMS, and at 1-second period, SM1, adjusted for site class effects shall be determined by Equations 16-37 and 16-38, respectively:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0073.jpg(Equation 16-37)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0074.jpg(Equation 16-38)

where:

Fa=Site coefficient defined in Table 1613.3.3(1).
Fv=Site coefficient defined in Table 1613.3.3(2).
SS=The mapped spectral accelerations for short periods as determined in Section 1613.3.1.
S1=The mapped spectral accelerations for a 1-second period as determined in Section 1613.3.1.

TABLE 1613.3.3(1)

VALUES OF SITE COEFFICIENT Faa

SITE CLASSMAPPED SPECTRAL RESPONSE ACCELERATION AT SHORT PERIOD
Ss ≤ 0.25Ss = 0.50Ss = 0.75Ss = 1.00Ss ≥ 1.25
A0.80.80.80.80.8
B1.01.01.01.01.0
C1.21.21.11.01.0
D1.61.41.21.11.0
E2.51.71.20.90.9
FNote bNote bNote bNote bNote b
  1. a.Use straight-line interpolation for intermediate values of mapped spectral response acceleration at short period, Ss.
  2. b.Values shall be determined in accordance with Section 11.4.7 of ASCE 7.

TABLE 1613.3.3(2)

VALUES OF SITE COEFFICIENT FV a

SITE CLASSMAPPED SPECTRAL RESPONSE ACCELERATION AT 1-SECOND PERIOD
S1 ≤ 0.1S1 = 0.2S1 = 0.3S1 = 0.4S1 ≥ 0.5
A0.80.80.80.80.8
B1.01.01.01.01.0
C1.71.61.51.41.3
D2.42.01.81.61.5
E3.53.22.82.42.4
FNote bNote bNote bNote bNote b
  1. a.Use straight-line interpolation for intermediate values of mapped spectral response acceleration at 1-second period, S1.
  2. b.Values shall be determined in accordance with Section 11.4.7 of ASCE 7.

1613.3.4 Design spectral response acceleration parameters.

Five-percent damped design spectral response acceleration at short periods, SDS, and at 1-second period, SD1, shall be determined from Equations 16-39 and 16-40, respectively:

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0075.jpg(Equation 16-39)

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0076.jpg(Equation 16-40)

where:

SMS=The maximum considered earthquake spectral response accelerations for short period as determined in Section 1613.3.3.
SM1=The maximum considered earthquake spectral response accelerations for 1-second period as determined in Section 1613.3.3.

1613.3.5 Determination of seismic design category.

Structures classified as Risk Category I, II or III that are located where the mapped spectral response acceleration parameter at 1-second period, S1, is greater than or equal to 0.75 shall be assigned to Seismic Design Category E. Structures classified as Risk Category IV that are located where the mapped spectral response acceleration parameter at 1-second period, S1, is greater than or equal to 0.75 shall be assigned to Seismic Design Category F. All other structures shall be assigned to a seismic design category based on their risk category and the design spectral response acceleration parameters, SDS and SD1, determined in accordance with Section 1613.3.4 or the site-specific procedures of ASCE 7. Each building and structure shall be assigned to the more severe seismic design category in accordance with Table 1613.3.5(1) or 1613.3.5(2), irrespective of the fundamental period of vibration of the structure, T.

TABLE 1613.3.5(1)

SEISMIC DESIGN CATEGORY BASED ON SHORT-PERIOD (0.2 second) RESPONSE ACCELERATION

VALUE OF SDSRISK CATEGORY
I or IIIIIIV
SDS < 0.167gAAA
0.167g ≤ SDS < 0.33gBBC
0.33g ≤ SDS < 0.50gCCD
0.50g ≤ SDSDDD

TABLE 1613.3.5(2)

SEISMIC DESIGN CATEGORY BASED ON 1-SECOND PERIOD RESPONSE ACCELERATION

VALUE OF SD1RISK CATEGORY
I or IIIIIIV
SD1 < 0.067gAAA
0.067g ≤ SD1 < 0.133gBBC
0.133g ≤ SD1 < 0.20gCCD
0.20g ≤ SD1DDD

1613.3.5.1 Alternative seismic design category determination.

Where S1 is less than 0.75, the seismic design category is permitted to be determined from Table 1613.3.5(1) alone when all of the following apply:

  1. 1.In each of the two orthogonal directions, the approximate fundamental period of the structure, Ta, in each of the two orthogonal directions determined in accordance with Section 12.8.2.1 of ASCE 7, is less than 0.8 Ts determined in accordance with Section 11.4.5 of ASCE 7.
  2. 2.In each of the two orthogonal directions, the fundamental period of the structure used to calculate the story drift is less than Ts.
  3. 3.Equation 12.8-2 of ASCE 7 is used to determine the seismic response coefficient, Cs.
  4. 4.The diaphragms are rigid or are permitted to be idealized as rigid in accordance with Section 12.3.1 of ASCE 7 or, for diaphragms permitted to be idealized as flexible in accordance with Section 12.3.1 of ASCE 7, the distances between vertical elements of the seismic force-resisting system do not exceed 40 feet (12 192 mm).

1613.3.5.2 Simplified design procedure.

Where the alternate simplified design procedure of ASCE 7 is used, the seismic design category shall be determined in accordance with ASCE 7.

1613.4 Alternatives to ASCE 7.

The provisions of Section 1613.4 shall be permitted as alternatives to the relevant provisions of ASCE 7.

1613.4.1 Additional seismic force-resisting systems for seismically isolated structures.

Add the following exception to the end of Section 17.5.4.2 of ASCE 7:

Exception: For isolated structures designed in accordance with this standard, the structural system limitations including structural height limits, in Table 12.2-1 for ordinary steel concentrically braced frames (OCBFs) as defined in Chapter 11 and ordinary moment frames (OMFs) as defined in Chapter 11 are permitted to be taken as 160 feet (48 768 mm) for structures assigned to Seismic Design Category D, E or F, provided that the following conditions are satisfied:

  1. 1.The value of RI as defined in Chapter 17 is taken as 1.
  2. 2.For OMFs and OCBFs, design is in accordance with AISC 341.

1613.5 Amendments to ASCE 7.

The provisions of Section 1613.5 shall be permitted as an amendment to the relevant provisions of ASCE 7.

1613.5.1 Transfer of anchorage forces into diaphragm.

Modify ASCE 7 Section 12.11.2.2.1 as follows:

12.11.2.2.1 Transfer of anchorage forces into diaphragm. Diaphragms shall be provided with continuous ties or struts between diaphragm chords to distribute these anchorage forces into the diaphragms. Diaphragm connections shall be positive, mechanical or welded. Added chords are permitted to be used to form subdiaphragms to transmit the anchorage forces to the main continuous cross-ties. The maximum length-to-width ratio of a wood, wood structural panel or untopped steel deck sheathed structural subdiaphragm that serves as part of the continuous tie system shall be 2.5 to 1. Connections and anchorages capable of resisting the prescribed forces shall be provided between the diaphragm and the attached components. Connections shall extend into the diaphragm a sufficient distance to develop the force transferred into the diaphragm.

1613.6 Ballasted photovoltaic panel systems.

Ballasted, roof-mounted photovoltaic panel systems need not be rigidly attached to the roof or supporting structure. Ballasted non-penetrating systems shall be designed and installed only on roofs with slopes not more than one unit vertical in 12 units horizontal. Ballasted nonpenetrating systems shall be designed to resist sliding and uplift resulting from lateral and vertical forces as required by Section 1605, using a coefficient of friction determined by acceptable engineering principles. In structures assigned to Seismic Design Category C, D, E or F, ballasted nonpenetrating systems shall be designed to accommodate seismic displacement determined by nonlinear response-history analysis or shake-table testing, using input motions consistent with ASCE 7 lateral and vertical seismic forces for nonstructural components on roofs.

SECTION1614
ATMOSPHERIC ICE LOADS

1614.1 General.

Ice-sensitive structures shall be designed for atmospheric ice loads in accordance with Chapter 10 of ASCE 7.

SECTION1615
STRUCTURAL INTEGRITY

1615.1 General.

High-rise buildings that are assigned to Risk Category III or IV shall comply with the requirements of this section. Frame structures shall comply with the requirements of Section 1615.3. Bearing wall structures shall comply with the requirements of Section 1615.4.

1615.2 Definitions.

The following words and terms are defined in Chapter 2:

BEARING WALL STRUCTURE.

FRAME STRUCTURE.

1615.3 Frame structures.

Frame structures shall comply with the requirements of this section.

1615.3.1 Concrete frame structures.

Frame structures constructed primarily of reinforced or prestressed concrete, either cast-in-place or precast, or a combination of these, shall conform to the requirements of Section 4.10 of ACI 318. Where ACI 318 requires that nonprestressed reinforcing or prestressing steel pass through the region bounded by the longitudinal column reinforcement, that reinforcing or prestressing steel shall have a minimum nominal tensile strength equal to two-thirds of the required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.

Exception: Where concrete slabs with continuous reinforcement having an area not less than 0.0015 times the concrete area in each of two orthogonal directions are present and are either monolithic with or equivalently bonded to beams, girders or columns, the longitudinal reinforcing or prestressing steel passing through the column reinforcement shall have a nominal tensile strength of one-third of the required one-way vertical strength of the connection of the floor or roof system to the column in each direction of beam or slab reinforcement passing through the column.

1615.3.2 Structural steel, open web steel joist or joist girder, or composite steel and concrete frame structures.

Frame structures constructed with a structural steel frame or a frame composed of open web steel joists, joist girders with or without other structural steel elements or a frame composed of composite steel or composite steel joists and reinforced concrete elements shall conform to the requirements of this section.

1615.3.2.1 Columns.

Each column splice shall have the minimum design strength in tension to transfer the design dead and live load tributary to the column between the splice and the splice or base immediately below.

1615.3.2.2 Beams.

End connections of all beams and girders shall have a minimum nominal axial tensile strength equal to the required vertical shear strength for allowable stress design (ASD) or two-thirds of the required shear strength for load and resistance factor design (LRFD) but not less than 10 kips (45 kN). For the purpose of this section, the shear force and the axial tensile force need not be considered to act simultaneously.

Exception: Where beams, girders, open web joist and joist girders support a concrete slab or concrete slab on metal deck that is attached to the beam or girder with not less than 3/8-inch-diameter (9.5 mm) headed shear studs, at a spacing of not more than 12 inches (305 mm) on center, averaged over the length of the member, or other attachment having equivalent shear strength, and the slab contains continuous distributed reinforcement in each of two orthogonal directions with an area not less than 0.0015 times the concrete area, the nominal axial tension strength of the end connection shall be permitted to be taken as half the required vertical shear strength for ASD or one-third of the required shear strength for LRFD, but not less than 10 kips (45 kN).

1615.4 Bearing wall structures.

Bearing wall structures shall have vertical ties in all load-bearing walls and longitudinal ties, transverse ties and perimeter ties at each floor level in accordance with this section and as shown in Figure 1615.4.

FIGURE 1615.4LONGITUDINAL, PERIMETER, TRANSVERSE AND VERTICAL TIES

1615.4.1 Concrete wall structures.

Precast bearing wall structures constructed solely of reinforced or prestressed concrete, or combinations of these shall conform to the requirements of Sections 16.2.4 and 16.2.5 of ACI 318.

1615.4.2 Other bearing wall structures.

Ties in bearing wall structures other than those covered in Section 1615.4.1 shall conform to this section.

1615.4.2.1 Longitudinal ties.

Longitudinal ties shall consist of continuous reinforcement in slabs; continuous or spliced decks or sheathing; continuous or spliced members framing to, within or across walls; or connections of continuous framing members to walls. Longitudinal ties shall extend across interior load-bearing walls and shall connect to exterior load-bearing walls and shall be spaced at not greater than 10 feet (3038 mm) on center. Ties shall have a minimum nominal tensile strength, TT, given by Equation 16-41. For ASD the minimum nominal tensile strength shall be permitted to be taken as 1.5 times the allowable tensile stress times the area of the tie.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0077.jpg(Equation 16-41)

where:

L=The span of the horizontal element in the direction of the tie, between bearing walls, feet (m).
w=The weight per unit area of the floor or roof in the span being tied to or across the wall, psf (N/m2).
S=The spacing between ties, feet (m).
αT=A coefficient with a value of 1,500 pounds per foot (2.25 kN/m) for masonry bearing wall structures and a value of 375 pounds per foot (0.6 kN/m) for structures with bearing walls of cold-formed steel light-frame construction.

1615.4.2.2 Transverse ties.

Transverse ties shall consist of continuous reinforcement in slabs; continuous or spliced decks or sheathing; continuous or spliced members framing to, within or across walls; or connections of continuous framing members to walls. Transverse ties shall be placed no farther apart than the spacing of load-bearing walls. Transverse ties shall have minimum nominal tensile strength TT, given by Equation 16-41. For ASD the minimum nominal tensile strength shall be permitted to be taken as 1.5 times the allowable tensile stress times the area of the tie.

1615.4.2.3 Perimeter ties.

Perimeter ties shall consist of continuous reinforcement in slabs; continuous or spliced decks or sheathing; continuous or spliced members framing to, within or across walls; or connections of continuous framing members to walls. Ties around the perimeter of each floor and roof shall be located within 4 feet (1219 mm) of the edge and shall provide a nominal strength in tension not less than Tp, given by Equation 16-42. For ASD the minimum nominal tensile strength shall be permitted to be taken as 1.5 times the allowable tensile stress times the area of the tie.

https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0078.jpg(Equation 16-42)

For SI:https://cdn-codes-pdf.iccsafe.org/bundles/document/new_document_images/542/Eq0079.jpg

where:

w=As defined in Section 1615.4.2.1.
βT=A coefficient with a value of 16,000 pounds (7200 kN) for structures with masonry bearing walls and a value of 4,000 pounds (1300 kN) for structures with bearing walls of cold-formed steel light-frame construction.

1615.4.2.4 Vertical ties.

Vertical ties shall consist of continuous or spliced reinforcing, continuous or spliced members, wall sheathing or other engineered systems. Vertical tension ties shall be provided in bearing walls and shall be continuous over the height of the building. The minimum nominal tensile strength for vertical ties within a bearing wall shall be equal to the weight of the wall within that story plus the weight of the diaphragm tributary to the wall in the story below. No fewer than two ties shall be provided for each wall. The strength of each tie need not exceed 3,000 pounds per foot (450 kN/m) of wall tributary to the tie for walls of masonry construction or 750 pounds per foot (140 kN/m) of wall tributary to the tie for walls of cold-formed steel light-frame construction.

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