METAL BUILDING SYSTEMS：YESTERDAY AND TODAY.pdf

CHAPTER 1 METAL BUILDING SYSTEMS: YESTERDAY AND TODAY 1.1THE ORIGINS 1.1.1Whats in a Name? Some readers may not be clear on the exact subject of our discussion. Indeed, even a few design pro- fessionals tend to be confused by the term metal building system. “Are we talking about a structural steel building? Just what kind of a building is it? Is it a modular building? Or prefabricated? Or maybe pan- elized? Is it the same as a pre-engineered building?”you might hear a lot. Though all of these terms involve some sort of structure designed and partially assembled in the shop by its manufacturer, they refer to quite different concepts. Before proceeding further, the distinctions need to be sorted out. Modular buildings consist of three-dimensional plant-produced segments that are shipped to a site for erection and final assembly by a field contractor. One of the most popular materials for modular buildings is wood, and such factory-produced units are common in housing construction. Another common application involves precast concrete formed into modular stackable prison cells that are completely prewired and prefinished. These modules are composed of four walls and a ceiling that also serves as a floor for the unit above. Modular steel systems, consisting of three- dimensional column and joist modules bolted together in the field, were marketed in the 1960s and 1970s, with limited success. Modern metal building systems, however, cannot be called modular. Panelized systems include two-dimensional building components such as wall, floor, and roof sections, produced at the factory and field-assembled. In addition to the “traditional” precast con- crete, modern exterior wall panels can be made of such materials as metals, brick, stone, and com- posite assemblies known as EIFS (Exterior Insulation and Finish System). While the exterior “skins” of metal buildings generally employ panels, the term panelized does not capture the essence of metal building systems and should not be used to describe them. Prefabricated buildings are made and substantially assembled at the factory. While the metal building industry has its roots in prefabricated buildings, this type today includes mostly small struc- tures transported to the site in one piece, such as toll booths, kiosks, and household sheds. Modern metal buildings are not prefabricated in that sense. As we shall see, the changes in terminology parallel the evolution of the industry itself. 1.1.2The First Metal Buildings The first building with an iron frame was the Ditherington Flax Mill constructed in Shrewsbury, England, in 1796.1Cast-iron columns were substituted for the usual timber in a calico mill con- structed in nearby Derby 3 years earlier. These experiments with iron were prompted by frequent devastating fires in British cotton mills of the time. Once the fire-resistive properties of metal in buildings had been demonstrated, wrought-iron and cast-iron structural components gradually became commonplace. 1 In the middle of the nineteenth century, experimentation with rolling of iron beams finally cul- minated in construction of the Cooper Union Building in New York City, the first building to utilize hot-rolled steel beams. In 1889, Rand McNally Building in Chicago became the first skyscraper with all-steel framing.2 Prefabricated metal buildings first appeared at about the same time. As early as the mid-nineteenth century, “portable iron houses” were marketed by Peter Naylor, a New York metal-roofing contractor, to satisfy housing needs of the 1848 California Gold Rush fortune seekers; at least several hundred of those structures were sold. A typical iron house measured 15 by 20 ft and, according to the adver- tisements, could be put together in less than a day by a single man. Naylors ads claimed that his struc- tures were cheaper than wood houses, fireproof, and more comfortable than tents.1Eventually, of course, Californias timber industry got established and Naylors invention lost its market. In the first two decades of the twentieth century, prefabricated metal components were mostly used for garages. Founded in 1901, Butler Manufacturing Company developed its first prefabricated build- ing in 1909 to provide garage space for the ubiquitous Model T. That curved-top building used wood framing covered with corrugated metal sheets. To improve fire resistance of its buildings, the compa- ny eventually switched to all-metal structures framed with corrugated curved steel sheets. The arch- like design, inspired by cylindrical grain bins, influenced many other prefabricated metal buildings.3 In 1917, the Austin Company of Cleveland, Ohio, began marketing 10 standard designs of a fac- tory building that could be chosen from a catalog. The framing for these early metal buildings con- sisted of steel columns and roof trusses which had been designed and detailed beforehand. The Austin buildings were true forebears of what later became known as pre-engineered construction, a new concept that allowed for material shipment several weeks earlier, because no design time needed to be spent after the sale. Austin sold its buildings through a newly established network of district sales offices.4 In the early 1920s, Liberty Steel Products Company of Chicago offered a prefabricated factory building that could be quickly erected. The LIBCO ad pictured the building and boasted: “10 men put up that building in 20 hours. Just ordinary help, and the only tools needed were monkey wrenches.”1 By that time, steel was an established competitor of other building materials. The first edition of Standard Specification for the Design, Fabrication and Erection of Structural Steel for Buildings was published by the newly formed American Institute of Steel Construction in 1923. Several metal-building companies were formed in the 1920s and 1930s to satisfy the needs of the oil industry by making buildings for equipment storage; some of these companies also produced farm buildings. For example, Star Building Systems was formed in 1927 to meet the needs of oil drillers in the Oklahoma oil boom. Those early metal buildings were rather small8 by 10 ft or 12 by 14 ft in planand were framed with trusses spanning between trussed columns. The wall panels, typically 8 by 12 ft in size and spanning vertically, were made of corrugated galvanized sheet sec- tions bounded by riveted steel angles. 1.1.3The War Years and After During World War II, larger versions of those metal buildings were used as aircraft hangars. Their columns were made of laced angles, perhaps of 6 by 4 by 3?8in in section, and roof structure con- sisted of bowstring trusses. Military manuals were typically used for design criteria. These buildings, unlike their predecessors, relied on intermediate girts for siding support. The best-known prefabricated building during World War II was the Quonset hut, which became a household word. Quonset huts were mass-produced by the hundreds of thousands to meet a need for inexpensive and standardized shelter (Fig. 1.1). Requiring no special skills, these structures were assembled with only hand tools, andwith no greater effortcould be readily dismantled, moved, and reerected elsewhere. The main producer of Quonset huts was Stran-Steel Corp., a pioneering metal-building company that developed many “firsts” later. Quonset huts followed GIs wherever they went and attested to the fabled benefits American mass production could bestow. Still, these utterly utilitarian, simple, and uninspiring structures were widely perceived as being cheap and ugly. This impression still lingers in the minds of many,even though quite a few Quonset huts have survived for over half a century. 2CHAPTER ONE The negative connotation of the term prefabricated building was reinforced after the war ended and the next generation of metal buildings came into being. Like the Quonset hut, this new generation filled a specific need: the postwar economic boom required more factory space to satisfy the pent-up demand for consumer products. The vast sheet-metal industry, well-organized and efficient, had just lost its biggest customerthe military. Could the earlier sheet-metal prefabricated buildings and the Quonset hut, as well as the legendary Liberty Ship quickly mass-produced at Kaisers California ship- yard, provide a lesson for a speedy making of factory buildings? The answer was clearly: “Yes!” In the new breed of sheet-metal-clad buildings, the emphasis was, once again, on rapid construction and low cost, rather than aesthetics. It was, after all, the contents of these early metal structures that was important, not the building design. Using standardized sheet-metal siding and roofing, supported by gabled steel trusses and columnsa 4:12 roof pitch was commonthe required building volumes could be created relatively quickly. In this corrugated, galvanized environment, windows, insulation, and extensive mechanical systems were perceived as unnecessary frills. The sheer number of these pre- fabricated buildings, cloned in the least imaginative mass-production spirit, was overwhelming. Eventually, the economic boom subsided, but the buildings remained. Their plain appearance was never an asset. As time passed and these buildings frayed, they conveyed an image of being worn out and out of place. Eventually, prefabricated buildings were frowned upon by almost everyone. The impression of cheapness and poor quality that characterized the Quonset hut was powerfully reinforced by the “boom factories.” This one-two punch knocked respectability out of “prefabricated buildings” and may have forever saddled the term with negative connotations. The metal building industry understood the problem. It was looking for another name. 1.1.4Pre-Engineered Buildings The scientific-sounding term pre-engineered buildings came into being in the 1960s. The buildings were “pre-engineered” because, like their ancestors, they relied upon standard engineering designs for a limited number of off-the-shelf configurations. METAL BUILDING SYSTEMS:YESTERDAY AND TODAY3 FIGURE 1.1Quonset hut, Quonset Point, R.I. (Photo: David Nacci.) Several factors made this period significant for the history of metal buildings. First, the improving technology was constantly expanding the maximum clear-span capabilities of metal buildings. The first rigid-frame buildings introduced in the late 1940s could span only 40 ft. In a few years, 50-, 60-, and 70-ft buildings became possible. By the late 1950s, rigid frames with 100-ft spans were made.5 Second, in the late 1950s, ribbed metal panels became available, allowing the buildings to look dif- ferent from the old tired corrugated appearance. Third, colored panels were introduced by Stran-Steel Corp. in the early 1960s, permitting some design individuality. At about the same time, continuous- span cold-formed Z purlins were invented (also by Stran-Steel), the first factory-insulated panels were developed by Butler, and the first UL-approved metal roof appeared on the market.1 And last, but not least, the first computer-designed metal buildings also made their debut in the early 1960s. With the advent of computerization, the design possibilities became almost limitless. All these factors combined to produce a new metal-building boom in the late 1950s and early 1960s. As long as the purchaser could be restricted to standard designs, the buildings could be properly called pre-engineered. Once the industry started to offer custom-designed metal buildings to fill the particular needs of each client, the name pre-engineered building became somewhat of a misnomer. In addition, this term was uncomfortably close to, and easily confused with, the unsophisticated pre- fabricated buildings, with which the new industry did not want to be associated. Despite the fact that the term pre-engineered buildings is still widely used, and will be often found even in this book, the industry now prefers to call its product metal building systems. 1.2METAL BUILDING SYSTEMS Why “systems”? Is this just one more application of the cyber-speak indiscriminately applied to describe everything made of more than one component? Nowadays, even the words paint system or floor cleaning system do not provoke a smile. In all fairness, metal building system satisfies the classical definition of a system as an interde- pendent group of items forming a unified whole. In a modern metal building, the components such as walls, roof, main and secondary framing, and bracing are designed to work together. A typical assembly of a metal building is shown in Fig. 1.2. In addition to a brief discussion here, the roles played by various metal building components are examined in Chap. 3. A buildings first line of defense against the elements consists of the wall and roof materials. These elements also resist structural loads, such as wind and snow, and transfer the loads to the sup- porting secondary framing. The secondary framingwall girts and roof purlinscollects the loads from the wall and roof covering and distributes them to the main building frames, providing them with valuable lateral restraint along the way. The main structural frames, which consist of columns and rafters, carry the snow, wind, and other loads to the building foundations. The wall and roof brac- ing provides stability for the whole building. Even the fasteners are chosen to be compatible with the materials being secured and are engineered by the manufacturers. The systems approach, therefore, is clearly evident. The term metal building system is proper and well-deserved. Over time, it will undoubtedly displace the still-common name, pre-engineered buildings. 1.3SOME STATISTICS Today, metal building systems dominate the low-rise nonresidential market. According to the Metal Building Manufacturers Association (MBMA), pre-engineered structures comprised 65 percent of all new one- and two-story buildings with areas of up to 150,000 ft2in 1995. The 1995 metal build- ing sales of MBMA members totaled $2.21 billion; 355 million ft2of space was put in place. Large industrial buildings with areas of over 150,000 ft2added another 34.3 million ft2of new space.6The 2000 sales were $2.5 billion. 4CHAPTER ONE Metal building systems serve many applications. Commercial uses have historically accounted for 30 to 40 percent of metal building sales. This category includes not only the familiar beige warehouses (Fig. 1.3), but also office buildings, garages, supermarkets, and retail stores (Figs. 1.4, 1.5, and 1.6). Another 30 to 40 percent of metal building systems are found in manufacturing usesfactories, mate- rial recycling facilities, automotive and chemical plants (Figs. 1.7, 1.8, and 1.9). Some 10 to 15 per- cent of pre-engineered buildings are used for community purposes: schools, town halls, and even churches (Figs. 1.10 and 1.11). The catch-all “miscellaneous” use includes everything else and, notably, agricul