MODERN STRUCTURAL HISTORY
AN ARCHITECTURAL LOOK AT SPAN AND HEIGHT
Modern structural architecture was born 146 years ago in London, England with the construction of William Paxton’s celebrated Crystal Palace (see figure). Although it was a very large building with significant spans, the Crystal Palace was assembled and dismantled with unheard of efficiency due to its modular de-sign and use of prefabricated components. Also, unlike the masonry buildings of its time, only an iron lattice work supported the uniform sheets of glass in wood used throughout the building. This famous glass and iron building presaged the prefabrication and demountability of metal frame construction which has totally altered the structure and design of architecture in the twentieth century. The de-sign of the Crystal Palace was so revolutionary that it remained at the forefront of building progress until the erection of Eiffel’s timeless tower in Paris in 1889.
When the Eiffel Tower was completed it soared nearly twice as high as the Washington Monument, the tallest structure during that time. Through his knowl-edge gained from building high railroad viaducts through the windy valleys of the Massif Central, Eiffel designed the nearly transparent structure with graceful ta-pering lines to resist the force of wind (see figure). This tower was not only the first truly large-scale industrialized construction project, but also exemplified harmoni-ous integration of architecture and engineering. For the first time in history the design of a large public project was not dictated by formalistic preconceptions, but was truly an abstract form rooted in the laws of physics. Eiffel’s ingenuity also made possible the physical construction of this project. All the sections were pre-fabricated off-site because of time constraints and the enormous size of the struc-ture. Additionally, hydraulic jacks were placed at the base of each leg so the tower could be raised or lowered into perfect alignment – an invaluable idea since two and a half million rivets, locking 12,000 pieces together, needed to line up perfectly.
In the United States, bridge construction pushed the envelope of structural knowledge with singular daring: the most famous during this time being John and Washington Roebling’s Brooklyn Bridge, another engineering triumph and work of art. Hailed as the eighth wonder of the world when completed, the Brooklyn Bridge was the world’s longest suspension bridge with a span of 1600 feet. Its two massive Gothic towers soared 276 feet above the river, and the four main cables suspended from these towers were an enormous 16 inches in diameter. One of John Roebling’s many innovations, the slanted cable or “stay”, was used along with the suspension cables to help keep the roadway steady in high winds (see figure). He also invented a “traveling-wheel” rig for this project which enabled workers to lay looped cable wire one loop at a time – a method continued by bridge engineers to this day. This invention eliminated the necessity of hoisting heavy cable, and the possible harm inflicted on the towers due to hoisting.
The experiments and calculations of the bridge engineers led logically to the evolution of the contemporary steel-framed skyscraper – a unique American devel-opment centered in Chicago in the 1880’s. There were several factors which led to the development of the skyscraper. Elisha’s Otis’s invention of a reliably safe el-evator, and the soaring cost of land in the large metropolitan areas were two promi-nent ones, but the heights of the modern skyscrapers would not have been possible without the evolution of engineering knowledge with respect to the new materials iron and steel. Beginning with William LeBaron Jenney’s Home Insurance Build-ing in 1885 (see figure), a building’s design incorporated an internal steel frame to carry its weight. Earlier cast-iron and wrought iron frames had been used success-fully with masonry walls; however, it was the lighter internal steel skeleton, with significantly higher compression and tensile strengths, that made tall buildings practical, changing the urban skyline throughout the world.
Bridges and towers have continued to be on the forefront of technology and architecture in the area of structural steel design. One of the first people who un-derstood the significance of this new engineering, and used it artistically was Louis Sullivan around the turn of the century. He raised the technical achievement of the skyscraper to the level of great architecture. The 1920’s gave us the elegant Chrysler Building, while the Empire State Building and the Golden Gate Bridge were com-pleted in the 1930’s. All are known for their architectural greatness, and each broke the record for height and span respectively. Mies van der Rohe designed the Seagram Building in 1958, the prototype of the glass-and-metal, flat-topped, high rise. The awe-inspiring Verrazano Narrows Bridge, completed in 1964, is currently the record holder for the longest span in the world. The exterior x-braced John Hancock Cen-ter, designed by Fazlur Khan and Bruce Graham, was finished in 1968, and set the precedent for the 1980’s exterior braced Hongkong Bank (see figure) by Norman Foster and Shanghai Bank designed by I.M. Pei.
The iron and steel frame changed the world or architecture by significantly increasing the limits of height and span possible, but when steel bars were embed-ded in concrete to form reinforced concrete, a radical new style and structure was born. Concrete alone had been used by Roman builders to enclose large open spaces. The most famous example of this being the concrete dome of the Pantheon, which
Home Insurance Building
had a span of 144 feet. Notwithstanding, reinforced concrete’s unparalleled strength and unique monolithic nature made possible the enclosure of space with unprec-edented spans. These spans could be achieved by methods such as thin-shelled vaults and free-curving shapes impossible to the traditional post and beam con-struction. Through the work of architects like Nervi, Candela, Saarinen, and Calatrava reinforced concrete has shown its true potential, and has been lifted to a great architectural form of its own. A building which exemplifies reinforced concrete’s unique architectural form is Pier Luigi Nervi’s Palazzetto dello Sport (see figure), whose considerable span is supported by striking y-shaped columns along the entire perimeter of the roof. Ganter Bridge in Switzerland (see figure) shows the potential of reinforced concrete for bridge design and other industrial projects.
Throughout the ages technology has continued to enable new and fascinat-ing possibilities for architects and engineers. Normally the potential of a new in-novation is not realized in its early stages. The reasons for this are mainly two-fold: the designers need time to fully understand the new technology, and our natural resistance to change requires some time be allowed for adjustment. Many Parisian’s felt the Eiffel Tower was an eye sore when it was first completed, and critics ini-tially called the new structures using reinforced concrete “unsubstantial and aes-thetically unsatisfactory.” The complete readjustments of structural depth, in rela-tion to the loads and stresses made possible by steel and reinforced concrete, of-fended traditional sensibilities.
Changes in building technology have increased dramatically in the years since the dawn of the Crystal Palace. People have adjusted themselves to accept change more willingly because it is so common. In fact many would argue that one now has to be willing to accept change to survive. Even though new materials prompt original structures, the architecture of a building will always be based on the solidity of the design and attention to detail. Pier Luigi Nervi stated it elo-quently, “Today no one doubts that a work of architecture must be a stable, unified, enduring organism, in accordance with its surroundings and the functions that it must satisfy, balanced in all parts, sincere in its supporting structure and technical elements, and at the same time capable of giving that indefinable emotion that we call beauty. . . and that this result can be achieved with a liberty of means unsus-pected yesterday.”
RIVER’S EDGE SPORTS COMPLEX THE EXISTING SITE CONDITIONS
The River’s Edge Sports Complet is located in southwest Virginia, a relatively temperate climate with long pleasant spring and falls.
Winters are cold with normal lows in the mid 20’s Fahrenheit. Snow is common, the average annual snow fall in Roanoke is 23 inches, but amounts vary greatly depending on location. Summers are hot and humid with the normal highs reaching nearly 90 degrees Fahren- heit. According to BOCA, the win speed used for design is 70 m.p.h., and the average yearly precipitation is around 40 inches.
Roanoke is the largest city in Virginia west of Richmond with a population of nearly 100,000. It is the center of the Roanoke Valley, a 270,000 population area also comprised of Roanoke, Craig and Botetourt counties, the Town of Vinton and City of Salem. Relative to the middle of downtown Roanoke, the River’s Edge Sports Complex is located slightly to the southeast, just off the 581 bypass and Route 220. An important geological feature of this city and the complex is the Roanoke River, which flows through the heart of each.
MODERN STRUCTURAL HISTORY
RIVER’S EDGE SPORTS COMPLEX (SITE)
RELATED STRUCTURES AND DESIGN PROCESS
THE BRIDGE BUILDING AND FACILITIES
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