The World Trade Center—Model for the Future?
WHATEVER else they may be, the twin towers of the World Trade Center are colossal. Each tower is 110 stories, soaring upward from the sidewalk 1,350 feet—more than a quarter of a mile in the air! They completely dominate the famous New York skyline.
But it is not only their tremendous height that dwarfs the surrounding skyscrapers. It is also their monstrous bulk. Each building is a 209-foot square—about an acre in area. And since the buildings rise in a sheer, uninterrupted line, every one of the more than 200 floors has about an acre of space! That is enough area on each floor for more than nine professional basketball courts!
The World Trade Center, however, includes much more than the twin towers. It is on a sixteen-acre site on the Hudson River side of lower Manhattan island. Already included in the $800 million complex is the eight-story U.S. Customs Building and the nine-story Northeast Plaza Building. Yet to be constructed are the Southeast Plaza Building and a hotel. Eventually all six buildings will be situated around the large five-acre plaza.
At its formal dedication on April 4, 1973, the World Trade Center housed 304 firms employing 7,000 persons. More than twice that number of persons are now working there. Less than half the floor space is presently occupied; many floors are yet unfurnished. Completion is scheduled for sometime in 1975. Eventually 50,000 persons are to work at the Center, and some 80,000 business personnel and sightseers are expected to visit daily.
But why build such a mammoth complex? Is it practical? Are they, as claimed, “the buildings of the oncoming 21st century”?
Purpose and Motives
The complex was built as a central headquarters for firms representing every essential world trade service and activity. Thus, exporters, importers, freight forwarders, customhouse brokers, international banks, and numerous other world-trade-oriented firms can now be located under one roof. As Jack Zwick, head of the World Trade Institute, noted: “It’s all intended to make trading easier and make people better able to plan trading strategies.”
But why such huge buildings? Harry B. Helmsley, a director of the company that manages the Empire State Building, undoubtedly identified the reason when he said: “The image of having the tallest building is important.”
In October 1970 the Trade Center’s north tower eclipsed the Empire State to become the tallest building in the world. But that distinction was short-lived. For just last spring the Sears, Roebuck & Co. building in Chicago topped out at 1,450 feet, a hundred feet higher than the twin towers.
However, the competition is not over. As Helmsley noted: “We are considering plans to add to the Empire State.” Interestingly, last year certain workers at the World Trade Center were speculating regarding the apparent slowness in completing the south tower. Some wondered whether its height might be increased to regain the distinction of being the world’s tallest building.
New Generation of Skyscrapers
The present can-you-top-this skyscraper competition is reminiscent of what occurred a little over forty years ago. In 1931, as the economic depression worsened, the Empire State Building reached 1,250 feet, surpassing the 1,048-foot-high Chrysler Building. Soon afterward really tall skyscraper construction ceased, leaving New York city with seventeen buildings over 600 feet high.
More than twenty-five years later, in 1960, New York still had only seventeen buildings above 600 feet. Then new construction began. In 1970, New York city alone was in the process of erecting nine buildings over 600 feet high! Now the city has at least forty skyscrapers in that category! Chicago has ten; Los Angeles, four, and several other cities have two or three.
Obviously, few of these new skyscrapers were seeking to break a record. Only five of them are over 1,000 feet. Why, then, have so many tall buildings been put up? The president of one land development corporation explained: “The greatest plus of the skyscraper in highly concentrated cities is economic.” Land, for example, in downtown Atlanta, sells for $150 a square foot, and as one developer noted: “70 stories gives better productivity.”
Improvements in building technology also are a major factor in the skyscraper boom. More efficient elevator systems save on interior space. Use of lightweight cement and prefabrication methods have been important. Stiffer steel frames provide greater rigidity and strength. The Trade Center’s twin towers, for instance, have a maximum sway in high winds of eleven inches, compared to fifteen inches for older skyscrapers.
Owing to such improvements, it is reportedly feasible to put up skyscrapers 200 or more stories high. “We could start erecting a mile-high structure next year,” says L.E. Robertson, partner in the New York engineering firm that put up the World Trade Center.
Thus, the question is not whether man can erect gigantic building complexes modeled after the World Trade Center. But, rather, is the World Trade Center a good model to imitate?
However, before examining this question, consider what a remarkable achievement the World Trade Center is.
Revolutionary Construction
In 1962, early in the new skyscraper boom, the legislatures of New York and New Jersey directed that the World Trade Center be built. When the design plans were unveiled in 1964, the project was considered revolutionary, both in size and in engineering concepts. “It’s a pioneering effort,” said Mario Salvadori, head of the technology division in the Columbia University Architecture School.
True, some of the construction techniques had already been applied in certain earlier buildings. But the application of so many new techniques on one project is considered a tremendous technological achievement. Preparation for construction was itself an undertaking requiring unusual techniques.
Built in “the Bathtub”
It was the type of land that made construction particularly difficult. In the 1700’s the land upon which the twin towers now rest had actually been beneath the Hudson River! By 1890, however, landfill had made the area part of Manhattan island. Thus, excavation of the site involved removal of the landfill “garbage” from several generations, as well as Hudson River silt loaded with such underground obstructions as old wharves and parts of ships.
Down some seventy feet and more beneath this debris is the bedrock into which the skyscrapers had to be anchored. So, during excavation, the problem was to prevent the unsettling of nearby streets and buildings owing to the unstable land. Also, there was the question of how to prevent underground water from seeping in as excavation proceeded. The answer was “the bathtub.”
Work on “the bathtub” began even before the 164 buildings were removed from the fourteen-block section that the World Trade Center would occupy. This “bathtub” was a huge cement wall that extended down and was anchored into the bedrock. The wall stretched around the major part of the construction site, which had once been submerged beneath the Hudson River.
To build this underground wall, excavating equipment dug, section by section, a three-foot-wide trench all the way down and into bedrock. As the excavated material was removed from a section, a bentonite slurry, the consistency of pea soup, was piped into the trench. This slurry held back the ground water and maintained the sides of the trench so that shoring was unnecessary. Next, preassembled seven-story-high cages of reinforced steel were lowered into the slurry. Then concrete was fed into the bottom of the trench through a pipe, forcing the slurry out of the trench.
Finally, the result was a below-ground three-foot-wide concrete wall that stretched 3,100 feet around the site to be excavated. Excavation now proceeded within this huge “bathtub.” It was really, in effect, a four-sided dam. It kept the water out as excavation proceeded, rather than hold the water inside as does a regular bathtub. This “bathtub” was tremendous in size. More than 1.2 million cubic yards of material were excavated from within it and dumped into the Hudson River, to create 23.5 acres of new land!
As excavation proceeded, the underground railroad that crossed the excavation site in two cast-iron tubes became exposed. These tubes had to be jacked up and supported while digging went on around and beneath them. Thus, railroad service proceeded as usual, carrying more than 80,000 passengers daily through “the bathtub” even as excavation continued!
Eventually the tracks were relocated under the Trade Center, and the old tunnels were removed. In July 1971 the new World Trade Center train terminal was opened. Also located in this six-floor basement is a garage for almost 2,000 cars, with truck docks, storage areas and space for international shops and restaurants.
Other Construction Features
In time the building foundations were sunk into bedrock. And from that base the twin towers rose rapidly. At the peak of construction as many as 3,500 men worked on the project, and many are still working on it. The first steel for the north tower was placed in August 1968, and six months later work began on the south tower.
Huge cranes swung large, twenty-two-ton prefabricated steel panels into place. These formed the exterior walls of the towers. Just to put siding on the walls required 2.2 million square feet of aluminum, equivalent to that needed to cover 9,000 homes. Also, over 600,000 square feet of glass were required for the 43,600 floor-to-ceiling windows. Unmanned automatic window washers keep them clean.
Unlike conventional skyscrapers, which have the weight-bearing columns on the inside, the towers’ exterior walls carry most of the buildings’ weight. The only columns inside are in the core, which contains the elevators. Thus the floors have a maximum of open, column-free space.
Another unique construction feature is the 102 elevators in each building. In conventional skyscrapers, elevator shafts service all the floors. This consumes large areas of floor space. The World Trade Center divided each tower building into three zones, and introduced a system of express and local elevators connected by transfer points called “skylobbies.” As a result, space requirements for elevator shafts were considerably reduced.
Truly the World Trade Center is a technological marvel. But is it really a practical model for the future?
How Really Desirable?
Consider what F. L. Codella, the vice-president of an architectural firm, said: “Putting up a new tall-building project in a city is like plugging in a major appliance in your home. It affects everything around it.”
The World Trade Center is indeed comparable to a major appliance. It is expected soon to consume more power than a city of over 100,000 people! Its air conditioning system alone is reputedly the largest in the world, being sufficient to serve a city of more than 15,000 homes. It may well be asked, with energy sources so limited and air pollution a serious problem, is it practical to aggravate the situation with such an enormous building complex?
Also, the Trade Center is estimated to be soon expelling 2.25 million gallons of raw sewage into the Hudson River, the output of a city the size of Albany, New York, the state capital! In addition, workers and visitors are expected to produce 50 tons of garbage daily. Then there is the problem of moving 130,000 people daily in and out of an already congested city area.
Safety is another consideration. A recent rash of skyscraper fires points up a major weakness. As Arthur F. Sampson, commissioner of public buildings for the General Services Administration, noted: “Fire protection in highrise buildings is extremely difficult and, some say, nearly impossible.” In fact, a really catastrophic skyscraper fire is inevitable, some experts predict.
Yet, at the same time, the World Trade Center is certainly a remarkable technological achievement, even as have been man’s space ventures. But contesting their practicality, the well-known urban critic Lewis Mumford claims: “Skyscrapers have always been put up for reasons of advertisement and publicity. They are not economically sound or efficient.”
Whether this is really true or not, when all things are considered, the Trade Center’s twin towers hardly seem to be a desirable model after which to design future buildings.