In 1966, the National Academy of Sciences retained Wiss, Janney, Elstner Associates to conduct full-scale load tests on three buildings at the site of the 1964 New York World’s Fair. The buildings were only two years old and scheduled for demolition, making them ideal candidates for a study of ultimate building performance through failure. The fundamental purpose of the testing program was to ascertain the degree of correlation between actual performance of structural systems to that predicted from laboratory tests and design theory.
WJE tested three structures. The Chimes Tower was subjected to 17 levels of lateral dynamic excitation using four vibrators that were the only type in existence at the time. Jack Wiss took measurements of the natural frequency of the tower for comparison with the calculated value. At resonance, the top of the structure was displaced 1.5 inches, corresponding to an acceleration of 0.8 g. The test had $150,000 worth of instrumentation that recorded 50 channels of strain and acceleration data. Most of the equipment for this test was loaned from the U.S. Army Corp of Engineers or the State of California.
The Bourbon Street building was a steel structure with open-web floor joists. The floor and roof system was tested to failure using air pressure. A key was to convert the building into a nearly airtight vessel. By removing air from the sealed interior with compressors, a negative differential air pressure between the inside and outside was created, which constituted the superimposed uniform loading. The vacuum technique had been used on model tests, but this was the first time the technique was used to load test a full-sized building to failure.
The Rathskeller building featured a reinforced concrete waffle slab that was designed to support a 300-psf uniform live loading and tested to failure using hydraulic rams reacting against soil anchors installed through the basement floor. A total of 208 center-hole hydraulic rams of 30-ton capacity were used at each of three test locations to simulate a uniform loading. At the time, there weren’t suitable rams in existence — all rams had to be specially made for the tests.
The results of the tests led to improved understanding of how buildings behave and ultimately fail, especially the vulnerability of concrete buildings to failure in punching shear and the contribution of unbalanced moments in determining ultimate strength. At the time, the project was the company’s largest ever and required the combined efforts of WJE’s laboratory and structural engineering staff. The successful project was heralded as an innovative engineering feat and established WJE’s reputation as a leading investigative and testing firm. Years later, WJE founder Jack Janney would consider it “the project that put WJE on the map.”
Information and photos provided by Wiss, Janney, Elstner Associates (www.wje.com). Send information about historical civil and structural engineering projects and engineers to Bob Drake at email@example.com.