This 76-story reinforced concrete building contains both lightweight and normal weight concrete, as well as high-strength concrete and steel. When built in 1973, it was the world's tallest reinforced concrete building at 846 ft. The structure combines tubular design for the upper 64 stories with conventional design for the first 12 floors. The National Science Foundation initiated a program to measure elastic deformations in the structure, in order to confirm previously developed procedures for predicting the long-term shortening of individual columns and shear walls of high-rise buildings.
CTLGroup was engaged to develop an instrumentation program. The program included the installation of Carlson strain meters in foundation caissons to measure axial shortening, mechanical strain gage points on columns and walls at selected upper-level floors to measure vertical shortening, and survey points throughout selected floors to measure differential shortening. CTLGroup also performed material property tests of the concrete.
The data generated from this program indicated close agreement between measured deformations and the shortening calculated during construction. Thereafter, the calculated values tended to be less than the measured values.