Nonlinear behavior of a containment building during an earthquake

The nonlinear behavior of a 1/4-scale containment structure subjected to strong motion earthquake excitation is investigated by analyzing acceleration measurements on the structure and the site/soil surrounding the structure. Acceleration transfer functions obtained from the ratios of Fourier Transforms provide the means to estimate the dynamic characteristics of the soil-structure system. These are compared with results obtained from low-level vibration testing of the structure. Due to strong nonlinear effects during strong-motion excitation the fundamental frequency decreases by about 40% relative to the value obtained in low-level vibration tests (2.3 vs 3.8 Hz). In addition, this frequency as well as the shape of the transfer function moduli vary considerably with time during the strong motion excitation. This preliminary investigation indicates that the analysis of earthquake responses coupled with the results of low level vibration tests provide a means to gain understanding of the nonlinear behavior of soil-structure systems during strong motion, and may lead to the improvement in the modeling of soil-structure interaction phenomenology. 8 refs., 6 figs