Structural inertial interaction effects on foundation behavior

Abstract

The effect of inertial interaction of a superstructure with the soil must be understood to evaluate soil-foundation-structure interaction (SFSI) problems. Inertial interaction causes period lengthening and damping increasing and affects the foundation behavior, rocking and swaying motions. This effect is also significant in systems that induce foundation-yielding behaviors during earthquakes, such as rocking foundation. This study evaluates the structural inertial interaction effects on the foundation behavior through an analytical calculation to obtain the natural frequencies of the foundation's rocking and swaying motions. Dynamic centrifuge tests were also conducted to evaluate the variations in natural frequencies of an SFSI system on the rocking foundation. Test results demonstrate that the natural frequency of foundation motion is close to that of structural motion as far as foundation yielding behaviors are concerned. From strong seismic data, with free-field motion as the input motion, a reasonable natural period of the structure is identified. However, the structural natural period is considered abnormal when the foundation motion is used as the input motion. This phenomenon should be considered in future SFSI studies.