Forced vibration test of the Hualien large scale soil structure interaction model (pt. 2)

A large-scale seismic test (LSST) programme conducted at Hualien (stiff soil site), Taiwan, has started (Tang et al., 1991) to provide earthquake-induced soil-structure interaction (SSI) data as an extension of the same kind of program conducted at Lotung (soft soil site) (EPRI, 1989). Two tests have been performed: a forced vibration test (FVT) without embedment (Morishita et al., 1993) and the same test with embedment. Horizontal excitations were applied in two different directions both on the roof slab and on the basemat of a 1/4-scale containment model. Vertical excitations were applied on the basemat only. The concept of 'principal axes (D1, D2)' was introduced for the SSI system, and the basic dynamic characteristics of the soil-structure system were obtained for D1 and D2. As an example, resonance frequencies for horizontal excitations were 4.1 and 4.6 Hz without embedment, and 6.1 and 6.3 Hz with embedment for D1 and D2 based on results transformed to principal axes. Finally, a soil impedance function was obtained by a newly defined error minimizing method. This function also simulates the classic embedment effect. (orig.)