Abstract
This study investigates vertical response of seismically isolated building focusing on the differences of span length of superstructure. We investigate several base-fixed moment-resisting frame models with the equivalently added damping to incorporate the SSI effect. There is no difference between frame models and lumped mass models, when span length is short. On the other hand, the effect of beam vibration is large, when span length is long. Axial force of isolator is largely affected by beam vibration of superstructure. We tested equivalently added damping only to columns, setting the original damping to beams with distributed masses. Coupling effects of vertical responses with SSI can be adequately evaluated in comparison with added damping to beams and columns constantly.
