DYNAMICS OF SEISMIC IMPACTS IN BASE-ISOLATED BUILDINGS

A systematic study is made of the effects of seismic impacts between t he base of an isolated building and the surrounding retaining wall. Th e analysis is performed without using gap elements or assuming values of the coefficient of restitution and the duration of impact. The anal ysis captures the effects of wave travel along the height of the build ing and of the associated energy loss. It poses no numerical difficult ies. Results show that for elastic systems the base shear generated by impacts can be higher than the weight of the building; base shear inc reases with increase in the stiffness of the retaining wall, stiffness of the building and the mass of the base mat. A significant fraction of the initial kinetic energy of the system is lost by impacts; energy loss increases with increase in the stiffness of the retaining wall, system damping and mass of the base mat. (C) 1997 by John Wiley & Sons , Ltd.