DYNAMIC ANALYSIS OF BASE-ISOLATED SHEAR BEAMS BUMPING AGAINST STOPS

Base isolation requires a gap between the base-isolated building and i ts surroundings to provide space for the deformation of isolation syst em. Bumping against the surroundings may change the performance of the base-isolated building. In this study, the building is modelled as an elastic or inelastic shear beam and the surroundings is simplified as elastic or inelastic stops. The influence of stop stiffness, gap size and stop strength on the seismic response is studied. Numerical resul ts indicate that the impact wave induced by the bumping can create an extremely high acceleration response in the shear beam, if the shear b eam remains elastic. A non-linearly elastic stop model is observed to reduce the acceleration response. If the shear beam yields, the impact wave cannot propagate through the shear beam and the shear beam remai ns in the low acceleration response except for the base. Changing the stop stiffness or stop strength has little effect on the distribution of ductility demand along the shear beam. (C) 1997 by John Wiley & Son s, Ltd.