Multi performance seismic design through an enhanced first storey isolation system

In this paper the idea of the “shock-absorbing soft story concept”, originally proposed at the end of ‘60s by Fintel and Khan, is reviewed and developed within the framework of Performance Based Seismic Design. The purpose is to conceive a first-storey isolated building capable of satisfying selected seismic performance objectives. Among all the possible solutions, in this study the seismic story isolation is obtained through the insertion (only at the bottom level of the building) of special hysteretic devices, which are specifically designed in order to satisfy the prefixed seismic performance objectives. Without loss of generality, this design approach is fully detailed with reference to the specific case study of a five-storey steel frame building. The performances of the building under multiple earthquake design levels are finally verified through non-linear time-history analyses whose results confirm the effectiveness of the proposed approach.