Optimum lateral load distribution for seismic design of nonlinear shear-buildings considering soil-structure interaction

•A novel optimisation framework is developed for nonlinear flexible-base structures.•Over 30,000 optimum load patterns are obtained for 21 earthquakes on soft soils.•A comprehensive parametric study is carried out on key dynamic and SSI parameters.•SSI can significantly affect the optimum design loads especially in longer periods.•Optimum load patterns can reduce the structural weight of SSI systems by up to 55%.

The lateral load distributions specified by seismic design provisions are primarily based on elastic behaviour of fixed-base structures without considering the effects of soil-structure-interaction (SSI). Consequently, such load patterns may not be suitable for seismic design of non-linear flexible-base structures. In this paper, a practical optimisation technique is introduced to obtain optimum seismic design loads for non-linear shear-buildings on soft soils based on the concept of uniform damage distribution. SSI effects are taken into account by using the cone model. Over 30,000 optimum load patterns are obtained for 21 earthquake excitations recorded on soft soils to investigate the effects of fundamental period of the structure, number of stories, ductility demand, earthquake excitation, damping ratio, damping model, structural post yield behaviour, soil flexibility and structural aspect ratio on the optimum load patterns. The results indicate that the proposed optimum load patterns can significantly improve the seismic performance of flexible-base buildings on soft soils.