Seismic analysis and design of bridge piers considering P-Δ effects

To realize performance-based seismic design it is important to calculate the seismic demand of structures in a concise and reasonable way.P-Δ effect will cause second order forces and displacements in bridge piers,which is well solved in the elastic range,but under seismic action this problem is still not maturely studied.Based on the evaluation of current approaches to consider P-Δ effect in seismic analysis and design,a set of nonlinear time history analysis of bridge pier systems considering P-Δ effects is conducted in this paper,and the formulas of displacement amplification factor and strength increase coefficient due to P-Δ effect is proposed by a regression approach.The results show that,the influences of P-Δ effect in inelastic range differ largely from those in elastic range.This reveals the inappropriateness of simply extending elastic design approaches to inelastic range.The displacement amplification factor and strength increase coefficient predicted by all the current theories are less than statistics mean within allowed engineering stability index.Formulas proposed in this paper coincide well with statistical curves,making them suitable to be used within the frame of performance-based seismic design.