Research On The Seismic Vulnerability Of Double-column Piers Based On Performance And Their Simplified Calculation Methods

As a very important part of the transportation hub,the bridge structure has attracted more and more attention from people for its seismic fortification.The bridge pier is one of the most vulnerable component in the bridge structure.Once the pier is damaged,it may cause paralysis in the entire transportation.By analyzing the seismic vulnerability of bridge structures and components,the relationship between damage probability and ground motion of bridge structures and components can be effectively revealed.This article mainly did the following work:1)It was determined that the damage criterion based on performance was used to obtain the pier damage index.When determining the damage index of the transverse direction of the bridge pier,the damage index of the transverse direction was different with the longitudinal direction because of the dynamic axial force generated by the straining beam.Firstly,the moment curvature curves of the pier section was analyzed in the traditional method.The damage index of the bridge pier in the longitudinal direction was calculated by the formula.Then using OpenSEES to carry out pushover analysis on the piers and empirical formulas for calculating the displacement ability of the pier which subjected to transverse seismic waves were proposed.According to the empirical formulas,the damage index of the pier under different damage conditions was determined.2)The finite element model of the bridge was built by the Sap2000 finite element analysis platform.The influences of the bridge span,the number and height of the straining beam,the height of the bridge pier on the fragility curves of the pier were analyzed.The results showed that the bridge piers with double straining beams were better than those with single straining beam and the former had better seismic performance;When the bridge subjected to transverse seismic waves,the straining beam had little influence on bridge piers which subjected to longitudinal seismic waves.the damage probability of bridge piers will decrease with the increase of bridge span and the height of piers;When the bridge subjected to transverse seismic waves,the position of the beam was 0.3H-0.7H,the damage probability of the pier decreased with the position of the beam.When the single-span span of bridge pier was between 21m-30m,the pier damage probability increased with the increase of span.The damage probability of the bridge pier decreased slightly when the single-span span was over 30m.The damage probability of bridge piers decreased with the pier height increased.3)Based on the results of a large number of time-history analyses,the susceptibility of bridge pier vulnerability to seismic waves in different directions was performed.At the same time,the influence of the parameters change on the coefficient of the formula that forms the fragility curves were analyzed.Then the formulas for how to quickly calculate the coefficient when the parameter changes were proposed.The formlas were verified by three bridge models.These formulas could be used to quickly and optimally calculate the fragility curves of similar bridges.