Research On The Applicability Of FPB-transverse Shear Key Cooperative Seismic System For High-speed Railway Simply-supported Beam Bridge

Double concave friction pendulum(Hereinafter referred to as FPB)is a widely-used seismic isolation device in simply-supported beam bridges,which can effectively prolong the natural vibration period of the structure and avoid the failure of bridge piers during earthquakes.However,the use of friction pendulum bearings might cause excessive beam displacement response and increase the risk of beam unseating.Therefore,the focus of seismic isolation design is to utilize the advantages of friction pendulum bearings and determine its applicable scope on high-speed railway bridges.In this thesis,the simply-supported beam bridge was taken as an example to study the FPB-transverse shear key cooperative seismic system.The multi-index evaluation method was applied to assess the applicability of FPB-transverse shear key cooperative system on bridges.The main contents and results of this thesis are shown as follows:(1)Based on ANSYS finite element software,finite element models of 7-span 32 m simply-supported beam bridges with different pier heights were established.The nonlinear time history analysis of the bridge structure due to rare earthquakes was carried out.The result shows that compared with the spherical steel bearing,the friction pendulum bearing can reduce the displacement of the pier top and the maximum bending moment at the pier bottom when the pier height is less than 50 m and rare earthquakes are input.The seismic performance of the bearing decreases with the pier height.The pier-beam relative displacement is still large and might cause beam unseating.Therefore,it is necessary to set shear keys for cooperative earthquake resistance.(2)The seismic performance of FPB-retaining transverse shear key cooperative system is evaluated by pier-beam relative displacement,displacement of pier top,bending moment at pier bottom and the isolation efficiency.The result indicates that the transverse shear key can effectively limit the lateral displacement of the upper beam.When the pier height is less than 50 m,the maximum pier-beam relative displacement increases with the height of the pier.The FPB has better seismic isolation performance compared with the spherical steel bearing,and its performance is positively correlated with the pier height while negatively correlated with the key-pad relative displacement.(3)An evaluation method considering beam unseating risk,pier damage and isolation efficiency was proposed for the high-speed railway simply-supported beam bridges with the FPB-transverse shear key cooperative system to comprehensively evaluate its applicability.The results show that under rare earthquakes,the cooperative system is suitable for high-speed railway simply-supported beam bridges with pier height less than 25 m.For the FPB-transverse shear key cooperative system,it is suggested that the gap length between the shear key and bearing bases should be 8cm when the pier height is 10 m,while that should be 7cm when the pier height is between 15 m to 25 m.This thesis contains 98 figures,33 tables,and 117 references.