RESEARCH ON SEISMIC RESISTANCE OF SIMPLE SUPPORTED BEAM BRIDGES IN MOUNTAINOUS AREAS BASED ON THENEW SEISMIC RESISTANCE CODE

摘要

Western China is an earthquake-prone environment with frequent earthquakes and high intensity.Affected by complex conditions such as topography,geomorphology,and hydrogeology,bridge structures in these areas generally have the typical characteristics of large pier heights and obvious differences in pier heights between adjacent piers.In this paper,taking a multi-joint simply supported beam bridge in a mountainous area in western China as an example,the bridge numerical analysis software Midas Civil is used to systematically study the structural response and anti-falling beam and anti-collision measures under earthquake action.Based on the requirements of seismic input load in the new seismic code "Code for Seismic Design of Highway Bridges",the difference in structural response of bridge structures under the new and old seismic codes,as well as measures to prevent falling beams and collisions,are analyzed.The results show that the load effect value of bridge seismic design using the new seismic code is greater,so the design result is safer.The peak displacement response of the pier top calculated on the basis of the 20 rules is about 1.4 times the calculation result of the 08 detailed rules,which reaches 21 cm.For a simply supported beam bridge in mountainous areas with a period ratio of 0.5,the relative displacement between the expansion joints under the action of an earthquake can reach up to 40 cm.Therefore,it has the possibility of collision or falling beam damage.The period difference of adjacent structures can be effectively adjusted by changing the stiffness of the plate rubber bearing,and the structural response of the simply supported beam bridge under earthquake action can be significantly improved.When the period ratio changes from 0.5 to 1.0,the relative displacement peak value decreases from 40 cm to only 2 cm.This study can provide a basis for the design and calculation of similar bridges.