Seismic Response Analysis Of Continuous Rigid Frame Bridge With Double Thin-walled Piers In High Intensity Zone

Compared with ordinary girder bridges,continuous rigid frame bridges have many advantages,such as large span capacity,comfortable driving and good integrity,and are widely used in China.The pier-beam consolidation method is adopted for continuous rigid frame bridges,which can save large tonnage bearing.The main pier has two structural forms:single thin-walled pier and double thin-walled pier.When the pier is lower,double thin-walled piers are ideal flexible piers in prestressed concrete continuous rigid frame bridges because of their large longitudinal flexural stiffness and small thrust stiffness,which can effectively meet the displacement requirements of the bridge superstructure caused by concrete shrinkage,creep and temperature.The inertia force and seismic action often control the design of long-span continuous rigid frame bridges built in high intensity areas because of the high quality of the superstructure.Taking a(60+100+60)m continuous rigid frame bridge with double thin-walled piers as the engineering background in this paper,the finite element calculation model of the whole bridge by using MIDAS/CIVIL software is established,and the influence of geometric parameters of double thin-walled piers on its seismic response is studied.The concrete research contents are as follows:(1)Through reading the literature,the phenomena of seismic damage and the research progress of seismic resistance of continuous rigid frame bridges is summarized in this paper.(2)Taking a(60+100+60)m continuous rigid frame bridge with double thin-walled piers as the engineering background,the finite element calculation model of the bridge is established by using MIDAS/CIVIL software.By changing the wall thickness,center distance and pier height of double thin-walled piers,the influence of main pier geometric parameters on the dynamic characteristics of the bridge is studied.(3)In order to study the influence of main pier geometric parameters on seismic response of double thin-walled continuous rigid frame bridge,assuming that the calculation parameters of the superstructure of the bridge remain unchanged,and respectively changing the wall thickness of the main pier,the center distance between the two limbs and the pier height,the response spectra of 15 computational models established under frequent earthquakes are analyzed.The results show that the change of wall thickness of double thin walls has a significant effect on the longitudinal bending moment and shear force of the main girder and pier.With the increase of wall thickness,the internal force of the cross section of the main girder at the fulcrum and the cross section of the top and bottom of the main pier increases significantly,but the change of the center distance of the two limbs has a little effect on it.(4)In order to study the seismic performance of double thin-walled continuous rigid frame bridges under rare earthquakes,the moment-curvature analysis of the main pier control section under different wall thickness and reinforcement ratio is first established by using Ucfyber software,and the rotation ability of the plastic hinge region is obtained.Then,the elastic-plastic dynamic calculation model is established by using the lumped plastic hinge model,and the rotation demand of the plastic hinge region is obtained by using the non-linear time-history response analysis method.The influence of different wall thickness and reinforcement ratio of double thin-walled piers on ductility and seismic performance of bridges is studied by capacity/demand ratio.