Analysis Of Seismic Vulnerability On Curved Continuous Beam Bridge Under Near And Far Field Earthquake Of Different Bearing Arrangements

Our nation is a vast land.To overcome its myriad terrains,curved bridges are widely used in the construction of national roads and railways.Current studies on curved bridges provide some information on the seismic performance of curved bridges,but study on their seismic performance under different bearing arrangements seems to be lacking.Therefore,this paper carried out Incremental dynamic analysis(IDA)and vulnerability analysis for curved continuous beam bridges under different bearing arrangements to explore the seismic performance during near-field and far-field earthquakes.The main contents of this paper are presented as follows:(1)The IDA method and theories on vulnerability were described.Based on these,the method of building vulnerability curves was selected,by which some theoretical derivations were conducted.The displacement and displacement ductility ratio were determined to be the damage indices for basin and plate type bearings respectively,while curvature was decided as the damage index for bridge pier.(2)The constitutive models of concrete,steel and bearing were established.Based on the original bridge,3 types of design according to different bearing arrangements were presented,the finite element models of which were built using SAP2000.30 far-field and 30 near-field seismic records were selected for amplitude modulation.For each seismic wave,12 amplitude modulations were done to produce 720 seismic waves as the input of 4 bridge models to test their seismic performances respectively.(3)The IDA analysis and curve fitting methods were explained in detail before using them to measure the seismic performance of the bridge.Horizontally,the center of the pier suffered more damage than both ends and the damage on the bearing was more severe than that on the pier.Perpendicularly,the center of the pier also suffered more damage but the damage on the pier was more severe than that on the bearing.(4)The method of vulnerability analysis was introduced in detail followed by the analysis of bridges under 4 different bearing arrangements both horizontally and perpendicularly.The vulnerability curves for bridge pier,bearing and the whole bridge under different damage conditions were compared.The results showed that the position of plate type bearings was a key factor in seismic performance;using plate type bearings as the abutment bearing deteriorated the bridge's seismic performance.(5)The near-field and far-field earthquake vulnerability curves of 4 bridges under different bearing arrangements were comparatively analzed,followed by the analysis of the near-field and far-field earthquake vulnerability of the pier,bearing,and whole bridge under different damage conditions.The results showed that after using plate type bearings as the abutment bearing,the bridge was less affected by near-field earthquake;while the original bridge and bridges with plate type bearings as side pier bearing were more influenced by near-field earthquake.