Influences Of Nonlinearity And Soil-pile-structure Interaction On Seismic Response Analysis Of Large-span Steel Arch Bridge

As one of the most important parts of the traffic lifeline engineering the large-span steelarch bridge not only has complex static geometrical and structural characteristics but also hasrather complex dynamic characteristics in the earthquake response With its span increasinglyenhanced it seems more urgent and necessary to conduct the seismic response analysis for thelarge-span bridge structure and the powerful method of time-history dynamic analysis is themost rigorous way to carry out seismic response estimation and to confirm the bridge structureseismic performanceThe main content of this paper is based on the current seismic performances research onlarge-span steel arch bridges in domestic and abroad and a newly-built bridge is taken as theengineering background which is a half-through steel arch bridge structure with the main spanof380m Then a spatial finite element model for the bridge is established by the ANSYSsoftware and referring to the seismic design theory of large-span bridges the bridge modelcharacteristics and dynamic behavior are both analyzed by using the time-history analysismethod In order to confirm the influences of nonlinearity and soil-pile-structure interaction toseismic behavior of the bridge structure a three-dimensional time history analysis for thebridge is investigatedFirstly considering the compulsory evaluation of inelastic behavior the seismicresponse analysis process is greatly more complicated compared to conventional practiceespecially for the large-span bridge structure In this situation the foundation soil isconsidered to be rigid in general seismic analysis and the material nonlinearity of the bridge isanalyzed by introducing a relatively simple analysis method To prove the earthquake resistantperformance of the superstructure the substructure is assumed to be in elastic stage when theearthquake response analysis of the superstructure is made Considering the development ofthe plastic area in the superstructure cannot be explicitly predicted its plastic hinge is locatedfirst based on the above elastic analysis Then by introducing plastic parameters thenonlinear earthquake response analysis is conducted and the expansion of the plastic range is checked out in order to confirm the safety of the bridge structure In this way the earthquakeresponse behavior evaluation of the bridge could be reflected more exactly both in strength andductilitySecondly in order to consider the effect of the soil-structure interaction on the bridgestructure the pile foundation is simulated by using a mass-spring model in theo mp methodas specifications defined Thus the above two types of model are compared Based on themodel the modal analysis and the time history response analysis are both carried out andeffects of the soil-pile-structure interaction on the seismic response of the bridge structure areparticularly studied under earthquake simulationSome conclusions could be made about the bridge seismic performance that there areobvious differences between elastic analysis and nonlinear analysis result especially in theintense earthquake action in which the bending moment at the1/4span of the main beam isreduced by22.8%and at the1/4span of the main arch by29%It is usually overestimatedby total elastic seismic analysis so the inelastic earthquake response analysis is necessary forthe large-span steel arch bridge design and in this method the safety of the bridge structurecould be more definitely confirmed Moreover comparing with the foundation-fixedmodel the soil-pile interaction not only has influences on the structural dynamiccharacteristics but also has effects on its seismic response making the bending moments andshearing forces of several main sections reduced obviously such as the bending moment at themiddle span of the main beam is reduced by22.6%while at the middle span of the main archby26.1%From the above conclusions it could be seen that the traditional method is proved tobe valid for the seismic design and verification thus providing data references for the sametype of bridge structure seismic design and analysis...