Structural Dynamics And Seismic Response Analysis Of Prestressed Concrete Continuous Rigid Frame Bridge With Corrugated Steel Webs

Our country locates in between two major seismic belts bearing severe seismic damages. In recent years, prestressed concrete box-girder structure with corrugated steel webs are used more and more widely in bridging engineering. It is important to know the dynamic characteristics and reaction in seismic action. As a convenient method to analyze seismic response, pushover method becomes the focus in seismic research currently. This paper studies the application of pushover analysis method in seismic response analysis of bridge structure based on a prestressed concrete continuous rigid frame bridge with corrugated steel webs. This analysis method is explained in details from pier to entire bridge structure.The basic principles, basic assumptions and realization process of pushover analysis method is concluded systematically. Two main factors which influence the results are the selection of distributing patterns of lateral loads and the calculation of target displacement. The key procedures of using capacity spectrum method to assess structural seismic performance are introduced in detail.For thin-wall pier model, the distribution pattern of lateral loads (uniform distribution pattern) and basic vibration mode distribution pattern are chosen for pushover analysis. The results show that the capacity curve of structure (the relationship curve of the shear force of the pier bottom-the displacement of the pier top) in axial directions is consistent with that in lateral direction basically. The capacity curves of structure vary with different distribution patterns of lateral loads.Seismic performance of the thin-wall pier is assessed on the basis of the position of performance point. The structure of the pier is analyzed through response spectrum analysis, then the outcome is compared with that of Pushover. The results denote that the seismic response of structures in these two methods are basically the same, which illustrates that the Pushover analysis method is suitable for this kind of structure and convenient and efficient.Ritz vector analysis method is used for dynamic characteristics analysis on a prestressed concrete continuous rigid frame bridge with corrugated steel webs. There are two conditions which are lateral loads decided by main vibration modes+dead weight+secondary dead load and lateral loads decided by the first seventy vibration modes+dead weight+secondary dead load. Pushover analysis is done on entire bridge structure in axial and lateral directions under these two conditions. The result turns out that the capacity curve of structure under these two conditions are basically the same. The seismic responses of structure characterized by performance point are also in consistence. It indicates that to determine the distribution patterns of lateral loads according to main vibration modes with high contribution rate is feasible. More vibration modes could be selected to evaluate the seismic performance of bridge structure.The nonlinear dynamic time-history analysis method and wave selection method are introduced and seismic response of the entire bridge structure is obtained. The displacement response of the pier top obtained from the nonlinear dynamic time-history analysis and pushover analysis are similar and the results of pushover analysis are a little larger. It proves that the seismic performance evaluation of the background bridge of the subject based on pushover analysis are conservative.