A Pushover Analysis For CFST Arch Bridges In Consideration Of Mode Combination

The seismic performance of CFST arch bridges always has attracted moreattentions. This paper studies on CFST arch bridges in the background of designphilosophy based on the structure performance. On the analysis, there are twomethods to be used to achieve this requirement, the nonlinear dynamic time-historyanalysis and nonlinear static analysis (Pushover). Although the time-history analysisis acknowledged finer analysis method, it is very sensitive to ground motion recordsand computationally intensive, time-consuming; however, unlike the relativecomplexity, Pushover analysis method is becoming a hot object, because it is simpleand effective. So applicability of Pushover analysis based on seismic performanceevaluation for CFST arch bridges has theoretical and practical significance topromote the study and practice of performance-based design and evaluation of thebridge structure.Firstly, on the background of the actual project Chaobaihe Bridge, we establishthe simplified model of the bridge. Then, modal analysis is carried out to obtain thetop60modal parameters, which prepares the data for the further Pushover analysis.Secondly, paper studies the basic principles, assumptions of arch bridgesPushover analysis, the relevant factors and traditional Pushover analysis method.Unlike the traditional Pushover analysis method, this paper directly selects restoringforce Q and displacement x of equivalent-single-degree-of-freedom(ESDOF),thus directly building capacity curve of ESDOF, which not only achieves athree-dimensional loading mode, and is consistent with the theoretical derivation.Thirdly, paper select modes by way of loading, consider the impact of highermodes. A standard of modal effective mass over90%is used to select load vector.Directly establish the corresponding equivalent single degree of freedom systemESDOF1and ESDOF5. The nonlinear dynamic time-history analysis processes ofmuti-degree-of-freedom(MDOF), ESDOF1and ESDOF5are carried out in case ofthree earthquake record named Tianjin wave, EL Centro wave and Kobe wave. Theoriginal structure MDOF is compared with considering multi-modal combination ofESDOF and without considering the multi-modal combination ESDOF for dynamichistory analysis displacement peak. The results show that the method in combinationwith multi-modal is feasible, and errors are within15%; however, for the methodwithout considering the multi-modal combination ESDOF, errors are over the20%.The fact verifies the correctness of multi-modal Pushover analysis seismicperformance of CFST arch bridges, and the accuracy is very good.Finally, we combine the Pushover analysis method with the incremental dynamic analysis IDA together, trying to use restoring force model of approximateESDOF system replacing the original structure for the IDA analysis,which not onlyhas small price calculation, and the results are rational. The combination of twomethods achieves a comprehensive evaluation of the seismic performance of CFSTarch bridges.