Seismic Damage Evolution And Vulnerability Analysis Of Railway Long-span Deck Steel Truss Arch Bridge

With the increase of railway bridge construction,the seismic design of long-span railway bridges has become especially important.However,the provisions of existing specifications are only for medium and small span bridges,and the seismic performance of long-span bridges are required further study.As a common bridge type in long-span bridges,steel truss arch bridges have good stability and beautiful shape and are widely used in railway bridge construction.Therefore,a long-span deck steel truss arch bridge is studied to conduct damage evolution and vulnerability analysis.The main contents are as follows:(1)Corresponding damage indexes are selected for steel tube,CFST and reinforced concrete members.The seismic damage evolution simulation method is determind based on incremental dynamic analysis.The vulnerability curve is obtained based on probabilistic seismic demand analysis.(2)A refined elastoplastic fiber element bridge model is established by using the finite element software OpenSEES to consider the material nonlinearity and geometric nonlinearity.Eigenvalue analysis of the bridge is carried out to summarize the main vibration modes and deepen the understanding of the dynamic characteristics of long-span arch bridges.(3)The response envelope diagram of arch rib and main beam is obtained through nonlinear time history analysis.And then the key components of the bridge are determined.Based on this,the calculation of the corresponding component damage index is carried out.The difference and applicability of the two indicators are compared and analyzed.(4)Through the longitudinal,lateral,bidirectional and three-direction ground motions loading on the bridge,the multi-dimensional seismic damage evolution simulation analysis is carried out.The seismic damage sequence of bridge is discussed from the three levels of materials,components and structures.The damage law of the bridge structure with the change of the ground motion intensity is obtained by counting the damage quantity of the full bridge member and calculating the full bridge seismic damage index.(5)Considering the uncertainty of bridge,earthquake and damage index,the probabilistic seismic demand analysis is used to calculate the vulnerability curves of bridge members.The damage difference under multi-dimensional ground motions,near-field and far-field ground motions is explored.The Monte Carlo method is used to calculate the vulnerability curve of the system,and the damage probability is performed from the full bridge level.