A HYBRID SIMULATION STRATEGY FOR THE DYNAMIC ASSESSMENT OF LONG-SPAN BRIDGES AND MOVING TRAFFIC SUBJECTED TO SEISMIC EXCITATIONS

摘要

Earthquake ground motions are one type of the most devastating hazards threatening modern transportation systems,including the integrity of the bridge structures as well as the safety of moving vehicles on the bridges.Aiming at considering simultaneously the bridge-traffic coupling effects and various sources of nonlinearity on the bridge structure,a new time-domain simulation methodology for the system of long-span bridges and moving traffic subjected to spatially-varyingground motion excitations is established.The methodology involves two analytical models,which are the fully-coupled bridge-traffic interaction model based on the mode coordinates and the three dimensional finite element model developed in a commercial program.Different from most existing studies,the fully-coupled bridge-traffic interaction analysis is conducted by coupling the modal-based bridge model,all individual moving vehicles of the stochastic traffic flow,roughness excitation and seismic excitations simultaneously.The fully-coupled bridge-traffic interaction analysis is firstly conducted using mode superposition method to obtain the dynamic response of bridge and moving vehicles subjected to spatially-varyingearthquake excitations,which are simulated by the spectral representation method as one-dimensional,n-variate non-stationary Gaussian random process with a mean value of zero based on a scenario earthquake.The equivalent moving traffic load(EMTL)with respect to time is further obtained based on the stiffness and damping parameters of vehicles and relative displacement of vehicle and bridge at contact point.The time histories of EMTL at bridge deck joints are applied on the bridge finite element model in commercial finite element software for nonlinear seismic analysis.Numerical analysisis further conducted on the prototype long-span cable-stayed bridge and stochastic traffic system subjected to spatially-varying ground motions.