Inelastic random response analysis of long-span bridges under non-uniform seismic excitation

Seismic excitation at different supports of long-span bridges is usually non-uniform and essentially random, and some structural components of bridges will be in inelastic under strong earthquakes. So far, there is no effective method to calculate the inelastic random response of long-span bridges under non-uniform seismic excitation. Based on the large-mass method, the time-domain explicit expression for inelastic dynamic responses was derived for long-span bridges under non-uniform seismic excitation. By use of the time-domain explicit expression, only the degree of freedoms associated with the inelastic elements were involved in iterative calculation, thus inelastic time-history analysis could be conducted efficiently. Combined with the Monte-Carlo simulation, the inelastic random responses of long-span bridges under non-uniform excitation could be obtained efficiently. A suspension bridge with span of 1 200 m was taken as the engineering example, where the inelastic components were simulated by the fiber beam-column element model, and nonlinear random vibration analysis was conducted on the bridge under non-uniform seismic excitation along the bridge to verify the accuracy and efficiency of the present method. The result shows that the standard deviations and mean peak values of the internal forces of the bridge under non-uniform seismic excitations may be larger or smaller than those under uniform seismic excitations. © 2021, Editorial Office of Journal of Vibration and Shock. All right reserved.