Seismic Response of Suspension Bridges Under Multi-Component Non-Stationary Random Ground Motion

A Markov method of analysis is presented for obtaining the seismic response of suspension bridges to nonstationary random ground motion. A uniformly modulated nonstationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s ground acceleration. Both vertical and horizontal components of the ground motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of earthquake, the spatial correlation of ground motion and the quasi-static excitation. A suspension bridge is analysed under a set of parametric variations in order to study the nonstationary response of the bridge, The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s acceleration as input could provide more r.m.s response than the peak r.m.s response obtained by the nonstationary analysis; (ii) longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of earthquake has considerable influence on the deck response.