Abstract:To study the seismic response of long-span suspension bridges under multi-support excitation, an improved power spectrum model based on an existing power spectrum model is proposed and applied to the synthetic process of artificial seismic waves. A full-bridge finite element model for the suspension bridge with a main span of 720 m over a reservoir was established with Midas civil, and the seismic response of the bridge under multi-support excitation and different wave velocities was analyzed with a large-mass method. The results showed that under multi-point excitation, the internal force response and displacement response of the main tower and the displacement response of the main beam of the long-span suspension bridge are all affected by the traveling wave effect, the attenuation effect, the incoherence effect, and the superposition effect of seismic waves after attenuation, and the value of final response is determined by the combined effects of attenuation and superposition of seismic waves. Under 500 m/s multi-point excitation and the combined effects of superposition and attenuation of the seismic wave after attenuation, the axial force response of the main tower, the longitudinal shear response at the bottom of main tower, and the shear force and bending moment response at the beam of the left tower showed the maximum reinforcement effect. Under multi-point excitation and different wave velocities, (1) the relative variance rate of longitudinal displacement response of the main tower was greater than zero and almost unchanged; (2) the relative variance rate of longitudinal displacement response at the two sides of main beam reached maximum value when the wave velocity was 1 000 m/s; and (3) the vertical displacement response of the main girder reached the maximum value at 500 m/s, and was gradually close to than under uniform excitation with the increase of wave velocity.
