Abstract：The earthquake-induced ground motion is characteristized by complicated variation in space and time and may be different at dissimilar supports of structures. Relevant sdudies have shown that it is necessary for structures to consider the effects of multi-support excitations,especially for large span structures. The JIUJIANG Yangtze River highway bridge is a double-tower double-cable-side steel-box-beam cable stayed bridge, with 1432m full length and 768m main span length. In this paper, the presented spring impedance method for current displacement input model is firstly introduced. Spatially variable ground motion time histories are generated by the method of the reponse-spectrum-compatible artificial ground, then the responses of the highway bridge under uniform excitation and multiple support excitations are studied by adopting the time history analysis method. From the analysis results, it is founded that：considering multi-support can decrease the seismic response of the cable tower’s shear force、moment and displacement under longitudinal excitation, and the seismic design is favorable for cable stayed bridge; considering multi-support can increase, or decrease the seismic response of the cable tower’s shear force and moment under multi-dimensional excitation, the maximum of shear force may be increased about 10%；considering multi-support can increase the seismic response of the cable tower’s displacement under multi-dimensional excitation, the maximum of displacement may be increased about 100%; the response of considering multi-dimensional is larger than that considering longitudinal only. A conclusion is given that the multi-support and multi-dimensional earthquake excitations must be considered in the seismic analysis of the long-span cable stayed bridge.
2009, Vol. 28 
