SEISMIC RESPONSE ANALYSIS OF MULTI-SPAN SIMPLY-SUPPORTED BRIDGES ON QINGSHUI RIVER

The finite element model of multi-span simply supported bridges between DK1032+850.06 to DK1033+175.34 of Qinghai-Tibet Railway across Qingshui River is constructed. Large-mass method and multi-support excitation are adopted to analyze the dynamic behaviors of the multi-span simply-supported girder bridges considering wave passage effect and the influence of pile-soil interaction. The earthquake excitation is input on the horizontal direction. The results show that, the displacement, shears and moments of the control section increase with the apparent wave velocity, and that the amplitude of intermediate piers are more significant than that of side span and side pier. In the whole, the internal forces of pier and displacement peak values shift from the side piers to the middle pier when the apparent velocity increases. When the apparent velocity is relatively big, the influence of wave passage effect on the structure significantly reduces. For practical engineering, the prevailing approach of uniform excitation to assess seismic effects is relatively safe, especially when the apparent velocity is relatively small, the stress of the piers of calculating the middle section of the bridge is relatively high.