Abstract:As a key node of urban traffic network, the seismic safety of overpass is very important. In view of the vulnerability of overpasses under the action of near-fault ground motion and the fact that such ground motion records are few, a two-step method was proposed to construct near-fault ground motion input based on the comparison of simplified impulse simulation and real ground motion records. And the seismic response characteristics of overpasses under such action were studied. It was found that when the ratio of the simplified pulse period to the basic period of each substructure of the overpass is between 1 and 3, the structural reaction is intense, and when it is around 1.5, the internal force of the pier bottom reaches the maximum value. When the real near-fault ground motion records corresponding to the most disadvantageous simplified pulse period of each substructure are used to input the structure, the error of the seismic response of the ramp bridge in a short period is about 15% under the simulated input of a single simplified velocity pulse and real one. For ramp bridges and main bridges with medium and long period, it is necessary to adopt the two-step construction method to superimpose the high frequency components, so as to better restore the effect of the real ground motion record.
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