Seismic damage characteristics of steel tower of cable-stayed bridge and influence of input ground motion parameters
Taking a single-tower steel cable-stayed bridge with a main span of 165 m as a research object,a refined calculation model of the steel tower was established.The historical seismic records adjusted by peak acceleration were selected as the ground motion input for the elasto plastic time-history analysis in the longitudinal direction of the bridge.The local instability of the steel plates and ultra-low cycle fatigue cracking characteristics of the steel tower were studied,and the applicability of the fiber model was discussed.Results show that the Pushover analysis method loaded along the height can predict the sequence and location of the seismic plastic development in the longitudinal direction of the steel tower.Although the fiber model can obtain the elastic-plastic seismic displacement response and the seismic damage location of the steel tower,it cannot accurately evaluate the residual deformation and the damage degree of the structure.The peak ground velocity(PGV)/peak ground acceleration(PGA)value of the input ground motion is an indicator that affects the degree of structural seismic damage.Under the same PGA,the seismic damage of the steel tower caused by ground motions with larger PGV/PGA values is significant.Therefore,the seismic performance verification of steel towers cable-stayed bridges should adopt the ground motion time history with larger PGV/PGA values.
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