Study On Seismic Response Caculation Of High Pier Bridge

With the development of transportation, more long large bridges are built. As a result, anti-seismic design of high pier becomes very important. Based on research results written by domestic and foreign scholars, semi-analytical added water mass are calculated. Calculation studies are carried out on the effects of pier cross-section size, water depth, pier height to added water mass. Dynamic responses of piers considered water-pier coupling under earthquake are studied based beam-column element. The effect of pier structure parameters and earthquake characteristics on positions that plastic hinges form are studied by carrying out the nonlinear dynamic time-history analysis on elastic-plastic finite element model. A simplified method of calculation is carried out to study effects of different hinge positions on free vibration characteristics and seismic responses of piers. The main comments are as follows:1.The value of added water mass increases from0to a certain value in the shallow water region (within about0.2water depth). With the further increment of water depth, the value of added water mass increases little. And this certain value is in direct proportion with pier cross-section area.2. The increasing rate of pier seismic responses (displacement at the pier top, moment and shear force at the pier bottom) increases with the rate of water depth to pier height. The effect of added water mass to displacement at the pier top and moment at the pier bottom can be ignored when the rate of water depth to pier height is respectively less than0.5and0.25. The effect of added water mass to shear force at the pier bottom can not be ignored. The maximum of increasing rate of pier seismic responses is about45%when the rate of water depth to pier height is1.3.The maximum of difference rate of seismic responses of piers whose height are less than120m, considering water flow velocity to which in no initial speed water is is about5%.4.Different forms of high pier hinges are:(1) hinge forms at pier bottom at initial time, then another forms at midhieght of pier as long as the previous one expands;(2) hinge forms at midhieght of pier at initial time, then another forms at pier bottom as long as the previous one expands;(3) hinge forms only at pier bottom;(4) hinge forms only at midhieght of pier.5.With the increment of ground acceleration peak, plastic hinge of high pier gradually expands. The longer the characteristic period of earthquake wave is, the easier plastic hinge of high pier develops and extends. The range of plastic hinge decreases with the increment of longitudinal reinforcement ratio.6.The relation of reducing rate of pier seismic responses (displacement at the pier top, moment and shear force at the pier bottom) with different plastic hinge positions to shear span ratio approximately presents as the curve form of response spectrum. Reducing rate increases from a low value to the maximum (about75%) value when shear span ratio is2.5-3.5, then decreases with increment of shear span ratio. It is about0%-10%when shear span ratio is greater than12.