Analysis on Seismic Pounding Responses of Isolated Continuous Girder Bridge under Earthquake Excitation

The adjacent girders of isolated bridge with lead rubber bearings are easy to collide with each other under earthquake excitation.A three equal spans continuous girder bridge model was created with consideration of impact element and the nonlinearity of lead rubber bearings.Nonlinear time-history analysis was used to investigate the response of the longitudinal seismic impact between girders.The calculation result shows that(1)the pounding action easily leads to significant impact forces between the girders of isolated bridge which increases the girder axial force response evidently but has little effect on the horizontal displacement of girder as well as the shear force and displacement at pier bottom;(2) the primary factors that affect the pounding response are the period ratio and the values of natural periods of adjacent bridge segments,and gap at expansion joint;(3) the lead rubber bearing has the function of dissipate the pounding energy and reduce the impact force between the adjacent girders to protect the bridge from damage.