Abstract: In order to study the seismic response and mitigation measures of a multi-span simply suppor-ted beam bridge under near-fault ground motion,a 4-span simply supported beam bridge was taken as theresearch object.Three groups of near-fault ground motions were selected,which respectively considerfling step effect,forward directivity effect,and no pulse effect,along with one group of far-fault seismicmotions for comparison.The seismic response and damage degree of key components such as main beams,piers,and bearings.It was found that the velocitypulse-type near-fault ground motion amplifies the displacement response in both longitudinal and trans-verse bridges,which not only increases the damage degree of the piers and bearings,but also increases thenumber of longitudinal collisions between beams and the peak value of collision force.Therefore,a com-bined seismic reduction system of Buckling-Restrained Brace(BRB)and viscous damper was put forward.The influence of the arrangement and parameters of a viscous damper on the seismic reduction effect is an-alyzed.The results show that the mitigation scheme effectively reduces the damage to piers and bearingsand reduces the longitudinal displacement of main beams.Arranging dampers between the main beam andits abutment is more conducive to the seismic control of a multi-span simply supported beam bridge.It issuggested that the viscous damping coefficient C between the main beams should be 3 000 kN·s/m,whilethe viscous damping coefficient C between abutment and main beams should be 4 000 kN·s/m,with thevelocity correlation coefficient a of 0.4.

Key words: simply supported bridge, near-fault ground motion, seismic response, combined seismic reduction system, damage control