INFLUENCE OF TIE BEAMS ON THE SEISMIC PERFORMANCE OF TWO-COLUMNED HIGH PIERS

Two-columned high piers are widely used to continuous rigid frame bridges. The longitudinal flexural stiffness of high piers with height of over 40m is generally smaller, so tie beams are usually set between two columns to decrease the calculating height of piers to improve the stability behavior. In addition, under the seismic action, tie beams generally yield before columns, forming the plastic hinge and dissipating seismic energy, which decreases the damage of piers. To study the seismic performance of two-columned high piers with tie beams, nonlinear static and quasi-static analysis of a typical two-columned high piers with height 45m was conducted by two and three-dimensional finite element modeling techniques respectively. Factors of the longitudinal reinforcements and stirrups ratio of tie beams, the stiffness ratio of tie beams to columns and the number of tie beams on the seismic performance of high piers are all discussed. Analysis results show that the seismic performance two-columned high piers is effectively improved with increasing the number of tie beams and setting the stiffness ratio of tie beams to columns in a certain range, while there is little influence of the reinforcement ratio of tie beams. As a result, setting a reasonable number of tie beams is an effective way to improve the seismic performance of two-columned high piers.