Seismic resistance of locking ball devices and optimal design for irregular continuous bridges with one fixed pier

摘要

In order to reduce seismic response of fixed piers in irregular continuous bridges and improve the overall seismic resistance performance of bridges, locking ball devices were installed between the sliding piers and girders of bridges. These devices allowed the sliding piers to share seismic load from the superstructure with the fixed pier, according to the potential seismic resistance capacity of sliding piers. A shake table test and a simulation of the finite element model of a three-span irregular continuous bridge were conducted. Then, taking a typical five-span irregular continuous bridge as an example, the seismic resistance mechanism and the influence of locking ball devices on the seismic responses of sliding piers were analyzed. Optimal designs of locking ball devices were studied to protect sliding piers. The results show that locking ball devices installed on sliding piers can effectively reduce the seismic response of the fixed pier, but they may increase the seismic response of the sliding piers installed with locking ball devices, and that of the irregular continuous bridge as a whole. Both the acceleration threshold and the lock gap of the locking ball device strongly influenced the seismic resistance effect. The main parameters of the locking ball devices should be optimized based on the structural characteristics of the bridge, so as to obtain a better seismic resistance effect. Adjusting connection stiffness of locking ball device can reduce the seismic response of the short sliding pier and can protect it, but changing the lock gap is not an effective way of protecting the short pier. It is necessary to optimize the arrangement of the locking ball devices.