Extension of a simplified procedure for estimating nonlinear seismic responses of tall pier bridge systems

Abstract

Due to the rugged topology, bridges in Western China often contain piers over 40-m height. The seismic responses of these tall pier bridges are usually estimated using nonlinear time history analysis (NTHA) procedure, which is rigorous but time consuming and computational demanding when plastic performance is involved. This paper modified a procedure previously proposed estimating nonlinear seismic responses of cantilever tall piers columns, and extend it for the assessment of whole bridge systems. The formation of multiple plastic hinges, rather than a single one, was considered in this extended method. Furthermore, the selection of vibration modes in bridge systems was carefully considered as well, which was more complex than in the case of a single pier column. The efficiency of the method was verified with numerical examples of two typical tall pier bridges: a continuous-girder one and a rigid-framed one. The seismic demand computed by the simplified approach was compared with that from NTHA procedures, subjected to both far-field and near-fault input ground motions. The results showed that when the vibration modes were properly selected for this extended method, the seismic responses of both bridge systems could be estimated efficiently, which was quite helpful for preliminary seismic design of tall pier bridges.