Seismic testing of a bridge steel truss pier designed for controlled rocking

Shake table testing of a 1/5 scale model of a slender bridge steel truss pier that uses a controlled rocking approach as a means of seismic protection was conducted. The controlled rocking approach allows the pier to uplift from its base while passive energy dissipation devices (steel yielding devices or fluid viscous dampers) are implemented across the uplifting location to control the response. The fundamental static and dynamic bidirectional behavior of controlled rocking four-legged bridge piers has been developed and evaluated in past research. This paper discusses the experimental specimen's design, setup, and results of the testing. The testing program included the use of three sets of steel yielding devices and a set of fluid viscous dampers as the passive control devices. The specimens were subjected to ground motion records with increasing amplitude. The results of the testing were used to verify and further investigate the behavior of piers designed by the controlled rocking approach. Much of the fundamental behavior (self-centering, hysteretic behavior, and higher mode participation) are evident in the experimental results. Comparisons between the experimental results with design predictions and nonlinear time history analysis are made that show reasonable prediction of response.