Performance of double skin FRP-concrete-steel self-centered segmental bridge piers subjected to forward-directivity near-fault ground motion

Abstract

This paper investigates the damping energy and behavior of a proposed damage-resistant self-centering unbonded post-tensioned (PT) bridge pier system for accelerated bridge construction. The system is investigated with and without the addition of external energy dissipaters using two piers. The cross-section of each pier was a double-skin consisting of two tubes: outside glass fiber reinforced polymer (GFRP) tube and an inside steel tube. Self-consolidating concrete (SCC) was poured in between. The piers system has the benefits of accelerating construction using segments, self-centering capability due to rocking, and high energy dissipation from the steel bars. The piers were tested under ascending intensities of scaled ground motions. A near-fault pulse-like motion was chosen to examine the velocity impact effect on the piers. After being subjected to a series of ground motions of up to 250% of the design earthquake (DE), the piers had self-centering capability with almost no residual drift and no noticeable damage. The peak drift was 8.85%. The rocking motion reveals a complex induced dynamic behavior, in which a small change in the system can cause chaotic and butterfly effects. Hence, the energy of the system was investigated to better comprehend the dynamic behavior of rocking under forced vibrations. Two analytical models were developed to simulate the static and dynamic behaviors of the self-centering unbonded post-tensioned bridge piers.