Cyclic response of RC column-bent piers subjected to bidirectional repeated loading

Abstract

A reinforced concrete (RC) column-bent pier represents one of most popular piers used for highway bridge structures in Korea. Experimental investigation was conducted to evaluate the seismic ductility of circular RC column-bent piers subjected to bi-directionally repeated lateral loadings. Seven (7) circular RC column-bent piers were constructed with two circular columns of 400 mm diameter and 2,000 mm height. One RC single column with 400 mm diameter was also made to compare with the seismic performance of RC column-bent piers. Test parameters are the transverse confinement ratio, the lap-splice of longitudinal steels, and the load pattern. All column-bent piers were subjected to bi-directional lateral load reversals simultaneously under a constant axial load of P/f c'A g= 0.1 . Four column-bent piers including one specimen with lap-spliced longitudinal steels were quasistatically actuated by bi-directional cyclic loads which consisted of two main amplitudes in the longitudinal axis and two sub amplitudes in the transverse axis, called as L-load series herein. Other three column-bent piers were loaded by bidirectional load cycles in an alternate load sequence, called as T-load series herein. Test results showed that the strength and ductility of latter three specimens were generally better than those of former four specimens. Plastic hinge was formed at the bottom of former four specimens, but was observed both at the bottom and top parts of latter three specimens. The seismic performance of RC column-bent piers was more or less inferior to that of RC single column due to the effect of bidirectional load reversals. A significant reduction of the displacement ductility was observed for test specimens with lap spliced longitudinal steels. Test specimens with more transverse confinement steels showed an enhanced seismic behavior compared to the reference specimen. Copyright © (2006) by Earthquake Engineering Research Institute.