Shake Table Testing of Bridge Columns under Combined Actions

Abstract

Observation on damaged structures after recent earthquakes have shown that the force and deformation capacity of reinforced concrete bridge columns (RCBC) can be significantly affected by the combined effect of dynamic actions (axial, shear, bending and torsion); as a result of these load combinations, the RCBCs are subjected to unexpected large deformations and extensive damage that can seriously affect the seismic performance of bridges. To evaluate the impact of different loadings combinations on both circular and non-circular sections (double interlocking spirals), eight scaled cantilever-type RCBC specimens will be tested on the bidirectional shake table facility at the University of Nevada, Reno (UNR). As part of the study, a unique inertial loading system named the Bidirectional Mass Rig was developed to allow shake table testing of single cantilever-type RCBC under biaxial ground motions. Two sets of circular and interlocking RCBC will be subjected to different levels of biaxial, torsion and vertical loads through real time earthquake motions. The performance of the specimens will be assessed in terms of strength, deformation, and failure mode. Four of the eight specimens are reported in this paper.