Seismic Performance of Reinforced Concrete Bridge Columns Subjected to Combined Stresses of Compression, Bending, Shear, and Torsion

To explore the seismic performance of RC bridge columns subjected to combined stresses of compression, bending, shear, and torsion, reversed cyclic tests with eight column specimens were performed in the laboratory. Finite-element analysis (FEA) was used to evaluate the strains of the steel bars in columns and to carry out the parametric analysis. It was found that the coupling effect of bending and torsion was significant. Bending hysteresis loops were fuller than torsional hysteresis loops. Different torsion-to-bending ratios resulted in different bending or torsional failure modes. The plastic hinge length increased with an increase in the torsional effect. With an increase of the torsion-to-bending ratio, the flexural capacity was not fully used, but the torsional capacity, torsional stiffness, and torsional energy dissipation increased. With a decrease in column height, the flexural capacity, flexural stiffness, and flexural energy dissipation increased; however, the lateral deformation decreased, and the torsional capacity showed little change. When the longitudinal reinforcement ratio was increased, although the bending performance was enhanced, the torsional performance showed no significant change. An increase in the stirrup ratio improved torsional performance but not bending performance. Strains of longitudinal rebars and stirrups in the plastic hinge area increased greatly after steel yielding. The length of the torsional plastic hinge increased and the position of the plastic hinge moved upward when columns showed the torsional failure mode. The relationship between maximum torque and maximum shear force under different torsion-to-bending ratios is discussed. (C) 2017 American Society of Civil Engineers.