A Proposed Equation for the Estimation of Plastic Hinge Length of RC Columns subjected to Ground Motions

In a strong earthquake, a standard reinforced concrete column may develop plastic deformations in regions often termed as plastic hinge regions. A plastic hinge is basically a damping device that dissipates energy through the plastic rotation of a rigid column connection, thus triggering the redistribution of bending moments. The formation of a plastic hinge in an RC column in the regions that experience inelastic actions depends on the characteristics of the earthquakes as well as the column details. In this paper, 462 inelastic time-history analyses have been performed to predict the nonlinear behavior of RC columns under the ground motions. The effects of axial load, height-to-depth ratio and amount of longitudinal reinforcement, as well as different characteristics of earthquakes are evaluated analytically by finite element methods and the results are compared with the corresponding experimental data. Analytical models for the columns analysed under high axial loads exhibit longer plastic hinges than those analysed under low axial loads. Based on the results, a simple expression is proposed to estimate plastic hinge length of RC columns subjected to earthquakes.