Effect of load cycling on plastic hinge length in RC columns

Due to the high complexity of the plastic hinge in reinforced concrete (RC) columns, investigation of its behavior under cyclic loading has largely been studied by experimental testing. However, different experimental works reported in the literature have focused on a certain aspect or special cases only, due to the high cost of testing. Different and even contradictory conclusions have been reported. The present paper reports an investigation on the behavior of plastic hinges in cyclically loaded RC columns through three-dimensional finite element method (FEM). The accuracy of the finite element model is first verified by test results. After that, the lengths of plastic hinge zones, including rebar yielding zone, curvature localization zone, concrete crushing zone, and equivalent plastic hinge, of RC columns subjected to monotonic and cyclic loading are studied in detail under different parameters. It is found that all three zones are significantly affected by loading types. Finally, the research findings are synthesized into a new model for plastic hinge length that allows for number of load cycle.