Plastic Hinge Capacity Prediction for Existing RC Rectangular Columns to Load Reversals

A prediction model for evaluating the effective plastic hinge length for existing Reinforced Concrete (RC) columns under lateral load reversals is presented. The plastic hinges were observed during the test of twenty-four column specimens, which were fabricated to simulate the existing columns by using mid-strength materials of concrete and reinforcing bars with the details stipulated by old Chinese code. The testing factors included axial load level, slenderness ratio and transverse reinforcement ratio. The observations indicated that a 2% drift of RC columns could provide a satisfactory approximation of the ultimate flexural strength, which corresponded to the limiting compressive strain in the concrete compressive zone. The 2% drift is assumed as the ultimate state, and it is applied to the Paulay and Priestley plastic hinge model to conservatively determinate the rotation capacity of the plastic hinge for existing RC columns. The prediction model is based on the results and is compared with four current design codes, and the results suggest that the plastic hinge capacity specified in current codes could plausibly be higher when the axial level is high.