Simulation of reinforced concrete beam-column joints strengthened by ferrocement jackets

Abstract

Beam-column joints are critical members in a moment-resisting structure to maintain the stability of the whole structure. Failure of beam-column joints is likely to cause the collapse of the structure. Many methods have been proposed to strengthen reinforced concrete beam-column joints. Among others, relocation of plastic hinges away from beam-column joints has been proved to be effective. However, there exist limited studies on numerical simulation of seismic performance of beam-column joints failed with the formation of plastic hinges at end of beams. This paper examines modeling of this type of beam-column joints using OpenSees. It is recognized that rotation due to the strain penetration of longitudinal reinforcements at the end of a plastic hinge has a substantial effect on the overall response of a beam-column joint. Omission of this effect will result in an overestimation of the hysteretic behavior. To simulate the behavior of a beam-column joint failed with the formation of plastic hinge, a numerical model based on a macro joint element combined with bond-slip zerolength element or moment-rotation spring element to account for the effect of strain penetration is proposed. This model has been successfully implemented into OpenSees for representing beam-column joints strengthened by ferrocement jackets with chamfers. It has been shown that accuracy of the numerical predictions is significantly improved by taking into account the rotation induced by strain penetration.