Shear Strength Prediction of Interior Beam-Column Joints Under Seismic Loading

Beam-column connections in a ductile reinforced concrete frame is a critical region because of the high shear force and bond breakdown within them. The vast number of parameters affecting the joint behavior have stimulated many researchers to experimentally investigate and analytically study the connection under simulated earthquake forces. Nevertheless no simple design tool has yet been found. Thus recommended design methods of beam-column joints in different countries vary significantly. As it is known in the joint core there is a biaxial stress state of tension and compression which causes failure. An analytical expression, which takes into account this stress state, is here presented to estimate the shear strength of interior reinforce concrete beam-column joints under seismic loading. This expression is based on the superposition of three resisting contributions to shear strength: the concrete, the longitudinal reinforcement and the stirrup ones. The reliability of the proposed model is compared with those obtained by means of American, New Zealand and European Code formulas, and also with those obtained by means of some analytical expressions recently proposed by other authors. These comparisons have been done in respect to the experimental results on more than 250 interior reinforced concrete beam-column joints found in the literature. The proposed expression is found to most adequately predict the shear strength of the joint and give the best correlation with the test results.