Discussion of “Modeling Reinforced-Concrete Beam-Column Joints Subjected to Cyclic Loading” by Laura N. Lowes and Arash Altoontash

This article comments on research in which a model is developed to represent the response of reinforced concrete (RC) beam-column joints under reversed-cyclic loading (Lowes and Altoontash, December 2003). The proposed model provides a simple representation of primary inelastic mechanisms that determine joint behavior: failure of the joint core under shear loading and anchorage failure of beam and column longitudinal reinforcement embedded in the joint. The authors concluded that comparison of simulated and observed response for a series of joint subassemblages with different design details indicates that the proposed model is appropriate for use in simulating response under earthquake loading. The discussion authors feel that the proposed constitutive model for the joint shear panel component of the reinforced concrete (RC) beam-column connection element presented by the authors in their paper may actually work quite well up to fairly high levels of joint shear demand (for well-detailed joints with adequate transverse reinforcement). However, they express concern that the model may not work nearly as well (possibly erroneously predicting joint failure at even moderate joint shear demands) for joints that are not necessarily well detailed with sufficient transverse reinforcement. Finally, the discussers are very much in agreement with the authors that proper robust simulation of RC frame response to seismic loading should include some sort of explicit treatment of inelastic joint effects on both stiffness and strength.