The accuracy of the lumped plasticity model for estimating nonlinear behavior of reinforced concrete frames under gradually increasing vertical loads

Abstract

Simplicity and computational efficiency of the lumped plasticity model have made it a popular approach for analyzing structures. However, it has been shown by researchers that the accuracy of the lumped plasticity model for representing the inelastic behavior of reinforced concrete (RC) structures needs further investigations. Two full-scale RC frames with different shear spans were constructed and subjected to the vertical load through their beam. Finite element (FE) models of the tested specimens were established in SAP2000 software, and their results were compared with the experimental tests. The effects of using different plastic hinge lengths, initial effective stiffness, and locations of plastic hinges were investigated. It was observed that regardless of the selected plastic hinge lengths, the established FE models estimated the yield and ultimate loads of the frames accurately. However, they did not estimate accurately the vertical displacements corresponding to the yield and ultimate loads. Results also indicated that the obtained yield and ultimate loads from the established FE models were significantly influenced by the selected locations for plastic hinges. Moreover, at the ultimate load of frames the estimated damage level to the mid-span of beams by FE models was lower than the results of experimental tests.