New Macroelement for Modeling Inelastic Shear–Flexure–Axial Interaction and Elongation of Plastic Hinges for Reliable Seismic Performance Assessment of RC Structures

Modeling plasticity in reinforced concrete structures is a challenging task due to the intricate behavior of concrete and reinforcing steel, and interaction between them. Although the distributed plasticity approach of modeling excels in capturing nonlinear behavior, it can be computationally demanding, especially for larger structures. On the other hand, the lumped plasticity approach often struggles to represent interactions among shear, flexural, and axial forces and the elongation of plastic hinges, limiting its accuracy. Combining the advantages of the distributed and lumped plasticity approaches while mitigating their drawbacks, this paper introduces a novel macroelement capable of capturing inelastic shear deformation, shear–flexure–axial interaction and plastic hinge elongation. The model is designed for use in nonlinear time-history analysis of reinforced concrete structures and is validated through numerical simulations of two-dimensional (2D) structures subjected to experimental tests, assessing shear deformation, axial force, moment rotation, and axial elongation. This approach addresses the limitations of previous models and offers a more comprehensive solution for the accurate simulation of plasticity in reinforced concrete structures, especially at high ductility levels. Sensitivity analyses highlight the importance of parameters like shear reinforcement strain-hardening, and reinforcing steel buckling in estimation of the elongation and shear deformation. The study also observes growth of member depth due to inelastic shear deformation of plastic hinges, challenging conventional assumptions and prompting further exploration of this complex interaction.