Damage-based RC beam element for nonlinear structural analysis

As a reinforced concrete member is subjected to loading of increasing intensity, it undergoes different phases of damage, from cracking up to ultimate failure. It is necessary to simulate this process mathematically to predict the capacity of damaged structures to resist further load. A damage-based modeling approach is presented in this paper to predict the nonlinear response of RC frame members modeled as elastic beams with two end inelastic hinges. Damage is assumed to be concentrated at plastic hinges and is quantified through a physically motivated damage index that is related to the damaged state of the structural component. The proposed damage-based element formulation combines matrix structural analysis, plastic theories and concepts from continuum damage mechanics. The model is shown to reasonably simulate the strength and stiffness degradation of cyclically loaded reinforced concrete members under uniaxial bending in combination with constant axial force. The study includes a regression-based identification to provide guidelines for estimating the required model parameters. The advantage of the model lies in its efficacy to evaluate the inelastic response of RC members that couples computationally inexpensive frame elements with classical moment–curvature analysis.