A combined peak-oriented and pinching model for the cyclic simulation of infilled RC frames: application to the Braz (2014) test

This paper presents a simplified numerical modeling strategy to simulate the hysteretic behavior of an infilled reinforced concrete (RC) frame, validated against both experimental data and numerical results from the benchmark study by Braz (2014). To accurately capture the complex interaction between the frame and the infill wall under a sawtooth cyclic loading history, a combined macro-modeling approach is adopted. The RC structural elements (columns and beam) are modeled using a peak-oriented constitutive relationship, which robustly captures the progressive stiffness and strength degradation induced by concrete cracking and steel rebar yielding. Simultaneously, the masonry infill panel is represented using equivalent diagonal strut elements governed by a pinching constitutive model. This formulation effectively replicates the opening and closing of diagonal cracks as well as mortar joint sliding, which drive the characteristic pinching of the hysteresis loops without requiring complex 2D interface contact elements. The numerical simulations show close alignment with both the experimental curves and the numerical results obtained by Braz (2014). The agreement is particularly strong in terms of ultimate load capacity under cyclic reversals and the evolution of cumulative energy dissipation throughout the loading history.  Expanding this combined approach can offer an optimal balance between physical fidelity and computational efficiency, establishing itself as a practical tool for the large-scale seismic vulnerability assessment of existing structures.