A simplified approach to simulate in-plane lateral response of reinforced concrete frames with masonry infills

For seismic design or performance assessment, reinforced concrete (RC) frame buildings with masonry infills are often modeled using strut-cum-masonry constitutive models. A number of models have been considered in the past, which lead to substantially different simulation results. Through an analysis of 106 one‑bay‑one‑story infilled RC frames experimentally studied in the past, this paper presents an evaluation of eight previously proposed masonry constitutive models with masonry panel represented using a set of three struts. The exercise enabled identification of suitable functional forms to characterize the constitutive behavior of masonry panel. Accordingly, a new constitutive model was developed with strength parameters defined in terms of the product of masonry prism strength and cross‑sectional area of struts, and stiffness parameters defined in terms of the masonry elastic modulus and cross-sectional area of struts divided by masonry diagonal length. Multipliers were established for ranges of masonry prism strength. In comparison with existing models, the proposed model could effectively capture the response of the 106 specimens despite its simplicity. Simulation results were not significantly correlated with relevant strength parameters of the RC frame, relative stiffness parameter, and observed failure modes. The proposed model can also be used in combination with one or two struts. However, one-strut model should be avoided if capturing shear failure in frame members is important.