Simplified model for the seismic performance of masonry infilled RC buildings

The accurate and rapid estimation of the seismic response of buildings is paramount for large-scale vulnerability assessments for planning purposes and for emergency management after an earthquake. This requires the development of computationally efficient alternatives to sophisticated finite element models. This paper presents an enhanced simplified 3D multi-degree-of-freedom model for infilled Reinforced Concrete (RC) buildings extending a previously proposed model for bare RC frames. The in-plane response of masonry infills is macro-modelled using two shear springs acting in parallel with inter-storey drift springs representing the RC columns. This simplified representation reduces computational demand while effectively capturing key aspects of the infilled building's structural behaviour. The model's accuracy and efficiency are validated against a refined model of an existing RC building with in-plan irregularity via nonlinear response history analyses. The reference case study is also used to explore the impact of different masonry mechanical properties on the infilled frame's lateral response. The results demonstrate the ability of the simplified model to accurately capture the frame global structural behaviour, including torsional effects and collapse mechanisms. A detailed analysis of the failure evolution of the frame members further substantiates the model's capability to simulate damage progression with satisfactory reliability. These attributes establish the proposed simplified modelling approach as a valuable, computationally expedient tool for large-scale seismic assessments of RC building stocks.