Simplified modelling and pushover analysis of infilled frame structures accounting for strut flexibility

Seismic assessment of structures is often performed using their force-displacement capacity or pushover curve computed via non-linear static analysis. However, these analyses' reliability depends on the numerical model's detail and its ability to capture salient failure mechanisms. Simplified analysis methods offer effective means of identifying structural deficiencies and provide analysts with a sound understanding of key structural characteristics, such as the strength hierarchy, status of the structural damage in terms of limit state exceedance or the progression of the inelastic mechanism, in addition to providing a method with which to check numerical analysis results. This work builds upon the existing literature for simplified analysis of moment frame structures and describes a simplified pushover-based analysis procedure for infilled frame structures. Individual storey responses are obtained by combining the flexural resistance of the frame and accounting for the axial resistance of the infill (modelled as an equivalent axial strut) and the boundary frame members, assuming both systems work in parallel. Then, the displaced shape of the structure is iteratively calculated for a given base shear, which can be repeated until a pushover curve is obtained with relative ease. The proposed procedure is tested and evaluated versus other available methods by analysing several infilled reinforced concrete frames. It is shown that the method can perform simplified pushover analysis with a high degree of fidelity while improving over the other similar methods currently available.