The influence of masonry infill on the seismic behaviour of RC frame buildings

Although in literature many studies show that infills modify the behaviour of framed structures under lateral loads, the contribution of panels is generally neglected in common structural analyses. The aim of this paper is to provide a simple tool able to reproduce the effect of infills in the global (stiffness) and local response (effects on the frame) of a building under earthquake loads. Finite Element analyses are performed, comparing the results to experimental data, in order to evaluate the local effects on the frame and underline the influence of the coefficient of friction at the infill–frame interface. Successively a suitable macro-model to simulate the infill behaviour is proposed, at the aim to reach acceptable results both in global and local analyses: two non-parallel struts are set in each frame according to the most significant parameters affecting the behaviour of an infilled structure. The obtained results are applied to a partially infilled building, in order to underline the peculiarities of the proposed approach and to compare it to other methods available in literature and in codes.

► We model an infill panel by two equivalent struts. ► The position of the two struts depends on the stress resultant at the panel–frame interface. ► The two-strut model is validated on the basis of experimental results available in literature. ► The two-strut model allows to evaluate both global and local responses. ► The two-strut model is characterized by simple use and short computational effort.