Influence of the Modelling Approach on the Failure Modes of RC Infilled Frames Under Seismic Actions

The influence of the masonry infills on the seismic performances of Reinforced Concrete (RC) frames is generally evaluated in analytical and numerical studies by adopting the equivalent strut model; it is based on experimental observations showing that at the onset of damage, stresses migrate to the diagonal of the panel and are transferred to the surrounding frame through the contact zones at the corners. Above the different equivalent strut models available in literature, single-strut models are generally used to evaluate the global behaviour, while multi-strut approaches are preferred to investigate on local interaction phenomena between panel and frame. In case of existing buildings, with poor transversal reinforcement of the columns, the presence of the infills can lead to pre-emptive brittle failure. The present study is aimed at evaluating the influence of the modelling approach on the evaluation of the seismic performance both in terms of global and local behaviour. Nonlinear dynamic analyses have been performed on an 8-storey infilled RC frame, following the Incremental Dynamic Analysis procedure, in order to evaluate structural performances depending on the model adopted to simulate the infills.