In-plane and out-of-plane model for retrofitted infill walls in reinforced concrete framed buildings

The retrofit of infill walls in reinforced concrete frames is often employed to avoid out-of-plane failure caused by earthquakes. Additionally, some strengthening techniques also increase in-plane capacity of the infill. The interaction between in-plane and out-of-plane response of infill walls significantly influences their contribution to the dynamic behaviour of the structure and, consequently, the seismic response. In some cases, the beneficial increase of global stiffness and strength caused by the infill can be nullified by out-of-plane mechanism. On the other hand, an excessive increase of infill's strength can cause brittle failure of gravity load designed columns, due to local interaction. In this study, a numerical macro model is developed to simulate the interaction between in-plane and out-of-plane response of infill walls in gravity load designed reinforced concrete frames. An infilled portal frame is modelled, considering the case of un-reinforced infill and two types of retrofitted infill. Non-linear dynamic analyses are conducted and the seismic performances are evaluated depending on the type of the infill.