Prediction of the out-of-plane response of infilled frames under seismic loads by a new fiber-section macro-model

During an earthquake the in-plane response of infills interacts with the out-of-plane response, primarily governed by the arching mechanism developed because of the boundary frame. The assessment of the out-of-plane capacity of infills and its reciprocal dependence with in-plane damage constitutes an open question. The paper suggests an extension of the capability of the traditional inplane macro-models to capture the simultaneous in-plane and out-of-plane response of infills. A practical modelling procedure is proposed and validated using experimental data. The possibility to simulate the arching action is achieved by using distributed plasticity fiber-section elements, able to directly account for the coupling between axial load and bending moment.