Numerical simulation of the in-plane lateral response of RC infill frames using a FEM-DMEM modelling approach

Reinforced concrete frame structures incorporating masonry infills are common forms of construction and can be found in many seismic regions of the world. Often these frames are designed for gravity loads only and neglect the effects of the non-structural masonry infill walls. A detailed simulation of infill frames requires refined mesoscale models to capture the behaviour of the reinforced concrete frame, the masonry infill and their complex nonlinear interaction. One of the most efficient modelling approaches is the Discrete Macro Element Model (DMEM), which has the advantage of providing a geometrically consistent description of the infill-frame interaction with limited computational effort compared to refined finite element models. In the original formulation of the DMEM approach, the frame is simulated by means of 1D beam/column elements interacting with the macro-elements, simulating the infills, by means of discrete interfaces. In this paper, a hybrid modelling strategy is developed using the commercially available software ABAQUS. The frame is modelled by means of nonlinear 3D solid finite elements, while the infills are simulated by adopting the DMEM model i.e. macro-elements. Unlike previous models, this model allows the novel simulation of the shear behaviour, which highly governs the lateral resistance, between the frame and infill via 2D continuum contact elements. The capability of the proposed model to simulate the non-linear response and failure mechanisms of masonry infill frames is demonstrated by comparing the numerical results to published experimental results. The results showed that the model predicted the ultimate horizontal load carrying capacity with an accuracy level of 95% and the predicted failure modes were in agreement with the experiment.