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The realistic modelling of seismically loaded infill masonry is a complicated task due to the complex interaction of the infill with the surrounding frame. Practical approaches, that take into consideration the non‐linear behaviour of the infill and the frame, are especially lacking at the moment. Within the framework of the European project INSYSME (Innovative Systems for Earthquake Resistant Masonry Enclosures in R.C. Buildings [1]), the behaviour of infill masonry in reinforced concrete frames is being investigated experimentally to derive different strategies for the modelling of infill masonry. In addition, systems for the improvement of the seismic behaviour will be developed. In the following, some initial results of the different modelling strategies are presented.

Masonry infilled reinforced concrete frames under horizontal loading Stahlbetonrahmen mit Ausfachungen aus Mauerwerk unter horizontalen BelastungenThe behaviour of infilled reinforced concrete frames under horizontal load has been widely investigated, both experimentally and numerically. Since experimental tests represent large investments, numerical simulations offer an efficient approach for a more comprehensive analysis. When RC frames with masonry infill walls are subjected to horizontal loading, their behaviour is highly non-linear after a certain limit, which makes their analysis quite difficult. The non-linear behaviour results from the complex inelastic material properties of the concrete, infill wall and conditions at the wall-frame interface. In order to investigate this non-linear behaviour in detail, a finite element model using a micro modelling approach is developed, which is able to predict the complex non-linear behaviour resulting from the different materials and their interaction. Concrete and bricks are represented by a non-linear material model, while each reinforcement bar is represented as an individual part installed in the concrete part and behaving elasto-plastically. Each brick is modelled individuallyand connected taking into account the non-linearity of a brick mortar interface. The same approach is followed using two finite element software packages and the results are compared with the experimental results. The numerical models show a good agreement with the experiments in predicting the overall behaviour, but also very good matching for strength capacity and drift. The results emphasize the quality and the valuable contribution of the numerical models for use in parametric studies, which are needed for the derivation of design recommendations for infilled frame structures.