Modelling of the behaviour of seismically strengthened masonry walls subjected to cyclic in-plane shear

A research project on the structural behaviour of seismically strengthened unreinforced masonry (URM) walls is underway at ETH Zurich. The main goal of the research project is to investigate the influence of the prefabricated, pre-stressed strengthening elements on the structural behaviour of masonry walls under cyclic shear loading. Load tests on a series of full scale clay block masonry specimens, which consisted of an URM wall strengthened with two pre-stressed elements have been completed. Test results are analysed and discussed in the present paper. Analytical modelling of the behaviour is accomplished by applying the methods of the theory of plasticity, namely the lower bound theorem, i.e. ideal-plastic material behaviour whereas numerical modelling assumes an elastic-plastic material behaviour. The procedure based on the advanced finite element model and continuous stress fields, and the analytical model based on discontinuous stress fields, which are able to predict the behaviour of the above-mentioned wall system, are proposed and verified by the comparison with experiments. In addition, a simplified model, adopted for practical application is introduced and two examples are calculated. A satisfactory agreement between the proposed models and test data has been found. The paper closes with a set of conclusions and recommendations for practical application and for future research.