In-plane—Out-of-plane interaction in the seismic response of masonry infills in RC frames

Current modelling techniques in dynamic analyses of RC frame buildings with masonry infills use macro models for estimating drift demand. Newly proposed models include the out-of-plane behaviour of the masonry infill walls during the analysis. Thus far, interaction between the in-plane and out-of-plane direction with respect to the infill wall has been approached by means of a displacement yield surface. A complete model showing good agreement with multiple experiments on different masonry typologies has not yet been proposed. In the proposal of a new model, two full-scale experiment campaigns with contrasting typologies, weak and strong, have been considered, the former being more susceptible to out-of-pane failure and the latter comprising of thicker, single leaf construction. Both typologies contribute significantly to the in-plane stiffness and strength of the story. The campaigns involve a series of experiments loading the infill wall out-of-plane direction after a maximum drift in-plane has been reached via cyclic loading. The data suggest a relation between the maximum interstory drift and the outof- plane strength and stiffness. The new model approaches the interaction by modifying the stiffness and the strength of the infill in the out-of-plane direction during the analysis. The nonlinear dynamic response to bidirectional excitation with and without the proposed interaction algorithm is examined using models of the experiment specimens. The results show an increase in out-of-plane displacement due to the effect of damage from in-plane drift on the infill wall.