Combined IP/OOP parametric non-linear static analysis on RC frame buildings infilled with strengthened thin masonry panels

The use of unreinforced thin clay masonry infills in RC frames as internal partition walls is widespread. Medium and more severe earthquakes are responsible of relevant monetary and human life losses caused by the interaction between the In-Plane and the Out-Of-Plane action that affects these non-structural elements. In order to reduce the Out-Of-Plane vulnerability of these weak panels, three external reinforcing solutions were experimentally investigated at the laboratory of the University of Padova. Such solutions consists of external plaster layers applied both sides of the masonry wall and the additional embedding of a basalt fiber mesh. This paper presents a new macro-model able to predict the combined In-Plane/Out-Of-Plane response of thin masonry infills through two non-linear fiber struts along each diagonal direction. The proposed macro-model was calibrated on the results of combined In-Plane/Out-Of-Plane experimental tests carried out on unreinforced and strengthened thin masonry infills. The aim of the numerical study is the evaluation of the benefits of the proposed reinforcing solutions on the RC infilled frames overall behavior. For this purpose, an extended parametric non-linear static analysis was carried out on RC frames representative of the Italian building stock, both traditionally and seismically designed. Two different incremental In-Plane force patterns were applied on the frame whereas Out-of-Plane equivalent static forces, calculated for three increasing values of Peak Ground Acceleration, were applied directly on the nonstructural elements. The analyses were carried out for both types of panels previously calibrated. The evaluation of the strengthening effectiveness is shown in terms of improvement of the overall structural response, postponement of all infill Limit States and thus different damage distribution along building height. Finally, the new Italian Seismic Classification procedure was implemented to evaluate the reduction of the expected annual seismic losses, as well as of the seismic Risk Class.