Non-linear behaviour of masonry infilled RC frames: Influence of masonry mechanical properties

Unreinforced masonry infilled R.C. frames are a widespread structural system worldwide; even if the damages observed during past earthquakes highlight the influence of masonry infills on the seismic performance of structures, the common practice considers the infill as nonstructural elements. The infills are made with a large variety of materials and with different construction typologies; nevertheless, a large number of studies have been carried out in the last years to investigate the interaction between the infill panels and the surrounding R.C. frames, few researches have been focused on the influence of mechanical properties of masonry infills on the structural performance. In this study the seismic performance of R.C. frames designed for gravity loads according to the code prescription in force in Italy between 1950s and 1970s has been evaluated. A parametric analysis has been performed to investigate the influence of the mechanical and geometrical properties of masonry infills on the whole structural response; the seismic behaviour has been analyzed in terms of capacity, ductility and collapse mechanisms. The results showed as the mechanical properties of masonry infills should be adequately evaluated before to proceed to the seismic vulnerability assessment of existing structures because they significantly affect the global behaviour of R.C. frames.