Investigation on the Column Shear Failure due to the Local Interaction with Masonry Infills in RC Frames

RC buildings designed for gravity loads only or according to obsolete seismic codes are widespread worldwide also in seismic prone areas. Numerical and experimental studies highlighted that the presence of masonry infills in Reinforced Concrete (RC) frames leads to the increase in their lateral strength and stiffness. Nevertheless, post-earthquake observed damage showed that infills can also cause potential brittle failures due to the local interaction with structural elements, thus producing a limitation of deformation capacity of the surrounding frame, especially in sub-standard frames. A reliable modelling approach for the assessment of the as-built condition and the design of retrofitting solutions about this kind of failure is still needed. Experimental tests on RC frames designed according to obsolete technical codes and infilled with clay bricks have been performed and presented in this work. The frames have been cyclically loaded with a quasi-static displacement pattern to simulate the seismic action. The experimental occurrence of significant shear damages is discussed, and the main outcomes are described, commented and compared to each other. The work lastly provides further data and modelling remarks towards a reliable numerical simulation of local shear interaction phenomena between infills and RC frames.