Effects of the In-Plane Flexural Behavior Modeling Choices for Hollow Clay Masonry Brickwork with Horizontal Holes

Buildings with load-bearing structures made of hollow clay blocks with horizontal holes and ce-ment-based mortar are quite common in Italy, yet the current design standards do not consider specific modeling issues to be addressed by practicing engineers. In the absence of peculiar specifi-cations, the prescriptions given for ordinary masonry walls are thus commonly adopted. However, experimental tests proved that walls built with hollow brick masonry performed quite differently from ordinary masonry walls. Considering the in-plane flexural behavior under horizontal loads, unlike ordinary masonry walls that exhibit some ductility, this construction typology performs quite poorly, showing very little deformation capacity and ductility. In recent experimental campaigns, a brittle collapse mechanism was observed due to the toe crush, which entailed the inability of the wall to further withstand the vertical loads. In this paper, the effects of incorrect modeling choices on the characterization of the in-plane behavior of this construction typology and the consequences related to overestimating ductility are discussed; the effects of the reduced ductility on the reliability of the assessment of an existing building as well as on the conceptual design of possible structural retrofit measures are investigated. From the critical discussion, the need emerged to accurately model the in-plane flexural behavior and to update the code provisions to explicitly consider masonry walls with hollow clay bricks with horizontal holes.