Infills with sliding joints to limit the post-earthquake damage: role and design of openings

Masonry infill walls are typically considered non-structural elements in building design. Nonetheless, their interaction with the structure during earthquakes is well documented in literature and their significant effect on the building seismic performance highlighted. A critical aspect is the damage suffered by traditional infills that can jeopardize the safety of inhabitants and lead to significant building downtime. Recently, different innovative construction techniques have been proposed, aimed at obtaining deformable infills characterized by low stiffness, low damageability and large deformation capacity, in order to limit the infill-frame interaction and the post-earthquake damage. The paper discusses the role of a fullheight opening in the seismic response of infills made deformable by adopting sliding joints. A summary of the test results obtained by the authors on a real scale infill with horizontal sliding joints and a full height opening is presented, together with a parametric study on the in-plane response of an infill with opening in a “one story-one bay” RC frame. Focus is made on the interaction of the infill with the surrounding frame and on the maximum actions in a critical component of the infill, namely the post located at the window’s side to control the infill’s sliding mechanism. The parametric study, based on a numerical micro-modeling approach, offers some preliminary guidelines for the design of the infilled frame, based on the opening position, infill length and sliding joint configuration. The results show the positive effect of the posts’ deformability in limiting the shear action on both the frame’s columns and the post itself, including its connection to the frame.