Out-of-plane resistance mechanism and analytical method predicting the out-of-plane performance of Damped Masonry Infill in reinforced concrete frames

Damped masonry infill wall (DMIW) is an efficient innovative solution to improve the in-plane (IP) performance of the ordinary masonry infill wall. While numerical methods are available for evaluating the out-of-plane (OOP) performance of DMIW, theoretical approaches are more direct and readily applicable for assessing seismic safety during the design process. To fill this gap, in this paper, the OOP behavior of the DMIW with two types of DLJ is introduced in terms of the force-displacement relationship, the deformation, and the failure pattern. The OOP resistance mechanism of the DMIW is discussed followed by the derivation of the theoretical methods for calculating the main OOP performance parameters (i.e., the OOP initial stiffness and OOP strength). The validation against the experiment result is carried out. The results indicate that the OOP resistance mechanism of the DMIW with MAW-based DLJs is mainly on the OOP bending capacity of each masonry unit together with the shear capacity of the DLJs. In contrast, the DMIW with mortar-based DLJs resists the OOP loading through the two-way arching action coupled with the two-way bending. The analytical model, based on the simply-supported beam concept, effectively predicts OOP initial stiffness and strength for DMIW with DLJs made of modified asphalt waterproof material. Additionally, the existing model for ordinary masonry infill walls, based on one-way arching action, is applicable to evaluate OOP strength when DLJs are made of low-strength mortar material.