PSI - Issue 78

Sara Mozzon et al. / Procedia Structural Integrity 78 (2026) 646–653

648

perspective, the model is compatible with established seismic assessment methodologies, enhancing its utility across multiple hazard contexts.

Fig. 1: Possible failure mechanism of an infill panel: (a) front view, (b) flat cross section, (c) and (d) vertical cross sections.

2.1. Key features of the model Key assumptions underlying the analytical model are outlined below:

• Plate-like response: consistent with approaches in the literature (e.g., Herbert et al., 2018; Milanesi et al., 2018), the model assumes that failure occurs through the formation of five internal cracks, dividing the wall into four rigid blocks. Once the initial crack forms, the panel is subdivided into segments near the boundary restraints and in the central zone. • Location of the horizontal crack: the horizontal fracture is assumed to develop where the bending moment, induced by the applied load profile, reaches its maximum value. • Double arching mechanism across thickness: Given the negligible tensile strength of masonry after cracking, the model assumes that load transfer occurs mainly through arching mechanisms − one vertical and one horizontal − across the panel thickness. This is consistent with the general assumptions of Eurocode 6 (2022) and commonly used OOP resistance models. • Rigid-body rotation of wall segments: when the panel is subjected to OOP displacements, wall segments rotate as rigid bodies around hinges located at the crack lines. No slip is considered between adjacent segments, following a simplified kinematic assumption (Milanesi et al. (2018)). • Triangular deformation profile: for the upper and lower wall portions, deformation is assumed to vary linearly along their height, reaching a maximum at the hinge and vanishing at the opposite end. • Finite stiffness of boundary elements: for infill panels, the model incorporates the vertical flexibility of the top beam (in the vertical arching mechanism) and the lateral deformability of the columns (in the horizontal arching mechanism), allowing for a more realistic interaction between the panel and its frame. • Non-linear material behavior: (a) masonry and potential reinforcement layers in compression are modeled using an elasto-plastic law with post-peak softening, represented by a trapezoidal stress – strain curve featuring elastic, plastic, and descending branches; (b) reinforcements in tension follow an elasto-plastic law, whereas masonry tensile strength is neglected.