Out-of-plane blast capacity of load-bearing masonry walls

A large percentage of the world’s population lives in buildings constructed with load-bearing masonry. Masonry is commonly used to fabricate structural building components such as walls, arches and vaults. The high vulnerability of load-bearing masonry walls to lateral dynamic loads induces a risk of human losses and progressive collapse in buildings, particularly in case of blast loads. This work is aimed at investigating the out-of-plane dynamic response of unreinforced masonry (URM) walls to explosions generated by uncontrolled gas leakage in residential buildings. As experimental tests are difficult to make in these loading conditions, dynamic simulation is a viable and effective strategy to assess a large number of structural models with different geometry, masonry properties, boundary conditions, and loads. A macro-modelling finite element (FE) strategy was adopted to perform numerical simulations and to identify out-of-plane wall collapse under dynamic loading through LS-DYNA software. A parametric study was performed to evaluate the effects of pre-compression vertical load, mechanical properties, and slenderness of load-bearing walls under a set of lateral pressure–time histories simulating deflagration blast loading. The output was the derivation of pressure–impulse diagrams that provide the combinations of lateral pressure and impulse able to cause out-of-plane wall collapse. It was found that slenderness and vertical pre-compression strongly affect the blast response of URM walls, while material strength and stiffness may have a relatively small influence. Numerical results were compared to analytical models, obtaining a satisfactory agreement in terms of lateral pressure capacity. A simplified model was also developed to predict the out-of-plane blast capacity