Assessment of resistance definitions used for blast analysis of unreinforced masonry walls

Abstract

Over recent decades, three distinct methods have evolved that are currently being used to generate resistance functions for single-degree-of-freedom analyses of unreinforced masonry walls subjected to blast loading. The degree of differences in these resistance definitions depends on whether the wall is assumed to be simply supported or whether compression arching forces result from rotation restraint at the supports. The first method originated in the late 1960s as a result of both experimental and analytical research sponsored by the US Department of Defense. That method, referred to as the Wiehle method, is the basis of Unified Facilities Criteria 3-340-02 and other derived analytical software such as the Wall Analysis Code developed by the US Army Corps of Engineers, Engineer Research and Development Center. The second method is based on elastic mechanics and an assumed linear decay function that follows and is the basis of the widely used Single-Degree-of-Freedom Blast Effects Design Spreadsheets software distributed by the US Army Corps of Engineers, Protective Design Center. The third method is largely based on concrete and masonry behavioral theories developed by Paulay and Priestly in the early 1990s. This article systematically compares the resistance methodologies for arching and non-arching scenarios, demonstrates the implications by plugging the disparate resistance functions into blast load single-degree-of-freedom models, compares the analytical results to full-scale blast test results, and offers conclusions about the accuracy and efficacies of each method.

A Discrete Element Method based-approach for arched masonry structures under blast loads

“…With rigid blocks, the normal and tangential stiffness (k n and k t , respectively) of the interfaces are modified with respect to the expressions previously derived (see Sect. 2) to account for the deformability of the blocks in the real structure (see also [31]): The elasticity lumping formulae (13) and (14) are derived for in-plane loading of planar structures [42]. For head joints, the block thickness h b represents the brick length, while for bed joints, h b is the brick height.…”

“…For head joints, the block thickness h b represents the brick length, while for bed joints, h b is the brick height. Table 10 displays the material elastic parameters used for the model with rigid blocks, derived from those given in Table 4 (for deformable DE) and considering the nondeformability of the blocks, see Eq.s (13,14). The material parameters that define the plasticity behaviour and the corresponding softening remain unchanged, see Sect.…”

“…Abou-Zeid et al [1] studied the response of arching walls made of hollow concrete bricks under several explosive weights, in a far-field scenario. Gagnet et al [14] performed full-scale explosion tests on masonry walls to investigate the influence of boundary conditions in the development of compressive arching actions. Keys and Clubley [20] investigated masonry debris distribution and failure patterns of masonry walls when subjected to long duration blast loading.…”

Blast resistance of membrane retrofit unreinforced masonry walls with flexible connections

“…The membrane retrofit methodology developed in the previous sections was combined with resistances that represent the flexural behavior of URM walls, integrated into an SDOF algorithm, and compared to full-scale blast test results involving membrane retrofit URM walls with flexible attachments. Several URM resistance function methodologies have been developed for the blast analysis application; the details of those approaches are summarized in Gagnet et al (2017). The method initially presented by Wiehle and Bokholt (1968) was used to generate the resistance of the non-arching walls.…”

“…The loading was measured at mid-height of the wall using miniature pressure transducers mounted flush with the structure and just to the side of the masonry wall. Details of the resistance function formulation and methods of calculating the arching resistance are provided in Gagnet (2013) and Gagnet et al (2017).…”