The Effects of Blast Loading on the Interface of Concrete Masonry Units and Mortar

Abstract

Masonry has always been a very efficient building material because of its low cost, availability, versatility, and construction simplicity. In terms of blast protection, masonry presents an enormous challenge: when subjected to blast loading, unreinforced masonry walls tend to break up into fragments that are propelled into the building interior at hazardous velocities. For these reasons, the response of unreinforced masonry walls subjected to impulse loads has been extensively studied through testing and advanced analyses and case studies of actual explosion events. However, as demonstrated by numerous blast load tests and investigations, the weakest part of an unreinforced masonry wall system is the interface between the masonry unit and mortar. However, as seen from observing previous relevant research, there is still a large amount of variation in approaches used to simulate that critical bond interface. This thesis therefore presents the results of an investigation intended to define the influence of masonry-mortar bond strength on the response of unreinforced masonry walls to far-field blast loads, and ultimately to provide guidance on optimum techniques for use in advanced finite element simulations. As a result of this work, it was determined that properly modeling the mortar in finite element models is important to obtain accurate results. It was also found that the shear and tensile strength of the connection between mortar and concrete masonry unit needed to be increased with dynamic loading. A testing setup for future testing was decided upon to validate such conclusions.