Resistance of Concrete Masonry Walls with Membrane Catcher Systems Subjected to Blast Loading

This paper describes a methodology for analyzing the impulse pressure response of unreinforced concrete masonry walls that have been retrofitted with membranes that are not bonded to the masonry (catcher systems). Membrane catcher systems can be used to protect building occupants from secondary debris resulting from blast pressure, and the effectiveness of systems comprising polymers, composites, geotextiles, and thin steel and aluminum sheets has been researched extensively over the past fifteen years. The methodology presented herein is based upon the large displacement response of the unreinforced masonry wall, with and without compression membrane arching, and the subsequent tension membrane resistance of the catcher system. The necessary equations are developed in the form of nonlinear resistance functions, which are then used in single-degree-of-freedom analyses to develop dynamic response predictions. The applicability of the approach is substantiated through comparison to full-scale blast test results, and demonstrations involving disparate materials and loading are made. 1. BACKGROUND AND INTRODUCTION Unreinforced, ungrouted, concrete masonry unit (CMU) walls, one of the most cost-efficient and effective methods of constructing infill exterior walls of buildings, are used extensively worldwide. However, unreinforced masonry (URM) walls are extremely vulnerable to fragmentation under blast impulse loads, potentially resulting in severe injury to occupants. For these reasons, the United States (US) Department of Defense (DoD) Antiterrorism/Force Protection Construction Standards [1] prohibit the use of unreinforced CMU exterior walls for construction of new DoD facilities. Although URM walls are no longer permitted for new DoD construction, there exist worldwide many buildings and facilities constructed of unreinforced exterior CMU walls that might be considered high risk, as well as industrial facilities that could be subjected to an accidental explosion. Therefore, over the past