Design, Detailing, and Architectural Impacts of Fiber Reinforced Polymers (FRP) and Geotextile Fabrics in the Blast Mitigation of Unreinforced Masonry Walls in Historic Buildings

Abstract

There is a growing need to reinforce historic structures to resist air-blast loading due to exterior blast events. The facade systems of these buildings are typically backed by unreinforced masonry walls, using either brick or hollow concrete masonry block (CMU), which must be retrofit in place to resist the design blast loading. Some of the associated design challenges include: installation of wall reinforcement while preserving the aesthetic qualities of the building facade, coordination of interior finishes and MEP elements with wall reinforcement and anchorage, and providing adequate load transfer from the reinforced walls to the structural diaphragm. Two options for the retrofit of existing masonry walls are the use of fiber reinforced polymers (FRP) and geotextile fabrics. FRP is a high tensile strength material directly laminated to the existing substrate that can significantly increase the flexural capacity of unreinforced masonry. Geotextile fabrics are effective as debris-catch systems that allow the wall to fail and prevent the masonry debris from entering the protected space. While both are viable options, the design, construction, and performance of FRP and geotextile fabrics under blast loadings are quite dissimilar from each other. Both options require careful coordination with the rest of the design disciplines for proper implementation. This paper will review the analytical tools that are available to predict the behavior of unreinforced masonry walls retrofit with FRP or geotextile fabric when subjected to blast loadings. Design considerations and options, anchorage detailing and construction aspects of both materials will be examined, and a discussion of the architectural implications will also be presented.