Out-of-Plane Static and Blast Resistance of UnreinforcedMasonry Wall ConnectionsStrengthened with FRP

Abstract

Synopsis: Recent world events have illustrated that the sustainability of buildings to blast loads is an ever increasing issue. Many older buildings contain unreinforced masonry (URM) infill walls. Due to their low flexural capacity and their brittle mode of failure, these walls have a low resistance to out-of-plane loads, which includes blast loads. As a result, an effort has been undertaken to examine retrofit methods that are feasible to enhance their out-of-plane resistance. The use of externally bonded and near surface mounted (NSM) Fiber Reinforced Polymer (FRP) laminates and rods have been proven to increase the out-of-plane load capacity. This paper investigates the out-of-plane behavior of URM walls strengthened with FRP subjected to static and blast loading and the capability of developing continuity between the FRP strengthening material and the surrounding reinforced concrete (RC) frame system. There were two phases to this research study. Phase I evaluated strengthened URM walls’ out-of-plane performance using static tests. Two strengthening methods were utilized, including the application of glass FRP (GFRP) laminates to the wall’s surface and the installation of near surface mounted (NSM) GFRP rods. In both methods, the strengthening material was anchored to boundary members above and below the wall on some of the specimens in the research program. The effects of bond pattern, and the effects of FRP laminate strip width were also investigated in this phase. Phase II involved the field blast testing of two walls to dynamically study the continuity detail for laminates and verify the results obtained in Phase I. The development of continuity between the FRP materials and the surrounding framing system is one approach to improving the blast resistance of URM infill walls.