Strengthening Concrete Masonry with Fiber Reinforced Polymers

Abstract

FRP materials such as carbon, aramid, and glass provide a potentially economical means of strengthening unreinforced and under-reinforced masonry. Potential applications include strengthening for a change in occupancy or load-testing; repair of inadequate construction; or possibly as an alternative reinforcing method for new construction. At the University of Wyoming, seven unreinforced concrete masonry walls were tested in out-of-plane flexure with carbon, aramid, and glass tape reinforcing. The initial three walls were tested with carbon tow sheets, laminates, and aramid tapes applied to the exterior surface of the wall. These initial tests indicated that the FRP strengths were well above the strength of the masonry causing shear failures in the unreinforced masonry. In addition, cost comparisons of the strengthening materials indicated that they were cost-prohibitive when compared to traditional strengthening methods. The four remaining walls were strengthened with narrow strips of unidirectional fiberglass fabric applied to the with epoxy. The objective of the second set of tests was to force a tension failure in the FRP rather than a shear or compression failure in the masonry. The failure modes included fracture of the GFRP, combination delamination/fracture, and complete delamination. Tension tests were also conducted on single lengths of the GFRP tape. The tension test was developed to provide a method of predicting the flexural tensile strength of the GFRP tape. Observed and potential failure modes are presented based on test observations along with a discussion of the desirable failure modes for the strengthening system.