Shear Strengthening of Reinforced Concrete Beams Using Pre-fabricated Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) Laminates: Experimental Investigation

This study examines the effectiveness of prefabricated ultra-high-performance fiberreinforced concrete (UHPFRC) laminates in shear strengthening reinforced concrete (RC) beams. A total of nine reinforced concrete beams were cast and tested under a four-point loading till failure. The following key parameters were investigated: the number of strengthening sides, the thickness of the UHPFRC layer, the reinforcement of the strengthening layer (by using two different types of steel mesh, and also, in case of no-steel mesh), the volume fraction of steel fibers, and bonding schemes steel dowels and / or epoxy. The ultimate load and ductility of the strengthened beams have increased up to 45.6% and 76%, respectively, compared to the unstrengthened beam. It has been found that using an epoxy bonding system performs more effectively than adding steel dowels. The ultimate load was raised by 7% and 12.5% where epoxy bonding system is applied only for laminates thickness of 15 mm and 30 mm, respectively on both sides (with 2% steel fiber) compared to specimens where steel dowels were added. As expected, the results also revealed that using the strengthening layer with reinforcement provides better shear performance than using UHPFRC layers without reinforcement. Using welded steel mesh and expanded steel mesh in the strengthening layer increased the ultimate load by 39% and 41.5%, respectively, in the case of a 15 mm strengthening layer on both sides with 2% steel fiber.