The aim of this study is to investigate the significance of U-wrap shear strengthening on the flexural behavior of Near Surface Mounted (NSM) Fiber Reinforced Polymers (FRP) strengthened Reinforced Concrete (RC) beams. It is well-known that the performance of NSM-FRP technique is strongly dependent on bond performance between adhesive-concrete and adhesive-FRP interface. Although a full development length is provided for the NSM FRP bar, rupture of the FRP bar is highly unlikely. This is attributed to the fact that the NSM FRP bar typically observes a stress level lower than 60% of its ultimate capacity at RC beam failure by debonding of NSM-FRP from the surrounding adhesive. Here, a typical three-side FRP U-wrap using wet layup was employed to improve the shear strength of the RC beam. A test matrix of 25 beams was tested under static load to failure. Four sets were considered including conventional RC beams, RC-beams with U-wrap only, RC-beams with NSM-FRP strengthening only without U-wrap FRP shear strengthening, RC beams with NSM-FRP flexural strengthening and U-wrap FRP shear strengthening, RC beams with NSM-FRP flexural strengthening and U-wrap FRP shear strengthening in shear zone only. The experimental results showed that incorporating FRP U-wrap has a significant effect of the performance of NSM-FRP strengthened RC beams. While a limited improvement of flexural strength of 20% was observed, NSM-FRP strengthened beams with FRP U-wrap experienced a significant reduction in ductility causing sudden failure. The change in the NSM-FRP strengthening system behavior might be attributed to the confinement provided by the U-wrap FRP which resulted in improving the bond strength of the NSM-FRP to the adhesive. This in its turn lead to NSM-FRP bar picking significantly high load level up to rupture with abrupt RC beam failure. The experimental results shed light on the need to consider design limitations when NSM-FRP flexural strengthening is combined with U-wrap FRP shear strengthening in RC beams.
Near Surface Mounting (NSM), Fiber Reinforced Polymers (FRP), de-bonding, abrupt failure, U-wrap shear strengthening, Flexural strengthening, ductility, Epoxy Adhesive
Level of Degree
Taha, Mahmoud Reda
First Committee Member (Chair)
Second Committee Member
ChennaReddy, RahulReddy. "SIGNIFICANCE OF U-WRAP FRP SHEAR STRENGTHENING ON FLEXURAL BEHAVIOR OF RC BEAMS STRENGTHENED USING NEAR SURFACE MOUNTED FRP BARS." (2016). https://digitalrepository.unm.edu/ce_etds/113