Shear Strengthening of R.C Beams with FRP Using (NSM) Technique

Abstract

This paper presents the experimental results of investigations the shear behavior of strengthened reinforced concrete beams by using glass fiber reinforced polymers (GFRP) rods. The strengthening system used GFRP rods were done by Near Surface Mounted technique (NSM), NSM technique contains a groove on the outside surface of the concrete member to adjust the depth to be less than the cover of the member. After cleaning, the epoxy paste was used to fill half of the groove's depth. The particular FRP element is then mounted in the groove. Finally, the groove is filled with epoxy and the too much epoxy is leveled with the outside surface of the concrete. This method enables the fiber reinforcement polymer FRP materials is covered completely by epoxy. The main objective of this research is to study the effect of NSM technique on shear resistance for RC beam. The parameters are considered in this study are effect of the material type used for strengthening (inner steel stirrups and external glass fiber stirrups), effect of FRP rods inclination on strengthened beams, shape with different end anchorage of FRP (strips and rods), and the effect of number of the used FRP rods. This paper involved 13 experimental investigations of half-scale R.C beams. The experimental program included two specimens strengthened with inner steel stirrups, eight specimens strengthened with stirrups of Glass Fiber Reinforced Polymer GFRP rods with the shape of different end anchorage and angle, and two specimens strengthened with externally bonded GFRP strips. The remaining un-strengthened specimen was assigned as a control one for comparison. The test results included ultimate capacity load, deflection, cracking, and mode of failure. All beams strengthened with GFRP rods showed an increase in the capacity ranging between 14% to 85% comparing to the reference beam, and beams strengthened with GFRP strips showed an increase in the capacity ranging between 7% to 22% comparing to the reference beam.