AbstractThe structural performance of reinforced concrete (RC) beams strengthened in shear with embedded through-section (ETS) glass fiber-reinforced polymer (GFRP) bars is experimentally and analytically investigated. Three-point bending tests are performed. The investigated parameters include the number of existing steel stirrups (ρsw = 0.28%), concrete compressive strength (fc′ = 27 and 43 MPa), shear span-to-effective depth ratio (a/d = 2.4, 3.6, and 4.8), anchorage presence (with and without anchorage), and anchorage properties (steel and GFRP anchorage systems, as well as the anchorage length). The results indicate that the shear capacity and stiffness of the beams are enhanced by applying ETS-GFRP, increasing concrete strength, and decreasing shear span-to-effective depth ratio. The ETS-GFRP-strengthened beams exhibit a more ductile failure mode than the unstrengthened beam owing to concrete crushing in loading areas. The beam stiffness depends significantly on the anchorage presence and properties, and the beam shear capacities differ considerably for different anchorage systems. Anchorage with four steel nuts or two GFRP nuts at the ETS bar ends provides the highest shear resistance and stiffness for the ETS-strengthened beams. The results of this study suggest that the details and configuration of the anchorage system should be carefully considered for the development of unanimous specifications. Additionally, previously proposed shear models can be used to conservatively analyze test results with sufficient accuracy. The newly developed model for estimation of the shear strengths of ETS-GFRP-strengthened beams and the effective strains in ETS-GFRP bars agrees well with the test data.
Practical ApplicationsThe experimental results obtained from the present study demonstrate the potential of the embedded through-section (ETS) method for practical applications in the shear strengthening of the reinforced concrete (RC) beams. The predrilled holes through the beam height are made at the marked positions, which could be determined by a rebar detector. Next, the adhesive resin is fully injected into the holes prior embedding the fiber-reinforced polymer (FRP) bars. In the present study, the glass fiber-reinforced polymer (GFRP) bars are used. Then, the ends of each FRP bar are anchored with screwed nuts. Comparing with the unstrengthened beam, the ETS-strengthened beam offers a larger capacity, more ductility, and safer failure. The shear performance of the ETS-strengthened beams is proportional to the concrete compressive strength. The decrease of the shear span-to-effective depth ratio increases the shear resistance of the ETS-strengthened beams. The anchorage at two bar ends with two GFRP or four steel nuts is deemed to be most effective. Additionally, the proposed shear strength model can be used for the design of the beam with an ETS strengthening system.