Mechanical and Structural Characterization of New Carbon FRP Stirrups for Concrete Members

Shear design of reinforced concrete beams with FRP longitudinal and transverse reinforcement

“…As stated in [1], [6] and [10], the tensile strength of the bent part of the FRP stirrups is significantly lower than that of the straight part.…”

“…As experimentally observed, the main difference of the shear behaviour of beams with FRP stirrups compared to conventional beams with steel stirrups is that stirrups do not yield, and they usually fail in their bottom bent zone. According to [25], [26], [27], and [6], this type of failure can be explained by the fact that bending of the FRP bars into the stirrups configuration, significantly reduces its strength at the bent portions, due to their unidirectional characteristics. A summary of the failure modes of some of the existing experimental programs is presented in the following .…”

Bend-strength of novel filament wound shear reinforcement

“…The ACI 440.1R [15] underestimates the strength of bent corners of the reinforcement whereas the equation proposed by Lee et al [8] overestimates it, whilst representing a closer match to the experimental values. A linear regression analysis performed on the 5% quantile experimental data suggests that the 0.47 constant proposed by Lee et al [8], equation (6), could be reduced to 0.34 for future use on filament wound reinforcement prediction. This allows to obtain the following predicting equation:…”

“…Bends in shear reinforcement, which help to develop sufficient anchorage with the concrete, are associated with additional stress concentrations: transverse stresses due to bearing on the concrete; longitudinal stresses along the length of the fibres due to tensile forces in the shear reinforcement; and kinking of the inner fibres due to the bend generation during manufacture As FRPs do not yield, the combination of these three factors creates an intrinsically weak point at the corners of the reinforcing cage. Bend strength capacities as low as 30-40% of the tensile strength in the direction of the fibres are often reported for FRP stirrups with circular cross section [6][7][8][9][10]. As a consequence, strength of the bend governs the capacity of FRP shear reinforcement.…”

Study on shear resistance of fiberreinforced polymer–reinforced concrete beams

“…The mechanical properties of concrete and GFRP reinforcement were determined experimentally. The compressive strength, tensile strength, and modulus of elasticity of the concrete were evaluated by The carried out tests 38,39 showed that tensile strength of FRP bar was significantly reduced because of tensile and shear stresses acting together. The test results showed that failure of the FRP stirrups occurs in the corner of the bent stirrup.…”