Theoretical Analysis Of The Shear Capacity Of Concrete Beams With FRP Stirrups

Reinforced concrete structure is widely used in the field of civil engineering, but the problem that the durability of concrete structures declines due to the steel corrosion and then the structure loses its function increasingly serious. Therefore, high durability material is produced, in which the representative fiber reinforced plastic(FRP) has developed rapidly, which has high-strength lightweight, small elastic modulus compared to steel, high corrosion resistance, etc., so it is widely used instead of reinforced. But now for FRP bars, most studies focus on the flexural properties of the beam(used the FRP as vertical bars), and the experimental study for using FRP as stirrups to resist shear is also less, therefore the inherent law of FRP stirrups to resistant shear is still lacking, so the further study on shear performance is a continuing issue.This paper mainly analysis the shear capacity of FRP stirrups concrete beams by two models which are ultimate strength theory and softened truss model. The main contents are as follows:1.Summarize the basic mechanical properties of FRP bars, analyze the research status of shear behavior of FRP reinforced concrete beams, and summarize the current computing theory of shear capacity of the reinforced concrete beams.2.Specifically for the ultimate strength theory, the first step is to establish a simplified linear beam octahedral strength criterion, then combining the force balance(beams under shear and compressive stress) to derive the shear capacity formulas of concrete beams with FRP stirrups, and finally discuss the formula’s applicable conditions for ordinary reinforced concrete beams.3.For the softened truss model, first to establish the shear model of the concrete beams without stirrups, next combining the balance equation, failure criteria, deformation compatibility conditions and provisions of the parameters to derive the shear capacity formula of concrete beams without stirrups, and secondly computing the shear by FRP stirrups, eventually, superimposing the two parts of the shear to obtain the final shear capacity formula of the beam.The accuracy of the practical formula derived by softened truss model is higher than foreign norms formulas, therefore, the formula derived by the softened truss model can be used as the recommendations shear formula of concrete beams with FRP stirrups.