Effect of axial stiffness ratio of frp bar on the behvior of hybrid frp/steel reinforced concrete beams

Abstract

This paper presents the research results on the influence of the axial stiffness ratio of fiber-reinforced polymer (FRP) bars on the steel yielding moment and the load-bearing capacity of the cross-section of FRP/steel hybrid reinforced concrete beams. To simulate the behavior of the beam, the author constructed a hybrid reinforcement beam model combining glass fiber bars and steel bars using the Lira-Sapr software. The simulation results of beam was verified with experimental research results. Based on the beam model in Lira-Sapr, the author analyzed the behavior of three different beam groups concerning steel reinforcement ratio, FRP reinforcement ratio and the elastic modulus of FRP, thereby assessing the impact of the FRP axial stiffness ratio on the steel yielding moment and the load-bearing capacity of the beam. The research results show that, with a fixed steel reinforcement ratio, increasing the FRP axial stiffness ratio from 1.06 to 1.67 increases the steel yielding moment of the beam by 51% and the load-bearing capacity by up to 87%. Simultaneously, the load-bearing capacity and steel yielding moment of beams using different types of FRP with various elastic moduli but the same axial stiffness ratio are equal. Conversely, with a fixed FRP reinforcement ratio, increasing the FRP axial stiffness ratio from 1.11 to 1.67 decreases the steel yielding moment by 73.3% and the load-bearing capacity of the beam by 35.4%.

Keywords: Beam; reinforced concrete; FRP, hybrid reinforcement; Lira-Sapr; Axial stiffness.