Torsional Behavior of Rectangular and Flanged Concrete Beams with FRP Reinforcements

Abstract

The demand for sustainable future infrastructures calls for new and innovative alternatives to avoid the problems associated with the conventional methods of construction. Fiber-reinforced polymer (FRP) bars have superior properties over conventional steel, mainly being noncorrosive. The objective of this study is to propose a model for predicting the full torsional behavior of concrete beams with the following: (1) carbon (C) or glass (G) FRP reinforcements, (2) different cross section shapes, and (3) adhesively bonded FRP stirrups or bent FRP stirrups. A brief recount of the findings from previous works is presented. Two previous models were adapted, and several new features were added to them, including but not limited to (1) recommending appropriate constitutive models for both the FRP and the concrete and (2) proposing failure criteria based on the experimentally observed failure modes. In addition, the first model was extended from an original strength model to a full behavior model (modified Collins). Moreover, the ability to analyze unsymmetrical beams with FRP reinforcements under torsion was added to the second model (modified Deifalla). The modified Deifalla model showed a slightly better agreement with the experimental results compared with the modified Collins model. In addition, modified Deifalla was capable of calculating the transversal strain at different faces of the cross section with a reasonable agreement compared to the experimentally observed ones. However, the modified Collins model was simpler than the modified Deifalla model. Further experimental data are needed before these findings can be generalized and refined.