Simplified Model for the Torsional Strength of Concrete Beams with GFRP Stirrups

Abstract

An international committee on shear and torsion reported that giving physical significance for the torsion design is an upcoming challenge. The purpose of this paper is to propose a reasonably accurate and relatively simple model capable of predicting the torsional strength of concrete beams reinforced with glass fiber–reinforced polymer (GFRP) stirrups. In this paper, a database for concrete beams reinforced with GFRP stirrups, tested under torsion, is compiled. The implementation of the torsion design provisions of the conventional steel-reinforced-concrete design codes is discussed. A few selected strength models were used to predict the ultimate torsional strength of the tested beams. The predicted strength was compared with that measured during testing. The comparison showed that more improvement is required in calculating the inclination of the diagonal concrete strut and the effective strain in the GFRP stirrups. Two strength models were modified and proposed. The proposed models showed better compliance and consistency with the experimental results compared to the available models and design codes. In addition, the proposed models are noniterative and simple to implement. However, further experimental testing will help refine the proposed models.