Torsional Behavior of Concrete Box Girders Reinforced with Longitudinal GFRP Bars and Without Stirrups

Abstract

AbstractSo far, the torsional strength and behavior of reinforced concrete (RC) box girders reinforced with glass-fiber-reinforced polymer (GFRP) bars have not yet been discussed. This paper reports on an investigation of the torsional behavior of large-scale RC box girders reinforced with GFRP and steel reinforcement. All box girders had the same dimensions with 4,000 mm long, 380 mm wide, 380 mm deep, and 100 mm wall thickness and were examined under pure torsion moment. The test specimens included one box girder reinforced with longitudinal GFRP bars and one box girder reinforced with longitudinal steel bars. All specimens have the same longitudinal reinforcement ratio with different reinforcement types and without any transverse torsional reinforcement to study the influence of the longitudinal reinforcement only on the torsional behavior. The test results pointed out that the GFRP RC box girder experienced cracking torsional strength slightly higher than the steel one. All girders did not achieve post-cracking torsional strength owing to the absence of the transverse reinforcement. The ultimate torsional strength for these specimens coincided with the cracking torsional strength. In addition, the ACI-318-19 cracking torsional strength design equation underestimated the cracking torque by an average of 21%.