Experimental and Analytical Studies of U-Shaped Thin-Walled RC Beams Under Combined Actions of Torsion, Flexure and Shear

• Published in: International journal of concrete structures and materials 2018-12, Vol.12 (1), p.1-17, Article 33
• Main Authors: Xu, Jianchao, Chen, Shenggang, Guo, Quanquan, Ye, Yinghua, Diao, Bo, Mo, Y. L.
• Format: Article
• Language: English
• Subjects: Bending moments; Building Materials; combined action of torsion and flexure; Concrete bridges; Ductility tests; Engineering; Failure; Failure modes; Flexing; Mathematical analysis; Original Article; Reinforced concrete; Shear; Solid Mechanics; Structural Materials; Thin wall sections; Torque; Torsion; U-shaped thin-walled beam; ultimate load; Ultimate loads; Warping; warping torsion
• ISSN: 1976-0485; 2234-1315
• DOI: 10.1186/s40069-018-0245-8

U-shaped thin-walled concrete bridge beams usually suffer the combined actions of flexure, shear and torsion, but no research about the behavior of U-shaped thin-walled RC beams under combined actions has been reported in literature. Three large specimens of U-shaped thin-walled RC beams were tested under different torque–bending moment ratios (T–M ratios) of 1:5, 1:1 and 1:0 to investigate the mechanical responses such as crack patterns, reinforcement strains, failure modes and ductility. The testing results showed that ductile flexural failures occurred for all three of the U-shaped thin-walled beam specimens, although the combined shear effect of circulatory torque, warping torque and shear force increased as the T–M ratio increased from 1:5 via 1:1 to 1:0, reflected by diagonal cracks and stirrup strains. More specifically, basically symmetrical flexural failure was dominated by the bending moment when the T–M ratio was 1:5; flexural failure of the loaded half of the U-shaped thin-walled section was dominated by the combined action of the bending moment and warping moment, while there were only a few cracks on the other half of the U-shaped section when the T–M ratio was 1:1; and anti-symmetrical flexural failure was dominated by the warping moment when the T–M ratio was 1:0 (pure torsion). A simple method to calculate the ultimate load of such U-shaped thin-walled RC beams under different T–M ratios was suggested, and the calculating results were corresponding well with the experimental results.