Title: GFRP-RC Columns with Varied Concrete Strength under Combined Bending-Torsion Cyclic Loading

Author(s): Yasser M. Selmy, Amr E. Abdallah, and Ehab F. El-Salakawy

Publication: Structural Journal

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Issue:

Appears on pages(s):

Keywords: circular columns; combined loading; cyclic loading; glass fiber-reinforced polymers-reinforced concrete (GFRP-RC); seismic; torsion; concrete strength; transverse reinforcement

DOI: 10.14359/51740869

Date: 6/4/2024

Abstract:
Under earthquake excitations, reinforced concrete (RC) columns could be subjected to lateral drift reversals and a combination of axial forces, bending moments, and torsional effects. This paper investigates the behavior of glass fiber-reinforced polymer (GFRP)-RC columns under seismic-simulated loading, including torsion, which has not been studied previously. Seven large-scale circular GFRP-RC column-footing connections were cast and tested under various combined reversed cyclic loading configurations to examine the effects of the torsion-to-bending moment (t_m) ratio, transverse reinforcement ratio, and concrete compressive strength. The test results revealed that increasing the t_m ratio reduced the lateral load capacity and deformability of the GFRP-RC column but resulted in a more symmetric torque-twist relationship. Increasing the transverse reinforcement ratio mitigated core damage and provided additional support (e.g., spiral turns) for torsion-induced tensile stresses. Moreover, increased concrete compressive strength bolstered torque capacity and torsional stiffness, while, under a t_m ratio of 0.4, it resulted in decreased twist capacity. When torsion was present, increasing the concrete compressive strength had an insignificant impact on the bending-shear response, differing from findings for GFRP-RC columns subjected to seismic loading without torsion.