Title: Assessment of Confinement Models and Minimum Volumetric Ratio for Glass Fiber-Reinforced Polymer-Reinforced Concrete Circular Columns
Author(s): Abdeldayem Hadhood, Hamdy M. Mohamed, Amir Fam, and Brahim Benmokrane
Publication: Structural Journal
Appears on pages(s): 305-317
Keywords: circular; confinement; design; glass fiber-reinforced polymer reinforced concrete (GFRP-RC) column; guidelines; model; spiral
The design provisions of reinforced concrete (RC) circular columns in ACI 318 are based on the work done by ACI Committee 105 in 1933 for steel spiral reinforcement. The provisions for volumetric reinforcement ratio and spacing were intended to ensure sufficient confinement after spalling of the concrete cover. This paper presents the development of similar provisions for columns reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bar and spirals that could be adopted in the upcoming version of the ACI 440.1R design guide. A comprehensive database of 56 experiments on concentrically loaded circular columns reinforced with GFRP was assembled from 12 studies with a wider range of parameters. The analysis carried out focused on the confined concrete strength and considered the softening response of the concrete cover, which was presumably omitted in the reported data. An assessment of the available confinement models was made. These models were mostly calibrated with a limited number of specimens. A simpler design-oriented confinement model was developed and accurately predicted the confined strength of the database columns. Additionally, the minimum volumetric ratio of steel spirals in ACI 318 was reviewed and modified for applicability to columns spirally reinforced with FRP.