The use of glass-fiber-reinforced-polymer (GFRP) composites as internal reinforcement (re-bars) for concrete structures has proven to be an alternative to traditional steel reinforcement due to significant advantages such as magnetic transparency and, most importantly, corrosion resistance equating to durability advantages and structural life extension. The number of projects in recent years using GFRP re-bars has increased dramatically. Typically, the GFRP re-bars are similar to the steel counterparts having external deformations to bond to concrete, as well as solid circular cross-section. Circular GFRP re-bars with a hollow-core have also become available. They offer the advantage of increasing the effective cross-sectional area that is engaged to carry load since fibers at the center of a solid cross-section are not due to shear lag. Additionally, they offer a larger surface area for improved bond. This paper presents an evaluation of the structural behavior of GFRP hollow-core bar reinforced concrete beams that showed to be comparable to members reinforced with solid GFRP bars. Also, design guidelines as per ACI 440.1R are shown to be applicable to GFRP hollow-core bar reinforcement.
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