GFRP hollow-core bars as internal reinforcement for concrete slabs

Glass-fibre-reinforced-polymer (GFRP) composites as internal reinforcement bars (rebars) for concrete structures have 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 and structural life extension. The number of reinforced concrete (RC) projects in recent years specifying GFRP rebars has increased exponentially. Typically, GFRP rebars are similar to their steel counterparts having solid circular cross-section as well as surface deformations or sand coating to develop bond to concrete. With increasing manufacturing innovation, a novel circular GFRP rebar with a hollow-core has been developed. Compared to bars with equivalent cross-sectional area, the two main advantages hollow-core rebars provide are: i) increase in surface area, yielding higher bond-to-concrete; and ii) reduction of shear-lag effect, increasing the effective cross-sectional area of glass fibres carrying load. This paper presents an evaluation of the structural behaviour of RC slabs reinforced with GFRP hollow-core rebars compared to slabs reinforced with round solid GFRP rebars with equal nominal cross-sectional area. Additionally, design guidelines as per ACI 440.1R are shown to remain applicable to the tested slabs reinforced with the different GFRP rebar types. © 2015, NetComposites Limited.