Abstract
The Fiber Reinforced Polymer (FRP)-concrete hybrid deck/beam is a structural system that combines the durable thin-walled FRP composite profiles and the cost-effective concrete by interfacial shear connections. The interfacial slip can reduce the composite action, thereby causing a degradation of flexural rigidity and capacity. Therefore, using stay-in-place (SIP) forms is a simple way to fully utilize the natural bonding between FRP and concrete, which plays a pivotal role in the structural design of FRP-concrete hybrid decks/beams. This paper presents an experimental study on the natural bonding provided by the SIP forms and the in situ cast concrete. First, four comparative push-out test specimens revealed that the use of SIP forms could improve the ultimate shear capacity of steel bolts by 11.1%. Moreover, it could provide an initial stage with nearly zero slip. The average natural bonding strength of FRP-concrete was evaluated as 0.27 MPa, which agreed well with previous tests in the literature. Second, the beam specimen also confirmed that there was a load response stage with nearly zero slip along the FRP-concrete interface when SIP forms were used as the permanent form. Third, the strain measurements on the steel bolts, FRP profile, and concrete revealed that the failure of the natural bonding was a brittle process. Finally, the flexural response of the FRP-concrete hybrid beam was analytically modeled as three distinct stages, namely the full composite action stage, the slipping stage caused by a natural bonding decrease, and the partial composite action stage.
Highlights
The advantageous properties of light-weight, high tensile strength along the fiber direction, and durability under harsh environments have made fiber reinforced polymer (FRP) composites an advanced and competitive solution to repair and retrofit civil engineering structures [1,2,3]
Fiber Reinforced Polymer (FRP) composites have a higher strength but lower modulus when compared with steel, which makes the structural design of FRP structures usually governed by rigidity and deformation [1]
FRP and a large amount to the interfacial shearproved connection at the natural bonding between and concrete contributes a large amount to the interfacial shear the beginning of loading, and (ii) the use of SIP forms can improve the contact area for natural bonding connection at the beginning of loading, andconnection
Summary
The advantageous properties of light-weight, high tensile strength along the fiber direction, and durability under harsh environments have made fiber reinforced polymer (FRP) composites an advanced and competitive solution to repair and retrofit civil engineering structures [1,2,3]. Among the various combinations of FRP and concrete, the FRP-concrete hybrid deck/beam system is one of the structures that has been developed both in laboratory research and field applications [19,20,21,22]. In the market of bridge decks and girders, the FRP-concrete hybrid deck/beam can result in an advanced and cost-effective solution by combining the reasonable stiffness and low cost of concrete with the light-weight, fast fabrication, high strength, and high durability of FRP composites [23,24]. The connection types, for example, steel studs, perfobond ribs, and channel plates, in steel-composite decks and beams cannot be directly used for FRP-concrete hybrid decks/beams as the interfacial slip can cause notable flexural rigidity degradation and normal stresses increase at the FRP and concrete parts. Experimental Determination of FRP-Concrete Natural Bonding by the Push-Out Test
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