Experimental Investigation of the Natural Bonding Strength between Stay-In-Place Form and Concrete in FRP-Concrete Decks/Beams

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.

Experimental and Numerical Study of Shear Interface Response of Hybrid Thin CFRP–Concrete Slabs

“…The shape of those load–slip curves has some similarity to that of the A-IM samples. It is also interesting to note that Gong et al [ 43 ] observed progressive failure before the bearing stage, due to the loss of the natural bond when using stay-in-place forms (SIP), and they achieved curves similar to those of samples AS-M. Later, when bolts bore loads, the performance was totally different from that of our samples.…”

“…Gong et al [ 42 ] studied the interfacial stress in FRP–concrete hybrid beams using the finite difference method (FDM) and push-out tests. Moreover, Gong et al [ 43 ] performed an experimental investigation of the natural bonding between FRP and concrete.…”

A State‐of‐the‐Art Review on Hybrid GFRP‐Concrete Bridge Deck Systems

“…In 2019, Gong et al conducted an experimental investigation of the natural bonding strength between FRP profiles and in situ cast concrete [64]. Four pushout test specimens were carried out as same as the part of [63], in which two specimens were equipped with steel bolts as the interfacial connection, and the other two were equipped with the SIP form and steel bolts together.…”

Fire Evaluation of RC Frames Strengthened with FRPs Using Finite Element Method

“…These artificial or natural phenomena cause devastating consequences because the deficiency of RC structures. Using Fiber Reinforced Polymer (FRP) is one of the most common methods of retrofitting RC members (Gong et al, 2019;Qin et al, 2019;Soleimani and Sayyar Roudsari, 2019). It can be used to enhance not only capability of RC structure for seismic loads but also, employing FRP material is suitable for extreme loading conditions.…”