The use of Fiber-reinforced polymer (FRP) composite materials in new construction and repair of concrete structures has been growing rapidly in recent years. FRP provides options and benefits not available using traditional materials. The promise of FRP materials lies in their high-strength, lightweight, noncorrosive, nonconducting, and nonmagnetic properties. ACI Committee 440 has published several guides providing recommendations for the use of FRP materials based on available test data, technical reports, and field applications. The aim of these document is to help practitioners implement FRP technology while providing testimony that design and construction with FRP materials systems is rapidly moving from emerging to mainstream technology.

An experimental study was conducted to determine the transfer length of prestressed Glass Fiber Reinforced Polymer bars. This paper is a part of a broad program that studies the long-term behaviour of GFRP prestressed concrete beams. 16 GFRP prestressed concrete beams were cast in this study. The parameters included were; prestressing level; 300 MPa (44 ksi) and 500 MPa (73 ksi), concrete compressive strength; 30 MPa (4440 psi) and 70 MPa (10000 psi), and the GFRP bar diameter;12Φ (No. 4) and 16Φ (No.5). Accurate estimation of the transfer length is necessary for elastic stress calculations at the service limit state and for the shear design of prestressed members. Strain gauges were used to measure strains on the GFRP bars and DEMEC gauges were used to measure the concrete surface strains at the level of the prestressed GFRP bar to determine the transfer length. The transfer length of 16Φ (No.5) GFRP bars in concrete with compressive strength of 30 MPa (4440 psi) was found to be about 17 db, and 14 db for prestressing levels of 500 MPa (73 ksi) and 300 MPa (44 ksi), respectively. The measured transfer length values were used to improve the transfer length estimates provided by the ACI 440.4 R-04 equation by calibrating the material coefficient factor (αt) used in the ACI equation.

This work presents an experimental investigation of composite girders consisting of precast Ultra-High Performance Fiber-Reinforced Concrete (UHPFRC) slabs placed on pultruded Fiber-Reinforced Polymer (FRP) Igirders. Two control girder specimens and seven large-scale composite girders were tested under static four-point bending. Two series of the FRP-UHPFRC composite girders were examined. H-series girders composed of hybrid carbon/glass FRP (HFRP) I-girders topped with either full-length precast UHPFRC slabs or segmental counterparts. G-series girders included segmental UHPFRC slabs placed on glass-fiber-reinforced polymer (GFRP) I-girders. Twelve precast UHPFRC segments were used in each slab of the segmental composite girders. Either high-strength mortar or epoxy adhesive were used to join the precast UHPFRC segments. The test results revealed that the flexural stiffness of the composite girder with the epoxy-connected segmental precast slabs is almost identical to that of the full-length precast composite girder. The mortar-connected girder exhibited slightly more ductile behavior than the epoxy-connected girder. The G-series girder with thick GFRP plate externally bonded to the soffit of the GFRP Igirder showed pseudo-ductile behavior. All the composite girders demonstrated significant improvements in flexural stiffness and moment-carrying capacity compared with the control FRP I-girders without the UHPFRC slabs.

A commonly reported failure mode through experimentation of fibre-reinforced polymer (FRP)-concrete bonded interfaces is premature debonding of the FRP. Such undesirable failure can occur at strains significantly lower than the strain capacity of the FRP and it can be sudden. Anchorage of the FRP is an intuitive means to delay and even halt debonding, and the addition of anchors can also lead to more deformable FRP-strengthened elements. The so-called FRP anchor has been shown to be an effective anchorage device and while there have been several experimental studies reported to date on FRP-strengthened RC elements anchored with such anchors, there has been decidedly less research on numerical modelling. This paper presents the details of a partial interaction model and a constitutive model for the FRP-to-concrete bonded interface as well as FRP anchors. The models are then used to simulate FRP anchors in single-shear FRP-to-concrete joints. The results of parametric studies on key variables such as plate geometry and plate material properties as well as anchor location and number of anchors are then provided. The parametric studies enable insights to be gained towards the contribution of FRP anchors in FRP-to-concrete bonded interfaces.

Strength and fatigue testing were conducted on concrete specimens strengthened with three different epoxy systems. These specimens were conditioned in elevated water baths, subjected to fatigue loading, then tested for strength. For all three systems, the bond strength of a single conditioned specimen was at least 90 percent of the bond strength of three samples that had been fatigued but not conditioned in elevated water baths. Because of the limited data the results are anecdotal and only preliminary findings can be drawn from this work.