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.

The development of fiber composite materials (FRPs) and their application to structural elements as externally bonded reinforcement is an effective means to increase the strength of existing bridge girders in flexure, shear and torsion. Despite the high strength of FRP materials, premature debonding of the FRP from the concrete substrate typically occurs well before the ultimate tensile strength of the material is reached. Recent research has found that the introduction of end anchorage systems such as bidirectional fiber patch anchors has been found to counteract the end peeling and interfacial shear stresses that occur at fiber ends, resulting in much higher material utilisation prior to debond. However, all of the research conducted on patch anchors to date has been based on near-end supported single shear pull tests and the performance of patch anchors when applied to large-scale beams remains to be investigated. The paper presents a finite element analysis of a large-scale bulb T beam which was calibrated using experimental results from the literature. The calibrated model was later modified by the addition of FRP shear strengthening and the inclusion of bidirectional fiber patch anchors which were found to significantly enhance the maximum laminate strains attained prior to beam failure.

Steel prestressed cored slab superstructures are a common structural system for multi-span bridges in coastal North Carolina. However, due to the aggressive marine environment several such bridges are in need of major repairs or replacement after being in service for little more than 40 years. To address this issue two research projects were undertaken in parallel. The first project involved a critical assessment of non-destructive evaluation techniques in an attempt to predict the extent of corrosion deterioration and hence, the residual strength of cored slabs from existing bridges. Twelve cored slabs taken from two in-service bridges scheduled for superstructure replacement were tested to failure in the laboratory to validate residual strength predictions. The second project involved the design, manufacture and testing of a full-scale CFRP prestressed cored slab reinforced with GFRP stirrups, and a typical steel prestressed cored slab control specimen. The results of the destructive laboratory testing enabled validation of the prediction of the flexural performance and strength of CFRP prestressed cored slabs relative to existing design recommendations. Direct comparison to the new steel prestressed control cored slab and similar existing cored slabs with varying degrees of deterioration from the first the research project was also undertaken.