International Concrete Abstracts Portal

Current design methods for predicting deflections and crack widths at service load in concrete structures reinforced with steel bars may not be necessarily applicable in those reinforced with fiber reinforced polymer (FRP) bars. In this paper, methods for predicting deflections and crack widths and spacing of glass fiber reinforced polymer (GFRP) reinforced concrete beams were proposed. In order to use the effective moment of inertia for concrete beams reinforced with FRP bars, the effect of reinforcement ratios and elastic modulus of the FRP reinforcement were incorporated in Branson’s equation. This paper also presents a new equation to predict crack width. Six concrete beams reinforced with different GFRP reinforcement ratios were tested. Deflections and crack widths were measured and compared with those obtained by the proposed models. The comparison between the experimental results and those predicted was in good agreement.

This paper summarizes research findings on the use of carbon fibre reinforced polymer (CFRP) sheets for shear strengthening of pretensioned AASHTO bridge girders. The research includes an experimental program conducted at the University of Manitoba using scale models of pretensioned concrete girders in composite action with the deck slab. Seven ten meter long beams were strengthened with three different types of CFRP sheets using ten different configurations and were tested to failure at each end. The paper describes the experimental program, test results, failure mechanisms and the effectiveness of each configuration of CFRP sheets. A rational model is introduced to define the contribution of the CFRP sheets to the shear resistance in addition to the contributions provided by the stirrups and the concrete for I-shaped pretensioned concrete members. Test results are used to verify the proposed model.

The use of non-metallic bridge deck reinforcement is of interest in regions where corrosion is a problem. A number of manufacturers have developed GFRP rebar for this application. Because the production of the material is relatively new, there is a great deal of variability among the products from different manufacturers. In addition, as the manufacturers continue to develop their own product, variations in GFRP from single manufacturers have been observed. The objective of this study was to investigate the bond between GFRP reinforcement and concrete using inverted half-beam specimen. The inverted half-beam specimen were designed to simulate the conditions likely to be found in a bridge deck (no transverse reinforcement and small concrete cover). Products from two different manufacturers were chosen for the study because of the widely varying characteristics of the product. One manufacturer produced reinforcement with surface deformations created by a helical wrap of glass fibers around the GFRP bar; the other manufacturer developed a ceramic coating that emulated the surface texture of a deformed steel bar. The two different bar types exhibited different bond behaviors. The bond for the bars with the ceramic deformations relied most heavily on mechanical interlock, as was evident from cracking patterns. The bond for the bars with the helical wrap deformations relied most heavily on friction. Both bar types demonstrated large variability for the bond specimen that failed in bar fracture, with some bar failure loads more than two standard deviations below the average bar tensile strength.

An experimental study on bond strength of Continuous Fiber Sheet (CFS) was conducted. Based on the experimental results the bond strength and various factors are clarified. Bond strength does not increase with bond length for bond length longer than 100 mm. As CFS stiffness increases, the maximum local and average bond stresses at delamination increase and CFS strain gradient decreases. CFS with a narrower width has a bond strength greater than that with a wider width. Non-uniform loading decreases the bond strength, however anchor steel plate with tensioned bolt increases it due to the bond between steel plate and CFS and confinement from the bolt. From the observed bond stress in CFS, the equation to predict the maximum local bond stress was proposed.

A two level parking facility formed the base of an apartment complex. The structural system incorporated a composite-steel deck for the upper level which provides bottom reinforcing for the structural slab. Other than Welded Wire Fabric (WWF), no top reinforcing was provided over the beams or girders. An inappropriate choice of construction for a parking deck due to the potential for corrosion from chloride contamination, the problem was compounded by inadequate reinforcing, poor drainage and no waterproofing. The result was a severely deteriorated deck. Slab cuts that would allow the installation of top reinforcing as required to develop the negative moment based on continuity were not feasible because the electrical conduit for the building was buried in the slab. Therefore, CFRP was used to save the existing structural system and minimize repair costs. Design concerns included load stress, shear strength and membrane integrity. Field testing was successfully conducted. The result was an innovative use of the material which decreased the severity and cost of repairs.