Upgrading often becomes a necessity due to changes in usage of buildings due to factors such as deterioration and aging, change in occupancy, or the need for installation of facilities such as air-conditioning, heating, escalators, elevators, additional skylights, or new façade structures. In a number of cases upgrading is related to changes which affect the load bearing components of the structure. Fiber reinforced polymer matrix composites provide an efficient means of both strengthening slabs for enhanced load carrying capacity and for strengthening slabs after installation of cut-outs. This paper reports on a series of tests conducted to assess the comparative efficiencies of a commercially available strip form and a fabric form of material vis-à-vis strengthening ability and ductility. It is shown that material tailoring can result in significant changes in efficiencies. The extension of this to the rehabilitation of cut-outs is also detailed and aspects of an on-going full-scale test program in that area are elucidated.

The bond between an aramid fibre reinforced plastic (AFRP) tendon and concrete has a significant effect on the flexural behaviour of a concrete beam pre-tensioned with AFRP. In particular, the performance of beams with prestressed AFRP tendons can be enhanced by the use of partially-bonded tendons. Two types of partial bond are possible; intermittent bond, where sections of the tendon are alternately bonded and debonded from the concrete, and adhesive bond, where the tendon is coated with a resin of known, low shear strength. However, the choice between these methods, and the determination of the values of the various parameters required, are not trivial problems. It is found that a major obstacle in the development of a generalised design procedure for the partially-bonded beams is the uncertainty regarding the rotation at which the concrete will fail. Nevertheless, insight into design aspects of the intermittently-bonded and adhesively-bonded beams is gained and a design methodology is proposed.

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.

Increasingly, existing concrete structures are being assessed as having insufficient capacity in shear; the development of an efficient and durable means of upgrading such structures is becoming of utmost importance. An exciting solution is the use of tensioned non-laminated carbon fiber reinforced plastic (CFRP) straps as active (stressed) external shear reinforcement for concrete. The use of an active system has several advantages over a passive (unstressed) reinforcement system. In particular, the prestressed CFRP straps provide confinement and enhance the performance of the concrete. Details of a series of tests carried out on a concrete beam strengthened using these novel CFRP shear reinforcing elements are presented. The strain in each of the straps was measured during testing and valuable insight into the shear behaviour of the concrete beam was gained. It was found that the strengthened beam had a much higher shear capacity than the predicted resistance of an equivalent unstrengthened beam.

Design guidelines for reinforced concrete structures (RC) with fibre reinforced polymers (FRP) use the concept of partial safety factors to ensure that structural safety is attained. However, when partial safety factors are used for the design of FRP RC structures, the structural reliability levels are not known. It is very important that structural reliability targets are met, in particular when there is a change in the predominant mode of failure. Furthermore, the resistance-capacity margins between various failure modes are not known. The work reported in this paper investigates these safety-related uncertainties. The notional structural reliability levels of two FRP RC beams are evaluated for the flexural and shear failure mode. The resistance-capacity margins for these two failure modes are also evaluated. Finally, the effect of the partial safety factors on the type of the expected failure mode is investigated.