International Concrete Abstracts Portal

Grid-shaped FRP reinforcement has been developed to prevent deterioration of concrete structures owing to corrosion of reinforcement. This reinforcement is made of high-strength continuous fibers impregnated with resin and formed into a grid shape to insure bond with concrete. When this development was carried out, joint research and development with some universities as well as a Japanese technological development project was conducted to clarify fundamental properties of this reinforcement and structural behavior of reinforced concrete members. Applications of this reinforcement to actual structures began with such civil engineering structures as tunnels, LPG tanks, etc. In Japan, applications of advanced composite materials to building structures require governmental approval. Therefore, to apply this reinforcement to precast concrete curtain walls, heat-resistance and fire-resistance tests were conducted to obtain the approval of the Minister of Construction. This is the first time that FRP reinforcement was used in Japanese building structures. Application of this reinforcement to box-framed reinforced concrete structures will be considered next.

A 30-ft span, 17-ft wide bridge was constructed in Rapid City, South Dakota, in the summer of 1991 to demonstrate the application of graphite and fiberglass cables for prestressing bridge decks. This bridge was designed by consultants and built by local contractors with the technology developed at the South Dakota School of Mines and Technology. Paper deals with the construction phase, testing, and monitoring of the bridge from September, 1991 to December, 1992. Post-tensioning bonded method was used for prestressing the bridge deck in the transverse direction, whereas nonprestressed reinforced reinforcement was used in the longitudinal direction as distributors. The slab thickness was 7 in. and was supported by three longitudinal girders. One-third of the bridge was prestressed with S-2 glass cables, while the second one-third was prestressed with graphite cables and the last one-third was prestressed with steel cables. Special anchorages were used for prestressing the cables. Electrical and slip gages were used to monitor the stresses in the cable and deck. After the bridge deck was constructed, it was loaded for static and dynamic loading before it was opened for traffic. Paper addresses the test methods and quality control for bridge cables, including the design guidelines for using new materials for the bridge decks. The actual test data for the bridge was compared with the design data and found very comparable in this project. This bridge project demonstrates the feasibility of using advanced composite cables for prestressing bridge decks. The information gained through the design, construction, and monitoring of this bridge will help provide guidelines for the design and construction of future bridges.

The three-dimensional fabric studied as reinforcement for concrete is a stereo-fabric made of fiber rovings, woven into three directions, and impregnated with epoxy resin. Fiber material, number of filaments, and distance between rovings can be varied easily. Efficient production is also possible, since three-dimensional weaving, resin impregnation, and hardening can all be done by an automatic weaving machine. The authors investigated the flexural and fire-resistance behaviors of three-dimensional fabric reinforced concrete (3D-FRC) toward applying the material to building panels. The fibers studied were carbon and aramid, and the matrix was vinylon short-fiber reinforced concrete. The results demonstrate that 3D-FRC panels have sufficient strength and rigidity to withstand design wind loads, and the fire resistance of 60 min was achieved. The 3D-FRC panels have been used for curtain walls, parapets, partition walls, louvers, etc., and installations amount to 7000 m 2.

Presents information on the development and use of carbon fiber reinforced plastic (CFRP) to strengthen reinforced concrete chimneys, bridge piers, and beams in Japan; bridge beams in Switzerland; and ongoing structural research and use of fiber reinforced plastic (FRP) composite materials to strengthen such structures in the U.S. The concept and equipment for strengthening existing reinforced concrete chimneys by wrapping them with carbon reinforced plastic materials began in Japan. The procedure permitted earthquake-damaged chimneys to be repaired without taking them out of service. Research in Switzerland has led to the use of adhesively bonded sheets of carbon reinforced plastic laminates to strengthen existing bridges. This concept is an extension of use of bonded steel plates to strengthen many types of structures throughout Europe. Research, development, and some use of these techniques has been done in the U.S.

FRP are new materials for structural engineers. Therefore, an overview on the important fiber properties, matrix resins, and composite elements becomes necessary to show the assets and drawbacks of FRP and to illustrate their potentials and limits. Besides several other fields, concrete prestressing seems to have become a promising field of application of FRP. In prestressed concrete construction, high strength and good corrosion resistance of FRP can be utilized optimally. In this field of application, FRP can compete with prestressing steel, especially in such cases in which the corrosion protection of prestressing steel becomes expensive or remains tarnished by residual risks. The post-tensioning of concrete structures requires anchorages with a high mechanical efficiency. The main avenues of development are discussed, and the necessary future research is outlined.