Title: Strength, Durability and Health Monitoring of Composites Overlays on Civil Engineering Structures
1 Strength, durability and health monitoring aspects of composite overlays on civil engineering structures are discussed. The perspective and benefits of the repair, upgrade, retrofit, and rehabilitation of US civil infrastructure using composite overlays is briefly reviewed. Bond strength, durability, and in-service health monitoring are identified as critical issues blocking the wide acceptance of these novel structural systems in the construction engineering community. A theoretical and experimental research program, set up at the University of South Carolina, is briefly presented. Test methods development, modeling efforts, and proposed outcomes are discussed. The wider perspective of developing national standards and engineering guidelines for the design and utilization of composite overlays on civil infrastructures is also addressed. INTRODUCTION According to the US Department of Transportation and the Federal Highway Administration, there are about 576,000 bridges in the national bridge inventory, and 23% of these are structurally deficient and in need of repair. Several States have demonstrated that advanced fiber reinforced polymers (FRP) can be used to improve the load capacity of concrete bridges. FRP repair technology offers a practical way to rehabilitate aging concrete bridges without disrupting traffic flow. Masonry buildings also form an important component of US civil engineering structures with historical value. Repairs, rehabilitation and upgrades of masonry are required to meet new strength and seismic requirements. The use of FRP composite overlay on masonry has many potential benefits. A major obstacle in the widespread use of these new engineering solutions is the lack of standards and practices for assessing the quality of the repairs and the durability of the composite-to-concrete bond. Figure Error! Not a valid link. presents a few examples of
FRP: THE EUROPEAN PERSPECTIVE
The intensity of research development and application of FRP in Europe varies from country to country and from one period of time to the other. The emphasis of development of FRP tensile elements for prestressing was at first on GFRP bars. Today, AFRP and CFRP rods gain in importance. Auxiliary reinforcement, cages and meshes are not being developed. While FRP for prestressed concrete lost in momentum, FRP for stay cables and ground anchors will become important. The use of FRP laminates for the upgrading of masonry, concrete and timber structures is well established. FRP plates and rods are also increasingly used for the consolidation of historical buildings. In all, the pace of use of FRP is slow but steady.
EXTERNAL STRENGTHENING OF CONCRETE BRIDGES WITH BONDED STEEL PLATES
There are occasions when an existing concrete bridge deck needs local strengthening to improve its serviceability under current traffic loading. The use of steel plates bonded to the surface as additional reinforcement can sometimes be an economically attractive solution. An example of the use of this technique to improve the working load capacity of a group of bridges at a motorway interchange is described. Full-scale loading tests on one of the bridges before and after strengthening demonstrated that the required improvements had been achieved. Results of associated laboratory tests are also given, with some indication of where further research may lead to improvements in performance for future applications. Until the long term durability of bonded joints in this type of construction has been established the technique is not recommended for general use but can be considered for certain applications. Exposure tests are being carried out to determine whether there is likely to be any deterioration of bond efficiency with time. (Author/TRRL)