Strengthening concrete structures with prestressed CFRP sheets: Laboratory and numerical investigations to field application

Many of the structures in Canada were constructed during the 1950's and 1960's and they are in need of rehabilitation due to deterioration. The application of carbon fibre reinforced polymer (CFRP) sheets for strengthening damaged structures is a viable and promising solution. CFRP is an emerging advanced composite material with very high tensile strength (i.e., 10 times stronger than that of steel). The strengthening effect when using CFRP sheets can be significantly improved by applying prestress to the sheets. This thesis presents the application of prestressed CFRP sheets for concrete structures and consists of four main categories as follows.; Computational simulation. A nonlinear 3-D finite element analysis (FE 1) is conducted to investigate the behaviour of prestressed concrete beams strengthened with prestressed CFRP sheets, including experimental validation. The flexural behaviour of the beams, before and after strengthening, is predicted and compared against experimental results including the increase of load-carrying capacity, failure mode, ductility, and cracking behaviour. The modelling technique is extended to a two-way flat slab strengthened with prestressed CFRP sheets, including investigations on the load-carrying capacity, numerical crack growth, and slab-column connection behaviour.; Experimental investigation. Ten reinforced concrete beams strengthened with prestressed CFRP sheets are tested as part of the development of a non-metallic anchor system. Non-metallic anchors are necessary to avoid corrosion damage. The load-carrying capacity of the strengthened beams using the innovative method is up to 3 times greater than the unstrengthened beam. Various failure modes are observed depending on the type of the applied anchor system. The developed non-metallic anchor system overcomes brittle and abrupt failures that are commonly observed in CFRP-strengthened structures.; Theoretical investigation. Closed-form solutions for the behaviour of strengthened concrete beams are derived, and they exhibited good agreement with the experimental results. Practical nonlinear fracture mechanics models, representing the behaviour of the anchor system that is required to prestress CFRP sheets, are also developed.; Site application. The technology studied in the laboratory is applied to a site application. The Main Street Bridge-overpass No. A, Winnipeg, MB, has been significantly damaged by frequent collisions of heavy trucks. The innovative strengthening method using prestressed CFRP sheets is successfully applied. The load-carrying capacity of the damaged bridge is recovered with respect to the undamaged state. Notice that this repair project is the first North American site application using prestressed CFRP sheets.