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The advantages of FRP strengthening have been shown time and again during the last decade. All over the world several thousand structures retrofitted with FRPs exist. There are various reasons why the retrofit is needed, but since buildings and civil structures usually have a very long life, it is not uncommon that the demands on the structure change with time. The structures may have to carry larger loads at a later date or fulfil new standards. In extreme cases, a structure may need repair, owing to an accident, or to errors made during the design or construction phase, such that the structure needs to be strengthened before it can be used. Over the past decade, the issue of deteriorating infrastructure has become a topic of critical importance in Europe, and to an equal extent in North America and Japan.The deterioration of bridge decks, superstructure elements and columns can be traced to reasons ranging from ageing and environmentally induced degradation, to poor initial construction and lack of maintenance. Added to the problems of deterioration are issues related to the need for higher load ratings and increased numbers of lanes to accommodate the ever‐increasing traffic flow on major arteries.As a result, a significant portion of our infrastructure is currently either structurally or functionally deficient. Beyond the costs and visible consequences associated with continuous retrofit and repair of such structural components are the real consequences related to losses in production and overall economic issues related to time and resources caused by delays and detours. As we move into the twenty‐first century, the renewal of our lifelines becomes critical. Here, FRP strengthening may be a tool in the overall toolbox to be used to overcome some of the problems related to repair and strengthening of structures.In this paper a short historical background to plate bonding is presented. The paper focuses on the possibility of improving the existing technology and how drawbacks can be overcome.

The need of maintenance, repair and upgrading of concrete structures has increased considerably over the last decade and will most likely continue to do so. There can be several reasons for this, but it can often be attributed to normal change of use, increased demands on the structure, errors in the design and/or construction phase or in the worst case, accidents. Different methods have been developed over the years for solving different rehabilitation problems. Recently, advanced composites used for external bonding in the form of fabrics or laminates have become an accepted method. Several thousands of objects around the world have been upgraded with advanced composites bonded to its surface. In most cases, this method is very competitive regarding both structural behaviour and economy, but there are also some drawbacks. The surface bonded composite material is relatively sensitive to fire, accidents or vandalism. In addition, the pre-treatment is relatively intensive and time consuming. However, if the composite material is placed in slots in the concrete cover some of these drawbacks can be overcome. This paper presents work carried out on near surface mounted reinforcement (NSMR) at Luleå University of Technology in Sweden.

At LuleåUniversity of Technology, research is taking place in the area of plate bonding, i.e. when concrete members are strengthened by bonding steel or fibre-reinforced plastic (FRP) plates to their surface. The research work started in 1988. Both comprehensive experimental work and theoretical work have been performed. This paper presents the results of tests performed on concrete prisms onto which steel or carbon-fibre-reinforced plastic (CFRP) plates have been bonded. The criteria for the necessary anchor lengths for both the materials are presented as well as the critical strain level in the concrete at failure. Tests are compared with the Volkerson theory for lap joints. The results from the tests show that there is a specific anchor length for each material used. The tests also show that the strain limit in the concrete is the governing factor for failure. Furthermore, a compression between test and theory shows that the derived elastic theory can be used for moderate levels of load.

Abstract: This paper presents the use of fracture mechanics for the plate bonding technique. Plates of steel or carbon-fibre reinforced plastic are bonded with an epoxy adhesive to rectangular concrete prisms and loaded in shear up to failure, what is normally known in fracture mechanics as mode II failure. In this special application a linear and a nonlinear approach are presented. The nonlinear equation derived for a realistic shear-deformation curve can only be used for numerical calculations. However, for simplified shear-deformation curves, the derived formula can be solved analytically. Results from tests, which are compared with the theory, are also presented.