Strengthening steel-concrete composite girders using prestressed fibre reinforced polymer

Metallic bridges may become structurally deficient for a wide variety of reasons. The use of Fibre Reinforced Polymer (FRP) composite material has received great attention in last decade as a possible solution for strengthening steel-concrete composite beams. The main objective of this study is to analytically and experimentally investigate the efficiency of using prestressed, externally bonded (EB) FRP for strengthening steel-concrete composite girders. Two types of composite material, Carbon Fibre Reinforced Polymer (CFRP) plate and Steel Reinforced Polymer (SRP) sheets, were used and the beams were prestressed with three different prestressing force levels. Ductility and flexural behaviour in the elastic and plastic zones were studied. An innovative, practical, mechanical system for anchoring and prestressing the FRP against the girder itself has been developed. Design guidelines to predict the ultimate load of the strengthened steel-concrete composite girder have also been proposed. A comparative study was conducted to investigate the effect of changing strengthening material area and prestressing force level on the ultimate load carrying capacity and the ductility of the strengthened beams.;Strengthening steel-concrete composite girders with prestressed EB FRP increased the moment capacity of the girder, efficiently. The serviceability behaviour of the beams was enhanced by the increase in the beam stiffness for both elastic and plastic stages, leading to an increase in the yielding and ultimate loads. The deflection at ultimate load for beams strengthened with prestressed CFRP plate was smaller than that of beams strengthened with prestressed SRP sheets and for both FRP materials the deflection was smaller than that of beams strengthened with non-prestressed FRP.