Experimental Investigation of Curved-Soffit RC Bridge Girders Strengthened in Flexure Using CFRP Composites

This paper investigates the performance of curved soffit reinforced concrete beams strengthened in flexure with carbon fiber reinforced polymers (CFRPs) under static loading. The effect of concavity on the effectiveness of flexural strengthening is explored using both pultruded CFRP laminates and wet layup CFRP sheets in terms of the degree of flexural strengthening, CFRP strain level prior to debonding, cracking resistance, and ductility. In the experimental program, eight simply-supported beams were tested under displacement-controlled static loading, including three beams strengthened with CFRP sheets, three beams strengthened with CFRP laminates, one unstrengthened beam with flat soffit and one unstrengthened beam with curved soffit. The concrete beams were 2.7 m long and had mid-span cross sections of 140 x 260 mm. The degree of curvature used in this study was 20 mm per 1 m. Owing to strengthening, the nominal flexural strengths of the beams were increased by up to 37% and the service load deflections were reduced by up to 14%. A curvature of 20 mm per meter was observed to reduce the FRP's maximum strain at the time of debonding by 31%-33%.