Experimental and analytical investigations on the flexural behavior of CFRP-strengthened composite girders

• The effect of CFRP amount on the overall performance of composite girders is studied.
• Strut-and-tie model is employed on fully anchoraged steel–concrete composite girders.
• Analytical procedure is presented and verified against experimental results.
• The analytical procedure showed good agreement with other experimental results.

This paper presents experimental and analytical studies on the flexural behavior of fully composite steel-concrete I-girders strengthened by externally bonded carbon fiber reinforced polymer (EB-CFRP) sheets. The experimental program consisted of four reduced-scale specimens composed of a hot-rolled steel I-girder section acting compositely with topping reinforced concrete slab using two rows of properly designed shear studs along the entire length of the girder flange. One girder was un-strengthened to act as a reference girder, while the remaining three girders were strengthened with 2, 3 and 4 layers of CFRP sheets mounted on the bottom side of the steel girder's tension flange considering complete anchorages of the CFRP sheets at both ends. The composite girders were tested under a four-point loading system in order to obtain a comprehensive overview of the flexural behavior of both un-strengthened and the CFRP-strengthened girders. Finally, an analytical design procedure was proposed in order to obtain the moment of resistance of the composite girders. Then, the proposed methodology was verified against the current experimental results as well as the experimental results obtained by other researchers. The comparison showed good agreement between the proposed analytical results and the experimental findings with a maximum variation less than 10%. Thus, the proposed equations for moment of resistance of CFRP-strengthened composite girders can be used by design engineers with confidence.