CFRP Rehabilitation of Welded RHS beams under combined bending and bearing

To rehabilitate damaged or sub-standard box girders, techniques utilising the lightweight, high strength and corrosion resistance of carbon fibres reinforced polymers (CFRP) composites have been proposed. This paper presents experimental results for three series of CFRP rehabilitated model box girders under quasi-static large deformation 3-point bending. The test program was for rehabilitation of 41 artificially degraded RHS beams strengthened using externally wrapped sheets or bonded plates. The main parameters examined in this paper were the section type, section and member slenderness and the type and number of the CFRP sheets. The flange and web slenderness examined in this paper was in the range of b/t =20 to 66.67 and d/tw=20 to 75. The CFRP sheets were wrapped around the section in the transverse direction with a sufficient overlap. The results show that the combined flexural and bearing strength of the steel box girder can be significantly increased by adhesively bonding CFRP sheets or plates. Expressions for the bearing strength and plastic moment of the composite section were obtained by means of an equivalent thickness approach derived by the author and published in a recent paper. The newly derived interaction equations were compared against the present design rules in steel specifications. A lower bound interaction equation was derived based on the composite properties and was found suitable for the design of corroded top and bottom flanges welded RHS repaired using CFRP