New small-diameter CFRP material for flexural strengthening of steel bridge girders

• Small-diameter CFRP strands strengthening system eliminate de-bonding failure.
• CFRP strengthening achieves failure due to crushing of the concrete.
• The proposed strengthening may be used to reduce deflection of members.
• The proposed system is effective for cyclic and fatigue loadings conditions.

This paper presents the research findings of an experimental program undertaken to examine the effectiveness of using small-diameter CFRP strands to increase the flexural capacity of steel beams and bridge girders. The experimental program included scaled steel-concrete composite beams, strengthened with these small-diameter strands. The CFRP strands were stitched together with a gap between the strands to allow the adhesive to penetrate and cover the entire perimeter of each strand. Results showed that the proposed system eliminated failure due to de-bonding of the strengthening materials and significantly increased the flexural capacity and stiffness of steel beams.