Improving steel behavior using carbon fiber reinforced polymer (CFRP) wrapping

Previous research has shown that carbon fiber reinforced polymer (CFRP) composites are particularly well suited for external strengthening of reinforced concrete members. The superior mechanical and physical properties of CFRP composites make them excellent candidates for repair and retrofit of steel structures as well. However, to date, the main focus of research on rehabilitation of steel structures with CFRP has been mostly limited to flexural strengthening. This research program investigates a new and promising application for CFRP; i.e. stiffening and improving the stability and inelastic behavior of steel members that are subjected to monotonic and reversed cyclic loading.; Experimental, computational and analytical studies are conducted to investigate the inelastic buckling behavior of small- and large-scale steel brace members strengthened with CFRP wraps. The proposed strengthening technique involves embedding the steel members within a core and then wrapping the entire system with CFRP sheets. The investigation shows that embedding steel braces within the proposed stiffening system can lead to significant improvements in the pre- and post-buckling responses. Design oriented models are derived to proportion the stiffening system so that brace members can yield in compression prior to buckling. A finite element model is developed and validated by using the test data and then used to further investigate important parameters identified during testing.; The effectiveness of CFRP composites for inhibiting the local and global buckling behaviour of double channel members under cyclic flexural loading is also investigated through an experimental program and finite element modeling. Both experimental and simulation results suggest that CFRP wrapping can increase the size of plastic hinge region and delay the occurrence of local buckling and lateral torsional buckling, leading to a significant improvement in cyclic response.; The results presented in this dissertation show that CFRP composites can be used for strengthening steel structural members prone to local and/or global instabilities. Other promising applications of CFRP for strengthening steel members are proposed and future research directions for this promising technology are identified.