S Movaghati - M.S. student
A Rahai - Professor, Department of Civil Engineering, Amirkabir University of Technology,

Carbon fiber reinforced polymer (CFRP) has been widely used to strengthen concrete structures, and has recently become an attractive option for retrofitting steel structures. Some experimental researches have been conducted to determine the feasibility of using CFRP on strengthening steel members. In this study after verification of the FE model with experimental results, slenderness ratio of hollow structural section members was changed and the effect of slenderness was investigated on the nominal flexural and compression axial force strength of models which were subjected to eccentric static load. For numerical analysis software ABAQUS was adopted. Both geometric and material (for steel only) nonlinearity were considered and initial out-of-straightness imperfection was indicated. Through-thickness residual stresses were also included in the models. In material property definition, CFRP was simulated as a high stiffness and linear material and a progressive damage model was generated for CFRP strips by using HASHIN failure criteria, fracture energy damage evolution and viscous damage stabilization. Numerical analysis revealed significant increases in compression force and flexural capacity simultaneous with reduction of member's axial shortening and member's end point rotation in beam-columns retrofitted with CFRP strips.

CFRP; beam-column; steel structure; hollow structural section (HSS); finite element