CYCLIC LOADING TEST AND ANALYTICAL EVALUATION OF CIRCULAR STEEL COLUMNS RETROFITTED BY EXTERNALLY BONDED CARBON FIBER SHEETS IN GRADED CONFIGURATION

In this study, the use of carbon fiber sheets in graded configuration aims to provide an optimal technique to address stress concentrations at the lower regions of the columns. The effect on the circular steel column specimen’s horizontal load capacity, energy absorption, and buckling behavior were experimentally and analytically evaluated by subjecting the specimen to a constant axial load and an increasing cyclic lateral load. Analytical results from the implemented finite element analysis models were verified using the experimental results. Two cases were considered: 1) the application of CF sheets on column specimen before loading (reinforcement model) and 2) application of CF sheets after the column specimen have undergone failure (repair model). For the finite element analysis model, the steel column and CF sheets were modeled as structural shell elements. The interaction at the steel and CF sheets interface was considered by accounting for the adhesive stiffness through contact condition analysis. The results showed that the reinforcement model can effectively increase the horizontal load capacity and the repair model can sufficiently retrofit the horizontal load capacity, and the implemented finite element analysis model can adequately evaluate the horizontal loading capacity, energy absorption, and buckling modes of reinforcement and repair models.