Influence of Slenderness on the Behavior of a FRP-Encased Steel-Concrete Composite Column

The compressive behavior of a steel-concrete composite column encased in a fiber reinforced polymer (FRP) tube is evaluated experimentally for columns with various slenderness ratios. The composite column consists of a FRP tube surrounding a steel I-section that is subsequently filled with concrete. A total of nine column specimens were tested ranging between 500 and 3,000 mm in height. Confinement and composite action resulted in enhanced compressive behavior of the composite columns. Maximum confinement occurred in the short column (slenderness ratio less than 0.2). Confinement action reduced with increased height of the column specimens. The column load- carrying capacity, ultimate axial strain, and compressive strength of the confined concrete core in the longest specimen (slenderness ratio of 0.9) were reduced to approximately 59, 14, and 51% of the short column values, respectively. A buckling strength curve of the composite columns was developed on the basis of the experimental results.