Structural behavior of concrete filled carbon fiber composite tubular columns

This paper investigates the use of premanufactured filament wound carbon tubes as reinforcement for concrete columns. Two initial design concepts are considered, a ductile design with steel anchorage bars to allow for large inelastic rotations at the column base and a strength design with the carbon shell continued into the concrete footing to give an essentially linear elastic response. The structural behavior of the two design concepts is investigated experimentally under simulated seismic loads and the performance of the test units is compared to that of a conventionally reinforced concrete column. The ductile design response was almost exactly the same as the conventionally reinforced reference column. The strength design suffered an early failure due to high stress concentrations at the footing interface. Analytical expressions for predicting the stress and strain state in the shell and concrete are presented for compression loading and compared to the test results from the strength design column under axial load only. Bending behavior is discussed qualitatively with an analytical approach described for the case when the shell and core act together (no slip). The ability to predict the strains in the section with existing analytical techniques is investigated. Issues pertaining to the case of slip between the shell and core are briefly presented.