Tensile Forces Behavior on Longitudinal Reinforcement and CFRP Strips on Circular Hollow Reinforced Concrete Columns

Currently, there is not much research on strengthening structural elements with hollows. This manuscript presents the test results from twelve circular reinforced concrete column specimens strengthened with CFRP strips. This study focuses on the strain behavior of longitudinal reinforcement and CFRP strips due to high shear force intensity. Hollows in the cross-section are used to see the effect of voids on the column strain distribution. Nine specimens have a hollow cross-section with hollow diameters of 1.5", 2.5", and 3.5" for each of the three specimens. Meanwhile, the other three specimens have a solid crosssection. All specimens do not use stirrups to determine the contribution of concrete and CFRP strips to resist shear. Strain gauges are placed in certain positions to read the strain on the longitudinal reinforcement and CFRP strips. The test results are in the form of tensile forces and are then analyzed to obtain the movement pattern of tensile forces in the longitudinal reinforcement and CFRP strips. Numerical analysis using a fiber element model is used to obtain the strain in each reinforcement layer. The numerical analysis results were then compared with the test results and showed close results. Then, an equation for calculating the tensile force in CFRP strips is proposed. The proposed equation approximates the test results with an accuracy level of 90%.