Strength and deformation of high strength concrete short columns confined with carbon fiber reinforced polymer sheets

In the present investigation, the properties of reinforced concrete short columns confined with CFRP sheets have been studied experimentally and theoretically reveling the confinement effect by reinforcement and CFRP sheets together on the strength and max axial deformation of confined concrete. For this study, forty eight reinforced concrete cylinders have been cast and tested in the laboratory with a special emphasis on HSC. Many parameters were investigated such as the influence of longitudinal reinforcement, the lateral reinforcement type and spacing, the CFRP layers arrangement and number, the concrete compressive strength and the slenderness ratio. A comparative study among the different specimens was conducted to highlight the parameters governing the strength and deformation of cylindrical specimens, and to clarify the economical usage of steel reinforcement and CFRP layers. The experimental results include ultimate load, axial and lateral deformations. In general, these results indicated an increase in the percentages of ultimate load of confined short columns about 123% to 280% compared to unconfined ones. Parameters such as max axial deformation and dilation ratio were enhanced considerably due to strengthening by CFRP sheets. An attempt was made to provide an analytical procedure to predict the load-deformation relationship of concrete reinforced with both longitudinal and transverse reinforcement, made from normal strength and high strength concrete and then confined with CFRP sheets. The model has an acceptable range of values, and correlate well with specimens of high confinement ratios, although the model results could not predict the suitable load-deformation curve of unconfined specimens.