Behavior of Concrete Cylinder Confined with Helical Composites Strips

This paper presents theexperimental investigations on the behavior of a short concrete cylinder confined with helical FRP strip under axial compressive load,the results show that the compressive strength increases with increase in the width of the FRP and the decrease in pitch of the helix that follows the FRP on the side surface of the concrete cylinder. The numerical analysis conducted to describe the behavior of confined cylinders confirmed the experimental stress-strain curves and the numerical ones are recorded. A new method for predicting the ultimate compressive strength is also presented. The model is quite simple and can be adapted to the concrete cylinders confined with other types of FRP, for different widths and different values of the pitch of the helix, and for different values of the compressive strength of reference concrete. The mathematical optimization, of the function that describes the ultimate strength of confined cylinder is adjustable. It allows predicting the optimal values of various parameters: the confinement strength, the width of the FRP, the pitch of the helix, and the compressive strength of concrete, for different expected strength gain rates and for different intervals containing the studied variables.