The Effect Of Confining Manners And Quantity On Steel Reinforced Concrete Rectangular Short Column Confined By Carbon Fiber Reinforced Polymer Strips

Based on the review and analysis of the research of axial compression performance of concrete column confined by fiber composite, the performance of axially compressed steel reinforced concrete (SRC) rectangular short columns partially confined with CFRP strips were studied by experimental investigation and numerical simulation.Two groups of total twelve specimens were designed and loaded, which considers the confining quantity and confining manners of CFRP. The failure modes and mechanism of confined columns were studied through the experiments, the influence on axial bearing capacity of the amount of CFRP and placement of CFRP reinforcement were analyzed and discussed. All of the confined columns failed directly in the fracture of CFRP laminates. As the amount of CFRP increased, the peak load of confined column increased, and the load-deformation curve changed from having descending part to having none. When the spacing of CFRP strips is suitable, the confining efficiency of partially confined columns is higher than the fully confined columns.The peak load of partially confined SRC columns with CFRP strips decreased with the increasing of spacing of the CFRP strips. The lateral strain of outer layer of CFRP was decreased with the increasing of CFRP layers.A finite element analysis model was established to simulate the compressive behavior of partially confined SRC column with CFRP strips by ABAQUS software, the numerical results were in good agreement wit the experimental results. The numerical results showed that, the distribution of lateral strain of FRP in vertical direction and circumferential direction was non-uniform. The distributions of axial compressive stress of concrete at the middle section of columns were also non-uniform:the compressive stress in the corner area was the largest, the compressive stress around the steel was the second largest, the concrete in the corner and around the steel was both strongly confined. Axial compressive stress of concrete was increase with the increase of FRP quantity.According to the existing research, the rectangular section was equivalent to circular section, the calculating formula of the lateral confining strength which considering the effect of cross section and spacing was proposed. The criteria of powerful or weak confinement was proposed, the confining ratio of 0.074 was limit of powerful or weak confinement.