The Effect Of Corner Radius On Axial Compression Behavior Of Steel Reinforced Concrete Rectangular Short Column Confined By Carbon Fiber Reinforced Polymer Strips

After summarization of the current researches on axial compressive behavior of FRP-confined RC columns, the experiments contain 13 components and divide them into three groups including reference group and two corner radius group. Effects of steel, corner radius and layers of CFRP (Carbon Fiber Reinforced Polymer) on axial capacity of CFRP-confined RC rectangular short columns are analyzed. In the experiments, the failure modes show that steel and longitudinal reinforcement yield. Then the concrete in core of section is crushed. In the final, CFRP reaches the maximum strain and ruptures which represent the failure of components. Through analysis, with the increase of corner radius, the axial capacity increases. Also, stress concentration in the corner is relieved; effective tensile strain of CFRP increases. Lateral compressive stress subjected to concrete increases leads to increase of axial capacity despite the cross section is shrunk. With the increase of corner radius, the failure modes transfer from softening confinement to hardening confinement. The descending portion in the load-displacement curve is disappeared. In addition, with the increase of CFRP layers, the ductility of components is enhanced.On the basis of experiment, numerical methods are conducted using ABAQUS software to simulate the axial compressive behavior of CFRP-confined RC rectangular short columns. The distribution of compressive stress and circumferential strain in CFRP is analyzed. In result, after increasing the corner radius, the compressive stress in the core cross section of 1/2 height of column is enhanced under the ultimate capacity. However, the compressive stress in the corner of section is reduced. Plus, with the increase of corner radius, the circumferential strain of CFRP is increased and the deviation of value is reduced.On the basis of numerical simulation and current theory, the equations linking corner radius to effective FRP tensile strain are proposed, considering the modified corner radius for rectangular section. With respect to concrete tri-axial stress theory, the ratio between maximum principal stress and minimum principal can effective reflect the effect of corner radius on strength of concrete. Thus, on the basis of numerical analysis, stress ratio valued 0.003, σ1,/σ3=0.003, is proposed to divide the effective confinement area and ineffective confinement area and consider σ1,/σ3=0.008 as enhancement area.