Experimental Study Of Stress-strain Behavior Of FRP-Confined Concrete Subjected To Eccentric Compression

Fiber reinforced polymer (FRP) composites have been widely used in civil engineering due to their high strength-to-weight ratio and high corrosion resistance. One important application of FRP composites is as a confining material for concrete columns. External wrapping of FRP composites can significantly increase the compressive strength and the ultimate axial compressive strain of concrete columns. Although FRP composites confined concrete columns have been extensively investigated, a satisfactory stress-strain model for the columns under eccentric loading has not been developed because of the complications of the problem.Therefore, this paper presents an experimental study of FRP confined circular concrete columns under eccentric loading, mainly study the effect of FRP layers and levels of load eccentricity on the stress-strain relationship of FRP-confined concrete columns, especially the ultimate axial strain and ultimate lateral strain. Otherwise, based on the equivalent ultimate lateral strain, a theoretical model for slender FRP-confined circular RC columns and Lam and Teng’s stress-strain model, this paper presents the stress-strain relationship of FRP-confined concrete columns subjected to concentric and eccentric compression loading. The theoretical results agree well with the experimental values.The experimental results show that an increase in load eccentricity and layers of FRP increases the ultimate axial strain, while the ultimate lateral strain decreases with the increase of load eccentricity. The ultimate load of columns under eccentric loading is lower than those under concentric loading, while the ultimate deflection is higher. The ultimate load and deflection of columns under eccentric loading increase with the layers of FRP.The theoretical analysis shows that a stress-strain relationship derived from concentrically loaded columns is not applicable to columns under eccentric loading; the ultimate axial strain and stress of columns under eccentric loading is higher than those columns under concentric loading, while the slope of the linear second portion of the stress-strain relationship of FRP-confined concrete columns is lower. An increase in layers of FRP increases the ultimate axial strain, stress and the slope of the linear second portion of the stress-strain relationship of FRP-confined concrete columns.