Finite Element Modeling of Large Rupture Strain (LRS) FRP-Confined Concrete Columns

Extensive studies have demonstrated that confining a concrete column by large rupture strain fiber reinforced polymer (LRS FRP) composites can increase significantly its ultimate axial strength and ductility. For finite element analysis of such passively confined concrete columns by plasticity-based approaches, the plastic dilation angle must be quantified. For LRS-FRP confined concrete column, by increasing the lateral strain, the rate of confinement pressure is nonlinear compared to the linear rate provided by conventional FRPs (i.e., carbon FRP, glass FRP and aramid FRP), due to the bilinear tensile stress-strain nature of the LRS FRP material. This will cause the dilation behavior of LRS-FRP confined concrete to be substantially different from that of conventional FRP confined concrete columns. This study uses the cyclic compression tests of LRS FRP-confined cylindrical concrete columns to understand how the nonlinear confinement pressure will affect the concrete loading paths in terms of the change in the plastic dilation angles. Axial and lateral plastic strains obtained in cyclic tests are used for quantifying the plastic dilation angle of the confined concrete. Compared to conventional FRPs, it is revealed that for LRS FRP confinement the plastic dilation angle decreases by a steeper rate as a function of confinement lateral stiffness ratio. Also, the plastic dilation angle shows a different style as a function of axial plastic strain. For LRS FRP confinement the peak of plastic dilation angle occurs around the axial plastic strain of 2% which is substantially larger than that of conventional FRP confinement. These observations are used to perform finite element (FE) analysis of LRS FRP-confined concrete columns based on the ABAQUS software. With the employment of the concrete damage plasticity model (CDPM), the FE model can predict successfully the axial stress-strain relationships of LRS FRP-confined concrete.