Lattice discrete particle modeling (LDPM) of fiber reinforced polymers (FRP) confined concrete columns

External confinement of reinforced concrete columns by means of FRP composites has become a popular technique for the rehabilitation of existing structures and for the strengthening and ductility increase of structural members. A comprehensive evaluation of the overall behavior of confined concrete columns through a numerical model requires the use of a concrete material model that can accurately capture the interaction between the lateral expansion of concrete, the corresponding stress increase in the external jackets and the influence of the internal steel reinforcement. In this study, experimental data gathered from the literature and relevant to FRP-confined columns are simulated by the so-called Lattice Discrete Particle Model (LDPM) which was recently developed to simulate concrete materials by modeling the mesoscale interaction of coarse aggregate particles. LDPM has been extensively calibrated and validated with comparison to a large variety to experimental data under both quasi-static and dynamic loading conditions but it has not been fully validated with reference to low confinement compressive stress states relevant to the targeted application. This task is pursued in the present research. The results show that with the improvement of the existing LDPM constitutive equations to account for low confinement effects, LDPM is able to predict the concrete material response governed by the nonlinear interaction mechanism of confined vertical members strengthened by means of externally bonded FRP composites.