Mesoscopic evaluation of the bond behavior of concrete with deformed rebar subjected to passive confinement employing 3D discrete model

Abstract

The bond between concrete and steel is one of the most critical properties of reinforced concrete and affects the overall structural performance. The current research realistically evaluates the macroscopic bond behavior, quantitatively highlights the detailed internal fracture process, and clarifies the internal fracture mechanism. The numerical analyses are conducted for cover confinement effects employing the coupled Rigid Body Spring Model (RBSM) and the nonlinear solid Finite Element Method (FEM) model with varying cover thicknesses and rebar diameters. The modeling of concrete and deformed rebar considering the actual geometrical features is performed employing 3D-RBSM and solid FEM, respectively. It has been determined that the mesoscopic numerical model adequately simulates the test stress-slip relationships, demonstrates the increasing tendency of peak stress and peak slip against the increase in cover thickness, and reproduces the post-peak softening. The model enables simulation of splitting failure with a small cover thickness and the transformation of failure into pull-out and showed the enhancement of peak stress and ductility with a large cover, while reproducing the splitting as well as pull-out for medium cover. Furthermore, the model accurately reproduces the different bond and internal crack propagation caused by variations in bearing stress and radial pressure against different rebar diameters. The model precisely captured the radial fractures arising from the ribs, such as Goto cracks, which is not possible using conventional one-dimensional beam elements to represent the reinforcing bar.