Finite element prediction of the influence of confinement on RC beam–columns under single or double curvature bending

The present study investigates the finite element prediction of the compressive strength of concrete near the flexural critical regions of reinforced concrete (RC) beam–column members under a single or a double curvature bending. For this reason, an analysis model of the three-dimensional hypoelasticity-based finite element predictions of RC structures has been presented. Using the developed program, three RC beam–column members subjected to axial forces combined with bending moments have been analyzed. From finite element predictions, it has been known that concrete in the vicinity of a beam–column joint reacts not only under a uniaxial compressive stress state but also under a multiaxial compressive stress state, and that a flexural critical cross-section is observed at a small distance away from the beam–column joint. This is because the concrete in that region is confined by the existence of a beam–column joint, and that region is commonly the flexural critical cross-section of the RC beam–columns in a frame. It is also observed that the confining effect on concrete in that region is larger under double curvature bending than under single curvature bending.