A study on compressive strength of concrete in flexural regions of reinforced concrete beams using finite element analysis

Based on the orthotropic hypoelasticity formulation, a triaxial constitutive model of concreteis proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancementis considered using so called the strain enhancement factor. It is also developed a three-dimensional finiteelement model for reinforced concrete structural members based on the proposed constitutive law ofconcrete with the smeared crack approach. The concrete confinement effects due to the beam-column jointare investigated through numerical examples for simple beam and structural beam member. Concrete atcompression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxialcompressive state but also by the biaxial and triaxial compressive states. For the reason of the severeconfinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a smalldistance away from the beam-column joint. These observations should be utilized for the economic designwhen the concrete structural members are subjected to high confinement due to the influence of beam-columnjoint.