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 concrete<br />is proposed. To account for increasing ductility in high confinement of concrete, the ductility enhancement<br />is considered using so called the strain enhancement factor. It is also developed a three-dimensional finite<br />element model for reinforced concrete structural members based on the proposed constitutive law of<br />concrete with the smeared crack approach. The concrete confinement effects due to the beam-column joint<br />are investigated through numerical examples for simple beam and structural beam member. Concrete at<br />compression fibers in the vicinity of beam-column joint behaves dominant not only by the uniaxial<br />compressive state but also by the biaxial and triaxial compressive states. For the reason of the severe<br />confinement of concrete in the beam-column joint, the flexural critical cross-section is observed at a small<br />distance away from the beam-column joint. These observations should be utilized for the economic design<br />when the concrete structural members are subjected to high confinement due to the influence of beam-column<br />joint.