Compressive Strength of Concrete in Flexural Critical Region of Reinforced Concrete Beam-Column Members

The compressive strength of concrete in flexural critical regions of reinforced concrete beam-column members is investigated experimentally and in terms of three-dimensional finite element predictions. Reinforced concrete beam-column members subjected to an axial load combined with single or double curvature bending were manufactured with special stirrups that minimize the confining effect of concrete by stirrups. Due to the existence of a beam-column joint near the flexural critical section at both ends of the members, the concrete on the compression fibers around the joint is subject to multiaxial compressive stress states; and the compressive stress in the region exceeds the uniaxial compressive strength of concrete. In the case of double curvature bending, the load-carrying capacities of the beam-column members which are measured experimentally and predicted by means of finite element analysis greatly exceed the moment and axial force interaction curve obtained from the uniaxial stress-strain curve of concrete.