Design Approach for Compressive Arch Action in Reinforced Concrete Beams

This paper addresses a direct design approach for compressive arch action in reinforced concrete beams. Equilibrium and compatibility of the beam are established on a plastic hinge mechanism. The effects of axial and rotational stiffnesses are considered explicitly in the approach by correlating the strains of compressive reinforcement and the bending moments with the axial compressive strain of beams. The expression for the axial compressive strain is obtained by solving a quadratic equation and used to calculate the neutral axis depths at the beam ends. Vertical load and the associated axial compression force can be quantified from flexural theory. The calculated load capacity and the peak axial compression force are in reasonably good agreement with test data. The effects of axial and rotational stiffnesses on compressive arch action are investigated through the design approach.