Rectangular Concrete Stress Distribution in Ultimate Strength Design

An ultimate strength design theory of broad applicability is developed, based on an equivalent rectangular stress distribution in the concrete compression zone and in general accord with the Appendix to the 1956 ACI Building Code. The theory is characterized by simplicity without significant loss of accuracy. The proposed method of ultimate strength design is applied to a wide variety of structural concrete beams and columns, subject to various combinations of bending and axial load. Calculated ultimate strengths are compared with experimentally determined ultimate strengths for a wide range of variables, and an excellent agreement results. It is concluded that the proposed extension of the rectangular stress distribution theory permits prediction with sufficient accuracy of the ultimate strength in bending and compression of a II types of structural concrete sections likely to be encountered in structural design practice, including odd-shaped sections and other unusual cases.