Combinations of Limiting Axial Force and Bending Moment for a Reinforced Concrete Section

Structural elements of reinforced concrete frames are likely to be subjected to combinations of axial force and bending moment. In this section, we shall develop a simple procedure to determine the limiting combinations of axial force and bending moment that a rectangular reinforced concrete section can resist. To simplify the process of calculations, we shall make three assumptions:

1. The moment acts about only one axis (Figure 23.1a). 2. The strain is distributed linearly over the section (Figure 23.1b), and the

maximum compression strain is εcu = 0.003, the nominal limiting strain of concrete in compression.