Figure 7.1 Minimum reinforcement concept For a rectangular cross section subject to combined bending and axial force, the cracking moment can be determined by:
After cracking this same bending moment, together with the axial force, must be taken by the cracked cross section:
The lever arm z, may be taken as a certain fraction a of h (around 0.8h for pure bending). Introducing the following notation:
Equation above can be rewritten as:
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