The neutral axis depth factor (k) of reinforced concrete sections depends only on permissible stresses in concrete (σc), steel (σst) and modular ratio (m). The value of k can be evaluated by:
1
k = \(\rm\left[\frac{m}{m+\left(\sigma_c / \sigma_{s t}\right)}\right]\)
2
k = \(\rm\left(\frac{280}{280-3 \sigma_{s t}}\right)\)
3
k = \(\left(\frac{280}{280+3 \sigma_{s t}}\right)\)
4
k = \(\rm\left[\frac{1}{1-\left(\sigma_c / m \sigma_{s t}\right)}\right]\)