Depth of Concrete Compression Zone

x = \frac{α_{E} \cdot a_{s}}{b} \cdot - 1.0 + \sqrt{1.0 + \frac{2.0 \cdot b \cdot d}{α_{E} \cdot a_{s}}}

b	Width of element (always 1m for plates)
a_s	Provided tension reinforcement