Moment modification factor for segments fully or partially restrained at both ends
Equation taken from AS4100:2020 Table 5.6.1.
Moment modification factor calculated
$$ \alpha_{m_{cal_{AS4100}}} = {1.0 + 0.35 \cdot \left({ 1 - {\left({ 2 \cdot a }\right) \over l} }\right) ^ 2} $$