A module of steel connection functions for Excel's AFE

Steel_Connection.txt

/** 
Calculates alpha as given by Appendix G in SCI P398.
Note: always omit last optional parameter
*/
Get_Alpha = LAMBDA(m, m_2, e, [alpha_DONT_INPUT],
    LET(
        lambda_1, m / (m + e),
        lambda_2, m_2 / (m + e),
        alpha, IF(ISOMITTED(alpha_DONT_INPUT), 4.45, alpha_DONT_INPUT),
        lambda_1_temp, Get_Lambda_1(alpha, lambda_2),
        step, 0.005,
        IF((lambda_1 / lambda_1_temp) < 1, Get_Alpha(m, m_2, e, alpha + step), MIN(alpha, 8))
    )
);

/**
Helper function for Get_Alpha
*/
Get_Lambda_1 = LAMBDA(alpha, lambda_2,
    LET(
        lambda_1_lim, 1.25 / (alpha - 2.75),
        lambda_2_lim, alpha * lambda_1_lim / 2,
        IF(
            lambda_2 >= lambda_2_lim,
            lambda_1_lim,
            lambda_1_lim +
                (1 - lambda_1_lim) *
                    ((lambda_2_lim - lambda_2) / lambda_2_lim) ^ (0.185 * alpha ^ 1.785)
        )
    )
);