Public Function AsREQ(b_cm As Double, d_cm As Double, fc_MPa As Double, _
    fy_MPa As Double, Mu_tonm As Double, optional Phi As Single) As Double
Dim Ao As Double, Bo As Double, Co As Double, D0 As Double
Dim fc As Double, fy As Double, Mu As Double
Dim b As Double, d As Double    'https://magnusdcweb.com/
'Versión 1.20 Revisión 2022 	 https://facebook.com/MagnusStructures
Const g = 9.80665               'Aceleración g en [m/s˛]
if Phi=0 then
Phi=0.90
end if
Mu = Mu_tonm * 10 ^ 6 * g       'Cambio de Unidades ton.m a N.mm
b = b_cm * 10                   'Cambio de Unidades cm a mm
d = d_cm * 10
fc = fc_MPa
fy = fy_MPa
Ao = (fy) ^ 2 / (1.7 * fc * b)  'Ao=fy˛/(1.7*f'c*b)
Bo = -fy * d                    'Bo=-fy*d
Co = Mu / Phi                   'Co=Mu/Phi
D0 = (Bo) ^ 2 - 4 * Ao * Co     'Do=Bo˛-4*Ao*Bo
If D0 >= 0 Then                 'Si se puede reforzar la Viga Do>=0
D0 = (D0) ^ 0.5
AsREQ = (-Bo - D0) / (2 * Ao)   'AsREQ=(-Bo-Do^0.5)/(2*Ao)
AsREQ = AsREQ * (0.1) ^ 2       'Cambio de Unidades de mm˛ a cm˛
End If
'Autor: Diego Ceballos magnusdcp@gmail.com
End Function