// Lateral-Torsional Buckling F4.2
public double GetLateralTorsionalBucklingCapacity(FlexuralCompressionFiberPosition compressionFiberPosition, double L_b, double Cb)
{
double M_n = 0.0;
double R_pc = GetRpc(compressionFiberPosition);
double M_yc = GetCompressionFiberYieldMomentMyc(compressionFiberPosition);
F_L = GetStressFL(compressionFiberPosition);
switch (compressionFiberPosition)
{
case FlexuralCompressionFiberPosition.Top:
Sxc = Section.Shape.S_xTop;
break;
case FlexuralCompressionFiberPosition.Bottom:
Sxc = Section.Shape.S_xBot;
break;
default:
throw new CompressionFiberPositionException();
}
double r_t = GetEffectiveRadiusOfGyration_r_t(compressionFiberPosition);
double h_o = this.SectionI.h_o;
double L_r = GetL_r();
double L_p = GetL_p(r_t);
LateralTorsionalBucklingType BucklingType = GetLateralTorsionalBucklingType(L_b, L_p, L_r);
switch (BucklingType)
{
case LateralTorsionalBucklingType.NotApplicable:
M_n = double.PositiveInfinity;
break;
case LateralTorsionalBucklingType.Inelastic:
M_n = Cb * (R_pc * M_yc - (R_pc * M_yc - F_L * Sxc) * ((L_b - L_p) / (L_r - L_p))); //(F4-2)
M_n = M_n > R_pc * M_yc ? R_pc * M_yc : M_n;
break;
case LateralTorsionalBucklingType.Elastic:
double Iyc = GetIyc(compressionFiberPosition);
double Iy = SectionI.I_x;
J = Iyc / Iy <= 0.23 ? 0.0 : J;
double Fcr = GetFcr(L_b);
break;
default:
break;
}
double phiM_n = 0.9 * M_n;
return(phiM_n);
}
//Lateral Torsional Buckling F2.2
public double GetFlexuralTorsionalBucklingMomentCapacity(double L_b, double Cb)
{
double Lp = GetLp(r_y, E, F_y); //(F2-5)
double rts = Getrts(I_y, C_w, S_x);
double Lr = GetLr(rts, E, F_y, S_x, J, c, ho); // (F2-6)
LateralTorsionalBucklingType BucklingType = GetLateralTorsionalBucklingType(L_b, Lp, Lr);
double M_p;
double M_n = 0.0;
switch (BucklingType)
{
case LateralTorsionalBucklingType.NotApplicable:
M_n = double.PositiveInfinity;
break;
case LateralTorsionalBucklingType.Inelastic:
M_p = GetMajorNominalPlasticMoment();
M_n = Cb * (M_p - (M_p - 0.7 * F_y * S_x) * ((L_b - Lp) / (Lr - Lp))); //(F2-2)
M_n = M_n > M_p ? M_p : M_n;
break;
case LateralTorsionalBucklingType.Elastic:
double Fcr = GetFcr(Cb, E, L_b, rts, J, c, S_x, ho);
M_n = Fcr * S_x; //(F2-3)
M_p = GetMajorNominalPlasticMoment();
M_n = M_n > M_p ? M_p : M_n;
break;
}
double phiM_n = M_n * 0.9;
return(phiM_n);
}
// Lateral-Torsional Buckling F5.2
public double GetLateralTorsionalBucklingStrength(FlexuralCompressionFiberPosition compressionFiberPosition, double L_b, double Cb)
{
double Mn = 0.0;
double r_t = GetEffectiveRadiusOfGyration_r_t(compressionFiberPosition);
L_p = GetLp(r_t);
Lr = GetLr(r_t);
Rpg = GetRpg(compressionFiberPosition);
double Sxc = compressionFiberPosition == FlexuralCompressionFiberPosition.Top ? Sxtop : Sxbot;
LateralTorsionalBucklingType BucklingType = GetLateralTorsionalBucklingType(L_b, L_p, Lr);
double Fcr = 0.0;
switch (BucklingType)
{
case LateralTorsionalBucklingType.NotApplicable:
Mn = double.PositiveInfinity;
break;
case LateralTorsionalBucklingType.Inelastic:
Fcr = GetFcrLateralTorsionalBucklingInelastic(L_b);
break;
case LateralTorsionalBucklingType.Elastic:
Fcr = GetFcrLateralTorsionalBucklingElastic(r_t, L_b);
break;
}
if (Mn != double.PositiveInfinity)
{
Mn = Rpg * Fcr * Sxc; //(F5-2)
}
double phiM_n = 0.9 * Mn;
return(phiM_n);
}
