Tuple <double, double> CalP(double NeutralDist, bool isVert = true)
{
double center = isVert ? PlasticCenterY : PlasticCenterX;
double top = isVert ? OuterLine.Ymax() : OuterLine.Xmax();
double na = center + NeutralDist;
int steps = PreRebars.Count;
double F = 0.0, M = 0.0;
double dz, zi;
double phi = -Conc.Epsu / (top - na);
double epsi, sigmai;
double Fi, Mi;
for (int i = 0; i < steps; i++)
{
zi = isVert ? PreRebars[i].Center.Y : PreRebars[i].Center.X;
dz = zi - na;
epsi = dz * phi;
sigmai = PrestressProperty.GetSigma(epsi);
Fi = sigmai * PreRebars[i].Area;
Mi = Fi * (zi - center);
F += Fi;
M += Mi;
}
return(new Tuple <double, double>(F, M));
}