public double DiffAlphaBending(int t, BarElement NextBar)
{
// when t 0:2 only thisBar derrivatives work
// when t 6:8 only nextBar derrivatives work
// when t 3:5 both thisBar and nextBar derrivatives work
double cosa = B.Dot(NextBar.B) / (L * NextBar.L);
double sina = Sqrt(1 - Pow(cosa, 2));
if (sina != 0)
{
return((-1 / sina) * ((DiffUnitB(0, t) * NextBar.B[0] + DiffUnitB(1, t) * NextBar.B[1] + DiffUnitB(2, t) * NextBar.B[2]) / NextBar.L +
(NextBar.DiffUnitB(0, t - 3) * B[0] + NextBar.DiffUnitB(1, t - 3) * B[1] + NextBar.DiffUnitB(2, t - 3) * B[2]) / L));
}
return(0);
}
public double Diff2AlphaBending(int i, int j, BarElement NextBar)
{
double cosa = B.Dot(NextBar.B) / (L * NextBar.L);
double sina = Sqrt(1 - Pow(cosa, 2));
double Part1 = (-1 / sina);
double dPart1 = DiffAlphaBending(i, NextBar) * cosa / Pow(sina, 2);
double Part2 =
(DiffUnitB(0, j) * NextBar.B[0] + DiffUnitB(1, j) * NextBar.B[1] + DiffUnitB(2, j) * NextBar.B[2]) / NextBar.L +
(NextBar.DiffUnitB(0, j - 3) * B[0] + NextBar.DiffUnitB(1, j - 3) * B[1] + NextBar.DiffUnitB(2, j - 3) * B[2]) / L;
double dPart2 =
(Diff2UnitB(0, i, j) * NextBar.B[0] + Diff2UnitB(1, i, j) * NextBar.B[1] + Diff2UnitB(2, i, j) * NextBar.B[2]) / NextBar.L +
(NextBar.Diff2UnitB(0, i - 3, j - 3) * B[0] + NextBar.Diff2UnitB(1, i - 3, j - 3) * B[1] + NextBar.Diff2UnitB(2, i - 3, j - 3) * B[2]) / L +
DiffUnitB(0, i) * NextBar.DiffUnitB(0, j - 3) + DiffUnitB(1, i) * NextBar.DiffUnitB(1, j - 3) + DiffUnitB(2, i) * NextBar.DiffUnitB(2, j - 3) +
NextBar.DiffUnitB(0, i - 3) * DiffUnitB(0, j) + NextBar.DiffUnitB(1, i - 3) * DiffUnitB(1, j) + NextBar.DiffUnitB(2, i - 3) * DiffUnitB(2, j); // correct
return(Part1 * dPart2 + Part2 * dPart1);
}