public static void ElasticK(double[,] k, List <Vec3Float> xyz, float[] r,
double L, double Le,
int n1, int n2,
double Ax, double Asy, double Asz,
double J, double Iy, double Iz,
double E, double G, float p,
bool shear)
{
double Ksy, Ksz; /* shear deformatn coefficients */
int i, j;
double[] t = Coordtrans.coordTrans(xyz, L, n1, n2, p);
for (i = 0; i < 12; i++)
{
for (j = 0; j < 12; j++)
{
k[i, j] = 0.0;
}
}
if (shear)
{
Ksy = 12.0 * E * Iz / (G * Asy * Le * Le);
Ksz = 12.0 * E * Iy / (G * Asz * Le * Le);
}
else
{
Ksy = Ksz = 0.0;
}
k[0, 0] = k[6, 6] = E * Ax / Le;
k[1, 1] = k[7, 7] = 12.0 * E * Iz / (Le * Le * Le * (1.0 + Ksy));
k[2, 2] = k[8, 8] = 12.0 * E * Iy / (Le * Le * Le * (1.0 + Ksz));
k[3, 3] = k[9, 9] = G * J / Le;
k[4, 4] = k[10, 10] = (4.0 + Ksz) * E * Iy / (Le * (1.0 + Ksz));
k[5, 5] = k[11, 11] = (4.0 + Ksy) * E * Iz / (Le * (1.0 + Ksy));
k[4, 2] = k[2, 4] = -6.0 * E * Iy / (Le * Le * (1.0 + Ksz));
k[5, 1] = k[1, 5] = 6.0 * E * Iz / (Le * Le * (1.0 + Ksy));
k[6, 0] = k[0, 6] = -k[0, 0];
k[11, 7] = k[7, 11] = k[7, 5] = k[5, 7] = -k[5, 1];
k[10, 8] = k[8, 10] = k[8, 4] = k[4, 8] = -k[4, 2];
k[9, 3] = k[3, 9] = -k[3, 3];
k[10, 2] = k[2, 10] = k[4, 2];
k[11, 1] = k[1, 11] = k[5, 1];
k[7, 1] = k[1, 7] = -k[1, 1];
k[8, 2] = k[2, 8] = -k[2, 2];
k[10, 4] = k[4, 10] = (2.0 - Ksz) * E * Iy / (Le * (1.0 + Ksz));
k[11, 5] = k[5, 11] = (2.0 - Ksy) * E * Iz / (Le * (1.0 + Ksy));
k = Coordtrans.Atma(t, k, r[n1], r[n2]);
for (i = 0; i < 12; i++)
{
for (j = i + 1; j < 12; j++)
{
if (k[i, j] != k[j, i])
{
if (Math.Abs(k[i, j] / k[j, i] - 1.0) > 1.0e-6 &&
(Math.Abs(k[i, j] / k[i, i]) > 1e-6 ||
Math.Abs(k[j, i] / k[i, i]) > 1e-6
)
)
{
Console.WriteLine($"elastic_K: element stiffness matrix not symetric ...");
Console.WriteLine($" ... k[{i}][{j}] = {k[i, j]} ");
Console.WriteLine($" ... k[{j}][{i}] = {k[j, i]} ");
Console.WriteLine($" ... relative error = {Math.Abs(k[i, j] / k[j, i] - 1.0)} ");
Console.WriteLine($" ... element matrix saved in file 'kt'");
}
k[i, j] = k[j, i] = 0.5 * (k[i, j] + k[j, i]);
}
}
}
}
