I am going through this example problem (picture below) and working it out myself. The problem is that I do not get the same mass matrix (M) as the example problem. I am able to get the same stiffness matrix (K). I used the same process of obtaining the stiffness matrix, which uses the connectivity array, but do not end up with the same mass matrix provided in the example. Can someone help me confirm whether the mass matrix in the given example is correct or incorrect?
This is what I obtain:
{
{4, 1, 0, 1, 2, 0, 0, 0, 0, 0, 0, 0},
{1, 6, 1, 0, 2, 2, 0, 0, 0, 0, 0, 0},
{0, 1, 2, 0, 0, 1, 0, 0, 0, 0, 0, 0},
{1, 0, 0, 6, 2, 0, 1, 2, 0, 0, 0, 0},
{2, 2, 0, 2, 12,2, 0, 2, 2, 0, 0, 0},
{0, 2, 1, 0, 2, 6, 0, 0, 1, 0, 0, 0},
{0, 0, 0, 1, 0, 0, 6, 2, 0, 1, 2, 0},
{0, 0, 0, 2, 2, 0, 2, 12,2, 0, 2, 2},
{0, 0, 0, 0, 2, 1, 0, 2, 6, 0, 0, 1},
{0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 1, 0},
{0, 0, 0, 0, 0, 0, 2, 2, 0, 1, 6, 1},
{0, 0, 0, 0, 0, 0, 0, 2, 1, 0, 1, 4}
}