EXPLANATION OF THE LOADING CODES:
Single tube:
-1: Only 3 dof's of one end are prescribed. These dof's
prevent rigid body motions. Then structure is relaxed.
0: all the x dofs of one end plus 3 dofs are prescribed. Then
the structure is relaxed.
1: bending
13: This is bend and Compress at the same time. the compression
is not given in %, but in nm.
11: bending so that the hypothetical semi-circle formed by the tube
has the length of the original tube, i.e. the ends are rotated
and compressed. Note this does not work if RESTART!!!
2: twisting
3: Compression with ends totally prescribed
4: Compression with only x dofs prescribed at ends plus 3 dofs
5: load at one end and the other is fixed
6: squeeze the tube
7: Compress the tube holding only 4 points
8: vertical forces at ends, upper and lower lines don't z-move, and
central 3 nodes fixed.
10: Ends and central lines don't z-move. in execution it becomes code 0
In nested tubes, option -1 does not exist.
In running the code, -69 means tha dynamical relaxation is carried out.