EXAMPLE: exs_spring.py ---------------------------
Stiffness matrix K:
+-------------+-------------+-------------+
| 3.0000e+03 | -3.0000e+03 | 0.0000e+00 |
| -3.0000e+03 | 7.5000e+03 | -4.5000e+03 |
| 0.0000e+00 | -4.5000e+03 | 4.5000e+03 |
+-------------+-------------+-------------+
Displacements a:
+------------+
| 0.0000e+00 |
| 1.3333e-02 |
| 0.0000e+00 |
+------------+
Reaction forces r:
+-------------+
| -4.0000e+01 |
| 0.0000e+00 |
| -6.0000e+01 |
+-------------+
Element forces N: