WHEN I AN RUNNING , CAESAR II IS SHOWING THIS ERROR :
STIFFNESS MATRIX HAS BEEN DETECTED AS BEING ALMOST NUMERICALLY SINGULAR .

You need to restrain, either directly or indirectly, all degrees of freedom somewhere in your model. Otherwise, it will be statically indeterminate. If you think you have a geometry that indirectly stops infinite motion in all degrees of freedom you can try this: Go to Tools->Configure/Setup->Computational Control and increase the Decomposition Singularity Tolerance (1.0E+15 to 1.0E+20 is good here).