B.C for 3D simply supported beam in ansys with SOLID95 element

Hi,

I am modeling a 3D simply supported beam in ansys using a SOLID95
element. In this case, how should I give
the B.C.s? Should I apply B.C.s to

1) the mid nodes on the edge of beam? or

2) to the entire edge? or

3)  just to the bottom nodes?

according to me, I have tried to use the various B.C case, but the
results are very different even though the nodes number taken in account
change slightly, and for all case, the result is not satisfactory with
my analytical solution. plz help.

 Thanks in avance!

 Van