*HEADING
******************
** MIDDLE LAYER **
******************
*NODE,NSET=SIDES
1,    0.,  -66.66
5,  100.,  -66.66
11,   0.,  -50.00
15, 100.,  -50.00
21,   0.,  -33.33
25, 100.,  -33.33
*NGEN,NSET=BOTTOM
1,5,1
*NGEN,NSET=MID
11,15,1
*NGEN,NSET=TOP
21,25,1
*ELEMENT,TYPE=CPE8R,ELSET=EALL
1, 1,3,23,21,2,13,22,11
2, 3,5,25,23,4,15,24,13
*SOLID SECTION,ELSET=EALL,MATERIAL=ELAS
*MATERIAL,NAME=ELAS
*DENSITY
1., 
*ELASTIC
2.8E7, .2
***INITIAL CONDITIONS,TYPE=STRESS,GEOSTATIC
**EALL, -833.33, -33.33, -1666.66, -66.66, 0.333
**
**
*STEP
*SUBSTRUCTURE GENERATE,TYPE=Z2,OVERWRITE
*RETAINED NODAL DOFS,SORTED=NO
BOTTOM,2
TOP,2
*BOUNDARY
SIDES,1
*SUBSTRUCTURE LOAD CASE,NAME=BOUND
*DLOAD
EALL,GRAV,25., 0.,-1.,0.
*END STEP