structure soil interaction

[newarrived]

Hi dears,
I am trying to to model 3d steel structure with soil interaction. i've modeled soil with "stdBrick" element and "PressureDependMultiYield" nDMaterial.
number of dofs for structure is 6 and for soil is 3.
I fixed rotational dofs of base nodal of structure and I used equalDOF for translational dofs of soil and structure at the base of structure.
for soil I used characteristics of "Loose Sand (15%-35%)".
structure is simple frame with X-bracing in both direction.
the question is why I am getting the same periods as the nodal base are fixed?!
thank you in advance

[fmk]

you should not be getting the same periods.
model basic -ndm 3 -ndf 6
node 1 1 1 1
node 2 1 1 2 -mass 10. 10. 10. 1.e-8 1.e-8 1.e-8
geomTransf Linear 1 1 0 0
element elasticBeamColumn 1 1 2 100 1000 100 200 300 100 1
fix 1 1 1 1 1 1 1
puts [eigen 2]

for {set i 1} {$i <= 3} {incr i 1} {
remove sp 1 $i
}

model basic -ndm 3 -ndf 3
nDMaterial ElasticIsotropic 1 1000. 0.25 1.27

node 11 0.00000 0.0000 0.00000
node 12 0.00000 0.0000 1.00000
node 13 0.00000 1.0000 0.00000
node 14 0.00000 1.0000 1.00000
node 15 1.00000 0.0000 0.00000
node 16 1.00000 0.0000 1.00000
node 17 1.00000 1.0000 0.00000
node 18 1.00000 1.0000 1.00000

fixZ 0.0 1 1 1

equalDOF 18 1 1 2 3

element stdBrick 2 11 15 17 13 12 16 18 14 1

puts [eigen 2]

[newarrived]

Thank you dear fmk,
I found the problem in input units.