Response analysis of an elastic soil layer

[nitadorakis]

Hi

It's the first time I'm working on soil-modelling, so I'm encountering a few problems with the analysis.
The problem is about a elastic 2D soil layer 980x50m, meshed by 2x2m quad elements, fixed in both directions in its base and right boundary.
This layer is being excited by an horizontal sinusoidal base shaking sin(2πt) for 10sec.
It goes like this:

# Displacement time history
# The excitation is applied at all the 491 nodes of the base
timeSeries Path 1 -dt 0.05 -filePath displ.txt -factor 1;
pattern Plain 1 1 {
for {set k 1} {$k <= 491} {incr k 1} {
sp $k 1 1
}
}
puts "Load pattern created"
###########################
# create the Analysis
constraints Penalty 1.0e18 1.0e18 ;
test NormDispIncr 1.e-12 25 0
algorithm Newton
numberer RCM
system ProfileSPD
rayleigh 0.0 0.0 0.05 0.
integrator Newmark 0.5 [expr pow(0.5+0.5, 2)/4]
analysis Transient
puts "Analysis object created"


The problem is that the results are not as expected, so I would be grateful if someone could help me with this. I think that the application of the displacement time history (which is in the file displ.txt) might be the problem or something with the analysis parameters (e.g constraints Penalty?)
The displ.txt is:
0.00 0.00
0.05 0.31
0.10 0.59
0.15 0.81
0.20 0.95
0.25 1.00
0.30 0.95
0.35 0.81
0.40 0.59
0.45 0.31
0.50 0.00
etc