question about eigen value...

[chris]

Hi...
For the time history analysis of bridge, I tested several cases for the zerolengthelement. so I used the rotSpring2D.tcl.
In two cases, I got a different eigen values...
Is it right? or I have some modeling errors ?

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case 1) M-rotation relation : bilinear

set fy 4326.0; # Yield stress
set E 618600.0; # Young's modulus
# tag fy E0 b
uniaxialMaterial Steel01 3 $fy $E 0.006918
.....
rotSpring2D 16 13 19 5



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case 2) M-rotation relation : Pinch4

set pEnvelopmoment [list 4326.0 4437.0 .......]
set pEnveloprotation [list 0.006993 0.032673 ........]
......
just used RCyclicPinch.tcl of the example...
for the same E, I set the pEnvelopmoment, pEnveloprotation...
like E=6168600=4326 / 0.006993
|
case1) E

[silvia]

when did you do the eigenvalue analysis?
you have to do it right away, as it uses the current stiffness values.

[chris]

Thanks... silvia...
I checked my source. Like your advice, even though I put the "eigen" command before and after the "analyze" command, I just checked the latter one.
Thanks again...