FEAP User Forum
FEAP => Input File Issues => Topic started by: cri on May 09, 2017, 09:00:59 AM
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Dear all
I am trying to perform a pushover analysis of a wall with elasto-plastic constitutive behaviour.
Using the same input file (that is attached below), I obtain different results in terms of global response curve (imposed displacement-base reactions).
I don't understand whether there is a mistake in my input file or I have to change something when I step from one version to another.
Thank you in advance
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I am not sure why there should be differences.
It would be good to check the behavior of the material models by doing, say one or two cycles on a tension test using a single element. I do not recall making changes in the model you are using. In finite strain you cannot use kinematic hardening with the isotropic elasto-plastic model (it is a blunder in the original development).
Next check that the two programs give the same final equation set. You can do this by using the command SHOW ID and look at the equation numbering. It could be that the linking is different in the two versions. But a careful check that you get the same problem before you run the multicycles is needed.
The input file seems to be running correctly for me -- I have not checked the actual load history, but since you are summing reactions to get the force any discontinuity should be evident to you.
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There are errors in ver8.4 that relate to the addition of the plane stress reduction algorithm. You can fix in part with the following.
In ./elements/material/small edit the routine: modlsd.f as follows
1. After if(stype.eq.1) then (line 67 about) add
eps(3,1) = h2(nh)
eps(3,1) = h1(nh)
After the plane stress update routine call (call fpstrs) and after
the statement
if(.not.conv .and. ict.lt.6) go to 100
add
h2(nh) = e33
2. In ./elements/solid2d modify: sld2d1.f as follows
Around line 141 comment all the statemens related to stype.eq.1 except
nn = 0
After call to strn2d comment all statements related to stype.eq.1
After call to modlsd comment all statements related to stype.eq.1
In the output of results area (around line 431) comment all statements
related to stype.eq.1 except
nn = 0
After call to strn2d comment all statements related to stype.eq.1
3. This should fix the use of the displacement element only. Similar
changes may be needed in other elements (both solid2d and frame elements)
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Sorry first part should read:
1. After if(stype.eq.1) then (line 67 about) add
eps(3,1) = h2(nh)
eps(3,2) = h1(nh)
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Dear Prof. Taylor,
Many thanks for your replies. I will try to follow your instructions and I will let you know.
Best regards