# Liner element - struct.force.nodal.local

**URL:** <https://forum.itascainternational.com/t/liner-element-struct-force-nodal-local/1387>\
**Category:** FLAC2D\
**Tags:** fish\
**Created:** [March 29, 2024, 10:46am UTC](https://forum.itascainternational.com/t/liner-element-struct-force-nodal-local/1387 "2024-03-29T10:46:16Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![AgustinMG](https://avatars.discourse-cdn.com/v4/letter/a/3be4f8/32.png) [@AgustinMG](https://forum.itascainternational.com/u/AgustinMG)\
**Post date:** [March 29, 2024, 10:46am UTC](https://forum.itascainternational.com/t/liner-element-struct-force-nodal-local/1387/1 "2024-03-29T10:46:16Z")

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Hi everyone,

I have performed a 2D model of an excavation with a lining that has been modeled as a “liner” element. The results of the liner that interest me are the axial stress, shear stress, and bending moment.  
I extract these results using a fish function using the “struct.force.nodal.local” command as follows:

def output\_support  
global i = 0  
loop foreach str struct.list()  
if struct.isgroup(str,“support”)  
i = i + 1  
end\_if  
end\_loop  
results\_support = list.create(i)  
;  
global ln = 0  
loop foreach str struct.list()  
ln = ln + 1  
id = struct.id.component(str)  
pos\_x = struct.pos.x(str)  
pos\_y = struct.pos.y(str)  
;  
N\_1 = struct.force.nodal.local(str)(1)(1)  
N\_2 = struct.force.nodal.local(str)(2)(1)  
;  
Q\_1 = struct.force.nodal.local(str)(1)(2)  
Q\_2 = struct.force.nodal.local(str)(2)(2)  
;  
M\_1 = struct.force.nodal.local(str)(1)(3)  
M\_2 = struct.force.nodal.local(str)(2)(3)  
;  
results\_support(ln) = string(id) + “,” + string(pos\_x) + “,” + string(pos\_y) + “,” + string(N\_1) + “,” + string(N\_2) + “,” + string(Q\_1) + “,” + string(Q\_2) + “,” + string(M\_1) + “,” + string(M\_2)  
end\_loop  
io = file.open(“support\_results.txt”,1,1)  
io = file.write(results\_support)  
io = file.close  
end

The stresses obtained with this function are different from those I obtain by querying the corresponding node (query tool), as you can see in the attached screenshot. Is this indeed a Flac bug? How could it be resolved?

 ![bug_flac](https://canada1.discourse-cdn.com/flex031/uploads/itasca/original/1X/9231eb64a2e2f5b3350c306a8613a8afdae6a165.png)

Thank you in advance. Best regards,

Agustin

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<div class="post-metadata">

**Author:** ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)\
**Post date:** [April 2, 2024, 8:58pm UTC](https://forum.itascainternational.com/t/liner-element-struct-force-nodal-local/1387/2 "2024-04-02T20:58:53Z")

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Hello @AgustinMG,

Thank you for this report. This seems to be a bug in _FLAC2D_ and we will begin fixing the issue.

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<div class="post-metadata">

**Author:** ![dblanksma](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@dblanksma](https://forum.itascainternational.com/u/dblanksma)\
**Post date:** [April 4, 2024, 3:27pm UTC](https://forum.itascainternational.com/t/liner-element-struct-force-nodal-local/1387/3 "2024-04-04T15:27:08Z")

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@AgustinMG This bug has been fixed and will be available in the next update.

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<div class="post-metadata">

**Author:** ![AgustinMG](https://avatars.discourse-cdn.com/v4/letter/a/3be4f8/32.png) [@AgustinMG](https://forum.itascainternational.com/u/AgustinMG)\
**Post date:** [April 4, 2024, 3:39pm UTC](https://forum.itascainternational.com/t/liner-element-struct-force-nodal-local/1387/4 "2024-04-04T15:39:05Z")

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@dblanksma thank you 👍