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Contributor
Khristopherson
Posts: 20
Registered: ‎01-15-2014

Structure Rigidity, software bug???? Help.

02-25-2014 09:07 AM in reply to: Artur.Kosakowski

Hello.

I have been trying to solve a problem i have with my model for the last three days.

The thing is that i built a tower, made of beam elements. After i had finished my model I realized that there was something wrong with it because when i ran the analysis, i could noticed that there was some deformation of my model, even in the static case considering only the structure weight. Then, when seeing the results of the modal analysis, I could see some of the bars were deattached from the node were they were supposed to be joint.

Then i knew that i had to check the model.

I went node by node making sure that they were joining the bars that they were supposed to join. Here is when i found that some nodes were only joining two bars, which meant they were not attached to all the bars, the rigidity of the model was not correct.

So i built again the tower, from scrath, making sure that every node and bar were properly in place and with its correct properties. Then again, when i run the model, i had the same issue.

The tower has 6 sections, i built each of them separately, so i could check each of the sections, and then i join them, inserting the geometry from other files. Just like it is shown in the next picture:

Joint.png

 

Before joining the structures, i checked avery single node in the structure as i said, i spent hours doing it over and over again. And yes, the structures were completely correct and rigid, with no isolated nodes or deattached bars.

 

Nodesbeforejoining.png

 

After checking on this, I put al the parts together, and checked again, each of the nodes, and it all seemed to be in the right place (same node, number 27):

 

 

attached.png

 

Having checked all of this, before and after joining the parts, my model was ready to run the simulation. But after running it, i still had deformation in the static case, and in the modal analysis i could see bars that were separate from the structure. So i went back to the model to check the nodes and bars. And this is what i found:

 

AfterRunningAnalysis.png

 

Same node, and now it says that it is deattached from the vertical bar which is the base of the structure. Same thing happened with a bunch of other nodes.

 spent 2 days working on this trying to solve it, and building it again, just to find out that it is something with the software, a bug or something that i have no idea what it is that makes the structure to separate from itself when the analysis is run.

Why is this happening? How can i avoid it? 

Thanks for your help.

 

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Contributor
Khristopherson
Posts: 20
Registered: ‎01-15-2014

Re: Structure Rigidity, software bug???? Help.

02-25-2014 03:19 PM in reply to: Khristopherson

Here the links with the two files that i need to merge.

I have to merge the bodies just like all the bodies in file "1". They are equally separate from each other and they are concentrically. Joint by the rigid link named "RigidLink". This means that node 1811 in file "1" and  node1799 in file "2" must overlap.

I hope i made it clear in my last post and that with these files you can see exactly what i am talking about.

 

File "1": https://www.dropbox.com/s/tf1anwk7b0amx00/1.rtd?m=

File "2": https://www.dropbox.com/s/6aqt31cbnmgmruf/2.rtd?m=

 

Thank you very much, it will be great if someone can help me understand and solve this problem.

 

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Artur.Kosakowski
Posts: 4,596
Registered: ‎12-17-2010

Re: Structure Rigidity, software bug???? Help.

03-03-2014 02:22 AM in reply to: Khristopherson

I have checked the model 2. You can calculate it provided you define supports at the bottom which are apparently missing. Is it the answer you are looking for?

 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.



Artur Kosakowski
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Contributor
Khristopherson
Posts: 20
Registered: ‎01-15-2014

Re: Structure Rigidity, software bug???? Help.

03-03-2014 09:49 AM in reply to: Artur.Kosakowski

Hello.

The problem, as i stated before, was that for no apparent reason when i bring geometry from file 2 to file 1, put all the parts together (the 6 bodies), 5 nodes of the first, bigger boddy suddenly sepaated from the vertical bar which them were part of.

I dont know why this happened, but i tried several ways of building the tower and finally one worked, i managed to put all the 6 bodies together.

Thanks for your help anyway.

Now I have a question regarding how to interpret the result of my analysis. But i am goind to post it in another thread so i don make a bigger mess of topics and answers.

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