Request for help meshing and and analysing a part {Solved}

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chrisb
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Re: Request for help meshing and and analysing a part

Post by chrisb »

I don't see any DatumPlane in your model.
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Laurie Hartley
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Re: Request for help meshing and and analysing a part

Post by Laurie Hartley »

chrisb wrote: Wed Sep 22, 2021 12:34 pm I don't see any DatumPlane in your model.
Yes Chris - I cleared them out. Thanks for getting back to me.

I am on an iPad at the moment but will be at my computer in a few hours time.

What I am trying to do is for example, on one of the side faces create a datum plane on the main origin and offset it by the distance of the side face from the main origin plus the length of the “HingeOffset”

Same with the diagonals except I have to rotate them 45 degrees.

If you change the the “chord profile” cell in the spreadsheet the whole model will “expand” proportionately. I want the datum planes to explode in the same proportion.

You will see that the placements have a formula linking them to the spreadsheet.

I thought it would be simple but every time I try they get left in the same position. I get messages like like “do you want to make a dependant copy”. I think that is the stage where I am going astray.

I have established that I can also make a polar array of each of the three datum plains so if I can achieve that I can draw a sketch on any of them for a chord, strut or plan brace and then build the frame using the array tool. The frame size can then be configured from the spreadsheet.

Hopefully, after some advice from you guys, on a suitable “hinge offset” dimension the frame can be meshed and analysed.

The reason for the upper and lower diagonal faces (fins in the image in my previous post) is so I can pick up four nodes with four struts leading down to a support node and column at the corners of the frame - but I am getting ahead of myself now. :D
Laurie Hartley
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Re: Request for help meshing and and analysing a part

Post by Laurie Hartley »

I think I have made progress. I am not sure quite why - I will have to start writing things down in my notepad!
See screen shots.
  • I was able to place the datum plane where I wanted it using formulas referencing the spreadsheet (including the "Hinge Offset")
    I selected the independent copy option.
    When I change the Chord Profile SHS from 65 to 50 everything was adjusted accordingly in the model.
I have attached the update file.

Hopefully I will have the frame assembled over the next couple of days.
Attachments
Datum Plane Attachment Query.png
Datum Plane Attachment Query.png (128.14 KiB) Viewed 26368 times
Chord Profile 65.png
Chord Profile 65.png (113.57 KiB) Viewed 26368 times
Chord Profile 50.png
Chord Profile 50.png (68.34 KiB) Viewed 26368 times
Parametric Spaceframe.FCStd
(47.37 KiB) Downloaded 537 times
thschrader
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Re: Request for help meshing and and analysing a part

Post by thschrader »

@Laurie:
The calculation of the entire framework and the calculation of the nodes, the connections, are two different problems.
We have calculated the stability of the entire system. With different programs.
pcae, Mastan2, FreeCAD...
Which give practically the identical result.
The frame was calculated without joints in the nodes.
This is ok for a structure of this type.

So..
We have the forces. This is the input for the details, lets say the nodes.
You have to separate the two problems.
The static calculation of the structure (1) and the design of the details (2).
I will show a "real life" example I am working on. Give me 2 days... aah lets say 4 days..
cad1234
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Re: Request for help meshing and and analysing a part

Post by cad1234 »

This thread becomes more and more an amazing FC-FEM real world project, I think..
Thanks to thomas for sharing his great knowledge with us and to Laurie , who started this thread with a great concept idea...
Highly interested what the next steps are...what an amazing run!!
Laurie Hartley
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Re: Request for help meshing and and analysing a part

Post by Laurie Hartley »

thschrader wrote: Sun Sep 26, 2021 8:15 pm I will show a "real life" example I am working on. Give me 2 days... aah lets say 4 days..
Terrific Thomas - I am really looking forward to seeing that.

I will keep plugging away at my parametric model because, in the course of doing so, I have been rediscovering the wonders of Archimedean solids and Euclidean geometry, as well as FreeCAD datum planes and hinges :D
thschrader
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Re: Request for help meshing and and analysing a part

Post by thschrader »

Laurie Hartley wrote: Mon Sep 27, 2021 5:50 am
thschrader wrote: Sun Sep 26, 2021 8:15 pm I will show a "real life" example I am working on. Give me 2 days... aah lets say 4 days..
...
Here is a small and fast example:
Calculate the tube forces (N,Q,M) with Smath-Studio, calculate the anchor plate and the
compound-anchors with Fischer-Software, calculate the cable-opening with FC-FEM.
https://www.fischer.co.uk/en-gb/service ... ixperience

Your spaceframe:
Calculate beam forces with FC or another software.
Calculate the nodes with FC
Calculate the fixings/anchor-points with...who knows...

Any news from the cathedral? :)
cable_opening.FCStd
(163.5 KiB) Downloaded 519 times
statics.JPG
statics.JPG (78.51 KiB) Viewed 25804 times
Laurie Hartley
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Location: Australia

Re: Request for help meshing and and analysing a part

Post by Laurie Hartley »

thschrader wrote: Tue Sep 28, 2021 3:09 pm Here is a small and fast example:

Calculate the fixings/anchor-points with...who knows...

Any news from the cathedral? :)
I downloaded your file and ran the mesh Thomas - it is wonderful the stress and displacement can be simulated using FEA software! I will explore it in more detail tomorrow and attempt to apply the principles to the node.

I have sent you a link to my cloud folder which contains some of the Cathedral engineering notes. Nothing overly exciting but I expect get more when travel restrictions are relaxed.

Regarding the fixings / anchor points for the spaceframe - if it is a roof structure perhaps it could be fixed to columns or walls with the arrangement in the screen shots.

The struts to the column assembly will have to have higher load capacity no doubt. I could upgrade them to 50SHS 6mm wall or better still 65X6 SHS - or hmm - how far can we push this? I think that node is pretty robust but there is no reason why it cannot be scaled up :D

EDIT - After thinking about this I think the arrangement in the screen shot is OK if it is a direct connection between the frame and column. On the other hand if it is “struts to column head” a simpler connection would be better - just a base plate and four fins like those on the node.
Attachments
Column Head Assembly Side Viewpng.png
Column Head Assembly Side Viewpng.png (76.45 KiB) Viewed 25727 times
Column Head Assembly Diagonal.png
Column Head Assembly Diagonal.png (89.02 KiB) Viewed 25727 times
Column Head Assembly.FCStd
(365.82 KiB) Downloaded 526 times
thschrader
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Re: Request for help meshing and and analysing a part

Post by thschrader »

@Laurie:
There is a lot of information in the old drawings.
Should be possible to reconstruct the main stage and do some calculations
with FC. Lets see how much load is on the 4 supports of the frame and how
the church reacts...
lower_main_stage.JPG
lower_main_stage.JPG (67.5 KiB) Viewed 25598 times
Laurie Hartley
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Location: Australia

Re: Request for help meshing and and analysing a part

Post by Laurie Hartley »

thschrader wrote: Thu Sep 30, 2021 3:06 pm @Laurie:
There is a lot of information in the old drawings.
Should be possible to reconstruct the main stage and do some calculations
with FC. Lets see how much load is on the 4 supports of the frame and how
the church reacts...
lower_main_stage.JPG
This will be interesting Thomas. As a Sub Contractor one of the items I always put in my quotation terms & conditions was that it was the clients responsibility to ensure that the supporting surface or structure could safely accommodate the loads to be imposed by the scaffold system. In this case this would have been checked independently by the Cathedrals Architect and Engineering consultants.
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