Truss Portal Frame

Hi,

I am trying to design a truss portal frame in Karamba. The first problem that I have is that I want the joints between the nodes of the portal frame to be pinned, but when I do that the system explodes. Additionally, when I import the model to model view I cannot see the view features such as loads, supports etc. Can someone help me please?

Thanks,

Olympios

Attachments:

Portal Frame 4.gh, 72 KB

Replies to This Discussion

Permalink Reply by Yike Qin on July 13, 2017 at 2:00pm

Hi,

I have a quick look at your model, and here is what I find:

1) The load you put on the structure is very huge so the calculated deflections are huge. With large magnification factors, it would let the deformed shape look funny. Try a smaller load and adjust magnification factor, you will find the deflected shape more reasonable.

2) You can use the "modify element" component for your beams to transfer all your beam members into truss members. So the boundary condition will be by default as pin and members only take axial load.

3) In your model, all your bottom chords are consist with two separate members in each panel. Without per-tensioining, they are not stable. Should be a quick fix.

I am not sure why you cannot see loads, supports, etc. Hope this helps.

Permalink Reply by Olympios Grigoriadis on July 15, 2017 at 9:05am

Hi,

Firstly, I want to thank you for your reply.

1) I got it. This was just a preliminary design.

2) I found the component that you said. I saw that if you turn the bending to false then the structure becomes truss. Is it correct? When I do that the bottom chord of the roof is acting weird.

3) I did not get what you mean here. My two top corners above the columns were designed separately from the rest. You mean that the line must be continuous and not imported separately?

I found how to see the loads etc.

Can you please have a look and tell me what I am doing wrong?

Attachments:

Portal Frame.gh, 85 KB

Permalink Reply by Yike Qin on July 17, 2017 at 9:25am

Hi,

If you look at your bottom chord output, you can see that you have 9 members on each side which would be 18 members total for your bottom chord. However, your geometry of truss only show you 10 panels which suggests there should only be 10 bottom chord members. The reason is that you divide the middle 8 members in halves.

Another suggestion, you should pin some nodes in Y direction to avoid instability.

Best,

Yike

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