Steel Plates and Stiffeners

[nuche1973]

Using Risa to model steel grain collectors and hoppers: How do I merge the plates and stiffeners in Risa? I have a collector 35' long segemented to 7' bays that are 8' wide & 8' tall. I am using L3x3x1/4 as stiffeners and C10x30 as the top and bottom horizontals. The support columns have to be at the ends (4 total). So I am relying on a large section modulus to carry the load (27k/ft), I have a model in Risa but do not know how to merge my plates, stiffeners and channels. Any comments would be appreciated. Thanks.

 

[nuche1973]

I was incorrect on my uniform load. It is 1.6k/ft not 27k/ft. Gotta remember to type s-l-o-w-e-r.

 

[bootlegend]

I am not sure what you are asking, but I'll try to answer what I think you are asking.

I take the plates and model the actual dimensions of the plates, probably 8'x8' in your case. For the channel "chords" I model them as directly attached to the plates.
For the vertical angles stiffeners I determine the distance that the centroid of the angle is away from the wall plate. I create rigid links to connect the wall plate to the stiffener.

 

[nuche1973]

Johnnycash:
What I am trying to model is a steel grain bin. The overall structure would be steel plate with verticle and horizontal stiffeners that are welded to the plate. I have done a few by hand, but if I could get a RISA model to work, especially the transfer of loads between the plates and stiffener, I would be more efficient. I think that I understand what you are saying. I'd have to try this in a model of a bin that has already been checked. Thanks.

 

[ishvaaag]

That's (I think easy). You simply model in Autocad your bin made of rectangular (or if required triangular) 3DFACE entities, then export at the correct scale to RISA 3D. You then give loads etc and you will have the stresses and deformations in the plates. Ensure you are doing it with P-Delta and check if you need to use a reduced Yung modulus out of the standing flexural or axial compression.

If you need to model some parts as linear members, proceed as ccb1 says for it will place your linear member properly at its place and showing the forces as one is accustomed to see in linear members. You may, however, for members lying in horizontal surfaces prefer to have them placed with a TOM Top of Member clause, RISA will check the member well both ways.

 

[nuche1973]

AutoCad! Duh, totally forgot that we can export from AutoCad into Risa. Thanks, this makes the process ALOT easier. Thanks guys.

 

[ishvaaag]

Of course I was saying as johnnycash was saying about rigid links. And I think it is my first Yung errata but giving my rate maybe it won't be the last.

 

[nuche1973]

I hear you. Thanks for the information.