Shear Transfer Elements in RISA 2

[spieng89]

Has anyone come across modeling shear transfer elements in RISA and have an effective way to model such conditions? Essentially, I have modeled a flexible diaphragm roof and need to model "shear elements" (W5 or small HSS members) to transfer shear from roof diaphragm into beam support and vertical bracing.

I really only need the shear load that the element would see, but without modeling the member I do not know an effective way to obtain shear load. My first thought is to use a member on top of member with a rigid connection in between, but the time needed for this would be significant given the model has already been created. Any tips for an easier path to my end goal would be appreciated.

I attached a pdf to show what I mean by shear element.

 

[JAE]

Not germane to your question but we use tubes like you do but orient them 90 degrees from what you show to better drag the load in without bending the tube walls in a parallelogram fashion.

If you have modeled the WF beam in RISA as a line member and the diaphragm as a finite element mesh, you could possibly raise the FE mesh up a small distance (5") and include small vertical rigid members to represent your tubes. Then use a perimeter member (edge angle) around the mesh to link in all the FE nodes. So you'd have a shear load path from the mesh, into the perimeter edge angle members (which connect to all the perimeter nodes) and then occasional vertical rigid members dragging load down to the WF. The shear force you get in the rigid members would be the shear to design for on the tubes.



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[JoshPlumSE]

I'm not 100% sure that I'm following. But, I'll take a stab.

You've got a shear load in your diaphragm that sits on top of the joists. The HSS (or W or WT) members are not the joist themselves, are they? That's what's not clear to me. I'm guessing they are not. Instead, I'm guessing that the WF girders are connected to the deck periodically with these HSS members for the sole purpose of shear transfer between the deck and WF. Is that correct?

Do you have the deck modeled? If not, then how are you applying the deck load to your model? Area load, distributed load, or what?

A small link member that takes the shear would be a reasonable way to create that load path. Though depending on how many of these shear transfer pieces exist, it might just be easier to assume (for modeling) that they are continuously connected. Is it really going to change the force distribution in that beam that much to model it as 3 distinct shear transfers rather than model it as continuous, distributed load?

 

[spieng89]

Correct the HSS members are not the joists themselves. Typically, one shear element is placed between joist spacing. In reality the force distribution may not change all that much, but I need to verify the load the shear elements will see. The loading is an area load with point loads for mechanical equipment. I am going to run the model after it has been updated and compare results to expected results to see if this is a applicable modeling method.