Duct/Utility Openings in Open Web Metal Trusses
Duct/Utility Openings in Open Web Metal Trusses
(OP)
We have been asked by a client to utilize an open web metal truss system to support a concrete roof slab. Because of architectural considerations the ceiling space is fairly crowded so it appears some A/C ductwork will pass through the trusses.
Does anyone have a good reference of how to reinforce these openings? One of my colleagues has recommended I just call out that the truss manufacturer should provide their standard reinforced opening detail for the contractor to reference.
Is this something normally done or should I actually design the reinforcement around the opening (thus the request for reference in Para 2 above)?
Would appreciate your thoughts and recommendations.
Does anyone have a good reference of how to reinforce these openings? One of my colleagues has recommended I just call out that the truss manufacturer should provide their standard reinforced opening detail for the contractor to reference.
Is this something normally done or should I actually design the reinforcement around the opening (thus the request for reference in Para 2 above)?
Would appreciate your thoughts and recommendations.






RE: Duct/Utility Openings in Open Web Metal Trusses
This can be modeled in any number of 2D or 3D frame programs.
Dik
RE: Duct/Utility Openings in Open Web Metal Trusses
RE: Duct/Utility Openings in Open Web Metal Trusses
Dik
RE: Duct/Utility Openings in Open Web Metal Trusses
RE: Duct/Utility Openings in Open Web Metal Trusses
RE: Duct/Utility Openings in Open Web Metal Trusses
B.E
You are judged not by what you know, but by what you can do.
RE: Duct/Utility Openings in Open Web Metal Trusses
Great recommendations and ideas.
We will go with throwing this back on the supplier as suggested by XR250 and GRAVITY AND INERTIA.
Hokie 66 - We tried your approach with our ME - he considered circular ducts and our meeting ended earlier than anticipated when we suggested triangular ducts!!! Some people have no sense of humor!
Anyway thanks much everyone - all helpful and insightful.
RE: Duct/Utility Openings in Open Web Metal Trusses
http://www.newmill.com/pdfs/steeljoists-sec1.pdf
RE: Duct/Utility Openings in Open Web Metal Trusses
RE: Duct/Utility Openings in Open Web Metal Trusses
RE: Duct/Utility Openings in Open Web Metal Trusses
Thanks!
Tim_B
RE: Duct/Utility Openings in Open Web Metal Trusses
On another project I recall seeing a vierendeel section of truss installed close to the joist ends in a similar situation. The vierendeel then switched back to an open face web truss. This is fairly routine on the part of the manufacturers I would assume?
Thanks.
RE: Duct/Utility Openings in Open Web Metal Trusses
I think it is far from routine to make the joists like that.
RE: Duct/Utility Openings in Open Web Metal Trusses
To be clear when I am referring to a vierendeel opening I am referring to a single rectangular opening in the middle of what is otherwise a regular open web steel joist with warren or modified warren panels.
With that said, putting a vierendeel opening in a joist happens occasionally but is not the norm. It is even less normal for them to be so close to the end of the joist for the reasons I describe above. I don't know how long your joists are and how many will be impacted but I can tell you it will likely more than double the weight of the joist and add 50%+ more labor. If it is only a couple joists it may be worth it. If it affects almost all the joists on the entire building that is a different story. If you have 100' a long duct I assume it is affecting in the ball park of 20 joists...? I could see that going either way. It may depend on the extra cost from the ME and HVAC installer to implement other solutions (if other solutions exist).
I will also note that that size duct should fit through a standard 32LH joist without a vierendeel opening if the duct is closer to the middle so long as the loading and deflection requirements are not excessive. However, you probably cannot get it through at 4'-6" from the end without a vierendeel opening.
Thanks!
Tim_B