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RE: conduit support truss

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Any of your proposed solutions will work. The least amount of labor will be either the HSS or the pipe. The pipe will have the least wind drag of your 3 proposed solutions. It may require a vortex shedding check, but that is probably over-kill.

Don't forget to add ice to your loads.

Another potential solution would be to provide 2 spaced messenger cables, and suspend the air line between the messenger cables. The down side is that they will "gallop" (aka vortex shedding) at certain wind velocities, but that can be mitigated with pre-tension in the messenger cable. You will have to design for the lateral thrust of the messenger cables at the anchor points. Again, design for the ice loads.

Harold Sprague

From: "Ken Peoples" <kspeoples(--nospam--at)>
Reply-To: <seaint(--nospam--at)>
To: "Seaint" <seaint(--nospam--at)>
Subject: conduit support truss
Date: Tue, 14 Dec 2004 12:49:06 -0500

I have a client who wants to install a 2" airline across a 60' outside space with vehicular traffic below so he needs some kind of structure to span the 60'. The request came in as "design me a truss" and I thought that maybe I could just use a pair of open web steel joists spaced a couple feet apart with bracing in between to make a pipe bridge that can be used for other runs of conduit or piping in the future. However, I can't help but wonder if there is an easier, more efficient way - like maybe just one larger diameter pipe with the airline run inside or a rectangular HSS with the airline run on top. Any thoughts/experiences to share?

Thanks in advance

Best regards,


Kenneth S. Peoples, P. E.
Lehigh Valley Technical Associates, Inc.
1584 Weaversville Road
Northampton, PA 18067

Phone: 610-262-6345
Email: kpeoples(--nospam--at)

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