Hanging Pipe in PEMB

I have dealt with this issue exactly one time, back in the late 1990s.

My task--sprung on me with one day's notice by my project manager--was to inspect all of the seismic bracing for all of the hanging pipes and ducts in the new headworks buildings at the local wastewater treatment plant. The headworks building is eight stories tall (half underground) and bigger than a football field. My task was to learn the requirements (I was starting from zero) and do the inspections over the weekend, so that come Monday morning the City could issue itself an occupancy permit. Needless to say, I was p*ss*d since I had plans for the weekend.

For guidance, my project manager handed me a copy of the SMACNA Seismic Restraint Manual, and that's the document you need. With SMACNA, the plans and specs, and binoculars, I got through the entire headworks in one long weekend. I needed the binoculars because some of the hanging pipes and ducts were more than thirty fee up.

I found so many problems, that the City couldn't issue itself the occupancy permit on Monday. It took the contractor more than a week to fix everything that I found was wrong.

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

Seismic bracing is common in California. Many manufactures have typical details. Probably not one specifically for 10” schedule 10 duct. But, they have details for pipe or round duct that can be adapted. A few manufacture off the top of my head are: Unistrut, Tolco/B-Line, Mason Industries, ISAT, Anvil, PhD . . .

What part of ASCE 7 were you looking at? Chapter 13 is all about non-structural building components subjected to seismic loading, with about half the chapter dedicated to plumbing/mechanical systems and their anchorage.

My concern is that it's being hung in a PEMB. Is this a new PEMB or an existing one? A 12" pipe can get pretty heavy when full, and those buildings are designed as lean as possible. I've checked them for the addition of a lightweight RTU (essentially a little residential unit) and couldn't justify it - we had to install columns from the floor to reinforce it.

As a side note, if you are adding the pipe to the PEMB, suggest you run the additional load by the EOR if you have not already done so.

PEMB's are notorious for being super sensitive to any increase in load, especially is the 12" pipe is filled w/ any sort of fluid.

Thanks for the replies.

We did work through Chapter 13 and I couldn’t quite nail this one down. The pipe is dust collector exhaust ducting, so there is no liquid load. The PEMB manufacturer listed a collateral load of 5 psf - we are below that globally and have checked the individual members against details they provided for point loads.

We did find some proprietary products that will do the trick.


-5^2 = -25 ;-)

Did you assume the pipe was 100% full of dust? Although dust is typically heavier than fluid (62.4 pcf), I believe you are granted some relief by assuming only a certain percent of the duct is full (can't remember off hand what percent).