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We have an issue with seismic bracing getting called out and I'm looking for clarification. Our point of attachment is a truss about 2'-6" away from the truss horizontally, we attached to the top of the truss with a #825 and a #980. We are offset, but vertical and the inspector is telling us that the bracing has to be on top or above the main. Is this correct? The other thing mentioned was that he can't find it in NFPA 13 where it allows angles (I am waiting for clarity with that comment in design). Below is a drawing of what I've got; any direction is much appreciated  
10 Comments
Marina A
7/15/2025 08:45:14 am
Will this answer your question?
Casey Milhorn
7/15/2025 08:50:57 am
I would agree with the AHJ, but I would also reach out to the manufacturer for guidance on listed installation and maximum allowed deflection from perpendicular. I would be very concerned with failure at connection points due to horizontal load, or at the very least, failure to properly restrain the horizontal (and possibly the vertical) movement of the system at this point. I would imagine these connections, and the overall assembly, is designed to act in tension and compression in a linear fashion.
Anthony
7/15/2025 09:04:40 am
I agree with the inspector per NFPA 13, I couldn't find an explicit sentence that says "must be directly above the pipe"
Todd
7/15/2025 09:08:26 am
If you can not achieve orientation, Inspectors will allow you to add additional brace to pipe attachment and structure which may seem to be overkill, but a solution.
Brian Gerdwagen
7/15/2025 09:24:32 am
Eccentric braces are discouraged because you need to account for the vertical component. Installing a second brace to eliminate the eccentric loading is the best option. The "ears" on the 4A clamp need to also be in line with the brace so that a moment is not created on that piece.
Jerry Clark
7/15/2025 09:36:45 am
NFPA 13 does not require seismic bracing to be connected only from above the main piping. Bracing can be installed from above, below, or the side, provided that 1) It meets the angular, load, and structural attachment requirements; and 2) The brace is properly anchored to non-yielding building structure elements.
Franck
7/15/2025 09:46:59 am
For EQ bracing, you need longitudinal and lateral bracing at specified maximum spacing. The first one is aligned to the pipe, the second one is perpendicular.
Jesse
7/15/2025 10:14:18 am
Seismic bracing is longintudinal and lateral in nature. That would be a sort of eccentric brace I'd be interested to see the manufacturer data sheet.
Jack G
7/15/2025 11:36:33 am
It has been my experience over 57 years with working fire protection with structural engineers is that the only way to prove or calculate forces attached to a bar joist is at the “ panel points” where the joist “ vees “ come together. Upper panel points allow larger loads and more accuracy. Lower is fine with lesser loads and harder to calculate.
Jack G
7/15/2025 11:42:22 am
The same goes for trusses. Panel points. Also some trusses and joists are only rated for hanging to the top——wood joists especially. Leave a Reply. |
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