Seismic Req'd for Outside Pipe on Pipe Stands?

7/19/2023

I am running 8” and 4” water storage tank fill and suction lines above ground in an exterior utility yard.

Is lateral and longitudinal bracing required for aboveground piping supported on pipe stands located outside of a building, in an exterior utility yard?

Due to underground conflicts with spread footing foundations the underground piping has to be routed above ground to the final location and connection points on the tank. The pipes are supported by 1’-6” non adjustable pipe stands attached to slab on grade.

This project is located in a seismic zone and the seismic force factor does not exceed 0.5Wᵖ and I am using ACI 355.2 qualified anchors as required by NFPA 13 2016 Edition. Sections 9.3.8, A9.3.8, 9.3.8.1, and 9.3.8.2. The pipe stands I am using are following the NFPA 13 2016 Edition prescriptive method detailed in sections 9.2.6.3.2, 9.2.6.4.2, 9.2.6.4.4.1, and 9.2.6.4.5.1, I’ve also attached a detail for clarification. Thanks in advance!

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10 Comments

Anthony

7/19/2023 08:14:33 am

You seem to satisfy all the requirements of 9.3.8. and 9.2.6. as I read them.

My next question would be are flexible couplings or rigid couplings be recommended between pipe segments?

Jesse

7/19/2023 08:45:25 am

I think you've covered the requirements.

Dan Wilder

7/19/2023 08:52:25 am

9.3.8 only requires a certified engineer to design the pipe stands when over 4' in a greater than .5 Wp. It does not say you can exclude seismic bracing if it's required on the system.

There is an EOD answer for this I need to look up and will post in a bit.

7/19/2023 11:12:51 am

It's an old answer...

Feb 2008 Ref NFPA 13/15 - 2007

No specific guidelines on how but references using the ground as the plane for brace angles vs the normal structure plane and check with Insurance Carrier for guidance.

NFPA 13-22 Annex A17.5.3.1 has some info on how the heights of pipe stands were calculated, but only refers to lateral loads, not longitudinal. This may be your best option to omit lateral bracing at least.

FM Global 2-8
Fig 2.2.1.1.2 for manifold risers indicates using 2x - 2-way braces within 2' of the end of a manifold when longer than 6' but really no other guidance.

Nothing new in NFPA 200 (draft-Section 6.8) on the matter.

NFPA 15-22' Section 6.3.2.2.4 says:
"Where pipe stands are used to support straight runs of piping or other configurations that are not looped or are not rigidly supported at the top of the pipe stand in a manner that will resist movement in all directions, the pipe stands shall be designed in accordance with the requirements of NFPA 13."

Jim Phifer

7/19/2023 09:03:42 am

I may be over thinking this, but...If lateral and longitudinal bracing is required, what would I attach it to?
concrete blocks? How big does the block need to be? How thick?
what strength does the concrete need to be?
I think this needs to be addressed more in NFPA 13.

7/19/2023 09:15:57 am

I was thinking similarly, since bracing is designed and listed with structural building connections (e.g. to move with buildings)

AHJ

7/26/2023 11:41:50 am

I have this same question and am dealing with a similar installation. I agree, I wish there was more guidance provided in codes/standards.

SCHULMAN

7/19/2023 10:42:51 am

I'm no structural engineer but I think the forces from the pressure of the water would be far greater than any overturning moment forces on an 18" high 2" diameter steel pipe. Unless someone is asking for it, I would follow your detail and move happily on. Maybe laterally brace it at the changes of direction similar to underground thrust restraints?

Todd

7/19/2023 01:41:36 pm

What is the Seismic Design Category as defined on the Structural and/or FP plans?

https://www.meyerfire.com/blog/how-to-determine-if-sprinklers-require-seismic

Franck

7/22/2023 04:02:35 pm

NFPA 13 is for sprinkler systems only, not for the feed from the water supply to the sprinkler system.

You can apply the same reuirements as for a supply piping (outside a building) as for any water supply.
If you provide possible flexibility, that should be fine.
A possible solution (for large size piping), to allow lateral movements: listed flexible piping such as the solutions provided by (but not limited to...):
https://www.metraflex.com/seismic-applications/
https://kineticsnoise.com/kinflex/seismic-v-loops
https://www.victaulic.com/accommodating-seismic-movement/

Seismic Req'd for Outside Pipe on Pipe Stands?

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