Seismic Bracing

[PRinspector]

Ok, once again I'm looking from information about seismic bracing. I was walking a projejet the other day and I came across two things that did not look right to me. So I got back to the office and started to search NFPA 13 chapter 9 to see if the seismic installation is IAW to code, so far I have not been able to find the correct answer so I'm I calling to all the experts out there.

QUESTION ONE

1. Can you brace the lateral brace to the longitudinal brace? In other word one or the other are not braced directly to the sprinkler pipe.

2. The sprinkler company anchored the seismic bracing to the mortar of the block wall not to the block itself or the structural. Is this right?

Thanks in advance for any information that you can provide.

 

[TravisMack]

There are specifically made 4-way braces that do exactly as you state in #1. The loads are relatively small, so the calculations need to support the use of them. You can find a data sheet at

http://www.vikinggroupinc.com/usrelated/tolco/fig907.pdf

#2 is a bit more interesting. What type of anchor did they use. It is my understanding that you can't use expansion anchors in block walls. I had a structural engineer tell me that many years ago. You have to use epoxy type anchors in block walls. He was saying that the block is not capable of handling the expansion forces. I would consult a structural guy on the use of anchors in the mortar.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[PRinspector]

Travis,
Thanks for the information provided. I was not aware of the 4 way brace that you indicated above. They are not using any brace they are simply connecting a brace clamp to the other brace pipe, no especial gismo at all.
As for the anchoring I do not know if the used epoxy anchor, I have not been able to take a close look. But still they did not penetrate the block the drill the hole in the mortar( between the blocks) which to looks like that is even weaker that the block himself.

 

[TravisMack]

I believe you have to attach directly to the pipe you are bracing. That is why the 4-way brace piece above works. I don't think it is correct to connect to another brace pipe.

I really think you need a structural engineer opinion on the anchoring system. It seems like it would not be adequate, but a structural PE should determine for sure.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

 

[Sdpaddler50]

I believe the term i have heard in the past, for connecting two braces together is "handcuffing". As as TM notes, I am fairly sure that is not allowed, at least per NFPA 13. Anchoring in to concrete block is unusual. I dont think i have ever seen that one. I would think someone is going to have to get the as-builts, and then determine if the brace loads can be absorbed. Contractors will sometimes install bracing to structural elements that are not adequate. For example, i have seen braces on 6 in mains attached to light weight Z purlins, or even braces attached to light weight metal wall panels. Zone calcs were either not done, or someone decided to fudge the numbers. A good quake would blow them right out.

 

[PRinspector]

SDP,
Thanks for the information, can you provide guidance as to where in NFPA 13 does this is prohibited. I have look in chapter 9 but I have not come across, or I keep missing it.
regards

Lou

 

[Sdpaddler50]

PR - I dont think you are going to find the exact wording - "dont connect two braces together". I believe its more of an issue of using equipment in a manner that it was not designed for. The bracing product link that TM provided is specifically listed for this application, so it underwent testing at a lab proving it could be used in this manner.

 

[PRinspector]

Thanks guys for all the input provided.

 

[sfallows]

Te most NFPA 13 would say something regarding using the equipment as listed. So you can ask them to can show it listed for this handcuffing (which I doubt).