Kyle -
Perhaps you've misinterpreted my comment, or I didn't make it very clear
that what I was categorizing as "rubbish" was not the issue that there
are net vertical reaction forces on seismic bracing. Far from it. What
I was referring to, and I thought I made it fairly clear, was the idea
that the lateral braces would have to "work harder" if the longitudinal
braces were configured in a way that resulted in eccentric loading of
the hardware (at either end) or the fastener to the structure.
In looking at your sketches I observed that the angle from vertical of
the brace was indicated as 45° in section view A. That would suggest to
me perhaps wrongly on my part, that what you were working with had a Wp
value that did not exceed 1.0. I gladly concede that the net vertical
reaction forces are present regardless of the Wp and the angle of the
brace. What I don't concede is that unless the Wp exceeds 0.5 and the
angle is less than 45°, or the Wp exceeds 1.0 and the brace angle is
less than 60°, those forces require a modification of the brace
arrangement. I didn't see anything in your sketches that suggested NVRF
needed to be addressed, and if it does under the provisions of 9.3.5.10
then it must be accounted for.
If you're installing rigid bracing it is designed to function in both
tension and compression at all times. In fact, the L/r limits in Table
9.3.5.11.8(a)-(b)-(c) are based on the brace member being in compression
and are a means to evaluate the resistance to buckling.
I think we've exhausted this. Thanks for the discussion.
sincerely,
*Ken Wagoner, SET
*Parsley Consulting***
*350 West 9th Avenue, Suite 206
*Escondido, California 92025
*****Phone 760-745-6181*
Visit our website <http://www.parsleyconsulting.com/> ***
On 08/01/2017 12:41 PM, Kyle.Montgomery wrote:
Rubbish? Challenge accepted!
Of course the “standard” configuration of seismic braces imparts a
vertical force on the main. A bunch of sketches would be helpful here,
but in lieu of, let me try to describe:
In a standard configuration, the brace works in tension and
compression to resist the horizontal seismic forces. As the brace is
compressed, it imparts a vertical force downward onto the pipe; as it
acts in tension, it imparts a vertical force upward onto the pipe. But
don’t take my word for it, you helped describe it in *9.3.5.10 Net
Vertical Reaction Forces*, particularly where it states “*the net
vertical reaction produced by the horizontal load*”. Maybe I was
unclear, it imparts this force as it is working (during an earthquake)
not in a static condition.
Now in the case of the bracing configuration we’re discussing: As the
brace works in tension as the brace works in compression, it will
impart a vertical force downward and a lateral force to the right;
vice versa in compression. This is what I mean by making the adjacent
lateral braces work harder, as they would have to account for the…
let’s call it “net horizontal reaction force”.
As far as the eccentric loads, I think you guys have a point there. I
think the 825 is designed to work perpendicular-to or parallel-to the
structure, but maybe not both conditions at the same time. My section
view B is kind of misleading (aka sucky), in reality the brace pipe
would point towards the center of the main, so it wouldn’t be as bad
as it looks.
Sounds like I might be back to square 1.
-Kyle M
*From:*Sprinklerforum
[mailto:[email protected]] *On Behalf Of
*Parsley Consulting
*Sent:* Tuesday, August 01, 2017 11:51 AM
*To:* [email protected]
*Subject:* Re: Longitudinal Bracing Question
Kyle,
The photos did show up, however they're very small.
From what I could discern from the photos I'd have to conclude that
the plan view and section view B would lead me to conclude that this
installation does conflict with 9.3.5.11.5, as the brace fittings at
the attachment to structure and attachment to the main would be
subject o eccentric loading for which they may not have been
listed/tested.
When in doubt check with the good people at B-Line to see if their
figure 825 was tested for such an installation, not to mention the
figure 4A. I would doubt that it was. It is also possible that there
are tension only brace fitting attachments to the structure which
would allow what you're showing, however I simply have not designed
bracing with that method enough to direct you to the correct
equipment. I believe this is a circumstance where you're going to have
to get the building structural engineer involved.
I'm not sure how you're reaching the conclusion that a "standard
configuration" would impart any sort of vertical force on the main.
As for the adjacent lateral braces "work harder", in as polite
language as I can generate - rubbish. Lateral bracing is only intended
to resist horizontal motion perpendicular to the axis of the pipe.
Consider - if the detail in the "top plan view" below was for a
lateral brace it would still generate eccentric loads on the hardware,
and that would be unacceptable.
sincerely,
*Ken Wagoner, SET
**Parsley Consulting
350 West 9th Avenue, Suite 206
Escondido, California 92025
**Phone 760-745-6181
**Visit our website <http://www.parsleyconsulting.com/> *
On 08/01/2017 11:06 AM, Kyle.Montgomery wrote:
Here is a picture of what I'm talking about (let me know if the
picture shows up):
It still maintains an appropriate angle from vertical. And it
still resists motion "parallel to the axis of the system piping".
But in doing so it will impart an additional horizontal load
perpendicular to the axis of the pipe (lateral) whereas a standard
configuration only imparts an additional vertical force. So it is
making the adjacent lateral braces work harder, so to speak; Is
that OK?
-Kyle M
-----Original Message-----
From: Sprinklerforum
[mailto:[email protected]] On Behalf
Of [email protected] <mailto:[email protected]>
Sent: Tuesday, August 01, 2017 9:18 AM
To: [email protected]
<mailto:[email protected]>
Subject: Re: Longitudinal Bracing Question
Thanks Ken.
I was referring to this:
* The only "angle" which really applies in providing longitudinal
bracing is the measurement from vertical. That angle must be at
least 30° and have a maximum of 90° from vertical (which is
perfectly horizontal, and would make the brace parallel to the pipe.
I am thinking in plan view, based on Kyle's original question, so
any angle from vertical would 'appear' to be parallel to the pipe.
To us Sprinkler Eccentrics, nothing is Minor
:)
Brad
Quoting Parsley Consulting <[email protected]
<mailto:[email protected]>>:
> Brad,
>
> While the quote from NFPA 13 is entirely correct and the brace pipe
> and fittings must be in a straight line, thus avoiding eccentric
> loading on the fittings and fasteners, I did not say that the brace
> has to be parallel to the pipe.
>
> What I did say was that a longitudinal brace resists horizontal
motion
> of the main in a direction which is parallel to that main.
>
> The angle, measured from vertical, must be at least 30° and can
be as
> much as 90° from vertical, which would make the brace pipe
parallel to
> the main, however that is not required.
>
> Minor but relevant clarification.
> *Ken Wagoner, SET
> *Parsley Consulting***
> *350 West 9th Avenue, Suite 206
> *Escondido, California 92025
> *****Phone 760-745-6181*
> Visit our website <http://www.parsleyconsulting.com/> *** On
> 08/01/2017 8:17 AM, [email protected]
<mailto:[email protected]> wrote:
>> From 13-2016:
>>
>> 9.3.5.11.5 All parts and fittings of a brace shall lie in a straight
>> line to avoid eccentric loadings on fittings and fasteners.
>>
>> The above means, to me anyway, that it is NOT ok to kick the
>> longitudinal brace out at an angle as seen in plan view. In this way
>> I think that is an angle that does matter, but Ken cleared it up by
>> saying the brace pipe has to be parallel to the main pipe.
>>
>> As always, I am willing to stand to be corrected,
>>
>> Brad
>>
>> Quoting "Kyle.Montgomery" <[email protected]
<mailto:[email protected]>>:
>>
>>> I knew where you were going, Steve, and I agree that this is a good
>>> approach. We’ve gone this route in the past, but when you get to the
>>> stage of the job where I’m usually involved (closer to
>>> construction) and everyone has contracts for construction, it can
>>> sometimes be contentious as far as who would provide and pay for
>>> this additional engineering. So I was looking for ways to control
>>> our own destiny, so to speak.
>>>
>>> Thanks for everyone’s input.
>>>
>>> -Kyle M
>>>
>>>
>>> From: Sprinklerforum
>>> [mailto:[email protected]] On Behalf Of
>>> Steve Leyton
>>> Sent: Friday, July 28, 2017 3:25 PM
>>> To: [email protected]
<mailto:[email protected]>
>>> Subject: RE: Longitudinal Bracing Question
>>>
>>> What he said. To clarify my earlier comment – I did not intend to
>>> suggest that you could use the trapeze values in NFPA 13 for hangers
>>> and apply them to EQB anchorage. However, we have worked with our
>>> structural engineers on previous projects to design for similar
>>> conditions where the shear load bearing value of the strut (notice I
>>> just said strut instead of trapeze) was specified by the SEOR and
>>> was adequate for the applied loads of the specific braces we needed
>>> to anchor. It CAN be done, but as Ken says, it can’t be done by
>>> simply using the trapeze section moduli published in NFPA 13.
>>>
>>> Steve L.
>>> Back Peddling, CA
>>>
>>> From: Sprinklerforum
>>> [mailto:[email protected]] On Behalf Of
>>> Parsley Consulting
>>> Sent: Friday, July 28, 2017 12:53 PM
>>> To:
>>> [email protected]<mailto:[email protected]
<mailto:[email protected]%3Cmailto:[email protected]>
>>> iresprinkler.org>
>>> Subject: Re: Longitudinal Bracing Question
>>>
>>> Forumites,
>>>
>>> Let's clarify a couple of items here. [All references to the 2016
>>> edition, and all emphasis is mine]
>>>
>>> * Longitudinal bracing on mains must be spaced no more than 80'
>>> apart, per 9.3.5.6.1
>>>
>>> * The distance from the end of the line and the last (or first)
>>> longitudinal brace must no exceed 40', per 9.3.5.6.
>>> * Your first longitudinal brace could be as much as 40' from
>>> the end of the pipe run.
>>> * The structural components of the building must be able to
>>> resist the added seismic loads, per 9.3.5.1.2
>>> * This is something the building structural would have to
>>> provide, as it's not something a sprinkler contractor should attempt
>>> without some training and experience in structural engineering.
>>> * A trapeze installed per NFPA 13 guidelines is not intended to
>>> address loads other than gravity in the vertical orientation, and
>>> any resistance to horizontal movement would have to be designed by a
>>> structural engineer.
>>>
>>> * As long as the brace member (pipe, rod, flat, etc) does not
>>> exceed the limits on the length imposed by tables
>>> 9.3.5.11.8(a)-(c) having it be four feet to the nearest bar joist
>>> should be no problem.
>>>
>>> * The only "angle" which really applies in providing
>>> longitudinal bracing is the measurement from vertical. That angle
>>> must be at least 30° and have a maximum of 90° from vertical (which
>>> is perfectly horizontal, and would make the brace parallel to the
>>> pipe.
>>>
>>> The addition of another flexible coupling on the main could create a
>>> further requirement for additional lateral bracing within 24" of the
>>> flexible coupling per 9.3.5.5.9.
>>>
>>> I hope that provides some guidance.
>>> As I am a member of the hanging and bracing committee of NFPA 13,
>>> please see the disclaimer below.
>>>
>>> sincerely,
>>> Ken Wagoner, SET
>>> Parsley Consulting
>>> 350 West 9th Avenue, Suite 206
>>> Escondido, California 92025
>>> Phone 760-745-6181
>>> Visit our website<http://www.parsleyconsulting.com/>
>>>
>>> IMPORTANT NOTICE: This correspondence is not a Formal Interpretation
>>> issued pursuant to NFPA Regulations. Any opinion expressed is the
>>> personal opinion of the author and does not necessarily represent
>>> the official position of the NFPA or its Technical Committees. In
>>> addition, this correspondence is neither intended, nor should it be
>>> relied upon, to provide professional consultation or services
>>>
>>> It should be noted that the above is my opinion as a member of the
>>> NFPA Automatic Sprinkler System Hanging and Bracing Committee in
>>> accordance with the NFPA Regulations Governing Committee Projects
>>> and should therefore not be considered, nor relied upon, as the
>>> official position of the NFPA or its Committees
>>
>>
>>
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