NFPA 13 Simplified Method vs. Dynamic in ASCE 7?

7/12/2024

I am designing the sprinklers for a building with unusual seismic criteria (it's designed to be seismically resilient and "floats" on seismic isolators).

The structural drawings note that design should be in accordance with ASCE 7-16 equation 13.3-4:
Fp = ai ap Wp Ax / (Rp / Ip)

I see from NFPA 13 (2022) appendix E that the simplified method is based on ASCE 7-16 equation 13.3-1.

Do you think the NFPA 13 simplified bracing method can still be applied/adapted to this alternate equation (without hiring a structural engineer)?

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

3 Comments

Dan Wilder

7/12/2024 08:43:44 am

I see a lot of our community taking on roles that should be by others (for various reasons good or bad)....seismic is one. While definitely not a seismic guy, my opinion would be:

The structural engineers should be doing these calculations and provide to us the results (Risk Category, Ss, S1, Site Class, SDS, SD1, Seismic Design Category to name the big ones). Our side only needs some of the results (Cp that is based on the Ss value).

A RFI could always be provided to confirm the use of one formula over another but as NFPA has used the simplified formula throughout, it would require review of all the NFPA formulas for the revised outputs. This also means that any software that could be used would also need to be reviewed for the potential formula adjustment.

Brian Gerdwagen FPE

7/12/2024 09:09:23 am

ASCE 7 allows seismic design complying with NFPA 13 as an alternate to presciptive compliance.

Jack G

7/12/2024 09:28:07 am

First of all, it would depend on your projects engineer that specified that.
Most of the time, the architect hires a seismic engineer specifies that each trade is required to use them , and he performs the calculation for each trade and each trade pays him for their systems.
Having said that ASCE 7 Is the IBC s referenced standard for eq protection. Tables 1613.2.5(1) and (2) are weighted by the risk and category.
A& B zones are wholly ecempt C&D sre not.
For seismic category C-D, components weighing 20 lbs or less or distributive systems weighing 5 lbs/ft do not require seismic protection.
The exemption clause is the same- 2.5 inch conduit or larger must be protected.
NFPA 13 and 72
Chpt 17 in nfpa 13 requires seismic protection requirements. It is important to note that complisnce to Both asce 7 and 13 is not required
In asce 7 paragraph 13.6.7.2, sprinkler sxstems designed and constructed per nfpa 13 are recognized as meeting the requirememts of asce 7.
13 enforces a simplified versiom of the requirement found in asce 7 based on a set of technical assumptions. This is found in Annex E of 13:
Development of design approaches to conform with asce 7.
Nfpa 13 section 18.6 requires branch sprinklers to be restrained ( even 5 /lbs/ft ) but not engineered to a seismic load but restrained so they dont whip around.
After saying all of that, it is all subject to the AHJ, the architect and the Engineer. It would be their call which to use.
I would also ask if there is a project seismic engineer to use on this project.
Opimion.

Leave a Reply.

Home
Our Cause

The Blog
The Forum

PE Exam Prep
The Toolkit
MeyerFire University

Pricing
Login
Support
Contact Us

MeyerFire.com is a startup community built to help fire protection professionals shine.
Our goal is to improve fire protection practices worldwide. We promote the industry by creating helpful tools and resources, and by bringing together industry professionals to share their expertise.

MeyerFire, LLC is a NICET Recognized Training Provider and International Code Council Preferred Education Provider.
All text, images, and media Copyright © 2016-2024 MeyerFire, LLC

We respect your privacy and personal data. See our Privacy Policy and Terms of Service. The views, opinions, and information found on this site represent solely the author and do not represent the opinions of any other party, nor does the presented material assume responsibility for its use. Fire protection and life safety systems constitute a critical component for public health and safety and you should consult with a licensed professional for proper design and code adherence.

Discussions are solely for the purpose of peer review and the exchange of ideas. All comments are reviewed. Comments which do not contribute, are not relevant, are spam, or are disrespectful in nature may be removed. Information presented and opinions expressed should not be relied upon as a replacement for consulting services. Some (not all) outbound links on this website, such as Amazon links, are affiliate-based where we receive a small commission for orders placed elsewhere.

NFPA 13 Simplified Method vs. Dynamic in ASCE 7?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES