When doing zone of influence calculations, NFPA 13 doesn't seem to be specific about whether the weight of drops and sprigs should be included in the weight of the branch line tributary to the lateral brace on the cross main. It states "The zone of influence for lateral braces shall include all branch lines and mains tributary to the brace, except branch lines that are provided with longitudinal bracing or as prohibited by 22.214.171.124.6.1" (NFPA 13, 2016 Edition, Section 126.96.36.199.6)
This ambiguity is frustrating because long drops are quite heavy and can double the weight in the calculation if they are included. It seems like some argument could be made that they aren't "tributary" to the lateral load because they can "swing" independently, but should their influence be considered negligible?
Posted anonymously for discussion. Discuss This | Submit Your Question | Subscribe
Subscribe and learn something new each day:
Thank You to Our Top
August 2020 Contributors!
Sprinkler Designer or Engineer?
Get all of our tools, including the Sprinkler Database, Friction Loss Calculator, Fire Pump Analyzer and more:
Daily discussions are open-ended fire protection, fire alarm, and life safety questions submitted anonymously for the benefit of sharing expertise and learning from other perspectives. Anyone can submit a question here:
2020 PE Prep Guide
PE Prep Series
2020 PE Prep Series
(Click to enlarge)
Visit July-October for daily Fire Protection PE Exam sample questions.
Solutions are posted the day after posting.
Comment with your solutions, questions or clarifications.
Please note that questions posted are unofficial and in accordance with NCEES rules are intended to be similar to actual exam questions, not actual exam questions themselves.