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 188.8.131.52.6.1" (NFPA 13, 2016 Edition, Section 184.108.40.206.6)
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?
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