BULLSEYE As a PE you don’t have the luxury of ignoring likely intent and simply being LITERAL. The identified types cover both obstructed and unobstructed so are effectively meaningless and misleading (since they don't identify all types). WE do have criteria that is affected by spacing of structural members (aka allowed area of coverage) but that’s mostly due to impact on spray patterns. The three real variables (that must be present to trigger listed sprinklers) are 1 - Horizontal, 2 - combustible UPPER DECK, 3 - short height. This combination creates an aggressive fire (radiant feedback plays a big role). You must ask yourself, what role does either a solid wood joist OR an open truss (assume obstructed and unobstructed as well as both being combustible) OR bar joist (assume noncombustible granted it can have wood chords) have on the fire risk so as to allow a judgmental call that any other structural assembly can ignore this requirement.
It’s now on my 6 pages of potential PI’s for next NFPA 13 cycle (WHICH IS NOW - PI’s can be submitted until June 26, 2019) Roland Roland Huggins, PE - Senior VP Engineering American Fire Sprinkler Assn. Dallas, TX http://www.firesprinkler.org <http://www.firesprinkler.org/> Fire Sprinklers Saves Lives > On Dec 26, 2018, at 10:53 AM, Kyle.Montgomery <[email protected]> > wrote: > > I can’t argue with you on the code, but I’m still wondering “Why?” > > What is the difference between the scenario in question and, say, “bar joist > construction having a combustible upper surface”, that requires you to > protect them differently? > > -Kyle M >
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