se responsible for ul rating

huangyhg

se responsible for ul rating?
i just finished talking to an architect who ask me if having a steel stud of a lighter gauge than shown in a certain ul assembly violated the ul rating.  i told him that it was an architectural issue.  he acted like i just didn't want to my job.  do any structural engineers out there determine the ul ratings of the various assemblies on a project?  isn't that the architects realm of expertise?
any comments would be appreciated.
j
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the first half of my career i worked for a large a-e firm where the structural engineers often times looked for the proper ul floor or roof assembly, in cooperation with the architects.  in the second half of my career i have worked for a small structural consulting firm, dealing with a wide variety of architects, most of whom are used to coming up with a ul assembly themselves.  that said, i think it is still a good idea to keep an eye on the assemblies they select, to make sure none of the many requirements in the assembly conflict with what you are doing (concrete strength, type of deck etc.)  for building components that you are not directly involved in designing i would have no problem in telling the architect that it is his responsibility.  (of course you may want to be flexible about this with valued clients).
perhaps it is in your contract language that the engineer is not responsible for fire proofing.  if it isnt, it should be.
i would tend to agree with you that it is their responsibility.
while i do believe that it is important that a structural engineer be well versed in fire ratings, various assemblies and appropriate details, the architect should be taking the lead on this. if the stud wall is not something shown on your drawings or something that you designed or spec'd then i would tell you it is his baby. the contract should clearly spell out the responsibilities between the architect and engineer in this regard, although this is one of those areas where things often fall thru the cracks and fingerpointing happens.
i have worked with architects that often knew very little about fire rating and would stumble their way thru these issues, pointing fingers at others.
architect:
   1.  perform the code analysis on the building
   2.  determine what fire ratings are required both in terms of assemblies and individual   
many architects are not well versed in fire protection, and neither are most structural engineers.  it is becoming more of a specialty, fire engineering.  but back to the original question, the ul assemblies generally have to be followed exactly.  the architect should be asking ul, not the structural engineer.  
amen, jae.
1. if it's the architect's job to spec out anything related to life safety, like, imo, fire-rated assemblies, then it's his job.
2. how much does this or that fire-rated assembly weigh? and, what thickness of concrete slab is rated for how long in a fire? these are structural issues and they're the kind of things i should know and be able to assist the architect or anyone who asks. n.b.: assisting is not the same thing as "being responsible for." i get asked fire-rating questions every now and then. if i can provide assistance, i do. but we've also got a registered fire protection engineer on retainer and i always add the caveat, "you should ask the fire protection engineer for the final word..." some folks hate that because it means they have to get on the phone or write and e-mail; why couldn't i have just given them the right answer?
ok, i will be devil's advocate here (or architect's advocate)--we are a design team.  answering his question would not cause you to blow your budget, and would not expose you to additional liability, so i think the proper response would have been, "if you don't match ul exactly, then you can't guarantee the ul rating," or, "i don't know--perhaps you should call ul."
daveatkins
dave,
i don't think that ul answers questions like that.  they are simply a laboratory that does tests for hire on specific assemblies and then sets fire design parameters around those assemblies.  they are not a code-writing type of organization.  
i do agree with your sense of team.  that is why i suggested in my post above that the engineer should assist the architect in the selection of assembly components and advise them of issues related to fire protection.
getting back to the orginal post, if the ul listing specifies, let us say, a 20 guage stud, then yes, using a 25 guage would not comply with that ul.  however, the listing may give you a range of product specifications so it may be worth looking up the listing to ensure it does not comply.  
but the ul books are chock full of hundreds of tested assemblies that may work with a 25 guage stud.  of course, you can have an untested assembly tested for compliance but third party testing is very expensive.
don phillips