Collateral or Live Load? 1

[BSVBD]

During the foundation design for a metal building, while extracting the reactions provided by the metal building company, i notice that they listed the mezzanine loads as "Collateral".

My understanding is that “Collateral Load” is the weight on the inside of the building acting as gravity. Examples of this are MEP; Mechanical, HVAC, Electrical, lighting, Plumbing, sprinkler system, etc.

Should'nt those mezzanine loads be listed as Live?

 

[canwesteng]

That's the only way I've heard the term used

 

[BAretired]

A mezzanine floor is not collateral load. It is a combination of dead and live load. See the attached for a more detailed opinion from a metal building representative.

http://www.nucorbuildingsystems.com/Builder/engineeringtips/4.07.pdf

BA

 

[CANPRO]

do they break the mezzanine loads into dead/live? I would expect the mezzanine dead load to be listed as collateral. I've always viewed the collateral loads as the loads that should be considered/ignored when it presents the worst case. If the building is left as an empty shell (no HVAC, mechanical, mezzanine ect...) you're going to be in a worst case condition for uplift. Unlikely the building is going to blow away because someone removed the mezzanine, but I think that is the idea behind putting it in the collateral loads - there is no guarantee it will always be there.

 

[BSVBD]

BA and CANPRO, you both offer useful information and perspectives.

BA, within the article you provided, the author states, "Collateral loading values specified by the customer should contain the weights of items to be supported but not supplied by Nucor." The mezzanine on my project is, "...to be supported but not supplied by..." the metal building company. Therefore, i can understand why the metal building company may have listed it as collateral.

CANPRO, likewise, as you stated, there is no guarantee the mezzanine will always be there. That understanding brings up another topic regarding whether we or the metal building company should be expected to consider the future intents of the current or future owner(s) of the building. In this case, if that was the intent of the metal building company, they are apparently covering themselves for such worse case scenario.

CANPRO, the metal building company did not break the mezzanine loads into dead/live. It is simply listed: "C (includes mezzanine)". The metal building company does provide live load reactions, but, having inquired of this in the past, i've been informed that the live loads, unless specifically stated otherwise refer to roof live loads. I can also reason that the low magnitude of the provided live loads do not include the storage live load reactions.

 

[EngineeringEric]

I have seen collateral listed as the items such HVAC, plumbing, elec, lights.... that can effect the overall gravity loading in a negative way (D+L) but should not be considered to help in an upward loading situations like 0.6D + 1W. Yes those are ASD Combinations.

Could their comment be that Collateral for roof = Collateral for Mezzanine floor =/= Mezzanine Live Load ???

 

[ajh1]

We generally think of collateral loads as loads that could be deemed "dead loads", but that aren't part of the building structural system. As noted above, things like sprinklers, HVAC, etc. that are supported by the structural system but are not a part of it. We also attempt to distinguish between collateral loads that we know are going to be present versus those loads that have been conservatively estimated for gravity purposes but are not necessarily going to exist to the level of the design assumption. For example, if one was to assume 3 psf for sprinkler lines, this would be a conservative gravity load on each member, but not all members would necessarily see the full 3 psf over their entire supported area. An overall assumption of 1 psf might be reasonable and that should be the only collateral load assumed under wind uplift conditions.
Mezzanine loads should be split between dead and live loads, but in my opinion would not be generally thought of as collateral loads.