100 psf live load at second floor lobby

[deereman]

Asce 7-05 and IBC both call out for a live load of 100 psf at lobbies and first floor corridors. Is the lobby being referred to here for all floors? I generally design all upper floors of office buildings for a live load of 80 psf. You could have a large lobby area around an elevator shaft, should I design this area for 100 psf (may or may not know the lobby size if it is a shell space)? Another unknown on shell space is assembly areas. Say the owner puts in a large conference room, would you consider that an assembly loading and require the 100 psf loading. What size area would warrant assembly loading in an office building?

 

[dik]

A conference room, I'd go for the 100 psf... for lobbies, unless they are for assembly purposes, I'd not label them as lobbies... maybe on the main floor only.

Dik

 

[WARose]

Public assembly can happen on any floor. Aside from my own judgement, I also look at what the architect his labeling the area in his/her GAs.

 

[dik]

Even if assembly occurs, you would have a difficult time producing a live load of 100 psf... concur about labelling...

Dik

 

[WARose]

Even if assembly occurs, you would have a difficult time producing a live load of 100 psf..

Agreed. You run the numbers on some of these live loads and it's like a bunch of heavy folks packed in there like sardines.....but I try not to take any chances.

 

[Archie264]

My understanding is that the 100 psf for lobbies and corridors is for fire egress. Consider a crowd trying to get away from a fire...personal space will not enter into the thought process. Further, at the point the area in question should be robust in the event rescue is needed.

I found the following passage interesting. It is taken from an article written by Richard S. Fling, former president of ACI:

Live loads specified by building codes are usually higher than expected in actual service, but not always. Consider the school classroom when everyone rushes to the wind to see the passing parade. Actual loading could be easily double the specified live load. On the other hand, I have yet to see a place of assembly loaded to the 100 psf normally specified. It is usually in the range of 3 to 8 psf, but occasional may rach as high as 20 to 25 psf. Wind loads are even more variable, as some engineers have found to their sorrow.