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RE: Live load / occupancy correlation

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Jim,
 
If your looking for a way to cover your butt, I would turn to the ASCE 7 Minimum Live Load tables.  Sit down with them and ask them how they are using the facility.  Let them describe it, and both of you look in the ASCE 7 for the applicable minimum live load.  Then, pick a section and walk them through some very simple analysis, with your steel, concrete, or timber book right there with you.  Show them the equations that you are using, so they realize that you are not making things up, and show them, with numbers, now things don't quite work.  What you have done is effectively showed them the codes that you are using, how you have used them, explained some simple engineering concepts (tributary area and what have you), and proved that by using said tools, things just don't work out and you are not making things up.  And if you can hang your hat on such design standards and codes such as the ASCE 7, IBC, NDS, ACI, and others, there is little worry you should have for your butt.  Something like this may take some time, but if you are looking to convince, it may be worth it.
 
Dave Maynard, PE
Gillette, Wyoming
-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Monday, October 25, 2004 6:05 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Live load / occupancy correlation

Dave/Jordan/Charley
 
Thanks for the considerations - I'm walking a fine line with a client who represents a community center at a residential complex.  The building was designed as residential, but is really an assembly for "town hall" type meetings.  I'm searching for various ways to say the same thing - that the building doesn't meet code - but in terms of visualizations they can understand.  And of course in a way that covers my butt when I don't say outright that the building must be abandoned for a lesser use group.
 
And the maximum occupancy approach doesn't fly anyway because it would only take one small group huddled together on one beam to potentially cause a failure.  But the people density is almost an interesting tangent.  This 36'x33' room should be able to hold about 600 people weighing 200 lbs each, per current codes.  That couldn't be more unrealistic.
 
Thanks,
Jim

David Maynard <davemaynard(--nospam--at)ceincorp.com> wrote:
Jim,
 
I have tried to use some of the same reasoning as you, but have not found anything truly concrete.  One would think that a house should be rated for at least 100 psf, because there is always the possibility of entertaining, and the living room can easily be considered an essembly area.  But, that is getting a little too serious.
 
My rule of thumb has always been to assume that the average weight of a person is 200 lbs.  Some are heavier, some lighter, but on average, 200 lbs. is a good assumption.  In your example, with a room 10 ft by 10 ft (100 S.F.) at 40 PSF, that accounts for a total load of 4,000 lbs.  At 200 lbs per person, you are looking at 20 people.  Now, if the average person (I consider my self average size) takes up a space of approximately 2 ft by 2 ft, and you pack into your 100 S.F. room elbow to asshole, you can stuff in 25 people into a room the size of my office.  Can it be done?  Sure.  Is it practical, probably not.  Now, give everyone a 3 ft by 3 ft area all to themselves, and you are talking approx. 11 people in the room.  A little more reasonable, considering the size.
 
Now, if you are looking for an occupancy number, I believe the fire code is where to go for this number, as I believe it is a factor of square footage and certain fire protection criteria have to be met (like a sprinkler system).  If you are just looking for a "piece of mind" number, the 200 lbs. per person is probably a good rule of thumb.  However, to come up with some sort of technical data to back that up, I just can't.  Hope this helps.
 
Dave Maynard, PE
Gillette, Wyoming
 
-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Monday, October 25, 2004 10:32 AM
To: seaint(--nospam--at)seaint.org
Subject: Live load / occupancy correlation

Is there an accepted average weight per person for purpose of correlating between a floor live load rating and a maximum occupancy number?  For example, if a 10ft x 10ft room has a floor rating of 40psf live load (assume 100% human live load), how many people could the room support?
 
I can't find any such reference in ASCE and Google is coming up short on this one.
 
TIA,
Jim Wilson, PE
Stroudsburg, PA


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