"Assembly" Live Load

[RESENG2]

A few years ago I performed a structural analysis for a very old factory which was being converted into a storage building for the local Historical Society. I was just recently contacted by the group asking if they could have a party in the building. I re-ran the numbers and determined that the allowable live load is 45 psf. The building code requires 100 psf for an "assembly" live load but doesn't give a definition of what an assembly is (or maybe I'm missing it??). The building is 3 stories with 5000 sq. ft. per floor. They intend to invite 500, expect 200, and spread these 200 over the 2nd/3rd floor. Would you guys be comfortable with this type of loading and an allowable calculated load of 45 psf? 10000 sq. ft. / 200 people = 50 sq ft / person.
Also, while I'm on the topic, does anyone know why fixed seating lowers the live load?
Thanks!

 

[JAE]

They intend to invite 500, expect 200, and spread these 200 over the 2nd/3rd floor.

...and then whoops...672 show up. And everyone congregates on one floor - at one end of the floor - to hear a speaker present something.

I'd be nervous about a public gathering on a 45 psf floor.

Fixed seating inherently limits the density of people, boxes, furniture, etc. where the live load is more controlled, less variable.

 

[SLTA]

Did you use today's wood values for analysis? Those old factories were amazingly built, with much denser wood than today's values allow. You might consider taking some cores and having them tested together better ideas. I bet you can get a lot closer to that 100. Good luck!

 

[SteelPE]

Interesting that you converted a factory to a storage building and you are now coming up with an allowable live load of 45psf? I have always thought of storage as 125psf minimum. How did you certify the structure before or am I not understand the situation? Is the 45psf in addition to the storage load?

I find it interesting that assembly live load is 100 psf while I can design a house for 40psf that gets rented by some college kids who have a party, cram as many people into the party as possible and proceed to jump up and down on the floor in unison. I say if you want to sleep at night use 100psf, if you want to test the limits of your liability coverage use less than 100psf.

 

[RESENG2]

That's a good catch Steel, I mis-spoke in my original post. I actually didn't certify the building as a storage building, I gave them allowable loads for fixed shelving locations. I'm sure my report and layout is posted at every entrance to the building...
Your point about the residential live load is what lead me here. I would think that there is some reasoning to the 40 psf and 100 psf based on anticipated density?? Or maybe it's based on past performance.
slta, yes I did use today's pine numbers which are far less than the dense pine which is in place. However, this being a low-budget and time sensitive endeavor I couldn't find a way to justify an increase in allowable strength.
JAE has a great point, the potential variability involved with occupant load has me leery to make any formal statements about what they can or can't do. Especially when it has been proven to not meet the code requirements for its intended use.

 

[SLTA]

How old is very old? By not using the accurate values in your analysis, you could lead to serious renovation work, or unnecessary demolition of the building.

http://www.astm.org/Standards/D2555.htm

 

[msquared48]

Just don't play any Credence...

Mike McCann
MMC Engineering

 

[JAE]

Clearwater...

 

[msquared48]

JAE:

Your last post just has no Credence...

Mike McCann
MMC Engineering

 

[JAE]

Someone was supposed to write:

Revival

after my post. Lost opportunity...

 

[msquared48]

You just did... I guess you are "someone" JAE!

Mike McCann
MMC Engineering