Live Load Means How Many People?
Live Load Means How Many People?
(OP)
If analysis of an existing structure reveals a live load capacity of 20psf, but the code mandates a live load for this structure of 60psf (balcony fixed seating), how many people is 20psf?
I know ASCE uses 60psf to include dynamic forces due to people moving around on an elevated floor. I believe that I'll have to take the number of fixed seats that are existing, ratio them by 20/60, count the number of seats left, and make that the restriction. Any other ideas?
I know ASCE uses 60psf to include dynamic forces due to people moving around on an elevated floor. I believe that I'll have to take the number of fixed seats that are existing, ratio them by 20/60, count the number of seats left, and make that the restriction. Any other ideas?






RE: Live Load Means How Many People?
RE: Live Load Means How Many People?
We've seen the shenanigans going on at parties and athletic events.
Are you going to gamble they won't happen on your balcony just because of a "sign" on the wall?
So you have "fixed seats" - how are people going to get to and from the seats, how many other people are going to crowd around without ever sitting down in those fixed seats?
RE: Live Load Means How Many People?
RE: Live Load Means How Many People?
Crush loading in a passenger rail vehicle is often taken as 6 persons per square meter, each at 95th percentile male (220lb) - sorry about mixing units...
tg
RE: Live Load Means How Many People?
The Code official would not accept this. On my project, he said a room originally designed for 60 psf live load simply cannot be used for storage without reinforcing the floor members.
DaveAtkins
RE: Live Load Means How Many People?
Where people are involved, and can gather in close spaces such as a balcony, a crosswalk, or mezzanine, a high unit load is necessary. Go back and read a few of the articles about the Hyatt-Regency walkway failure.
People will ignore posted signs as racookepe1978 noted.
If you are considering rating an area that you know will hold people and it's capacity is less than the code-allowable (in this case much less), you are being irresponsible and you are not meeting an acceptable standard of care. If anything ever happened and this came out through investigation...and it would, your actions would likely constitute professional negligence.
Tell the owner it won't work for the application. If you're the owner, it won't work for the application.
RE: Live Load Means How Many People?
My point is, if it's available for occupancy, you need to design for that load. That's your best legal protection against litigation, plus it's the law.
RE: Live Load Means How Many People?
RE: Live Load Means How Many People?
When in doubt, just take the next small step.
RE: Live Load Means How Many People?
RE: Live Load Means How Many People?
If there is ever a fire in this area do you think people will evacuate and spread out in an orderly fashion - no, there will be a lote of people crushing into a small area near the exit door trying to get out.
Use the code limits as it is often impossible to justify using anything less.
RE: Live Load Means How Many People?
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RE: Live Load Means How Many People?
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I would argue that the above linked failure should never have happened. If you can fit 150 people on a structure, then you need to design for 150 people.
RE: Live Load Means How Many People?
Its been argued to me that the structure is 90 years old, served well for 90 years, and why stiffen it now? I've stated that that may be true, but its probably never been fully loaded, and I can only report the numerical findings and make a recommendation.
It is to be stiffened.
RE: Live Load Means How Many People?
A good engineer will respond:
"For 90 years the structure has stood because of a combination of luck and statistics. For whatever reason, the smaller than required safety margin has not been exceeded. Today, under the current code, and as your engineer, I am liable for the future performance of the structure and I can tell you definitively that it does not provide the required safety margin as is. If you want to leave it as is two things will happen. I will have to step away from the project and report the lack of safety margin to the building official, and I will write you a letter documenting this opinion and all liability will fall on you. I urge you to accept what I'm saying. If you want a second opinion to confirm my opinion, feel free to do so."
....OK....I live in an ideal world and been smoking something - but you have to admit it sounds good, eh?
RE: Live Load Means How Many People?
Can you pass some of that stuff around?