How to convert Design Live Load to Occupancy limit?

[Tomfh]

How can you calculate maximum occupancy limits based on floor area and floor design load? For example, a 500m² room with a live load capacity of 3kPa. How can this be converted into a maximum room occupancy (e.g. max 500 persons)?
Does anyone have references or established statistical methods for assessing this?

 

[EZBuilding]

Traditionally occupancy is determined as a part of "life-safety" capacity of a space, not it's structural capacity. The Life-Safety capacity is traditionally limited by the capabilities of people to exit a building during a fire event.

 

[dauwerda]

Agree with EZBuilding, that is how it is in the US. Number and size of exits is what is used to limit the occupancy.

 

[DaveAtkins]

I think Code commentaries have explanations on how live load per square foot is determined. As I recall, there are studies on people packed in corridors, furniture in offices, etc.

DaveAtkins

 

[phamENG]

The issue is this: if you limit it to 50 people, what's to stop those 50 people from crowding into a small area?

I've seen live load capacities listed so owners/ managers can put some sort of controls in place.

 

[lexpatrie]

They don't strictly correlate mathematically if you ask me, the occupancy is based on a square footage and a division based on the use (fixed seating, non-fixed seating, etc). I usually don't see anything above 300 occupants for a "given area". I've seen exactly one restaurant with an occupancy above 300 and it's kind of a little side hobby of mine to note it wherever I am. Theaters tend to be subdivided so the theaters themselves are 299 occupancy at most and the smaller theaters in a multi-screen complex have the smallest ones at 100 occupancy.

 

[JoshPlumSE]

To be honest, I don't think most "occupancy limits" have all that much to do with structural issues. My impression is that they have more to do with fire regulations, means of egress and the like.

To be fair, I've never asked an architect about this sort of thing. But, if I'm correct, it would be more up their alley than mine.

 

[JAE]

Agree with several of the others – occupancy, the term used in most building codes, is based on fire protection and exiting requirements and have nothing to do with structural load capacity.

 

[Tomfh]

Traditionally occupancy is determined as a part of "life-safety" capacity of a space, not it's structural capacity. The Life-Safety capacity is traditionally limited by the capabilities of people to exit a building during a fire event.

Yes, and that check is being done. The client also wants to know if this hall is structurally adequate to support a given number of people.

I think Code commentaries have explanations on how live load per square foot is determined. As I recall, there are studies on people packed in corridors, furniture in offices, etc.

Thanks, do you have any codes in mind?

The issue is this: if you limit it to 50 people, what's to stop those 50 people from crowding into a small area?

Yes, that's the issue; smaller groups can still apply crowd loading to individual members, and this is what we are trying to get our head around. While nothing physically stops such concentrated loads from occurring, when you have smaller numbers of people it's less likely for crowd loading to occur on individual members than when you have larger numbers of people, hence codes prescribing lower design loads for floors with less occupants (e.g. residential living space compared to office spaces), even though crowd loading can still theoretically occur on any given floor member.

 

[MintJulep]

For a rough idea of what various crowd density looks like.

https://www.gkstill.com/Support/crowd-density/CrowdDensity-1.html

 

[EZBuilding]

I would rely on defining an assembly type and then utilizing the live load ratings from ASCE 7 which most closely resembles that assembly.

A lot of work went into defining the live load requirements per occupancy - I think you would spin your wheels trying to redefining it. This likely seems to be an assembly type of space with a 100 PSF Superimposed Live Load - note that concerns regarding serviceability (such as vibrations) may require further in-depth analysis.

 

[Tomfh]

I would rely on defining an assembly type and then utilizing the live load ratings from ASCE 7 which most closely resembles that assembly.

Yes, that would be ideal. We initially checked that and came up short. It's in Australia, so we use AS1170 for load types, however it's the same logic as the American codes. According to the current code, the floor should be designed for 4kPa, however according to the current timber code the capacity is 3kPa. Rather than rebuild it, the client wants advice on how much to restrict numbers.