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Dance Classroom Live Loading 100psf - this is a long one...

Dance Classroom Live Loading 100psf - this is a long one...

Dance Classroom Live Loading 100psf - this is a long one...

I have been asked to work on an interesting project.  The client is a Dance Studio where dance classes are taught.  The Architect (interior designer) originally received a permit from the building department to modify the floorplan for 3 dance studios on the 2nd floor of an old three story 1920's Hotel (in Florida).

1st Problem: Her plan required the demo of 3 load bearing walls.

2nd Problem: Existing structure was not designed for 100psf (Dance Hall / Ballroom - live loading)

3rd Problem: I was originally told that the floor loading was not an issue as the building department classified it as "business occupancy"

It turns out that the building department was actually speaking in turns of the life saftey plan.

Based upon the original permit the owner has already performed 90% of the construction and now she is being required to show that the floor can handle 100psf live load (this is where I come in... yeah!)

My 1st question is: Based upon knowledge of the intended use of the rooms (max size 610sf) and max occupancy (based upon 15sf/per person the Max room occupancy is 40 individuals.  At 250lbs per person statically we are talking about 16.4psf live load. From what I can tell the original structure has at least 40-50psf capacity.  This results in a 2.4 to 3 factor for impact loading (before any standard code saftey factors come into play)... Can this be used to modify the requirements of the code?

My logic is based on the fact that a stadium with fixed seating (approx. 6 sf per person) is designed only for 60psf... and using the same 250lbs person (drunk and jumping up and down screaming for their favorite team) results in 41.67psf static and a impact factor of only 1.44?

My belief is that the 100psf is for DANCE HALLS or BALLROOMS which are both assembly occupancies and as such can result in localized concentrations of people and therefore for saftey the entire floor should be designed to handle this.

In this this case the Client is only capable of teaching a MAX of 20 individuals which results in a static loading of 8.2 psf and a resultant SF of 4.87 (at 40psf LL).

I currently can rationalize this in my mind but I do not know my limitations when trying to prove this (or if it is even allowed by code).

Any and all help would be a great help,

Thanks, Joe

RE: Dance Classroom Live Loading 100psf - this is a long one...

This is not an assembly occupancy.  Instead of a dancehall or ballroom, it is a classroom.  It will do you no good to rationalise the live loading based on actual weight of the people, etc.  I would check and/or reinforce the floor for classroom loading and present my case to the building official.

RE: Dance Classroom Live Loading 100psf - this is a long one...

You can't take an estimated number of people - their weight/the area and come up with a design live load.  You can "understand" the loading that way, but you can't, or shouldn't, certify the floor for a code-defined use at a lower load than what the code actually defines it.

The only out would be to write a report/request to the local building department and request a waiver, or opinion, of an acceptable live load based on the intended occupancy.

I would argue that a dance classroom does serve a function, at times, as a public assembly.  My own daughter took years of dance classes in a building where many times there was a shoulder-to-shoulder crowd watching at one end.  This certainly would fall under a public assembly - no fixed seating condition.

Stadiums, with fixed seats, fall under the 60 which is similar to public assembly-fixed seating = 50 psf.


RE: Dance Classroom Live Loading 100psf - this is a long one...

Cancel my earlier opinion.  JAE is correct.  If your loading code gives a loading for a "dance studio" or "dance classroom", that is what you have to use.  If not, request a determination as suggested.

RE: Dance Classroom Live Loading 100psf - this is a long one...

Thanks hokie66 and JAE,

I spoke with the local building official (who is a retired GC... nice) and he is accepting a comparison of the loading (between fixed stadium and classroom) to justify my use of the loading.

JAE, I would normally agree with you that it would be assembly but this case is an except due to the very small class size.  I a new structure over 750sf in size I would use the Dance Hall / Ballroom loading because more than 50 people can congregate in one area.

Thanks again, Joe

RE: Dance Classroom Live Loading 100psf - this is a long one...

Dynamics likely may be an issue, also...


RE: Dance Classroom Live Loading 100psf - this is a long one...

Canadian Codes permit design for a stipulated occupant load, i.e. max posted limit. A class room load of 50 psf would be reasonable as long as an assembly occupant load of greater than 60 persons is not reached with in the floor space.  At that point you would need to consider assembly loading.

Design for 50 psf and post the max permitted occupant load if your floor space would permit greater than 60 persons based on square footage occupant load. ( assuming your codes permit this design rationale

RE: Dance Classroom Live Loading 100psf - this is a long one...

Structural Joe,
You are doing the right thing by getting an opinion from the building department.

Dik is also correct in that you should check dynamic effects.  This is a very real problem and is especially so on long spans - which I'm guessing you now have.  At the very least you should check all long spans using 18/SQRT(deflection).  You probably should have a more sophisticated analysis.

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