Floor Collapse Near Clemson Univ. 1

[JAE]

This probably isn't an "Engineering Disaster" per se. Perhaps a residential-type floor (40 psf live load capacity?)
With a large crowd jumping to the beat....then collapse.

https://nypost.com/2018/10/21/dozens-injured-after-floor-collapses-at-house-party-near-clemson/

The Twitter clip below in the article shows a bit better view.


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[JohnRBaker]

But what was the criteria was used to determine maximum occupancy? Was it available square footage or floor load? And even if it was floor load, was it static or dynamic?

I ask this because here in SoCal, virtually all commercial establishments like restaurants and bars, have the 'Maximum Occupancy' posted near the entrance, and most newer buildings, at least here in SoCal, have no basements, they have a solid floor. Therefore the only conceivable criteria for this determination would have to be related to square footage and perhaps the ability to safely exit the facility in the case of an emergency. Floor load would not be a factor at all.

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[RVAmeche]

Ah, that makes sense.

 

[JAE]

I think most occupancy limits are based on fire egress and not floor loading.

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[RVAmeche]

To my dumb mechanical mind that seems somewhat counter-intuitive. I would've assumed that if you have a max of 135 people allowed due to egress, the building would also be able to sustain that load? If not, how do event buildings and the like know how many people can be safely be in the space?

 

[charliealphabravo]

'Max occupancy' is probably not the best metric in this case since that is more closely related to egress than it is to structural capacity. An architect or an engineer would have designed the floor for 100 psf, say, and the fire marshal would have set the max occupancy based on aisle widths and lengths, lack of fixed seating, fire sprinklers, etc. Maybe 'effective live load' would be a better term.

From watching the videos there could have been 80 people in a 16'x16' space. That only works out to about 40psf static live load. The dynamic live load was easily twice that and certainly much higher since they were in phase and possibly near a natural frequency of the floor system.

Edit: The witnesses statements were that just before the collapse "the beat was about to drop". If I translate that into engineering/geezer speak, it means that the occupants were about to apply an extra high impulse at a precise and simultaneous moment.

Another video just after the incident with better lighting:

https://twitter.com/ShaleRemien/status/1053895641439571968

 

[BUGGAR]

It's not unusual to see storage mezzanines and similar posted with an allowable live load of, say, 100 pounds per square foot.
So Engineers always get the panic call when someone sees that someone else has spread that 100 pounds over many square feet, thinking it should only be over a single square foot.

 

[XR250]

I just dealt with a partial collapse in a 1920's college rental house - same thing 100 people dancing in a small space.
The joists were full 2x10's spanning 16 ft. spaced 16" O.C.
6 joists broke. Fortunately, the floor only dropped about 12" in the middle and no one was hurt to my knowledge. The damage was a combination of flexural failure - mainly at knots on the tension side of the member and shear failure at the ends due to the joists being notched 4" for the 2x4 ledger.

 

[charliealphabravo]

A photograph from the local station shows the floor trusses.

=]]

 

[IRstuff]

Looks like cardboard was used for the underlayer ;-)

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[jgailla]

Those trusses are laid out weird. I noticed in the video. It shouldn't fail like that with standard framing.

 

[Wallache]

It looks like a mechanical chase/Vierendeel panel down the middle of the floor trusses.

 

[charliealphabravo]

The space doesn't really look like it was meant to be used for assembly or a dance floor.

The scale is hard to work out but the truss members and plating almost don't look like a typical parallel cord truss. Could the chords and webs be less than 2x4s?

 

[gte447f]

As a public room in a multi-family residential building, I think it would have been designed for 100 psf, which is the same as dance halls, so is it likely that the actual load exceeded the code required design live load?

What is that floor sheathing material? It doesn't look like plywood or OSB? Maybe this truss system wasn't braced adequately?