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FlxRevenant

Confirmation on Ballroom Concert Structural Safety?

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I'm sure the people in my group weren't the only ones who noticed the center of the ballroom floor on Floor 3 bowing in significantly during the Yousei Teikoku/FLOW concert, particularly during parts of FLOW's set, such as Go!!! from Naruto, where everyone was jumping like crazy. Now it sounds like even people on the 2nd floor noticed significant vibrations and thought there might have been an earthquake.

During the concert, I couldn't help but think about the video of the Versailles wedding hall disaster, where the dance floor of a poorly constructed 3rd floor collapsed through to the lower floors and caused many deaths and injuries. Even though I'm 99.99% sure the Washington Convention Center ballroom is extremely well designed and that this sort of scenario is impossible, I couldn't help but feel nervous about this contingency during the event, and in thinking about it afterwards - especially with the floor noticeably warping under our feet.

So I just wanted to request from the staff for the record, so that this can be settled once and for all with certainty, can we get some confirmation that the 3rd floor ballroom is rated for the number of people at these concerts, jumping in sync in the way that we were? And are there any further assurances/explanations that the floor is actually designed to warp in the way that it did in order to absorb the load and remain strong?

I just hope that this issue can be resolved early, so that the word can spread and people can be absolutely comfortable at these events in the future.

Thanks in advance!

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20 minutes ago, FlxRevenant said:

I'm sure the people in my group weren't the only ones who noticed the center of the ballroom floor on Floor 3 bowing in significantly during the Yousei Teikoku/FLOW concert, particularly during parts of FLOW's set, such as Go!!! from Naruto, where everyone was jumping like crazy. Now it sounds like even people on the 2nd floor noticed significant vibrations and thought there might have been an earthquake.

During the concert, I couldn't help but think about the video of the Versailles wedding hall disaster, where the dance floor of a poorly constructed 3rd floor collapsed through to the lower floors and caused many deaths and injuries. Even though I'm 99.99% sure the Washington Convention Center ballroom is extremely well designed and that this sort of scenario is impossible, I couldn't help but feel nervous about this contingency during the event, and in thinking about it afterwards - especially with the floor noticeably warping under our feet.

So I just wanted to request from the staff for the record, so that this can be settled once and for all with certainty, can we get some confirmation that the 3rd floor ballroom is rated for the number of people at these concerts, jumping in sync in the way that we were? And are there any further assurances/explanations that the floor is actually designed to warp in the way that it did in order to absorb the load and remain strong?

I just hope that this issue can be resolved early, so that the word can spread and people can be absolutely comfortable at these events in the future.

Thanks in advance!

I can understand your worry, but the room is fully capable of supporting the weight from the crowd and them jumping.

 

Think of it like an big structure (bridge/tower) - They move a lot - if buildings and bridges didn't move they would collapse, engineers realised this after structures collapsed when they attempted to make the structures very rigid.

If you've previously attending otakon in Baltimore and don't remember the floor bouncing during a concert - it's because there was just layers and layers of concrete underneath hall D.

https://www.google.com/amp/gizmodo.com/how-much-do-skyscrapers-actually-move-1707522178/amp

 

http://observer.com/2012/10/skyscrapers-may-shake-and-shiver-but-theyre-perfectly-safe-just-stay-away-from-the-windows/
 

 

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Essentially using this data I gathered reasonable info -

 

Usable space 52,000 square feet times that by the 100 (pounds) per square feet will give us:

5,200,000 pounds total(rooms weight capacity) divide this by 9,000 (amount of people - this is way more than fire marshals limit) will give us 577.77 pounds per person.

Which is still very very very strong.

 

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That much flex would be expected in a building designed to handle an earthquake. Whether the WEWCC is such a building, I don't know. I do know that we on the second floor did not experience any indication of structural failure (cracking sounds, creaking sounds, dust/debris falling from the ceiling)

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That's good to know as, not gonna lie, I was really scared during JAM Project's set and felt the floor the shaking so much. I moved to the back for T.M. Revolution and didn't feel a thing so that made me feel a lot better. Didn't realize it was worse the next day as again I sat in the back and didn't feel any shaking at all.

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8 minutes ago, ServerGhost said:

Essentially using this data I gathered reasonable info -

 

Usable space 52,000 square feet times that by the 100 (pounds) per square feet will give us:

5,200,000 pounds total(rooms weight capacity) divide this by 9,000 (amount of people - this is way more than fire marshals limit) will give us 577.77 pounds per person.

Which is still very very very strong.

 

The usable space includes the stage area and buffer which would not be shared by the audience, and the floor load capacity is a STATIC load, of which the audience most certainly was not. So your calculations are not indicative of the actual load put on the floor by a jumping crowd of 9000.

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Just now, Fadamor said:

The usable space includes the stage area and buffer which would not be shared by the audience, and the floor load capacity is a STATIC load, of which the audience most certainly was not. So your calculations are not indicative of the actual load put on the floor by a jumping crowd of 9000.

We didn't have a jumping crowd of 9,000 - that was just prove it's capacity.

 

The max attendance was roughly 2,000.

 

Please, do tell me how I'm inaccurate on these calculations

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Just now, Fadamor said:

The usable space includes the stage area and buffer which would not be shared by the audience, and the floor load capacity is a STATIC load, of which the audience most certainly was not. So your calculations are not indicative of the actual load put on the floor by a jumping crowd of 9000.

Yeah, the point is there was nowhere near 9000 people in that room, and there never will be. With only 2000 people in the room, each person would need to generate over 2500 pounds of force at the same moment to reach the stated max load (which is probably much less than the actual max load based on typical engineering practices). So unless everyone is driving their car into the concert, this is actually impossible.

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Well, as I stated the crowd was NOT a static load, but instead one that was jumping up and down in unison. The floor was experiencing a dynamic load up to around twice the weight of everyone jumping. Your calculations took it out to 9000 people (I'm still not sure where THAT number came from) and confidently stated a weight per square foot assuming the weight was evenly distributed across the entire floor, which it most assuredly was not unless you let the crowd up on the stage to balance everything out. So yes, your calculations are not indicative of the actual load put on the floor by a jumping crowd of 9000.

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PSF is a measure of force, not weight. Divide that number by acceleration of gravity to get weight.

So 100 lbs-force/sq. ft. (PSF) x 52,000 sq. ft. = 5,200,000 lbs-force

5,200,000 lbs-force / 32.174 ft/sec^2 = 161,621 lbs-mass

161,621 lbs-mass / 2,000 attendees = 80.8 lbs-mass per attendee average

So yeah you may want to get an actual mechanical engineer to weigh in... (I'm Chemical, so not really my expertise).

EDIT: Of course, they could always mean mass per square foot instead of force, which would make the numbers make much better sense, but that's not the standard Engineering notation, so it can be confusing.

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1 minute ago, Fadamor said:

Well, as I stated the crowd was NOT a static load, but instead one that was jumping up and down in unison. The floor was experiencing a dynamic load up to around twice the weight of everyone jumping. Your calculations took it out to 9000 people (I'm still not sure where THAT number came from) and confidently stated a weight per square foot assuming the weight was evenly distributed across the entire floor, which it most assuredly was not unless you let the crowd up on the stage to balance everything out. So yes, your calculations are not indicative of the actual load put on the floor by a jumping crowd of 9000.

Pretty sure this was just a reference to the fact that the ballroom is still extremely safe even if the attendance is over 9000. xD

(a.k.a. 9001 attendees)

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2 minutes ago, Dostovei Illuminas said:

PSF is a measure of force, not weight. Divide that number by acceleration of gravity to get weight.

So 100 lbs-force/sq. ft. (PSF) x 52,000 sq. ft. = 5,200,000 lbs-force

5,200,000 lbs-force / 32.174 ft/sec^2 = 161,621 lbs-mass

161,621 lbs-mass / 2,000 attendees = 80.8 lbs-mass per attendee average

So yeah you may want to get an actual mechanical engineer to weigh in... (I'm Chemical, so not really my expertise).

This calculation is not correct - the specification above is floor load capacity, the lbs-mass that each section of the floor can carry. So despite the existence of an engineering unit PSF for lbs-force/sq. ft., this is talking about 100 lbs-mass/sq. ft., using the definition we use in daily life for lbs. Thus the correct calculation is 5,200,000 lbs-mass / 2,000 attendees = 2600 lbs-mass per attendee. (If anyone can think of a way for an attendee to generate 2,600 lbs even of dynamic force, I'd be very interested to hear it - yes the FLOW set was very good, but it didn't break the laws of physics ^_^)

Anyway, clearly they're talking about lbs-mass there because a rated 80 lbs-mass per attendee would be absurd - the ballroom would have already collapsed if that was the case.

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1 hour ago, Dostovei Illuminas said:

PSF is a measure of force, not weight. Divide that number by acceleration of gravity to get weight.

So 100 lbs-force/sq. ft. (PSF) x 52,000 sq. ft. = 5,200,000 lbs-force

5,200,000 lbs-force / 32.174 ft/sec^2 = 161,621 lbs-mass

161,621 lbs-mass / 2,000 attendees = 80.8 lbs-mass per attendee average

So yeah you may want to get an actual mechanical engineer to weigh in... (I'm Chemical, so not really my expertise).

EDIT: Of course, they could always mean mass per square foot instead of force, which would make the numbers make much better sense, but that's not the standard Engineering notation, so it can be confusing.

67a148ae3313c226ec99aa61796d9e92--teaching-science-science-classroom.jpg.3c9f81caac29eee43c9ff9591cc9ee54.jpg

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1 hour ago, FlxRevenant said:

This calculation is not correct - the specification above is floor load capacity, the lbs-mass that each section of the floor can carry. So despite the existence of an engineering unit PSF for lbs-force/sq. ft., this is talking about 100 lbs-mass/sq. ft., using the definition we use in daily life for lbs. Thus the correct calculation is 5,200,000 lbs-mass / 2,000 attendees = 2600 lbs-mass per attendee. (If anyone can think of a way for an attendee to generate 2,600 lbs even of dynamic force, I'd be very interested to hear it - yes the FLOW set was very good, but it didn't break the laws of physics ^_^)

Anyway, clearly they're talking about lbs-mass there because a rated 80 lbs-mass per attendee would be absurd - the ballroom would have already collapsed if that was the case.

Yeah, that's what I figured too after writing all of that. I'm just used to dealing with the force end of things rather than the mass end of things. So many pressure rating calculations...

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That's good to know as, not gonna lie, I was really scared during JAM Project's set and felt the floor the shaking so much. I moved to the back for T.M. Revolution and didn't feel a thing so that made me feel a lot better. Didn't realize it was worse the next day as again I sat in the back and didn't feel any shaking at all.


I was in the front row for both and it felt like the time an earthquake hit the mid-Atlantic, especially during JAM. But the building has certainly hosted concerts before, and will again.

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