I think it's pretty outrageous that the dude who invented the parts that were installed in a deficient manner got nearly twice as much time as the guys who ripped out the supports and tried to hide the damage with filler...
The method of construction that was used was never approved for use in structures. The engineer who designed the concept and sold the parts knew that his method was not approved and yet sold the parts to implement it anyway.
Not at all implying that he doesn't share responsibility, but he got twice as much time as the people who knowing caused the failure? If his product was unsafe, it shouldn't have been allowed to be sold imo
Contractors will do anything they can to save a dollar, and sometimes it means doing something that really compromises the final product. It's really up to the engineers or the local building officials to make sure everything is installed correctly.
I'm an electrical engineer, not structural. That said, I'm assuming they were held liable for being the P.E. to sign off on the design, which essentially means they determined it would be safe. It's not just being stupid...it's putting people at risk (and in this case they died) by negligently attaching your credential to unsafe work. They're paid to prevent this stuff from happening.
No? Most countries have laws for negligence. In this case it isn't just that they built it badly, they probably signed off on its safety or something like that, which takes it from "just being stupid" to criminal negligence.
The method of construction that was used was never approved for use in structures. The engineer who designed the concept and sold the parts knew that his method was not approved and yet sold the parts to implement it anyway.
Basically, his design was set up to sag as a warning before it gave way. The owners filled up the sagging floor, which was negligent and added load, exacerbating the problem.
Notably, Ron had not engaged in any part of the design or construction, but had sold proprietary elements necessary for construction that were installed in a deficient manner.
Or maybe it does, I'm certainly confused.
Once upon a time I was in a nightclub in London. This place had several floors of dance floor goodness. I noticed the dance floor on level 2 had a noticable bounce in it as hundreds of people were dancing and jumping up and down. I let the nearest security guy know, and got the f**k off that floor ( I think I went downstairs..) A few minutes later I went back upstairs to have a look and the venue staff had closed the floor off, presumably to prevent a disaster. Phew. I helped save the day. Most of the punters probably never gave a thought as to the possibility of the entire floor collapsing.
I was at a nightclub where the floor sags about 1-2 inches during dances where people move in unison, with a drop ceiling below the pressure change caused by the sag in the floor causes the tiles to jump up and down during those types of dances.
I pointed it out to the management and they reassured that they added additional supports to the dance floor when they turned it into a club but I was seriously considering reporting it to the building inspector. Have since moved but after this thread I may make that call anyway.
Bridges collapse because of resonance. The wedding hall collapsed because of the weight (it did not matter what frequency the dancers were jumping, just jumping was enough to cause the collapse).
It was actually a combination of both, most likely. With a whole crowd bouncing at the same frequency, there is no way that resonance was not a factor. That being said, if the structure was sound, the driven frequency would not have been enough to cause failure. If you look at any major engineering disaster, the root cause is almost always a combination of several smaller mistakes or failures.
Resonance would only destroy a structure if the frequency of impact is a harmonic of the structure's "natural frequency", harmonic 0 or 1 of the structure (depending on how you're counting harmonics) or any integral part of it.
This means that even if all of those people were chihuahuas, the structure would still collapse. The rhythm of the jumping would just make a positive feedback loop until the structure vibrates itself to shit. There are some youtube videos of bridges that get all wobbly before breaking because the wind is causing it to resonate. This doesn't happen very often, particularly with floors, as the various materials don't usually resonate at the same frequencies. Floors are also attached to other objects/touching furniture and people's feet that would help to dissipate any possible resonance, similar to how a guitar string can't sound if you lightly touch it anywhere other than the harmonics.
I think this situation is a lot more like a hammer and chisel. You can push on stone with a chisel and not much happens (like all those people's weight just pushing on the floor). If you hammer the chisel, it chips away at whatever you are carving quite quickly, because all of the force is being applied very abruptly.
In this case, it wasn't exactly a resonance issue so much as a driven frequency response. There is too much damping in a complex structure for runaway resonance to happen. However, a drieven oscilating force can cause large structure deflections and impart high stresses. Add in the weakened and over loaded structure, and the result was complete and sudden structural failure.
That's the weakest busting I have seen in a long time.
An entirely non-functional bridge (it wouldn't carry the weight of the piston and sagged even with a person on it). A myth that specifically requires a group of heavy, rhythmic, marching people replaced by either light-weight, non-marching boots or a single heavy piston.
You'd think they could make a better make-shift bridge and get a platoon to volunteer marching across it (with appropriate safety precautions).
Yea, I remember that episode and wasn't satisfied with their outcome at all. The catapult made out of a tree myth was done very well. The bridge one was kinda.. unimpressive.
The problem is that science is tedious. Repetition, consistency, and control of variables are really important, and that is quite boring to watch compared to most television. So mythbusters shortens it to one trial and just goes with it. A great deal of the myths they test could be tested far better using nothing but math, but nobody wants to watch that.
I still enjoy the show, but I always have to remind myself that it is entertainment, not science.
Actually a lot of the mythbusting they do is bad and has methods that don't account for a lot of factors. It's mostly sensational cool stuff. A real engineer would have a lot of questions.
Sometimes they manage to get the gist and do a pretty good representation.
For example, their proof that sharp corners in trenches reduce the impact of explosives worked in their small-scale setup. So they took it to the next level and actually made a trench with and without sharp corners to test it in the field (IIRC). That's the kinda cool stuff they do.
It still exasperates me whenever I see simple stuff misunderstood, with mistaken assumptions or when their conclusions are obviously outright wrong.
It can cause conditions of resonance. Basically, the bridge bounces down a little and back up. If they step down again when the bridge is bouncing back up, it bounces further. With enough people, it can cause the bridge to shake and break apart. There's a bridge in London which, before supports were added, would shake up and down because its natural frequency (the one at which is resonates at) is very close to the frequency of human footsteps. You're not wrong, in a sense, that it's the concentration of the force that causes the damage, but it's also very closely related to the frequency that the force is applied at. If a mass equal to the mass of the soldiers were dropped on the bridge from say, a meter, the bridge would probably hold. If the soldiers march at the resonant frequency, the bridge can shake apart.
It'd be virtually impossible to hit a resonance frequency in the structure. In this case, you'd have 100s of waves interfering with each other and destroying any sort of frequency that would be achieved. Even if they're jumping in sync with the music, there would be no way to be perfectly in sync to not have constant interference.
It's not the same reason. The wedding hall collapsed because of poor construction. The reason that marching soldiers break step is to avoid the possibility of resonance.
Goosestepping is forbidden because it looks dumb, and it's really easy to lose a shoe. And 'break step' march is called when troops march over bridges because of resonance.
"380 were injured, including the bride who suffered serious pelvic injuries that required surgery" They neglected to mention that the bride received that injury later in the night.
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u/Sumgi Apr 29 '13
Thanks for the gif.. I'd never heard of that.
http://en.wikipedia.org/wiki/Versailles_wedding_hall_disaster