This is interesting.
I was puzzled by the odd angling of the zigzag cross bracing in the bridge and once you see *why* they zig and zag like that, the reason it failed becomes a bit clearer.
In essence, the bridge is actually a cable-stayed design, but the deck
*should* have been strong enough to be self supporting until the support cables were installed.If you fast forward to 7:33 you can seen what the finished bridge should have looked like.
Tim
Thank you for that. I had wondered why it had collapsed the way it did and that makes it clear.
There was one report that a substantial lump of crane had fallen onto the bridge. Don't know how significant that was. No doubt it will all come out eventually.
Seems unlikely that a crane would be in any sort of position to drop lumps while the road was open to traffic.
Tim
Very odd. All the reports I've heard say how quickly it was built. Don't mention it not being finished.
So are we saying then that the design was at fault, ie the length too great for self supporting while being constructed, or was it faulty materials. Not so big but there is going to be a new pedestrian and Cycle bridge in Kingston Upon Thames built this year. in order to get the old one down they are going to cause chaos after Easter in the town centre and cut it into three pieces and crane it onto the low loader. No idea how they are going to build the new one. Brian
Yes over here the road would have been closed during any dodgy parts of the operation, say doing it off peak or at night. I've also seen protective temporary structures erected over roads during these construction systems, to catch any falling junk. I'd suggest not enough care generally here. Oh no we cannot close a major road, kind of thing. Brian
Some of the speculation out there are that the supports used to move it into place were supposed to be directly under the struts, but ended up between them, and that a loud cracking noise was heard during install and then several cracks appeared two days before it collapsed.
The road was closed while the prefabricated section was inched into place on heavy crawlers
Catching 950 tonnes is a little tricky.
+1
The only time I have seen cable staying mentioned. Some of the reports talked of failure during a stress test. Obviously (I *hope* obviously) you don't do a stress test before moving the temporary supports right out of the way, OR fitting the cable stays.
Yes, visible in the designs, and obviouslyh correspond with the angled struts that act as the "web"
It was not pre-stressed concrete, but post-tensioned so maybe something went wrong during the tightening-up of giant nuts and bolts?
The reports are cr@p. It has taken weeks/months to build. It was put in position in a few hours. They do the same sort of thing in the UK with bridges, build it and then move it into place. Roads/railways closed for hours rather than months.
The actual bridge doesn't look the same as the artists impression in the video to me.
If (as the video suggests) it was to be cable stayed, it does seem a bit odd to put it in place as a simply supported span and then remove all the other supports before fitting the stays. Even with a single support in the middle which would just lose one lane of traffic it would have been *much* more stable.
Apparently the cables are harmonic damping. The bridge was (meant to be) self supporting.
I've read that they were in the process of re-tensioning it when a hauser on the crane failed allowing the whole thing to break up.
You don't do that sort of thing when you have people underneath.
Maybe but it was on the BBC and the BBC never lies of course.
But we are talking about the land of the free, here. Right to bear arms, and so forth.
Except that the bridge deck is supposed to be supported by big cables from a tower which has not yet been built, and before they build the tower, those HV power lines need to be relocated.
Looks rather strange.
The artists impression had a central tower AFAICS and there isn't provision for one that I can see.
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