M 20 bridge cpllapse

And, if the lorry was doing 56 MPH the bridge wouldn't have droped on the front part of the trailor, to me he/she wasn't going fast ie 56 mph

Pic from the net



Some bridges will have expanion joints, also has the motorway been resurfed and the gap narrowed, one inch makes a lot of differents

 

Looking at the photos that @fat controller posted, I'm inclined to think that the initial bridge design was either flawed or it was constructed incorrectly. An accident waiting to happen...

Anyone have any idea how old that bridge is?

 

If there was some free play in the digger, then would it not have effectively been like a giant sledgehammer? I can plough a sledgehammer straight onto concrete and the concrete will break without any damage at all being sustained by the hammer. The head of my sledgehammer weighs about 2kg I think, and it will typically be doing maybe 10mph at the moment of impact. If you multiply the masses and velocities it's easy to imagine that a digger striking at 50mph could be enough to destroy a foot bridge.

 

One would hope they are sufficiently over engineered to take the occasional accidental wallop without collapsing. Perhaps there are multiple factors at play. That said, I have seen a much more solid bridge than that (a railway bridge) rendered unsafe and needing a partial rebuild after a bus struck it at relatively low speed.

 

Saw the pictures on TV I used to work for a company that made bridges the Thermal Viaduct being one and the Milfield Avon Bridge. I just wonder how long that bridge has been there??

 

I get the feeling, looking at the pics of the downed section of bridge, we are looking at the wrong end, we are looking at the joint, which appears to be intact.
More interesting would be the other end of the downed section where the digger hit it and possibly the condition of the joint in question that is still up there.

Got a feeling that part of the motorway was widened back in the 80s, when all bridges were widened or replaced.

I've seen quite a few pedestrian bridges with that kind of half lap joint, centre section just lowered into place.

 

Asked daughter's boyfriend about the bridge incident, he is a Class 1 lorry driver and owns a fleet of 10 lorries so knows a fair bit about motorways. His opinion is that he has seen dozens and dozens of foot bridges with the same what would appear to be cracks in them. He says it's not a crack but is where the section of bridge is slotted in and yes would be the weakest part of the bridge and "go" if belted by as clueless describes it a sledgehammer. At the same time it is only a footpath and designed as such.He also isn't surprised that the damage to the bridge is large but not much to the digger.
He is wondering if either the low loader driver was on the hard shoulder either because he could sense the loader was breaking down or realised the digger arm wasn't in the right position and intended to do something about it and drove onto the shoulder.
In any event he is fairly sure the owners of the loader and possibly the driver too are in big trouble unless they can prove they were not at fault. It costs £1000s and £1000s to just cone off 1 lane of a motorway evidently far less close 1 whole carriageway. Hopefully the company is very well insured as the final costs involved to repair the bridge etc will no doubt run into millions.