Norway, wooden bridge collapse, engineering explanation?

[Skyrocket21]

A 10 year old Norwegian wooden bridge failed today, leaving a lorry driver stranded who was air lifted off, knowing Norway is a very safety conscious and wealthy nation, what happened for such a huge mistake in engineering or materials to have happened in this day and age?



https://www.bbc.co.uk/news/av/world-europe-6255656...

[dudleybloke]

Lose a bridge, gain a bike ramp!

[JayRidesBikes]

In my expert opinion, I can indeed confirm that it is broken.

[Simpo Two]

The Grauniad thinks 45 degrees is 'nearly vertical'

As for the cause of the disaster, I lay the blame firmly on gravity. The proof of this is that if there was no gravity, it wouldn't have collapsed. Damn that pesky Mr Newton.

[Roofless Toothless]

Lorry too heavy? It seems to be carrying aggregate of some kind, plus a trailer full of the same. Perhaps it wasn’t the bridge engineer’s fault.

[Frik]

It does look like the deck snapped either side of the pier which would tally with a heavy lorry and trailer either side of it. Can't see any weight limit signs on the road though.

It definitely shouldn't have done that.

[Beati Dogu]

Isn't it good Norwegian wood?

[dudleybloke]

Pine for the fjord.

[ReverendCounter]

dudleybloke said:

Pine for the fjord.

We are

[dukeboy749r]

Beati Dogu said:

Isn't it good Norwegian wood?

Cue the Beatles song...

[The Wookie]

Roofless Toothless said:

Lorry too heavy? It seems to be carrying aggregate of some kind, plus a trailer full of the same. Perhaps it wasn’t the bridge engineer’s fault.

I'd say if a single truck, even a grossly overloaded one, was enough to bring it down then it's still at least partly the engineer's fault

More likely it was simply the edge case load that sent it over the... er... edge

I'd guess it will be some obscure combination of some aspect of the design and/or construction being marginal when considering material variability/environmental factors/traffic/etc etc

Either that or they've just found out that constructing a modern bridge out of wood is a stupid idea

Edited by The Wookie on Thursday 18th August 10:49

[Bob-iylho]

Roofless Toothless said:

Lorry too heavy? It seems to be carrying aggregate of some kind, plus a trailer full of the same. Perhaps it wasn’t the bridge engineer’s fault.

That would imply 2 heavy lorries in a row would cause it to collapse.

[The Wookie]

Bob-iylho said:

That would imply 2 heavy lorries in a row would cause it to collapse.

You're right, looks like 2 trucks, both near points where they would create the largest moment over the vertical supports

ETA looks like the last photo with the dry river bed was the collapse of a different bridge, may have only been one truck

Edited by The Wookie on Thursday 18th August 10:28

[vaud]

https://www.newcivilengineer.com/latest/norways-co...

Some more speculation by an expert.

[TGCOTF-dewey]

My guess is the lorry is knot the root cause.

[The Wookie]

TGCOTF-dewey said:

My guess is the lorry is knot the root cause.

They'd be barking if they didn't do a fault tree analysis

I'm guessing whoever gave the design the oak-ay will be in for the chop

[spitfire-ian]

The Wookie said:

Either that or they've just found out that constructing a modern bridge out of wood is a stupid idea

Edited by The Wookie on Thursday 18th August 10:49

From the pictures they look like glulam beams which are engineered and not just pieces cut from trees. They've been building bridges and the like with them for years. Saying that though, I imagine some structural engineer will be digging through their files and checking the fine print of their PI Insurance pretty urgently!

[The Wookie]

spitfire-ian said:

From the pictures they look like glulam beams which are engineered and not just pieces cut from trees. They've been building bridges and the like with them for years. Saying that though, I imagine some structural engineer will be digging through their files and checking the fine print of their PI Insurance pretty urgently!

I was only being flippant but it is interesting isn't it?

From the sound of it it's basically a composite material from a natural source.

I'm far from a structures engineer but my limited understanding is that it's challenging to model strength and fatigue characteristics of composites because of non-linearity/different strengths in different directions depending on the layup as well as variability in consistency of material and manufacture. I also know on carbon race cars it difficult to assess the condition and strength of older parts, particularly if they've suffered an impact or damage

It must be an absolute ballache to design something in composite that is big, long lived, high cycle-fatigue and in a harsh environment like a river bridge, particularly when you add in the fact that the composite you're using is inevitably biodegradable to some extent.

You'd expect a wooden bridge to be massively redundant or over engineered to prevent this sort of thing from happening.

ETA just read that civil engineering article, interestingly one of the highlighted areas of concern was the connection areas between the wood and steel, I know that's also a challenging aspect of composite layup on racing cars is achieving sufficient strength in each direction and load bearing in the mounting areas.

Also interesting that other collapsed wooden bridge pictured above was put down to the design engineer cocking up the load calculations in one of the joints, so a basic engineering error rather than it being about the construction material.

Edited by The Wookie on Thursday 18th August 11:47

[bmwmike]

This is why i never go on wooden rollercoasters.

Or any rollercoasters actually, but especially wooden ones.

Wooden you believe it hehe.

[Beati Dogu]

Part of the bridge goes over the E6 highway, which is the main north-south road.

Google street view here:

https://www.google.com/maps/@61.3124552,10.3014406...

Should be easy to clear with some chainsaws though I guess.