Nanfang'ao bridge collapse Yilan Tiawan 2

[charliealphabravo]

I haven't found any mention of fatalities. Reported 20 injured.

Location

Collapse video

Bridge details

Photo of bridge system.

Edit: Updated dead video link. Thanks to JAE.

 

[SFCharlie]

izzotsai (Structural)
We are sad to hear of the lost of lives. We can only hope that lessons will be learned and future lives saved.


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[Agent666]

Probably not related to the failure, but I found it interesting that bwing08's picture shows no traffic barrier to the middle to protect the tendons against any traffic collisions, the kerb is sort of good for nothing in this respect.

 

[IRstuff]

I get that the stays are multiple strands of single or multi-strand cables; I just used to seeing them wound, as I think that gives them more uniform and repeatable strength.

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[Ingenuity]

I just used to seeing them wound, as I think that gives them more uniform and repeatable strength.

Suspension spans typically have their main cables 'compacted' (compression wound) - not common for cable-stayed bridges.

 

[hokie66]

Ingenuity,

So which would you call this one? It is/was an arch, but the hangers perform a similar function to those in a suspension bridge.

 

[Ingenuity]

hokie66: Vertical hangers to suspension bridges seldom are compacted (wound) - usually only the main suspension cables. I think these cables to the 'hangers' of the arch were detailed like stays. I may be wrong - but the photos I reviewed show no signs of compaction.

Single strands stays (and/or hangers) make replacement easy (relative term!). I am aware of one 300 m (1000 ft) long stay that was damaged by a barge and replaced strand-by-strand using small, light weight equipment.

 

[IRstuff]

On the GG bridge, even the vertical hanger cables are wound; actually, they're double wound, since the individual strands are also wound.

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[charliealphabravo]

Wires are wound into strands and strands can be wound into rope. There are many options including straight bars, but from the photos we have so far it looks like each hangar consisted of several strands or ropes in an HDPE duct. I also don't see any signs that the strands or ropes were wound or compacted together but I think this is pretty common for hangars. One reason is that compaction and field winding can have negative effects on creep.

Edit: Ahhh, Ingenuity and IRstuff already said most of this. Creep issues and ease of maintenance are the two reasons why the hangars might not be wound.

 

[IRstuff]

It just seems to me that winding, aside from looking nicer, makes it harder to ensure uniform loading of the strands.

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[LeuBong]

It seems a concrete-filled steel tube arch bridge.
I guess it fell by fatigue or corrosion of cables , but that's a guess!

 

[Alistair_Heaton]

I am in a photography group as a hobby and one of the other members uploaded these iages and gave permission for me to show them here.

So they are copyrighted to Kang Lin.

 

[IRstuff]

That Y joint looks like it's pretty rusty

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[LittleInch]

When it failed it almost looked to me like the two legs of the Y were slotted inside the main arch Y piece and just seam welded on but the main connection was internal by simple gravity / weight of the bridge.

Some construction photos or drawings of how those cables were connected inside the arch would shed a lot of light.

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[3DDave]

The y-joint may look rusty because of the truck fire.

 

[IRstuff]

The scorch marks are black-ish, but there are regions that show brown and appear to be roughened.

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[3DDave]

Oxidation in a fire does that. Most burned cars I've seen look like they have 50 years of rust the day after. As for being roughened it may be a weld joint that was torn apart.

In the Google maps images there weren't rust streaks like normally happens with long term corrosion.