Overhead sign crushes car on freeway in Melbourne Australia. 3

[MDEAus]

This happened a few days ago, but the article has just been updated with dash-cam footage from the car immediately behind the one involved.
very quickly it can be seen that the failure point is at the welded joint for the bolted connection. the grainy footage makes things harder to see, the base off the standoff looks weird, why would you close the end off the SHS to be welded to the main beam? Galvanising requires drainage points and a minimum area open between closed sections. Unless that is a solid block off steel? I'm not sure why they would have used a solid block off steel though.

https://www.abc.net.au/news/2019-01-08/tullamarine-freeway-sign-falls-and-crushes-car/10700470

 

[MDEAus]

I didn't notice it when I watched the video but it would be interesting to know if that corrosion on the fracture site has happened pre or post failure. I would like to know the date of those images, I tried to see if I could find the source off those images to see if exif data was still attached but had no luck.

I doubt it was meant to be removed as those appear to be approx 50mm or longer stitch welds on the backing, which was likely used to help keep the top plate in position during fabrication. notice that the welds are only on what would have been the front face of the gantry and not the top plate.

I will revise my material thickness estimate up to 6-8mm (based estimates of a stub post of 125x125mm SHS and a M22 bolts I don't think it is 10mm). These could very well be what you saw at the industrial painter in 2017. I had a thought about estimating proportions from a weight I thought I saw in an article which I think was 4000kg but a rough estimate for the main structure of the sign itself is 1026kg using 200shs 10mm wall thickness. Now I can't see the rest of the sign making up 3000kg but I cant find what article I read that in anymore.

Until there is a report produced I don't think we will get much more new info.

P.S. whoops I thought I posted this half an hour ago

 

[hokie66]

MDEAus,
For what it is worth, the sign fell on 8 January, and the photos were taken from the 7News video of 20 January. So less than 2 weeks after the failure.

 

[Tomfh]

You can see it's already all brown and corroded in the original collapse video.

 

[MDEAus]

Tomfh
I was mainly concerned with the fracture zone; while that shows the inside off the gantry it's about what I would expect from a fabricated steel section that has been painted/powder-coated. I.E. you can't sandblast and paint the inside of a closed section.

Thanks hokie66.

At this point in time though with the evidence we have corrosion would have only sped up the final result rather than been the cause; the gantry would have started to fail for corrosion to have formed. The corrosion may paint a picture of when the initial cracks started to form though and whether they should have been picked up on by inspections.