Wild inaccuracies in the plans for the Queensferry Crossing

As I blog tonight, I fear that there are no accurate plans for the Queensferry Crossing, not held by Transport Scotland anyway, maybe not held by anyone.

I’ve gained that impression because the distance figures in the one “AS BUILT” engineering drawing provided to me by Transport Scotland bear no accurate resemblance to a photograph of the bridge.

Here’s part of the “STAY CABLES ARRANGEMENT” drawing

and taking a closer look at the blue box area I’m drawing attention to, I have annotated what the drawing is claiming the stay distance figures were built as.

I’ve used red ink for the identification numbers of the stay cables and for the North Tower Midline and black ink for the figures which the drawing claims are the distances in mm between them.

 

So the drawing claims that the distance between the ends of cables 501 and 502 is “4.75 metres shorter (30% shorter)” than the distance between cables 502 and 503, which isn’t how it looks in this photograph, at all!

The photograph distances are in pixels but regardless it is clear enough that that distance between 501 and 502 (120 pixels) is not in the least “shorter” than the distance between 502 and 503 (117 pixels).

So something’s not right and the drawing has many other issues with it, like this lack of alignment between its figures and the features in the drawing.

There is also a typo “162000” instead of “16200” and the length numbers don’t add up in places. The drawing presents as a shoddy effort with no accuracy and no credibility. If this drawing is typical for the other engineering drawings then Transport Scotland have no plan nor clue as to what accurate size the Queensferry Crossing has been built to.

I’ve written to Transport Scotland suggesting that they might want to hire a surveyor to draw up some accurate plans for the Queensferry Crossing because without accurate plans it is not possible to know for sure if something of safety concern ever changes with the bridge that may need urgent remedial action.

Ideally, Transport Scotland would now commission for the Queensferry Crossing the same 3-D laser scanning survey which was done in 2015-16 for the 3D Forth Bridges Project, but before the Queensferry Crossing was constructed.

I don’t think we should wait until the Queensferry Crossing develops the sort of lean that the Leaning Tower of Pisa has, or some other serious problem that everyone – even without an accurate plan – can notice, before they call in the structural engineers to make the bridge safe, do you?

UPDATE 21st May 2021

I’ve received an email reply from a Transport Scotland official and he claims that regardless of the fact that the wildly inaccurate drawing clearly states “STAY DISTANCE”, as I have highlighted with red ink –

– the distances given do not refer to distances between the stay cables at all but refer rather confusingly to the lengths of the individual deck segments which are not drawn. Whatever. 🙄

Transport Scotland have now provided me with detailed stay distance information extracted from other drawings, which was nice. 🙂

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