Queensferry Crossing stay cable strands – insulating timetable

Transport Scotland’s recent release to me 😀 of the details of the number of strands in each stay cable of the Queensferry Crossing allows me now to update my “Restranding Timetable” to allow the strands to be electrically insulated so as to carry a heating current for de-icing purposes.

The number of strands in the bridge 21,186    100%
To be replaced with a new longer strand 440 2%
Replace with an old strand from a longer cable 7,764 37%
To be left as now 12,982 61%

Insulating Timetable South Tower Stay Cables

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Insulating Timetable Centre Tower Stay Cables

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Insulating Timetable North Tower Stay Cables

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Note that the south and north towers stay cables would take longer to insulate / re-strand because the bridge designers apparently specified that those towers’ shortest, most vertical, most efficient cables with the easiest work-load should paradoxically use the strongest of the bridge’s stay cables.

Being shorter those cables are better re-stranded last so that they may re-use strands replaced from longer cables.

The centre tower stay cables seem to be designed more as expected from a structural engineering science point of view. I’m curious as to why the discrepancy?


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