On Tue, 20 Mar 2018 16:27:37 +0000, Jim K wrote:

Johnny B Good Wrote in message:

====snip====


Sadly, I've not been able to find an "Earth's curvature compensation"
figure for the slightly shorter Severn bridge (1 mile span versus the
Humber bridge's 1.4 mile span), just that 388mm[1] 'lean back' on the
towers during construction to compensate for the suspension cable
forces.
It might have been mentioned in the Timewatch/Timeshift documentary on
this record breaking bridge but I've not got the time right now to spin
through the recording just to find out whether or not a figure was
actually mentioned.

Why would any bridge need to be 100% "flat"?

It had nothing to do with making the road deck "100% flat". The 'lean
back' was to compensate for the final cable loading so that the towers
would become perfectly aligned to the vertical downthrust forces once
construction had been completed. I dare say the same thing applied with
the Humber bridge.

--
Johnny B Good