Bridge building, earth curvature, and math nerd
I watched an old TV show yesterday about NYC bridges. It said that the towers for the Verrazzano Narrows bridge are 1 5/8 inches further apart at the top than at the bottom because of the curvature of the earth. Furthermore, that was a design criterion.
The towers are 693 feet tall and 4260 feet apart at their bottoms. If the 1 5/8 inches is a design criterion, then it had to be calculated.
Here’s my CAD VVL (very very lite) drawing:
I used 3959 miles as the radius of the earth because that’s what my 1942 spherical trig book uses and got 1.694746 inches as the difference in distance between the top and bottom of the towers. That’s a bit more than 1.625, but the answer only has to round to the nearest eighth.
That means that it has to be less than half-way between 1.625 and 1.750. or less than 1.6875, which it isn’t
There’s probably rounding involved in all of the given lengths, but if there’s not, an earth radius of 3976 miles will give a difference of 1.6875 inches.
Forgetting the math nerd stuff, it’s instructive to see how curvature affects big construction.
Carry on, and for gosh sakes be more productive than I am.
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