Just look at it!
I recall reading that it was overdesigned because construction was soon after the Tay Bridge disaster so nobody was going to take any chances with this one. It was hoped that a) It would stay standing regardless of the weather and b) overdesigning it would give users confidence that this one wouldn't collapse.
If my memory serves me correctly, I think that the designer of the Tay Bridge was going to design the Forth Bridge but that was changed due to obvious circumstances.
Pretty much all of this. There was a
very good reason the Forth Bridge was built the way it was. Public trust in such gargantuan structures and those who designed them had been severely undermined by the Tay Bridge disaster; the Forth Bridge was intended to be a bold reaffirmation that it wouldn't fail in extreme weather and to help restore public/user confidence in these kinds of structures. The fact it's still with us, doing what it was built to do over 130 years after it's opening merely reaffirms this. And despite being overengineered to the nth degree, it still manages to be one of the most elegent, beautiful bridges anywhere in the world. Beauty born out of tragedy.
The original Tay Bridge's designer (Sir Thomas Bouch) had indeed been contracted to build a suspension bridge over the Forth in the 1860s (the North British Railway's bankruptcy in 1867 put paid to it then) and the 1870s; this later one got as far as work starting in 1878 on a pier in Inchgarvie, but all work was immediately halted following the Tay Bridge's fall the following year and the resultant ruination of Bouch's reputation; Bouch's design was officially dropped in January 1881. Here are some design drawings of the 1870s proposals for a suspension bridge across the Forth (from
thethreebridges.com).
