The photos are not mine :
Pont de la roche Bernard, an old bridge but the proportions looks right to my engineers eyes :
It is now superceded by this one, same architect as the "pont de Normandie" :
And near Nantes is the pont de Cheviré, not quite as big as pont de St Nazaire but more elegant in my view.
Personnaly, I don't like the proportions of the pont de St Nazaire, it doesn't look very efficient to me, I might be wrong as I've never designed something spanning more than 50m!