This picture caught my eye when reading the news today. Look at the size of those things!
The first bridge in the picture is the North Clarke Street Bridge. It’s 66 meters wide, 105 meters long and weighs 1400 tons. Enormous counterweights at either end are carefully balanced with the structure so that it takes only a small amount of energy to raise the leaves.
The bridges have been raised in this case to try and prevent looting in downtown Chicago – but, you know, they are nice bridges, and clever engineering.