| Posted by Ken Ramsley , Nov 14,2002,13:59 | Forum |
Long ago in history the high point of bridge-design revolved almost exclusively around stone arches. Because of physical limitations the greatest distance for a single-span stone arch is perhaps 30 meters and a longer stone bridge must be constructed from multiple spans. Witness the remaining Roman aqueduct systems for the supreme example of this technology.
During the middle ages the gothic arch was developed, and although it still could not span distances any better than the Roman style, the load-bearing characteristics of this new arch required far less stone, and they were easier to build than the old massive Roman curved arches (check out the Brooklyn Bridge for examples of some of the largest gothic stone arches ever built).
Beginning with the Industrial Revolution in the early 1800's various researchers and engineers developed new bridge-building materials such as steel, structural wire, and reinforced concrete. And with these advances, bridge-designers began to have even more options at their disposal when searching for practical solutions.
But there is always a limit to technology.
In one of the Star Trek movies, Scotty conjures up the formula for 'transparent aluminum' as a way to build a giant light-speed flying fish tank. My design juices got rolling and I could imagine all sorts of other uses for such a marvelous material. But it does not exist in the real world, and so I could never really use 'transparent aluminum' in a practical design.
A designer can only work within the limits of what is technically possible.