When we think of bridges, it is the dramatic and monumental long spans that come to mind first, especially the lithe suspension bridges such as the Golden Gate and the pure geometric arches such as Sydney Harbour. But the majority of bridges are not such spectacular structures. Most of them are ordinary overpasses, with spans of 30 or 40 feet, carrying roadways or rails across other thoroughfares or over small streams. You see such bridges by the dozen on any drive down the Interstate. They may be lacking in glamour, but they are more representative of a bridge builder's art.
The engineering and construction of girder bridges are pretty routine these days, but the bridges are not quite standard items you order from a catalogue. The girders, whether of steel or concrete, are custom-build for each bridge, then trucked to the site and hoisted into place with a crane. The designer still has scope for variation and creativity, and it shows out on the highways: some overpasses are prettier than others.
The details of a building cannot be made alive when they are made from modular parts
If the builder wants to build the room from modular four-foot panels, he must change the size of the rooms, and change their shape, to fit his panels.
In such a building system, it is impossible for a person to create a plan which reflects the larger subtleties of site or plan. Each plan will always be chopped and disfigured to make it fit the building details.
To make the building live, its patterns must be generated on the site, so that each one takes its own shape according to its context.