How did they build the thing?
They must build the towers first, lift them upright and temporarily brace them in place. Towers are obviously there to transfer weight to the ground so the ground must have been carefully prepared to bear down on solid bedrock. The towers look elegant because they don't require any bulky bracing to keep them from tipping over. That's the genius of the suspension bridge, that the hardworking cables not only hold up the deck and its traffic, transfer their weight to the towers, the cables also keep the towers from tipping over. ( In this way cables are a little like mothers.) The cables don't appear to be attached to the tower in any way, just draped over them: thehttp://www.blogger.com/img/blank.gif angle of the cables and their tension keep the tower in place.
How do they get the cables in place? They are too heavy to bring to the site in coils and sling across. Instead, they bring huge spools of wire and make the thick cable in place. Using an invention of John Roebling (the reknowned builder of the Brooklyn Bridge) they feed the wire back and forth across the bridge, splicing in a new spool when the old one runs out and then clamp the wires together and wrap them with..more wire. So, if I understand this correctly, there are very few splices or breaks of any kind in the cable, unlike with rope, say, which is made of huge numbers of relatively short strands woven together.
Of course there has to be some sort of beginning cable and catwalk for all this weaving. Here in Castelfranc, someone probably rowed across the river with one end of a long rope. In the case of a bridge Roebling was to build over Niagra, he was reduced to offering boys $10 reward for flying a kite with a line attached across the span.
When they build the deck in sections. They must have to start at both ends and work toward the middle in order to keep the towers from falling over. They suspend the deck from the cable with rods and clamps
