|Narrative history of Big Money Opening Day: IV
||[Jul. 26th, 2005|08:11 pm]
You Big Dummy
It looks like just another highway in Mt. Pleasant, with all the concrete and the Jersey barriers and the tangle of piers and girders and beams and caps. Going up the proper ramp, the actual superstructure of the bridge is visible one mile away. But on Opening Day the only entrance to the empty bridge that was easily accessible to us was an off-ramp. The ramp passed under a viaduct, and the viaduct blocked the view of the bridge from us. So when we walked into the cement maze we took it on faith that we would first of all somehow exit, and that when we did we would be on the foot of the bridge.|
Actually somewhere in that interchange we took our first steps on the bridge, so that when we came out we were already aboard. It wasn't hard to notice, but it was in an otherwise inconspicuous spot. At a point underneath the viaduct the black road suddenly abutted onto an expansion joint. From the other side a white ribbon of concrete fairly leapt outward, made a graceful curve, and rose out of sight behind the overpass. One hop over the joint and we no longer stood on the ground, but we couldn't tell the difference.
It was some 200 yards later, when we passed out of the shadow into the broiling heat, that we finally saw the two towers. Good thing we parked in the east side, we realized. The bridge was built on a line running roughly east-west, so that it could lie athwart the channel, which was north-south. So the sun was at our backs and could reflect off of the towers and cables before us. It made it all the easier to understand what they meant by the "sail motif" that the architects (Parsons Brinckerhoff and, specifically, Riyad Ghannam of Donald McDonald) had been talking about. More to come on that later.
As is the case with most suspension or cable-stayed bridges, the towers are what everyone notices first. Many are shaped like the letter H or a pair of Is. The Sunshine Skyway in Florida features towers that come up through the deck, not around it. The Pont de Normandie's towers look like upside-down Ys. The Ravenel's towers don't really look like any of these.
At water level rests two artificial islands, made of giant Newfoundland boulders. Only an acre of rock breaks the surface but at the bottom of the river each island takes up five acres. It is on these rock islands that the towers seem to rest, but in reality the tower bases are surrounded by the rocks. The purpose of these is to force a wayward ship to set ground long before reaching and possibly damaging the towers.
From each two beams spring upward and outward, reaching their widest point at the deck crossbeam, and then gently converge to a point 575 feet above mean high water. At the apex of each a "beacon of light" was to have been placed, but after everyone slept on it that idea was scrapped; Joe Riley said the things looked like Pez dispensers. (Look carefully at that famous computer rendering of the bridge made around 2001; they are there.)
At a distance the towers look as if they have been carved from one single block. Up close one notices that the tower beams are composed of segments. This is actually an illusion. The towers really were built as one solid piece: the dividing lines of the "segments" were added so that the eye could more easily digest the largeness of the towers. That the move didn't make the structure any bigger or stronger, nor saved any money, shows us that designers really do appreciate bridges as works of art nowadays.
From deck level each tower describes a triangle; that fits in well with the many triangles formed on one side by the cables, on another side by the towers, and at the base by the deck. So the towers don't really stick out oddly, as vertical or H-shaped towers might. They blend in with the rest of the structure nicely. But your eyes are still drawn to them.
Even better that way, because each set of cables is in the same plane as its respective tower beam, so, when the approach begins, the towers and cables seem to "line up." When closing in each plane of cables, one on the left, one on the right, seems to widen a bit, but that the cables are separate from each other can not yet be discerned. So from certain points on the bridge, when the light is just right, a faraway group of cables looks almost like...well, a sail.
Such an effect could work only if there were a hell of a lot of cables spaced not far apart from each other. Guess what. There are 16 on either side of the bridge for each of the side spans and each half of the main spans, 128 in all. The cables do not go into the tower and come out the other side; each cable is anchored in the tower. As these actually hold up the bridge and its traffic, the cables might be the most important part of all. But getting them there in the first place led to what might well have been the tensest moments of the entire construction process.
Each cable is composed of several strands of wire sheathed in a polyethylene pipe. A French company called Freyssinet erected the cables. The process began when a master strand was threated through its pipe and anchored to the deck. The other end was hoisted by crane to its proper anchorage in the tower and there attached. The rest of the strands were wound through the pipe about the master strand. The wire itself was made by Georgetown Steel, just an hour up the coast. For this project the plant manufactured the wire through a special process that had never been used in the United States. About half of the specially made wire had been shipped to the bridge site by 2003, and then Georgetown Steel went bankrupt. There were plenty of wire makers in Europe that made the special wire, but Freyssinet was under contract to buy American. After frantic searching the cable erectors asked a company in Texas to learn the process in a hurry and start shipping out cable as soon as possible. There were poor test strands sent out at first, but eventually the manufacturers got it right, and the months of delay that no doubt would have resulted otherwise were avoided.
It was circumstances such as this that the builders had in mind when they promised to finish the bridge in five years; the work was done in four. The "extra year" was basically saved for a rainy day, where a rainy day meant a hurricane, an earthquake, a supply shortage, a strike, or anything else that could lead to delays. Looking back, the only other thing that had a chance to cause the bridge to open after July 2005 was the threat of hurricanes in the late summer of 2004. At that time parts of the deck were already hanging by the cables, but were still vulnerable to high winds. The builders strung up temporary lines leading to anchorages in the harbor or on the rock islands. A couple of storms did brush the coast, but the bridge held.
And so on 11 March 2005 the last slab was placed, and the record for the longest cable-stayed span in the Americas had been broken. There followed months of paving, as well as erecting barriers, signs, and street lights, after which the bridge was, finally, declared ready for business.