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Costly bid for flamboyance


When it was decided that it would not be economic to seismically upgrade the cantilever truss eastern section of the Oakland Bay Crossing, the only practical option was to construct an entirely new structure from Yerba Buena Island to Oakland, a distance of some 3.5km. Most of this could be a straightforward concrete viaduct 2km long and costing more than ú600M, now dubbed the Skyway. But there was still the problem of the shipping channel close to the eastern shore of the island.

On any other crossing the designers would almost certainly have gone for a cable stay design for this section.

However, the crossing to the west of the island, built in 1936, is based on multiple suspension spans which were relatively easy to upgrade. Local residents voted overwhelmingly for the SAS option - but not just because it would blend in with the western crossing.

This would be the world's first single tower SAS structure - and it would be distinctively asymmetrical. It would also be the world's longest span SAS crossing. The end result would be a world famous landmark, one which the residents and legislators of northern Californians would be prepared to pay over the odds for. Southern Californians were less impressed.

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