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[lepidopteran]

In the United States, how many new suspension bridges have been built since the Verrazano opened in 1964?

Except for the twinning of the Delaware Memorial and Chesapeake Bay bridges, I'm not aware of any.  It seems like most new longer spans prefer the cable-stayed model.

So it appears that the engineers have decided, for whatever reasons (economic and practical) that suspension bridges are only to be built for especially long spans.  And the Verrazano remains the longest single-span in the Western Hemisphere (corrections welcome).  Other suspension bridges have since been built in other parts of the world, but most if not all have longer spans than the Verrazano, starting with the UK's Humber Bridge in 1981.

If New York's East River were being spanned today, the Williamsburg and Manhattan Bridges would probably be cable-stayed.  I would say the same thing about the George Washington, but -- can a cable-stayed bridge handle 2 decks of traffic?  Twin spans seem to be the preference where there's heavy traffic demand.  Note: there is a double-decked, cable-stayed candidate for the Brent Spence Bridge replacement (I-71/I-75 between Cincinnati and Kentucky, Ohio River), but that is just a concept drawing.

[Duke87]

What happened is that:

1) advances in construction technology made it a lot easier to build cable stay bridges than it used to be
2) increases in the prices of steel and concrete made the cable stay design more attractive because it requires less material than suspension or cantilever bridges do.
3) the new Sunshine Skyway Bridge made everyone go ooh and ah and suddenly it became the trendy thing.


As for the question of new suspension bridges built since 1964, the Dent Bridge in Idaho opened in 1971. This does however appear to be the newest one in the US that isn't a replacement or twinning of an older suspension bridge.

[SteveG1988]

2003 for New Carquinez Bridge could have been built as a cable stay bridge, but was built as a suspension bridge. Twinning a cantilever bridge and replacing one too

The new Eastern Span of the Oakland Bay Bridge is a single tower suspension bridge. Replacement for a cantilever.

A bridge design is a tool, you use the right tool for the right job. For example in the 40s up to the 70s it was the going design to build arched truss bridges that have suspended sections. The Belle Vernon Bridge, the NJ Turnpike Connector bridge, the Bridge of the Americas in panama, etc. Now all of them would be cable stay. At the time they were the best tool for the job. Now the best tool for the job is a concrete cable stay bridge if it is a shorter crossing. For long crossings a suspension bridge is the best tool.

[triplemultiplex]

The US has ran out of places that need suspension bridges.  We've already accomplished all of our Golden Gates and Mackinacs and Verrazanos.

[Rothman]

<.<

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Oyster Bay - Rye!

*ducks and runs*

[Duke87]

On that note, though, it's also worth looking at how many new large bridges have been built in the US since the 1960s.

Currently the Verrazano (1964) is the newest major bridge in the NYC metro area. The new Tappan Zee will soon take that title (and subsequently lose it to the new Kosciuszko and/or Goethals), but only if you count new bridges that directly replace old bridges by the age of the current structure.

There certainly are major bridges that have been built in the past 50 years which are in locations where there was no bridge previously, but they are not nearly as numerous in the US as bridges that are older. There's a lot more red tape in the way of construction now than there was then, and it's grown more expensive such that we can't afford as much of it as we used to.

[Bruce]

The new Tacoma Narrows Bridge (2007) is probably the newest major suspension bridge in the country. It, along with the New Carquinez Bridge (2003) in California, are the only suspension bridges longer than 500 meters (at the main span) built in the U.S. since the 1960s.

[cl94]

<.<

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Oyster Bay - Rye!

*ducks and runs*

I think it'll be built eventually, but probably as a tunnel or combination. Less impact to the rich bastards on the LI side. Seems to be bigger now than it was at any time in the past.