Joe Cool wrote:
On Jan 8, 2:52*pm, Joe Cool wrote:
On Jan 7, 5:13*pm, Jon Anderson wrote:
On 1/7/2011 6:28 AM, Randy wrote:

Seems like the old way is better.

Well as per the video, the suspension bridge is self anchored, not
anchored to shore. Maybe that has something to do with seismic issues,
designing to survive "the Big One"...

I almost always take the Benicia-Martinez that crosses the Carquinez
Straight when returning from the SF Bay Area. It's also being replaced
and I've seen that crane fairly close as I drove past. It is MASSIVE!

Technically that new bridge is NOT a suspension bridge, but a cable-
stayed bridge.

As far as I can tell from the video there are no suspension cable
catenary; *all cables from the towers go directly to the road deck.
Hence cable-stayed. *There are quite a few bridges of this type in the
USA and the world.

To carry on: This type of bridge can and has been built without the
"support bridge" to hold it up. I seem to recall that a similar
bridge was built some years ago across the Mississippi River without
support steel; but I could be mistaken.

To do so the towers are built first (as usual) and the road bed
sections cantilevered out from each side of the tower while supported
in position by a crane. At this point the cable stay for that section
is installed on each side of the tower to keep things in balance. The
crane is then moved to hoist the next section into position. Rinse and
repeat as required.

Why the constructors chose to go with this "auxiliary bridge" routine
one can only guess at.

If anyone here knows of the reasons for this construction methodology
I'd be pleased if it is pointed out here.

Union labor, on the taxpayer dime.

Cheers!
Rich