On Jan 9, 9:54*am, Robert Roland wrote:
On Sat, 8 Jan 2011 15:47:13 -0800 (PST), Joe Cool

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

Not quite. It is a sort of a hybrid between the classic suspension
bridge and the cable stayed bridge. If you look closely at the
pictures, you can see that all cables except the outer ones attach to
the outer cable. Here is a picture of another such bridge, where the
cable are clearly visible:

http://www.newsworld.co.kr/cont/0207/50.html

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.

The tallest bridge in the world, the Millau Viaduct, is a cable stayed
bridge. It was built using support towers between the actual towers,
but no support bridge.

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.

In the case of the Millau Viaduct, the road sections were slid in
place using a hydraulically operated wedge system, sliding on Teflon
bearings. This is probably why the intermediate support towers were
necessary.
--
RoRo


After having another look at the OP video on a large screen, I concur
that it is indeed a true suspension bridge that is being constructed.

Nonetheless, I still question the need for the "auxiliary" bridge to
support the road deck. Perhaps it is for scheduling reasons ie. it
permits faster erection with less impediment of the shipping channel.
Or perhaps the tides and/or currents are too great for the stability
of the free-floating crane.... Just conjecture I agree.

The first large-scale suspension bridge is the Brooklyn Bridge in New
York, built in the 1880's now over 120 years old! This bridge was
erected without an "auxiliary" bridge. The construction of this
bridge is an interesting story in itself. Compare this bridge to the
Tacoma Narrows Bridge!

Wolfgang