e-mosty March 2019 Long Span and Multiple Span Bridges | Page 45

MULTIPLE-SPAN SUSPENSION BRIDGES
David Collings
Figure 1: Taizhou Yangtze River Highway Bridge
3
This article provides a brief overview of multi-span
suspension bridges for this issue of e-mosty
magazine.
Multi-span suspension bridges are a form steeped
in history, as many of the early suspension bridges
were multiple span structures 1 .
It is also a re-emerging form with significant
advantages over more conventional very long span
bridges. A form of bridge which I am sure we will
see more examples of in the near future.
The traditional single span suspension bridge has
been used for many of the world’s longest spans;
this arrangement is ideal for a single obstacle of
reasonable size and gives the stiffest suspension
bridge form.
Three span bridges with end spans of 20% to 40%
of the main span can also be used for long spans;
the shorter side spans do not adversely affect the
overall behaviour of the bridge if kept within
reasonable limits.
The recent Ozmangazi Bridge across the Izmit Bay
in Turkey 2 or the current longest span of 1991m of
the Akashi-Kaikyo Bridge completed in 1998 are
good examples of this bridge form.
Other slightly longer conventional bridges such as
Carnake at 2004m are being built.
Longer spans such as the 2700m span Messina
Crossing or bridges over fjords in Norway have
been seriously proposed but not built, they tend to
be very expensive.
If the length of the side spans on these bridges is
greater than 50% of the main span then the bridge
becomes significantly more flexible and starts to
behave as a multi-span structure.
1/2019