Proceedings of Bridge Engineering 2 Conference 2007
27 April 2007, University of Bath, Bath, UK
THE BRIDGE ENGINEERING 2 CONFERENCE
AKASHI BRIDGE
Wai Tak Yim
1
1
University of Bath Civil Engineering
Abstract: The aim of this conference paper is to analyse the Akashi Bridge. This analysis procedure will
generally include considerations of aesthetics, loading, strength, serviceability, construction, temperature,
creep, wind, durability, susceptibility to intentional damage, and possible future changes which the bridge
might have to undergo. All aspects above will be critically examined in the context of how the design and/or
construction of the bridge could have been improved.
Keywords: Akashi-Kaikyo Bridge, Suspension bridge, Laying down caisson method, Truss stiffening girder system,
Tuned mass damper, Dry air injection system
1
General
Introduction
1.1
Background of the bridge
The Akashi-Kaikyo Bridge, also known as pearl
bridge, is a suspension bridge in Japan that crosses the
Akashi Strait, it links Maiko in Kobe and Lwaya on Awaji
Island as part of the Honshu-Shikoku Highway.
1.2
The reason to build Akashi-Kaikyo Bridge
Before the Akashi-Kaikyo Bridge was built, ferries
carried passengers across the Akashi Strait in Japan. This
dangerous waterway often experiences severe storms, and
in 1955, two ferries sank in the strait during storm, killing
168 children. The ensuring shock and public outrage
convinced the Japanese government to draw up plans for a
suspension bridge to cross the strait. The original plan was
for a mixed railway-road bridge but when the bridge was
begun in April 1986, it was restricted to road only, with
six lanes. Actual construction did not begin until May
1988, and the bridge was opened for traffic on April 5,
1998. The Akashi Strait is an international waterway and
required a 1500 meters wide shipping lane. Ref [1]
1.3
The spans length of the bridge
The bridge has three spans. The central span is 1991
meters, with the two other sections each 960 meters. The
bridge is 3911 meters long overall. The central span was
originally only 1909 meters but was stretched by a further
meter in the Kobe earthquake on January 17, 19995. The
earthquake moved the main towers of the bridge
approximately 0.8 meters apart as well as shifting them
horizontally and causing one to sink and the other one to
rise by a small amount. Fortunately the stiffening girder
had yet to be erected. Without the girder in place, the
structure was lighter and more flexible to take the
movements.
It is the longest suspension bridge in the world to
date, as measured by the length of its center span 1991
meters, substantially longer than the second longest
suspension bridge, the Danish Great Belt Bridge. Total
length is 3911 meters. Ref [2]
2
Designs and Construction
2.1
Main design conditions
There were six main design conditions for the
Akashi-Kaikyo Bridge:
1. The width of the straits is about 4 km, and its depth
along the proposed bridge route reaches about 110m.
2. The natural conditions are: The water depth at the
main pier site is 45m, maximum tidal current of 4.0 m/s
and maximum wave height of 9.4m
3. The wind conditions are: basic wind speed for
design was 46m/s which was defined as 10 minutes
averaged speed at 10m above the water level with the
return period of 150 years and with a reference wind
speed against flutter of 78 m/s
4. The geological conditions are: The base rock
beneath the straits is granite, on which Kobe Formation
(alternating layers of sand stone and mud-stone in the
Miocene), Akashi formation (semi consolidated sane and
