The Akashi-Kaikyo Suspension Bridge

The Akashi-Kaikyo Suspension Bridge

1. Cable Suspended Bridges
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Akashi - Kaikyo Bridge
JAPAN
ENG.\ Mahmoud
zaghlal

2. SITE MAP
The Akashi Strait, which connects
Osaka Bay and Harimanada, is about 4
kilometers wide. The segment spanned
by the bridge has a maximum depth of
110 meters and a maximum current
speed of 4.5 meters per second. The
Strait has been a productive fishing area
since ancient times, and is an important
waterway, used by over 1,400 vessels a
day. To ensure the safety of marine
traffic, an international water-way 1,500
meters wide has been set by marine
traffic safety law.
Several severe conditions were
encountered, such as strong currents,
deep water in which divers were unable
to explore the seabed. It was also
necessary to preserve the fishing area
and to ensure the safety of marine traffic.
Those difficulties were conquered
through investigations and technical
examinations .SOIL PROFILE

3. 3 SPAN – 2 HINGED TRUSS
GIRDER

4. The Great Hanshin Earthquake, a great epicentral
earthquake caused by an active fault, measured 8.5
magnitude on the Richter scale at 300km from this point

WATER VELOCITY
MAX RICHTER SCALE
WIND SPEED
PHYSICAL
CONDITIONS

5. (Main Elements)

1-Foundations
2-Two towers
3-Two suspension cables
4-Hangers
5-Deck (Steel or R.C)
6-Four Anchorages

6. SYSTEM RESISTING INTERNAL FORCES

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Foundations
Tower
Crane
Inner
Elevator
DAMPERS
Each tower contains damping
devices to counteract
deflective and torsional
vibration caused by wind.
Weighing about 10 tons each,
20 of the devices are
distributed on the 17th, 18th,
and 21st tiers of the towers.

9. Passive -- This is an uncontrolled damper, which requires no input power to
operate. They are simple and generally low in cost but unable to adapt to
changing needs.
Active -- Active dampers are force generators that actively push on the
structure to counteract a disturbance. They are fully controllable and require
a great deal of power.
Semi-Active -- Combines features of passive and active damping. Rather
than push on the structure they counteract motion with a controlled resistive
force to reduce motion. They are fully controllable yet require little input
power. Unlike active devices they do not have the potential to go out of
control and destabilize the structure. MR fluid dampers are semi-active
devices that change their damping level by varying the amount of current
supplied to an internal electromagnet that controls the flow of MR fluid.
Dampers are used in machines that you likely use every day, including
car suspension systems and clothes washing machines.damping systems
use friction to absorb some of the force from vibrations.A damping system in
a building is much larger and is also designed to absorb the violent shocks
of an earthquake. The size of the dampers depend on the size of the
building. There are three classifications for dampening systems:

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•Depending on the size of the building, there
could be an array of possibly hundreds of
dampers. Each damper would sit on the floor
and be attached to the chevron braces that
are welded into a steel cross beam. As the
building begins to shake, the dampers would
move back and forth to compensate for the
vibration of the shock. When it's magnetized,
the MR fluid increases the amount of force
that the dampers can exert.
•Buildings equipped with MR fluid dampers will mitigate vibrations during an
earthquake.

12. Note: Water Depth 60 m
The foundations of the main towers transmit the 120,000 ton weight of
the bridge from the main towers to the support ground. The support
ground, 60 meters under water, was excavated by grab bucket dredger.
Various high-tech devices, such as the Remotely Operated Vehicle
System, were used to overcome the challenging conditions in the
Strait, including strong currents and deep water, as well as waves that
caused the grab bucket to vibrate during excavation. Ultimately, the
excavation was finished within the vertical variation of +/-10 cm needed
for caisson installation.
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The caissons were installed using the "setting
down method," which entailed manufacturing
the caissons beforehand at a factory, then
towing them to the site, submerging them, and
finally filling them with underwater and
standard concretes. The circular shape of the
caissons has no directional property, and
therefore makes them more stable and easier
to handle in the strong currents of the Strait. A
new type of underwater concrete, "underwater
nondisintegration concrete," was developed for
the foundations.

13. CASTING FOUNDATIONS
UNDER WATER

14. TOWER & HANGERS
AND BRACING SYSTEMS
HANGER
CABLE
TOWER CROSS SECTION
DECK

15. CABLES

16. CABLE
300,000 KM LONG OF WIRES
Each cable is composed of 290 strands, each strand
containing 127 wires made of high tensile galvanized steel
and measuring 5.23 millimeters in diameter. The strands are
hexagonal in shape and factory produced beforehand, in
what is known as the prefabricated strand [PS] method.
One of the biggest technological advances achieved in
constructing the bridge was the improvement in wire
tensile strength. Although prior to construction of this
bridge the wire tensile strength was only 160 kgf/mm2, a
new wire with an increased tensile strength of 180 kgf/mm2
was developed . This slight increase in tensile strength
made it possible to use only one cable per side instead of
two, reducing the weight and making construction easier.
The length of the wire used totals 300,000 kilometers,
enough to circle the earth 7.5 times.

17. WIRES TO STRAND TO CABLE

18. SADDLES OVER TOWERS
SADDLE
CABLE

19. CABLE INSTALLATION
The first stage of cable installation was pilot rope
spanning, which was done by helicopter so as to
avoid the affects of currents or interference with
marine traffic. Using light-weight, high strength
poly-aramid fiber rope measuring 10 mm in
diameter, the pilot rope was installed over each
span in succession.

20. CROSS SECTION IN DECK
PROFILE OF BRIDGE

21. STIFFENING GIRDERS
90,000 tons of steel was used in constructing the
stiffening girders. Due to the tremendous size of the
bridge, the wind load they sustain is greater than that of
any other bridge in existence. Using high tensile strength
steel for the girders made them very strong but relatively
light, and therefore more economical.
The stiffening girder construction, by the plane block
method, began at the main towers and anchorages,
where a floating crane was used to install 6 panel blocks
on the towers, and 8 on anchorages. The truss members
that had been assembled in panel shape at the factory
were transported to the construction site, where they
were erected inwards from the anchorages and from the
towers.

22. * Wind At stiffening girders:
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To reduce stiffening girder torsional vibration caused by wind,
stabilizing plates were installed under the median strip of the
deck. The stabilizers act to guide the wind, reducing torsional
vibration by achieving a balance between pressures on the
bridge lower and upper surfaces. The effect of the stabilizers
was verified in large scale wind tunnel tests. Stiffening Girder
Specifications .
wind

23. wires
cable
saddle

24. ANCHORAGE
DETAILS

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,

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