Civil Engineering Reference
In-Depth Information
Teflon sliding surface
Boot
Outside face of
tunnel
Wire rope assembly
Boot
Teflon sliding
surface
Rubber
gasket
Inside face of
tunnel
Wire rope assembly
US steel shell tunnel joint detail
Cover plate
Steel shell
(outer plate)
Sacrificial anode
Outer bellows
Sliding surface
Outside of
tunnel
End plate
Concrete
Void
Stiffener plates
Void
Inside of tunnel
Steel shell (inner plate)
Sliding surface
Inner bellows
Inner cover plate
Bellows joint detail used in Japan
Figure 10.19
Seismic joints in steel tunnels (sections through walls).
The terminal joint was a complex sliding telescopic joint. The joint holds
the tunnel vertically and horizontally, but allows longitudinal and rotational
movement. Seals are placed around the tunnel to give a watertight seal as the
tunnel element moves in and out of the terminal joint. Enough allowance has
to be made in the movement capability to allow for some creep that is likely
to occur over time with repeated seismic movements. Stops are provided to
prevent excessive movement, which would result in the joint opening.
In 1989, the BART tunnel withstood the earthquake that destroyed
many of San Francisco's bridges. It was inspected and reopened three hours
after the earthquake, and was the only fully operational public transport
system in the area.
