peter rice

Originally conceived to recall a
Japanese style footbridge, this
pedestrian bridge spans l OOm
between buildings on either side of a
busy main rood at Lo Defense, Paris.
The structure is steel with a precost
concrete deck covered by a 3m high
glazed walkway. Taking into account
the inability of the supporting building
to take significant horizontal thrust,
the bridge is designed as a tied arch.
The main arches ore 900mm
fabricated triangular sections, and the
tendons 200 mm diameter solid bars.
Arches and tendons follow parabolic
curves modified to take account of the
real self weight distribution so as to
minimise arch bending under dead
load. Whilst the bridge is highly
stable against uniform vertical load,
the presence of the glazed walkway
gives rise to high wind loads which
load the bridge laterally and in
torsion about its axis. The lateral
loads ore token simply by the braced
plane between the tendons, and the
torsion transmitted via action of the
two arch-tendon planes.
originally envisaged as cost pieces.
For ease of erection the contractor
chose the solution of forged 'deminodes',
threaded onto the tendons
and bolted together on site. The use
of such high steel thicknesses for such
critical tension elements led to the
specification of very high notch
toughnesses for the steel to ovoid
potential problems of brittle fracture.
The principal nodes, which form the
connection between tendons, hangers
and deck support structure, were
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