THE SINGAPORE ENGINEER - Institution of Engineers Singapore

CIVIL & STRUCTURAL ENGINEERING
Punggol Walk Vehicular Bridge under construction.
Typical stress bar details.
Construction sequence for the vehicular bridge.
Construction of box girder (top) and installation of post-tensioning system (bottom).
Completed Punggol Walk Vehicular Bridge.
the vehicular bridge at every hanger. The hanger system for the
footbridge has been designed to allow for replacement of any
one of the hanger rods. Due to the arch, there is an outward
force at the base of the arch and a pre-stressed tie beam has
been introduced at the deck level in the plane of the arch. The
complete stage-by-stage construction sequence was set up in
the analysis model to capture correctly the stress history in the
structural elements from construction to completion.
In consideration of future maintenance issues, corrosion-resistant
Macalloy stainless steel stress bars (50 mm diameter), were chosen
for the Iconic Bridge. These were imported from the UK.
In consideration of the aesthetics of the bridge, the stainless
steel stress bars have been encased in 200 mm diameter
stainless steel pipes, to conceal the stress bars between the
external face of the concrete arch and the footbridge structure.
A small diameter cast-in conduit within the concrete arch and
footbridge structure facilitated the installation of each stress bar.
In order to ensure that the stress bar can be installed without
any obstruction, great emphasis was placed on the accuracy of
the alignment of the cast-in conduit, as every stress bar has a
different inclination. In addition, the allowable gap between the
stress bar and cast-in conduit was kept to a minimum.
The diameter of the concrete arch is 1.5 m and it stands
approximately 25 m above the promenade level. In order to
plot out the exact alignment of the arch, a 3D programme was
used to calculate the individual coordinates at 1 m apart and
a similar programme was also used to design the temporary
staging supporting this unique shape of the arch.
PUNGGOL WAY VEHICULAR BRIDGE
The construction of the Punggol Way Vehicular Bridge was
another challenge. As the waterway intersects the existing
Punggol Way and the LRT structures, it was necessary to realign
Punggol Way with part of it becoming a vehicular bridge to
overcross the waterway.
30 THE SINGAPORE ENGINEER April 2012