e-mosty December 2018 e-mosty December 2018 | Page 15

SUNGAI PRAI BRIDGE, BUTTERWORTH, MALAYSIA
As a designer I am guided by my mantra of the ‘3-Es’ –
Economy, Efficiency and Elegance. An example of this
approach is my design for the Sungai Prai Bridge in
Butterworth, Malaysia, which was awarded the
Institution of Structural Engineers (UK) Supreme
Award with the judges’ citation:
‘The Sungai Prai Bridge is an excellent example of
structural engineering, and bridge engineering in
particular. And it is a superb example of bridge
engineering at its most effective and imaginative - a
landmark structure for the 21 st Century’.
This is a relatively conventional project of 3km of dual
3 lane road viaduct with a 185m main span river
crossing.
It is an example of my work that brings high quality
design and finish to an urban structure not just to a
‘signature’ set piece project.
As such it reflects my consistent approach to
engineering quality.
The complexity of the project came from the location,
geometry of multiple ramps and integration of ramps
into the main line.
It formed an alternative design and hence my focus
was about capital cost as well as whole life-cost and
construction.
But as these are fundamentally linked I brought a
clarity of thought at an early stage that gave benefit
overall.
Figure 21: Sungai Prai Bridge Main Span
4/2018
I devised a concept that showed ease of construction
with uniform deck depth, standardized elements
giving elegance in that environment.
The bridge is an example of my use of concrete as a
mouldable material. I utilised my understanding of
how concrete elements are formed to allow changes
of geometry creating a deck family that had the same
base form for all the different elements in the bridge
from ramps to main line to cable stayed span by
simple variations such as moving stop ends.
This is part of my fundamental approach to holistic
concept design with all the structure being developed
together not a focus on a main bridge with ramps as
afterthought.
On the main span, my design solution was the
interaction of the 3-E’s: I replaced the reference
scheme twin deck by single deck with multi-cellular
box with side cantilevers.
The 185m main span is carried by a single tower using
saddles at a time when they were not in vogue. This
avoided need for access in the tower and hence
produced slender towers and narrower deck.
My concept embodied elements of safe construction
and operation:
 Cable anchorages within the deck cell made
for safe stressing and easier longer term
maintenance;
 Pier diaphragms designed as split into two to
allow construction with an unmodified
launching girder;
 Side cantilevers allowed a straightforward
route to accommodate varying deck width;
 Side spans built to the tower by launching
girder so that main span erection only from
deck – requiring no work in the river even for
barges (hence a safe method, with no
disruption to marine traffic, and being less
wind sensitive – less construction down time,
and
 Low maintenance – integral deck and towers
only bearings at junction with approach spans
and where piers are short at ramps.