e-mosty December 2018 e-mosty December 2018 | Page 37

Figures 2 and 3: Location of the bridge
Source: Maps Google(Left) and OpenStreetMap © OpenStreetMap contributors
https://www.openstreetmap.org/way/206031539#map=14/-37.7500/144.8437
INTRODUCTION
Modern transport demands on bridges continue to
increase.
By their very nature, bridges are often highly utilised
structures located at key points in a transport net-
work.
There is rarely excess capacity, or convenient alterna-
tive routes, and so users come to depend upon the
operation of these highly critical pieces of infrastruc-
ture 24 hours a day, 365 days a year.
Because of this dependence, maintenance periods are
short, and the consequences of over-running works
are severe in terms of disruption and financial penal-
ties imposed.
theless, the anticipated future loads were exceeded,
and constraints within the existing structure de-
manded innovation and alternative approaches to
successfully realise the widened design.
EJ WHITTEN BRIDGE
The EJ Whitten Bridge (formerly named Maribyrnong
Bridge) is a twin post-tensioned prestressed concrete
box girder viaduct that forms part of the M80 Ring
Road around Melbourne, Australia.
The viaducts cross the Maribyrnong River Valley and
are composed of ten spans with a total viaduct length
of 520m.
Historically, the design of bridges has not fully antici-
pated or catered for this level of high service demand,
and unfortunately, we see shortcomings being ruth-
lessly exposed when designers have not anticipated
the future well enough. In addition to longitudinal post-tensioning of the gird-
ers, the concrete box girder decks are also trans-
versely prestressed, with the tendons running from
cantilever tip to cantilever tip, typically at 3.6m inter-
vals.
This article looks at EJ Whitten, a comparatively re-
cent bridge, to review how it has been adapted to
meet current demands, and the innovation needed to
enable this. Lessons are then drawn on how designers
and owners can better future-proof their bridges. HISTORY OF THE BRIDGE
This major viaduct structure has recently been modi-
fied to carry additional lanes of traffic. Unusually for a
bridge structure, some provision had been made at
the time of original design for future widening. Never-
During the original design and construction on the
bridge in the early 1990s, provision was made for
future widening through infilling the central reserve
gap between the two viaduct structures.
The concept incorporated a third concrete box girder,
supported on a concrete crosshead beam between
existing piers (Figure 4).
4/2018