e-mosty June 2017: Osman Gazi B. US Suspension. Hålogaland B. e-mosty June 2017: Suspension Bridges | Page 50

Figure 1: Bay Bridge – Aerial view (left) and suspended spans (right); photos courtesy of MDTA
The Eastbound Bridge was completed in July 1952 and
the Westbound Bridge was completed in June 1973,
just a little over two decades later.
Both of the suspension bridges were designed by the
J.E. Greiner Company, a Maryland based engineering
firm owned today by AECOM through the acquisition
of URS Corporation. Although the bridges are similar
in many ways, there are several distinguishing
features between the two of them.
The Eastbound Bridge carries two lanes of traffic
towards the eastern shore and is comprised of steel
girder, steel truss and suspension spans. When the
bridge was built, it was the world’s longest continuous
over-water steel structure.
The bridge provided a vital link that did not exist at
the time when Marylanders were using a ferry service
to traverse the Bay. After four decades of planning
and under the leadership of Governor William Preston
Lane, Jr., the first bridge was directed to be built.
By the early 1960s, the bridge traffic was near
capacity. It was not long before the second bridge was
commissioned and construction began in May 1969.
The second bridge was constructed 137m north of the
existing crossing and would carry three lanes of
traffic. This bridge would become the Westbound
Bridge carrying traffic from the Eastern Shore of
Maryland to the metropolitan regions of Baltimore
and Washington.
The Westbound Bridge is generally similar in
construction to the Eastbound Bridge with a
combination of steel girder, steel truss, and
suspension spans. However, the suspended spans of
the bridges were slightly different in both the
stiffening truss and main cables.
The eastbound and westbound suspended spans are
each approximately 884m long with a 488m main
span and 198m side spans. The eastbound suspended
spans were supported by a through-truss with
backstays and low-level anchorages; whereas, the
westbound suspended spans were supported by a
deck truss and taller anchorages, allowing the cables
to be anchored at near-deck level without backstays.
In terms of the cables, each was similar in diameter
but constructed differently, including the cable
corrosion protection system.
The Eastbound Bridge used galvanized helical strands
coated with zinc paste, galvanized wrapping wire and
a neoprene overwrap.
In contrast, the Westbound Bridge main cables were
comprised of galvanized prefabricated parallel wire
strands (PPWS) with a neoprene overwrap. The wires
of the Westbound Bridge were compacted and
banded together but no zinc or lead paste or
wrapping wire was used (Figure 2).
Each of the cable types was rather unique for their era
of construction and different than the system first
notably used on wire cables by John A. Roebling for
the Brooklyn Bridge in 1883. This system included
galvanized wire, red lead paste, galvanized wrapping
wire and paint, and became a generally adopted cable
corrosion protection system used around the world.
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