Gulph Creek Stone Arch Bridge - Delaware Department of ...

Chapter 3—Historic Context for Common Historic Bridge Types
3.3.5 Reinforced Concrete Girders
History and Description: The first reinforced concrete girder bridge was built in
France about 1893, and the first of the type constructed in the United States appeared in
the first decade of the twentieth century. In the 1910s, several of the early state highway
departments issued standardized plans for concrete girder bridges. In 1912, Maryland’s
State Roads Commission included a design for a girder bridge in their state’s first
standard bridge plans.
Although the through girder was common from the 1910s to the 1930s, the type is
best suited to short spans from 15 to 40 feet and was not economical for wide roadways
of more than about 24 feet. Concrete through girder bridges gradually gave way to deck
girder designs, as the need for wider roadways increased and concerns about traffic safety
rose in the 1930s. In many parts of the country during the 1940s, the use of concrete
girders faded in favor of steel I-beam and pre-cast concrete spans due in part to the cost
of scaffolding and formwork. But, many of the concrete girder bridges still in service are
deck girder bridges built in the 1940s.
Precast reinforced concrete girders were used on a few projects to widen existing
cast-in-place concrete girder spans. Another form of the concrete girder is the continuous
reinforced concrete girder. These began being used by highway departments in the
1950s, pushing span lengths upward to between 50 and 80 feet. This type of structure
was not used after the late 1960s because of the complication of falsework and forms,
which increased costs and, usually, increased construction time.
According to the FHWA Bridge Inspector’s Reference Manual (23, p. 7.3.1),
reinforced concrete girder bridges (non-prestressed) generally consist of cast-in-place,
monolithic decks and girder systems. The primary members of a girder bridge are the
girders, the deck, and, in some cases, floorbeams. The deck or travel surface is cast on
top of the girders in deck girder bridges, and the deck is cast between the girders in
through girder bridges. In either case, the deck slab does not contribute to the strength of
the girders and only serves to distribute live loads to the girders. If floorbeams are used,
they are part of the superstructure and not the deck. In through girder bridges, the deck is
cast between the girders and the girders extend above the deck, thus forming the bridge’s
parapets. This arrangement of members makes it virtually impossible to widen a through
girder bridge. Most of these bridges have now been replaced because their roadway
widths were too restrictive for the safety of modern traffic.
A good example of a simple-span concrete through girder bridge from the 1920s
is the Main Street-Black River Bridge (1923) in Ramsey, Michigan. This bridge is a
three-span configuration, with a 50-foot girder above the waterway and 40-foot girders
on either end of the central span. The Michigan State Highway Department first adopted
a standard design for concrete through girder bridges in the 1913-1914 biennium.
Generally used for span lengths of 30 to 40 feet, this design featured a very shallow floor
system that provided a maximum clearance above waterways. The Main Street-Black
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