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WHY
USE AN EXODERMIC™ BRIDGE DECK?
LIGHT WEIGHT
An Exodermic™ deck typically weighs 35% to 50% less than a reinforced
concrete deck that would be specified for the same span. Reducing
the deadload on a structure can often mean increasing the liveload
rating. The efficient use of materials in an Exodermic™ deck means
the deck can be much lighter without sacrificing strength, stiffness,
ride quality, or expected life. Further weight reductions are
possible using a lightweight concrete mix.
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A lightweight Exodermic™
deck allowed the famous Eads Bridge over the Mississippi in St
Louis
to achieve an HS-20 load rating. |
RAPID CONSTRUCTION
Precast Exodermic™ decks can be erected during a short, nighttime work window,
allowing a bridge to be kept fully open to traffic during the busy daytime hours.
Cast-in-place Exodermic™ decks also permit considerable savings in construction
time – the steel grid panels come to the site essentially ready for concrete.
The steel grid component of an Exodermic™ deck acts as a pre-cut, pre-formed,
stay-in-place form. Panels are quickly placed, and layout of the single mat
of rebar is simple and straightforward, without the need for chairs or other
aids
in most cases. Cantilevered decks can be formed without temporary supports.
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Precast Exodermic™ panels allowed
250,000 s.f. of the Tappan Zee Bridge to be redecked working only
at night; all seven lanes were open from 6am to 8pm, with only 3 of
7 lanes out of service at night. |
EASE OF MAINTENANCE
An Exodermic™ deck is easily maintained with standard materials and
techniques, since the top portion of an Exodermic™ deck is essentially
the same as the top
half of a standard reinforced concrete deck. If desired, any overlay compatible
with concrete can be used, including latex modified concrete, polymer concrete,
microsilica concrete, or a membrane with asphaltic concrete overlay.
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The Exodermic™ deck on the 17th Street
Causeway Bridge in Ft. Lauderdale spans over 14 feet floor beam to
floor beam (without stringers). The deck is composite with the floor
beams and the top flanges of the main bascule girders, adding significantly
to their structural capacity. |
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OVERALL
DESIGN EFFICIENCY
An Exodermic™ deck adds substantially to the capacity
of beams with which it is composite. On the 17th Street Causeway
Bridge in Ft. Lauderdale, for example, the main bars of the
grid portion of the Exodermic™ deck are oriented parallel to traffic.
The deck was made composite with the main box girder top
flanges and the floor beams (no stringers were used). The substantial
steel in the grid and the top reinforcing in the concrete slab
added the equivalent of 3 1/2-inches of steel to the top flanges
of the main girders.
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