University of Wisconsin will develop and assist in the design
of a modified concrete deck and girder system for a major bridge
structure. This new technology includes a steel-free deck system.
The corrosion of steel reinforcement in conventional deck systems
is the main cause of deterioration of deck slabs. Initial construction
cost is lower without steel reinforcement and life cycle cost
is reduced because of replacement of deteriorated deck is not
required. This project is part of a bridge replacement and widening
project on Dane County Highway BB over Interstate Highway 39/90
in Madison, WI. The existing two lane, four span slab type bridge
will replaced with a four lane, two span bridge using a concrete
deck on precast concrete girders. The new bridge will also include
two bike lanes and sidewalks. The new spans will be 115 and 125
feet with a bridge width of 82.5 feet. The total deck area will
be 19,800 square feet. Construction of the bridge is planned to
begin in spring 2006.
The replacement bridge will be built using new deck design technology
with innovative materials. This new technology includes a steel-free
deck system. Steel reinforcement in conventional deck systems
are the main cause of deterioration of deck slabs subjected to
deicing salts or exposed to the environment. Steel reinforcement
will be totally removed in the new deck system and the girders
of the bridge will be tied together to provide lateral constraint,
which compensates for the lack of steel reinforcement. New materials
such as fiber added to the concrete mix, fiber reinforced polymer
(FRP) reinforcing bars or FRP grid will be also used for temperature
and shrinkage crack control.
new technology addresses numerous themes of the Innovative Bridge
Research and Construction Program:
Rapid construction - improving construction speed while reducing
construction labor by eliminating placing and tying of two layers
of steel reinforcing in the deck; reduced construction time
should improve construction safety
Innovative materials - combining innovative material including
new efficient prestressed girders, high performance concrete,
a single layer FRP reinforcing grid and FRP stay-in-place formwork
will create a new system
Reduction of maintenance and life cycle costs - eliminating
maintenance due to corrosion prone steel reinforcing and reducing
initial construction cost will reduce life cycle cost
Shallow superstructure and longer spans - eliminating the conventional
deck forming system and using a thinner deck with membrane action
to resist wheel loads will reduce superstructure depth, will
substantially reduce the structural dead load and allows higher
love load capacity and will allow longer span applications.
half-scale specimen of the bridge superstructure was constructed
and tested in the Wisconsin Structures and Materials Testing Lab
(WSMTL) to verify the adequacy of the new deck system. The specimen
was inverted, i.e. up-side-down, for the convenience of the test.
first series of test focused on a deck span with #2 glass fiber
reinforced polymer (GFRP) bars as reinforcing to provide flexural
crack control. The deck was tested on 54W girders with 8 foot
center to center spacing. A single wheel load was applied in the
test and the peak deck capacity was approximately 180 kips which
provides safety factor of more than 11 against structural failure
due to wheel load.
failure and peak capacity was reached as a punching shear failure
occurred. The UW will continue the specimen testing in WSMTL to
finalize the design technology and concept of the new deck system.
The completed structure will also be monitored in order to evaluate
the in place performance of the structural system.