HIGHWAY IMPROVEMENTS DRIVE UH ENGINEERING
EFFORTS IN BRIDGE DESIGN
Researchers Work to Increase Efficiency and Economy of Texas Bridges
HOUSTON, Aug. 2, 2005 – A way to build steel bridges cheaper
and quicker has been developed by engineers at the University
of Houston.
Associate Professor Todd Helwig and Assistant Professor
Reagan Herman, both in the Department of Civil and Environmental
Engineering at UH’s Cullen College of Engineering, collaborated
on a project to develop new, more effective and less expensive
bridge construction methodology. Helwig and Herman were awarded
a Top Research Innovation award from the Texas Department of Transportation
(TxDOT). Each year, TxDOT selects top research innovations based
on anticipated or already realized dividends to TxDOT and the
state. These dividends may be in terms of saved lives, more efficient
operations, improved services or financial savings. In addition
to the recognition of this research by TxDOT, a paper written
by Ozgur Egilmez, a graduate research assistant on the project,
earned Helwig and Herman the Vinnakota Award from the Structural
Stability Research Council (SSRC).
“The main drive for the project was to achieve better economy
during both construction and over the life of steel I-girder bridges,”
Herman said. “The results of the research study, which enable
utilization of permanent metal deck forms for bracing, will facilitate
easier bridge inspections and generate fewer ongoing maintenance
concerns.”
Laboratory tests were conducted in the UH Department of Civil
and Environmental Engineering Structural Research Laboratory,
with full-scale experimental investigations conducted with a variety
of girder cross sections and bracing layouts utilizing a 50-foot
long test setup. The research work will be put into practice this
fall in the construction of bridges used in the renovation of
the Fulton and Irvington overpasses on Loop 610 in north Houston.
The current overpass bridges will be removed, and metal deck forms
will be used for bracing in the construction of the replacement
bridges. Construction of the implementation bridges will be monitored
by UH.
Addressing not just bridges in the city of Houston, but those
across the state of Texas, the research idea came from initial
collaborations between Helwig, Herman and TxDOT engineers. The
key with this work is that the research enables an existing bridge
element – metal deck forms – to be used to brace the
bridge girders during construction. The research work has generated
a modified connection detail that enables the deck forms currently
being used to do double duty as both a form for the wet concrete
deck and a brace to the steel bridge girders.
In the past, design engineers typically have used cross frames
to brace bridge girders during construction. Cross frames are
conventional bracing systems that are used to prevent twist of
a bridge’s girder cross section and are specifically used
on the bridge to maintain stability of the bridge girders during
construction. According to Helwig, this type of framing is expensive
and there can be long-term problems associated with their use,
such as fatigue and added cost and length of inspections throughout
the life of the bridge. Cross frames also are expensive to fabricate
and require heavy machinery to install.
The UH research proposes that permanent metal deck
forms that are already used in bridge construction to hold the
wet concrete in place as it cures can be used for stability bracing,
thereby eliminating a number of cross frames from the bridge.
By using an element of the bridge that is already in place, the
cost of these bridges is lowered significantly, without reducing
their stability.
While cross frames will still be required at all support locations
and some intermediate locations, using the permanent metal deck
forms for bracing will allow elimination of approximately half
of all intermediate cross frames. Although permanent metal deck
forms are currently used in the bridge industry to hold the weight
of the wet concrete deck during construction, they are not currently
relied upon for bracing. The connection details developed at UH
allow the metal deck forms to be used to provide bracing for the
bridge girders, thus lessening the demand for cross frames on
the bridge.
“This simple method can dramatically improve
the bracing,” Helwig said. “The implementation project
on Loop 610 where TxDOT is using metal deck forms as bracing is
the first time they’ve been relied on and have eliminated
340 cross frames on the implementation bridges, saving more than
$200,000. One application of this work has almost paid for the
research, so it’s been money well spent.”
About the University of Houston
The University of Houston, Texas’ premier metropolitan research
and teaching institution, is home to more than 40 research centers
and institutes and sponsors more than 300 partnerships with corporate,
civic and governmental entities. UH, the most diverse research
university in the country, stands at the forefront of education,
research and service with more than 35,000 students.
About the Cullen College of Engineering
UH Cullen College of Engineering has produced five U.S. astronauts,
ten members of the National Academy of Engineering, and degree
programs that have ranked in the top ten nationally. With more
than 2,600 students, the college offers accredited undergraduate
and graduate degrees in biomedical, chemical, civil and environmental,
electrical and computer, industrial, and mechanical engineering.
It also offers specialized programs in aerospace, materials, petroleum
engineering and telecommunications.
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