Perfect Project for Steel Grid Decking
William L. Beaumariage, P.E., Project Manager, PENNDOT
Engineering District 12-0; and
Christopher J. Earls, Ph.D., Associate Professor & William
Kepler Whiteford, Faculty Fellow, University of Pittsburgh, Department
of Civil & Environmental Engineering
Beginning in 1988 the University of Pittsburgh, in cooperation
with several grid deck manufacturers from Southwestern Pennsylvania,
has been conducting research into the behavioral aspects of
filled grid bridge decks with the purpose of developing design
procedures that will more fully utilize their considerable potential.
Some two dozen deck panels of various geometries have been tested
for elastic deflections, ultimate strength, and fatigue resistance.
The result of this effort is a body of knowledge that will permit
the predictions of stress, deflection, and resistance to failure
by fatigue or collapse for any filled grid deck geometry under
any vehicular loading.
Mr. Michael H. Dufalla, P.E., District 12-0 Engineer for the
Pennsylvania Department Of Transportation, recently arranged
a collaboration between the Department and Chris Earls, Ph.D.
from the University of Pittsburgh. The existing Meadowcroft
Bridge on state route 4018 near Avella in Washington County,
Pennsylvania was scheduled for replacement and was a perfect
place to use as a test site for this bridge decking. Engineers
from District 12-0 along with staff from the University of Pittsburgh
and Interlocking Deck Systems International, a grid-decking
manufacturer, worked as a team to design, construct and test
the bridge decking.
What is being pursued within the framework of the present research
project is a plan to monitor instrumentation installed on the
Meadow Croft Bridge with the intent of quantifying the nature
of the stress levels present in the deck under field conditions.
In this way, the field measured response of the as-built structure,
under the action of trucks of known weight, can be compared
with full-scale experimental test results obtained from the
testing of life-size mock-ups of the bridge deck system present
in the Meadow Croft Bridge. The full-scale specimens have been
tested in the Watkins-Haggart Structural Engineering Laboratory
at the University of Pittsburghs Main Campus. The experiments
demonstrate the safety and satisfactory performance of the deck
system to be installed in the Meadow Croft Bridge. The field
tests will further support these findings.
Upon completion of this project, the team will demonstrate
the conservatism associated with current design standards and
specifications with regard to applications involving concrete
filled steel grid bridge deck. Safe and economical design recommendations
will be another outcome from this study along with recommendations
for updates to PENNDOT Bridge Design Standards and recommendations
for changes to the AASHTO LRFD Specification.
As a side note, there are only three grid fabricators in the
U.S. and they are all in Southwestern Pennsylvania. The outcome
from this research will pave the way for more efficient utilization
of grid deck in bridges installations around the Nation; thus,
allowing the local grid deck industry to enjoy a greater market
share within the bridge industry.
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