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 (http://www.pitt.edu/~cjearls/lab.html) at the University of Pittsburgh’s 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.