Construction of a Virginia Short-Span Bridge with the Strongwell 36-Inch Double-Web I-Beam
Cousins, Thomas E.
Lesko, John J.
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The Route 601 Bridge in Sugar Grove, VA, spans 39 ft over Dickey Creek. The bridge is the first to use the Strongwell 36-in-deep fiber-reinforced polymer (FRP) double-web beam (DWB) in a vehicular bridge superstructure. Construction of the new bridge was completed in October 2001, and field testing was undertaken shortly thereafter as well as in June of 2002 to assess any potential changes in structural performance. This paper details the field evaluation of the Route 601 Bridge. Using midspan deflection and strain data from the October 2001 and June 2002 field tests, AASHTO bridge design parameters were determined, namely wheel load distribution factor g, dynamic load allowance IM, and maximum deflection. The wheel load distribution factor was determined to be S/4, a dynamic load allowance was determined to be 0.50, and the maximum deflection of the bridge was L/1110. Deflection results were lower than the AASHTO L/800 limit. This discrepancy is attributed to partial composite action of the deck-to-girder connections, bearing restraint at the supports, and contribution of guardrail stiffness. It was found that diaphragm removal had a small effect on the wheel load distribution factor. An examination of the 36-in DWB capacity and failure mode indicates that the strength of the girder is controlled by compression failure in the flange and not shear failure, as originally thought. An attempt to predict the girder fatigue performance shows that small losses in bending stiffness would be expected at fatigue loads 26% of the ultimate capacity, which was confirmed through experiments. Moreover, there is no concern that fatigue alone will cause a failure during the reasonable life of the structure as presently operated.