Investigation of Large Web Fractures of Welded Steel Plate Girder Bridge
Publication: Journal of Bridge Engineering
Volume 15, Issue 4
Abstract
Constructed in 1972 with ASTM A36 (250 MPa) steel, a highway bridge in Maryland is comprised of seven welded steel plate girders of a constant web depth of 2,286 mm (90 in.). In March 2003, the web fractures of two steel girders were discovered in a three-span continuous superstructure unit. A full-height web fracture occurred in an interior girder at a cross frame connection plate; and a partial-height web fracture occurred in an exterior girder at an intermediate transverse stiffener next to a cross frame. The investigation of the girder fractures involved fracture surface examination, material testing, fracture mechanics analysis, and comprehensive finite-element modeling for fracture driving forces. The fracture mechanics analysis indicated that a brittle web fracture could occur at a high stress level with either a surface crack or a through-thickness crack of certain dimensions. Finite-element analysis using a global model and submodels investigated three possible causes: (1) localized distortion of the unsupported web gap due to the lateral forces of cross frame members; (2) fabrication induced out-of-flatness of the web plate under in-plane loading; and (3) residual stresses at the fracture origin area due to the stiffener-to-web welds. The investigation concluded that one or a combination of these can result in the high local tensile stresses triggering a brittle web fracture with certain crack dimensions at the fracture origin area. Several retrofit concepts were investigated for their effectiveness in reducing stresses in the fracture origin area. Bridge inspections in the subsequent 6 years after the web fractures have not reported any other cracks in the bridge.
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Acknowledgments
The writers would like to express their appreciation for the support and advice they received from the following individuals: Dr. William Wright of the Federal Highway Administration; Mr. Bruce Abernathy of the Metals Laboratory of the Maryland State Highway Administration; and URS colleagues Messrs. Tom Feroli, Nick Deros, and Tom Jenkins (retired).
References
AASHTO. (2002). Standard specifications for highway bridges, 17th Ed., Washington, D.C.
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AASHTO (2007). LRFD bridge design specifications, 3rd Ed., Washington, D.C.
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Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 15 • Issue 4 • July 2010
Pages: 373 - 383
Copyright
© 2010 ASCE.
History
Received: Sep 25, 2008
Accepted: Feb 22, 2010
Published online: Feb 24, 2010
Published in print: Jul 2010
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