Fatigue Strength Upgrading of Cover Plate Ends by Welded Extensions in Existing Steel Bridge Girders
Publication: Journal of Bridge Engineering
Volume 23, Issue 7
Abstract
This paper investigates the fatigue upgrading of typical cover plate joint connections in existing steel bridge girders through cover plate extension. The upgraded detail is created by removing the existing transverse end weld, then welding the extension to the existing cover plate with the underlying plate acting as backing. The extended cover plate should end in a zone of low stress variation. The fatigue resistance of this detail is investigated by means of scaled specimen and beam testing as well as a corroborating detailed finite-element parametric study. The different potential crack initiation sites as well as the three-dimensional effects due to the presence of longitudinal welds are considered. It is found that, depending on the exact geometry of the joint, cracks may initiate either from the weld toe or the weld root. A classification of the joint in appropriate detail categories is proposed. Depending on the thicknesses of the cover plate extension, the existing cover plate, and the underlying plate, the detail category may vary between FAT 50 (or E') and FAT 80 (or D) according to standard classifications.
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Acknowledgments
This research project was financed by the Swiss Federal Railways (CFF SA). The authors wish to thank CFF SA engineers Alexandre Michon and Jean-Jacques Reber for the fruitful discussions and practical propositions made during the course of this research project as well as the experimental report drafting. They also wish to thank Martina Paronesso for her help in the final preparation of the paper. Financial support was also provided by École Polytechnique Fédérale de Lausanne (EPFL) for the completion of the finite-element studies discussed in the paper. Any opinions, findings, and conclusions or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of sponsors.
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© 2018 American Society of Civil Engineers.
History
Received: Jan 26, 2017
Accepted: Nov 10, 2017
Published online: Apr 23, 2018
Published in print: Jul 1, 2018
Discussion open until: Sep 23, 2018
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