Orthotropic steel decks, directly subjected to traffic loads in road bridges, are very sensitive to fatigue: in most cases, fatigue defects appear as fatigue cracks, which affect top plates, longitudinal ribs and cross-beams of the deck. The main causes of fatigue in steel decks are inappropriate structural details adopted, welding defects included at the time of fabrication, unforeseen stresses and deformations at the joints. The case study examined in this paper regards an Italian highway bridge, built in 1992, and located on the "Milan- Venice" A4 highway. It has an orthotropic steel structure, composed by two separated box girder decks with three spans, for a total length of 152m, the central one being 70m long. The trapezoidal steel boxes have a constant height, about 3.50m. Recent inspections revealed that the deck is affected by a diffuse cracking in the top plate and longitudinal ribs. A monitoring system was therefore installed by positioning 56 straingauges along one of the steel decks of the bridge. The results of the monitoring campaign are presented herein, evidencing the deficiencies of the original design and detailing for fatigue effects.
Fatigue cracks in orthotropic plates - A case study
TECCHIO, GIOVANNI;CALDON, MAURO;MARCHESINI, FABIO PIETRO;ZANINI, MARIANO ANGELO;DONA', MARCO;PELLEGRINO, CARLO;MODENA, CLAUDIO
2014
Abstract
Orthotropic steel decks, directly subjected to traffic loads in road bridges, are very sensitive to fatigue: in most cases, fatigue defects appear as fatigue cracks, which affect top plates, longitudinal ribs and cross-beams of the deck. The main causes of fatigue in steel decks are inappropriate structural details adopted, welding defects included at the time of fabrication, unforeseen stresses and deformations at the joints. The case study examined in this paper regards an Italian highway bridge, built in 1992, and located on the "Milan- Venice" A4 highway. It has an orthotropic steel structure, composed by two separated box girder decks with three spans, for a total length of 152m, the central one being 70m long. The trapezoidal steel boxes have a constant height, about 3.50m. Recent inspections revealed that the deck is affected by a diffuse cracking in the top plate and longitudinal ribs. A monitoring system was therefore installed by positioning 56 straingauges along one of the steel decks of the bridge. The results of the monitoring campaign are presented herein, evidencing the deficiencies of the original design and detailing for fatigue effects.
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