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Steel bridge in Japan.
The fatigue cracks were found at butt weldings of trough ribs. These cracks were found after 20 years service.
The outline of the bridge structure is as follows.
- Bridge length : 418.0m
- Span length :86.550m+3×87.000m+69.550m
- Structure : box girder bridge with orthotropic deck system
- thickness of deck plate : unknown
Side view,plane view and cross section view of the bridge are shown in Fig.1.
Fluctuating loads due to vehicles live load.
These cracks propagated from the boxing welded joints at the upper end of vertical stiffeners to web plates of end diaphragm(Fig.2).
Cause of fatigue cracks was as follows:
- Out-of-plane bending stress repetition which resulted from girder action and bridge vibration.
Stop holes (φ=24.5mm) were drilled at the crack tips.
Masui et al,A study on The Fatigue Crack at The End Diaphragm of Orthotropic Steel Bridge Structure with Box Girder,Prc.of Annual Conferenece of JSCE,vol.61,2006.(In Japanese)
