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Steel bridge of The Metropolitan Expressway, Japan.
Many fatigue cracks were found in the upper end of vertical stiffener which was at end diaphragm.These cracks were found after more than 30 years service.
The outline of the bridge structure is as follows.
- Bridge length : 64.45m
- Structure : simple two Boxes girder bridge with orthotropic deck system
- thickness of deck plate : 12mm
- thickness of end diaphragm web plate : 16mm
- thickness of vertical stiffener : 19mm
The cross section and clack location are shown in figure 1.
Fluctuating loads due to highway 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).
File not found: "v_e_d_crack.jpg" at page "Steel bridge on roadway bridge(butt wellding of trough rib)"[ź]
Fig.2 Detail of crack
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)
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