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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.
Fig.1 Side view,plane view and cross section viwe of the bridge
Fluctuating loads due to vehicles live load.
The crack that was found at butt welding of trough rib is shown in (Fig.2). Types of cracks are shown in (Fig.3).
Causes of fatigue cracks were as follows:
- Increase of the traffic.
- Upsizing of the vehicle.
After removing by gouging, the slightly damaged part was repaired by rewelding(Fig.4(b)). In the case that the crack propagated to the fillet welding between deck plate and trough rib, the part of trough rib which was damaged was replaced to new trough rib(Fig.4(a)).
Casebook of repairs and reinforcements on road bridge(In Japanese)
