The third line of the metropolitan expressway, Tokyo.
Fatigue cracks were found in the welded joints which joined the gusset plates of lateral bracings to the web panels of the main girders in 2000 after 28 years of service.
The outline of the bridge structure is as follows.
- Span length : 28.9m
- Structure : Simple composite I-beam girder bridge
- Structural steel : unknown
Fluctuating loads due to expressway live load.
The one of the fatigue cracks is shown in Fig.1.Fig.2 shows classification of the crack position that occurred in the weld of gusset.These cracks were found from 2000 to 2004.The result in Fig.2 indicates that the most cracks is tpye2.
Type of crack | TYPE1 | TYPE2 | TYPE3 | TYPE4 |
Number of crack | 30 | 54 | 14 | 1 |