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Steel bridge on Shinkansen-railway, Japan.
The Tokaido Shinkansen is the first bullet train system in Japan. This line connects between Tokyo and Osaka 515km in length, has been carrying almost 300 trains a day since 1964.
There are totally 1511 steel bridges, about 27 km in length, in Tokaido Shinkansen.
- Location of fatigue cracks
Main girder, end of girder, web and upper surface of the lower flange.
- Traffic and service time
Opened in 1964, found in 1994, found by periodical inspection
Deck plate girder with box section.
End of girder are copes.
Curve R=2500m. The girder is slanted considering centrifugal force
Fluctuating loads due to Shinkansen trains traffic.
- Detail of fatigue cracks
Table 1
Web copes of radius r=100mm Size of weld 12mm Settlement of supporting point 0.05mm
There is a difference of web height at left and right side at supported points. Crack was originated around weld bead of vicinity of notched corner with the lower height of web, and propagated web and the lower flange.
Fig.2 Crack at the coped end of girder
- Probable causes of fatigue cracks
Stress concentration due to the cope.
It was found stress in the tangent direction surpassed from the result of stress measurement. Comparing inner and outer stress in the tangent direction is doubled or tripled and the change of neutral axis was remarkable. It is influenced by the difference of depth of notch of inner and outer.
Fig.3 result of stress measurement
- Table 2 Repair procedures and effects
Temporary retrofitting Reinforcement by splice plate Permanent retrofitting Reinforcement by truss structure of angle members
Fig.4 temporary retrofitting
