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Ohira viaduct of R-50 in Tochigi, Japan.
Fatigue cracks were detected on welded joints between longitudinal trough rib and orthotropic deck plate after over 20 years of service.
The outline of the bridge structure is as follows.
- Bridge length : 147.0m,
- Span length :40m+56m+50m
- Structure : Box girder bridge with orthotropic deck system
- Deck plate thickness : 12mm
The cross section is shown in figure 1.
Fig.1 Cross section
Fluctuating loads due to vehicles live load.
The fatigue cracks were detected on welded joints between longitudinal trough ribs and orthotropic deck plates.
Cause of fatigue cracks was as follows:
- Localized stress concentration which resulted from the out-of-plane of the deck plate deflection due to the wheel load.
Emergency repair
Stop holes were drilled at the crack tips(Fig.2).
Fig.2 Stop hole
Permanent repair
The SFRC pavements were constructed on the orthotropic deck plates instead of asphalt pavements.(Fig.3,Fig.4,Fig.5,).And the change of the driving lane was carried out to move a wheel position and a fatigue damage point.
Fig.3 The typical cross-section of SFRC
