![[PukiWiki]](image/pukiwiki.png "[PukiWiki]")
Steel bridge of Route 43, Japan.
国道43号の鋼橋
Fatigue cracks at intersection of bulb ribs and transverse ribs were found.
バルブリブと横リブの交差部に疲労き裂が見つかった。
The outline of the bridge structure is as follows.
- Bridge length : 211.0m
- Span length : 60.0m+91.0m+60.0m
- Structure : Box girder bridge with orthotropic deck system
構造諸元は次のとおりである。
- 橋長 ： 211.0m
- 支間長： 60.0+91.0+60.0m
- 形式 ： 鋼床版箱桁橋
Fluctuating loads due to vehicles live load.
活荷重
Fatigue cracks were detected on boxing weld joints between bottom of bulb ribs and web plates of transverse ribs .Cracks initiated from the toe of the boxing weld joints and propagated at the web plates of the transverse ribs (Fig.1).
バルブリブと横リブ間の溶接部下端（回し溶接）で疲労き裂が見つかった。き裂は回し溶接の止端部を起点とし、横リブのウェブへ進展した(図.1)。
Cause of fatigue cracks was as follows:
- Localized stress concentration which resulted from the restraint of the deck plate deflection due to the wheel load.
Retrofitting procedures for the cracks were positive attachments by using bolted angle connections between the bulb ribs and the web plates of the transverse ribs(Fig.2).
バルブリブと横リブウェブ間にアングル材を設置してボルト固定し補強した(図.2)。
