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Ikituki Br. in Nagasaki, Japan.
Fatigue crack was found at the panel point of the diagonal member in Dec.2009 after 19 years of service.
The outline of the bridge structure is as follows.
- Bridge length : 800.0 m
- Span length : 200.0 + 400.0 + 200.0 m
- Structure : Tree spans continuous througy-type truss bridge
- Structural steel : SS400,SM490Y,SM520,SM570
Photograph of Ikitsuki Br. is shown in Fig.1.
Fluctuating loads due to wind load.
The fatigue crack was found by the visual inspection.The crack location and detail are shown in Fig.2,Fig.3.
Fig.2 Crack location.
Fig.3 Crack detail.
Cause of fatigue cracks was as follows:
- Vibration of the diagonal member which was caused by wind.
Firstly,stop-holes(φ=20mm)were drilled at the crack tips(Fig.4).
Fig.4 Stop hole.
Secondaty,bolted splice plates was installed on the web plat of the diagonal member(Fig.5).
Fig.5 Bolted splice plates.
Finaly,steel bars were tightened to moderate stresses(Fig.6).
Fig.6 Moderate stresses by tightened steel bar.
The original diagonal member was replaced with new one in May 2010. (Fig.7).
Fig.7 Completion view.
Kaneko Tetsuya,A study on the Retrofits of Ikitsuki Bridge,Kyushu Gihou,vol.48,2011.01(In Japanese)
