Yamazoe Bridge のバックアップ(No.3) - PukiWiki

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Yamazoe Bridge へ行く。
- 1 (2014-04-04 (金) 09:41:13)
- 2 (2014-04-04 (金) 13:10:48)
- 3 (2014-04-04 (金) 13:23:08)

Yamazoe Bridge †

1.Field of application †

Yamazoe Bridge of Route 25 in Nara, Japan.

2.Circumstances of Repair †

Fatigue crack was found at the web panel of the main girder in Oct.2006 after 35 years of service.

3.Types of structure †

The outline of the bridge structure is as follows.

Bridge length : 128.02 m

Span length : unknown

Structure : Three spans continuous noncomposite plate girder

Structural steel : unknown

Photograph of Yamazoe Bridge is shown in Fig.1. Elevation and cross section are shown in Fig.2.Red circle in Fig.1 shows the location of the crack.

Fig.1 Yamazoe Bridge.

Fig.2 Elevation and cross section.

4.Details of loading †

Fluctuating loads due to vehicles live load. 57099 vehicles / 24hr.

5.Description of damage †

The crack detail is shown in Fig.3.The detail of the structure where the crack was generated is as follows.The lower flange of the cross beam penetrated the slit of the web panel of the main girder.And only upper side of the flange was joined to the web panel of the main girder by welding.

The following things are assumed by the aspect of this crack. At first, the fatigue crack was generated from the vicinity of the toe of the boxing welding which joined the flange of the cross beam to the web of the main girder. Next, after the fatigue crack propagated for about 100mm, the brittle fracture occurred.

Fig.3 Crack detail.

Cause of fatigue cracks was as follows:

Detail of the weld joint indicating the low fatigue strength.

6.Repair method applied †

Bolted splice plates were installed on the web of the main girder(Fig.4).

Fig.4 Bolted splice plate

Reference †

Chitoshi Miki,Fatigue and destruction of bridge,2011.10(In Japanese)