Shemimaru Bridge of Meishin Expressway のバックアップ(No.1)

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- 1 (2013-07-24 (水) 10:17:08)

Shemimaru Bridge of Meishin Expressway †

1.Field of application †

Shemimaru bridge between Kyoto-Higashi interchange and Otsu interchange of Meishin expressway.

2.Circumstances of Repair †

Fatigue cracks were found in the floor system members 1984 after 21 years of service. Further, fatigue cracks were found in the top and bottom ends of the vertical member in 1987 after 24 years of service.

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3.Types of structure †

The outline of the bridge structure is as follows.

Bridge length : 62..2 m

Span length : The stiffening girder 61.6 m, Between the arch ribs 54.0 m

Skewed degree : 62 degree

Structure : 2 hinge arch deck bridge

Deck : Reinforced concrete deck (16.0 cm thickness)

Structural steel : SS 41, SM 50

Elevation and plan are shown in figure 1. This bridge is composed of two main girders and two arch ribs. No the cross bracing existed between the arch ribs. The top and bottom ends of the vertical members are weld connected to the base plates which are rivet connected to the arch ribs and the stiffening girders.

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Fig.1 Elevation and cross section.

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4.Details of loading †

Fluctuating loads due to vehicles live load.

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5.Description of damage †

Fatigue cracks were found in the weld at the gusset plate connection with the stiffening girders and the arch ribs (Fig.2). The cracks also occurred in the fillets of cut-out gussets (Fig.2). One of them had propagated into the stiffening girder bottom flange.

Cause of fatigue cracks was thought as follows:

Notch of the fillets caused by gas cutting.

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Fig.2 Crack locations.

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6.Repair method applied †

Emergency repair

At the locations where the crack propagated in the stiffening girder flange, repair was performed by hole-drilling and splice joint by high strength bolts (Fig.3).

Permanent repair

Permanent repair was performed by improvement of the structural detail. The original intermediate vertical members were improved to new structure such as increasing the stiffness of the vertical member. In the damaged vertical member ends except for the intermediate vertical members, Pin connections were performed (Fig.4).

At the inspection in 1990, it had not been reported that the crack re-initiated and propagated.

File not found: "Twohin3.jpg" at page "Shemimaru Bridge of Meishin Expressway"[ź��]

Fig.3 Emergency repair.

File not found: "Twohin4.jpg" at page "Shemimaru Bridge of Meishin Expressway"[ź��]

Fig.4 Permanent repair.