Mashita Bridge †

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1.Field of application †

Through-type Langer bridge on the roadway bridge, Japan.

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2.Circumstances of Repair †

Fatigue cracks were found at the joint of the vertical member and the tie girder.

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3.Types of structure †

This bridge is the through-type Langer bridge of which arch span length is 66m (Fig.1). The vertical members were H-type section and were weld connected to the top flange of the tie girders.

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Fig.1 Through-type Langer bridge.
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4.Details of loading †

Fluctuating loads due to wind load.

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5.Description of damage †

Fatigue cracks occurred in the joint of the vertical member and tie girder (Fig.2). The vertical members at the middle part of the bridge suffered the vibration due to wind of which speed was about 15 m/s. Cause of fatigue cracks is as follows. Vibration of the vertical members which was caused by Kerman's vortex.

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Fig.2 Crack which occurred in the joint of the vertical member and tie girder.


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6.Repair method applied †

Fracture part were pulled back by wire rope. To prevent the vibration of the vertical members, each vertical member were connected to the adjacent members by making use of logs.

The modification of connection detail was performed so that the stress transfers smoothly to the web plate of the tie girder (Fig.3).

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Fig.3 Retrofit work.


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