Steel bridge on Hanshin Expressway (at bracket end) のバックアップ(No.1)

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  • 1 (2013-07-31 (水) 13:00:12)

Steel bridge on Hanshin Expressway (at bracket end) †

1.Field of application †

Steel bridge on Hanshin Expressway ,Japan.

2.Circumstances of Repair †

Fatigue crack was found in the interior vertical stiffener end at the bracket connection which supported the sign pole.

3.Types of structure †

The bridge is simple box girder bridge. The cross section is shown in figure 1. The brackets which supported the sign poles were bolt connected to the box girder webs (Fig.2,3).

Fig.1 Cross section.

4.Details of loading †

Fluctuating loads due to vehicles live load.

5.Description of damage †

Fatigue cracks were found in the coped corner at the hinge locations of Gerber bridge (Fig.2). The fatigue cracks occurred along the fillet weld beads at the coped corners (Fig.2,3). There were some cracks that propagated into the girder webs from the corner ends.

Cause of fatigue cracks was thought as follows:

• Stress concentration due to the cope.

6.Repair method applied †

• Emergency repair

Repair of parts subjected to cracking was performed by 24mm diameter stop holes at the crack tips.

High strength bolts (M22,F10T) were fastened there (Fig.4).

Because it was thought that the cracks initiated from the fillet weld root at the coped corner, all the fillet weld parts at the coped corners were gouged out and full penetration welded (Fig.5,6).

• Permanent repair

After the completion of the repair weld, Strengthening was performed by bolt connection with the rib plates (Fig.7).

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