Steel bridge on Hanshin Expressway (at web gusset) †

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1.Field of application †

Steel bridge on Hanshin Expressway ,Kobe, Japan.

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2.Circumstances of Repair †

Fatigue cracks were found in the weld of the gusset plates at the end vertical stiffener locations with the girder webs in Jun. 1983 after 13 years of service.

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3.Types of structure †

The bridge is composite simple I-section girder bridge. The framing plan is shown in figure 1. The end vertical stiffeners and gusset plates were fillet weld connected to the girder web (Fig.2). The lateral bracings were bolt connected to the gusset plates (Fig.2)


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Fig.1 Framing plan.


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Fig.2 Two kinds of lateral joints.


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4.Details of loading †

Fluctuating loads due to highway live load.

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5.Description of damage †

Fatigue cracks originated from the contact locations between the gusset plates and the vertical stiffeners (Fig.3,4). The occurrence of fatigue cracking was limited to type-2 structure of the lateral bracings.


Cause of fatigue cracks was thought as follows:

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6.Repair method applied †

In order to relieve high stress concentration, parts of the original gusset plates were removed and new gusset plates were bolt connected to the lower lateral bracings. Angles, which were installed under the gusset plates, were bolt connected to the lower lateral bracings (Fig.5). As a result, the structure of this repair became similar to type-1 detail of the lateral bracing which included no cracks (Fig.6).

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Fig.5 Replacement of the gusset plate and angle connection.


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Fig.9 Strengthening method.


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