Steel bridge on The Metropolitan Expressway(upper end of vertical stiffener at end diaphragm) のバックアップ(No.2)

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• Steel bridge on The Metropolitan Expressway(upper end of vertical stiffener at end diaphragm) へ行く。
  • 1 (2014-01-29 (水) 11:30:30)
  • 2 (2014-01-29 (水) 13:59:05)
  • 3 (2014-01-29 (水) 16:20:21)
  • 4 (2014-02-07 (金) 15:47:47)

Steel bridge on The Metropolitan Expressway (welded joint between longitudinal trough rib and orthotropic deck plate )(Part 2) †

1.Field of application †

Steel bridge of The Metropolitan Expressway, Japan.

2.Circumstances of repair †

Many fatigue cracks were found in the upper end of vertical stiffener which was at end diaphragm.These cracks were found after more than 30 years service.

3.Types of structure †

The outline of the bridge structure is as follows.

• Bridge length : 64.45m
• Structure : simple two Boxes girder bridge with orthotropic deck system
• thickness of deck plate : 12mm
• thickness of end diaphragm web plate : 16mm
• thickness of vertical stiffener : 19mm

The cross section and clack location are shown in figure 1.

4.Details of loading †

Fluctuating loads due to highway live load.

5.Description of damage †

These cracks propagated from the boxing welded joints at the upper end of vertical stiffeners to web plates of end diaphragm(Fig.1).

Fig.1 Detail of crack

Cause of fatigue cracks was as follows:

• Localized stress concentration which resulted from the out-of-plane of the deck plate deflection due to the wheel load.

6.Repair method applied †

Emergency repair

Stop hole and scallop were drilled at the crack tips(Fig.1).

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Fig.1 Crack location and emergency repair

Permanent repair

The new ribs with plates installed by high-tension bolts after removing the damaged trough ribs(Fig.2).

Reference †

Saito et al,The effectiveness of the repair of replacing the trough rib and the verification of the stress properties,Prc.of Annual Conferenece of JSCE,vol.63,2008.(In Japanese)

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