The Third line of The Metropolitan Expressway(Part 2) のバックアップ(No.3) - PukiWiki

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The Third line of The Metropolitan Expressway(Part 2) へ行く。
- 1 (2014-04-15 (火) 09:38:37)
- 2 (2014-04-15 (火) 12:56:32)
- 3 (2014-04-17 (木) 11:14:15)

The Third line of The Metropolitan Expressway(Part 2) †

1.Field of application †

The third line of the metropolitan expressway, Tokyo.

2.Circumstances of Repair †

Fatigue cracks were found in the welded joints which joined the gusset plates of lateral bracings to the web panels of the main girders in 2000 after 28 years of service.

3.Types of structure †

The outline of the bridge structure is as follows.

Span length : 28.9m

Structure : Simple composite I-beam girder bridge

Structural steel : unknown

4.Details of loading †

Fluctuating loads due to expressway live load.

5.Description of damage †

The one of the fatigue cracks is shown in Fig.1.Fig.2 shows classification of the crack position that occurred in the weld of gusset.These cracks were found from 2000 to 2004.The result in Fig.2 indicates that the most cracks is tpye2.

Fig.1 Photograph of the crack.

Type of crack	TYPE1	TYPE2	TYPE3	TYPE4
Number of crack	30	54	14	1

Fig.2 Classification of the crack position that occurred in the weld of gusset.

As a result of stress measurement and FEM analysis , the causes of the type1 and type2 to show as follows were estimated.The cause of type1 was the stress concentration in the edge of the gusset which occurred by local bending of the web plates of the main girder.The cause of type2 was the local deformation in the vicinity of the scallop which occurred by axial force of the lateral bracing.

6.Repair method applied †

The repair detail is shown Fig.3

Fig.3 Repaif detail.

Reference †

Chitoshi Miki,Fatigue and destruction of bridge,2011.10(In Japanese)