Steel bridge on Hanshin Expressway (at floor-beam coped end) の変更点

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*Steel bridge on Hanshin Expressway (at floor-beam coped end) [#kc174865]

**1.Field of application [#na470cb6]

>Steel bridge on Kobe-Nishinomiya line of Hanshin Expressway, Japan.&br;

**2.Circumstances of Repair [#u1acf3f3]

>Fatigue crack was found in the end floorbeam coped web in May 1988.  

**3.Types of structure [#n3e6960e]

>The bridge is I-section girder bridge with three continuous spans ([[Fig.1>#fig1]]). The floorbeams were bolt connected to the connection stiffeners.&br;
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CENTER:&aname(fig1);&attachref(Hanko920.jpg);&br;
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CENTER:Fig.1 I-section girder bridge.&br;
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**4.Details of loading [#hf692e63]
>Fluctuating loads due to highway live load.

**5.Description of damage [#p959672f]
>Fatigue crack occurred in the coped web of the end floorbeam ([[Fig.2>#fig1]],[[3>#fig3]],[[4>#fig4]]). At the detection of the crack, the crack length reached to 530mm at the G5 location. The support of the G5 girder had subsided 7mm.&br; 
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>Cause of fatigue cracks was as follows: 
-Vibration of the girders due to support subsidence.
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CENTER:&aname(fig2);&attachref(Hanko921.jpg);&br;
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CENTER:Fig.2 Crack location.&br;
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CENTER:Fig.3 Crack of the floorbeam coped end.&br;
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CENTER:Fig.4 Zooming up of crack.&br;
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**6.Repair method applied [#n907e46d]

>The original brackets were replaced with the new brackets of which the top flanges were full penetration groove weld connected with the webs ([[Fig.6>#fig6]]). The new brackets had the bed plates, which were of 19mm thickness, on the flanges themselves ([[Fig.7>#fig7]]). Also for the uncracked brackets, similar bed plates were inserted between the base plates of the sign poles and the bracket top flange plates.

>Firstly, repair of parts subjected to cracking was performed by stop hole, gouging and re-welding.



>Secondary, the cracked web was bolt spliced ([[Fig.5>#fig5]],[[6>#fig6]]). 



>Beside, the original base mortar under the shoe of the G5 girder were replaced by the new non-shrink mortar after re-installing the shoe.&br;

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CENTER:&aname(fig5);&attachref(Hanko924.jpg);&br;

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CENTER:Fig.5 Repair method.&br;

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CENTER:Fig.6 Detail of the bracket flange-web connection.&br;

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CENTER:&aname(fig6);&attachref(Hanko925.jpg);&br;

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CENTER:Fig.6 Complete view.&br;

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CENTER:Fig.7 Completion view.&br;

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