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

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Steel bridge on Hanshin Expressway (at floor-beam end) へ行く。
Steel bridge on Hanshin Expressway (at floor-beam end) の差分を削除

*Steel bridge on Hanshin Expressway (at floor-beam end) [#c200ca35]

**1.Field of application [#n534b287]

>Steel bridge, opened in 1970, on Kobe line of Hanshin Expressway, Japan.&br;

**2.Circumstances of Repair [#g1e4a80c]

>Fatigue crack was found in the weld toe of the floorbeam bottom flange at the floorbeam-girder connection.

**3.Types of structure [#c6cc3fa3]

>Simple composite plate girders bridge. The floorbeams were weld connected to the girder webs. Web gaps between the floorbeam bottom flanges and girder bottom flanges existed ([[Fig.1>#fig1]]).&br;
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CENTER:&aname(fig1);&attachref(Hanko18.gif);&br;
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CENTER:Fig.1 Cracked girder view.&br;
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**4.Details of loading [#y65ff45b]
>Fluctuating loads due to highway live load.

**5.Description of damage [#veed4c5a]
>Fatigue crack occurred in the weld toe of the floorbeam bottom flange at the floorbeam-girder connection ([[Fig.2>#fig2]]). The crack propagated vertical to girder web. Cause of fatigue crack was thought as follows. Stress concentration at the lower part of the girder-floorbeam connection due to the stress combination between out-of-plane distortion, which was caused by the floorbeam action, and principle stress by the girder action.&br; 
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CENTER:Fig.3 Crack which occurred in the weld toe of the floorbeam bottom flange at the floorbeam-girder connection.&br;

CENTER:Fig.2 Crack which occurred in the weld toe of the floorbeam bottom flange at the floorbeam-girder connection.&br;

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**6.Repair method applied [#j2c2f301]

>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.

>Trial retrofit and stress measurement in the field indicated that splicing by high strength bolts had the beneficial effects ([[Fig.3>#fig3]]).&br;

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CENTER:&aname(fig3);&attachref(Hanko110.gif);&br;

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CENTER:&aname(fig6);&attachref(Hanko818.jpg);&br;

CENTER:Fig.3 Bolt splice.&br;

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

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CENTER:&aname(fig7);&attachref(Hanko819.jpg);&br;

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CENTER:Fig.7 Completion view.&br;

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