Fremont Bridge の変更点

追加された行はこの色です。
削除された行はこの色です。
Fremont Bridge へ行く。
Fremont Bridge の差分を削除
*Fremont Bridge [#pb8a9159]

**1.Field of application [#q272653a]

>Fremont bridge over river which flows through Portland city, Oregon, U.S.A.

**2.Circumstances of repair [#x58d2658]

>Cracking was found near the weld connection between the stiffening girder bottom flange and the junction piece in Dec. 1971 during erection. 

**3.Types of structure [#j810f631]

>The bridge is double-deck arch structure which consists of three continuous spans ranging 136.67m, 382.63m, 136.67m ([[Fig.1>#fig1]]). Stiffening girders and arch ribs are box-section. The stiffening girder bottom flanges were weld connected to the junction pieces which were weld connected to the arch ribs. The structural steel of the stiffening girder bottom flanges and junction pieces was A588.

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CENTER:Fig.1 Side view. 
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**4.Description of damage [#ef4ba291]

>Cracking occurred in the junction piece cope which connected the arch rib to the stiffening girder bottom flange ([[Fig.2>#fig2]]). Growing the full width of the stiffening girder bottom flange, the crack propagated into both exterior and interior webs of the box section stiffening girder ([[Fig.3>#fig3]]). 

>Causes of crack and fracture were thought as follows. 
-Introduce of high residual stress due to welding of the thicker plate near the crack location. 
-Impact value of rolled right-angled section of the junction piece below the requirement. 

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CENTER:Fig.2 Junction piece and crack location. 
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CENTER:Fig.3 Crack which propagated into the girder web. 
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**6.Repair method applied [#e97af0d3]
**5.Repair method applied [#e97af0d3]

>For a part subjected to cracking, modification of structural detail was immediately required. 

>As a new connection detail, the structure of the stiffening girder web with the 1219mm radius was recommended ([[Fig.4>#fig4]]). 
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CENTER:&aname(fig4);&attachref(Fremon56.jpg);&br;
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CENTER:Fig.4 Completion view.  
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