Deck-type two hinge arch Br.
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*Deck-type two hinge arch Br. [#nef26efe]
**1.Field of application [#m991f105]
>Steel bridge, highway in Japan
**2.Circumstances of Repair [#gbddb1b3]
>Fatigue cracks after 20 years service.&br;
**3.Types of structure [#k844ae23]
>One deck type two hinge arch bridge and two simply supported girders([[Fig.1>#fig1]])
&br;
&br;
CENTER:&aname(fig1);&attachref(deckty13.gif);&br;
&br;
CENTER:Fig.1 General view.&br;
&br;
&br;
**4.Details of loading [#k227ca89]
>1100 vehicles / 12hr. truck ratio : 25% in 1980
**5.Description of damage and Repair Method Applied [#iefbe6dd]
>In 1982, many fatigue cracks were observed. [[Fig.2>#fig2]] shows the locations of fatigue cracks.
&br;
>There are two types of cracks.
&br;
&br;
CENTER:&aname(fig2);&attachref(deckty14.gif);&br;
&br;
CENTER:Fig.2 Location of fatigue cracks.&br;
&br;
&br;
-Type 1: Cracks at the ends of side span girder ([[Fig 3>#fig3]]).
&br;
&br;
CENTER:&aname(fig3);&attachref(deckty15.gif);&br;
&br;
CENTER:Fig.3 Type 1 crack.&br;
&br;
&br;
-Type 2: Cracks in the connections between column members and arch ribs ([[Fig 4>#fig4]]).
&br;
&br;
CENTER:&aname(fig4);&attachref(deckty16.gif);&br;
&br;
CENTER:Fig.4 Type 2 crack.&br;
&br;
&br;
>In 1982, temporary repairing works were performed.&br;
-For [[type 1 cracks>#fig3]]: Stop holes, splicing and installing bracket ([[Fig 5>#fig5]]).
&br;
&br;
CENTER:&aname(fig5);&attachref(deckty17.gif);&br;
&br;
CENTER:Fig.5 Repairing works for type 1 crack.&br;
&br;
&br;
-For [[type 2 cracks>#fig4]]:Improving gusset details([[Fig 6>#fig6]]).
&br;
&br;
CENTER:&aname(fig6);&attachref(deckty18.gif);&br;
&br;
CENTER:Fig.6 Repairing works for type 2 crack.&br;
&br;
&br;
>In 1982-1983, investigations including field measurements and FEM analysis were carried out.
&br;
>The results indicated that followings are the causes of fatigue damage.
-high stress concentrations due to the coped flange detail at the end of side span girders ([[type 1 cracks>#fig3]]).
-relative movement between arch ribs and main girders which results fix end moment at the connection ([[type 2 cracks>#fig4]]).
-high stress concentration at the end of gusset plates ([[type 2 cracks>#fig4]]).
&br
&br
>In 1984, retrofitting works for [[type 2 cracks>#fig4]] were performed.
-In order to restraint the horizontal movement of main girders, horizontal shoes with visco-dampers were installed([[Fig.7>#fig7]]).
&br;
&br;
CENTER:&aname(fig7);&attachref(deckty19.gif);&br;
&br;
CENTER:Fig.7 Horizontal restrainer with visco-damper &br;
&br;
&br;
-Strengthening gusset plates were added in 11 connections among 24 damaged connections.
&br;
>In 1991, some amount of fatigue crack propagation was observed at the connection of column members which were remained as cracked conditions.&br;
>Strengthening gusset plates with improved detail were installed at these details as retrofitting.&br;
>In 1995, some fatigue cracks initiated at the end of strengthening gusset plates.&br;
>These cracks were re-welded and TIG dressing was applied.&br;
&br;
&br;
終了行:
*Deck-type two hinge arch Br. [#nef26efe]
**1.Field of application [#m991f105]
>Steel bridge, highway in Japan
**2.Circumstances of Repair [#gbddb1b3]
>Fatigue cracks after 20 years service.&br;
**3.Types of structure [#k844ae23]
>One deck type two hinge arch bridge and two simply supported girders([[Fig.1>#fig1]])
&br;
&br;
CENTER:&aname(fig1);&attachref(deckty13.gif);&br;
&br;
CENTER:Fig.1 General view.&br;
&br;
&br;
**4.Details of loading [#k227ca89]
>1100 vehicles / 12hr. truck ratio : 25% in 1980
**5.Description of damage and Repair Method Applied [#iefbe6dd]
>In 1982, many fatigue cracks were observed. [[Fig.2>#fig2]] shows the locations of fatigue cracks.
&br;
>There are two types of cracks.
&br;
&br;
CENTER:&aname(fig2);&attachref(deckty14.gif);&br;
&br;
CENTER:Fig.2 Location of fatigue cracks.&br;
&br;
&br;
-Type 1: Cracks at the ends of side span girder ([[Fig 3>#fig3]]).
&br;
&br;
CENTER:&aname(fig3);&attachref(deckty15.gif);&br;
&br;
CENTER:Fig.3 Type 1 crack.&br;
&br;
&br;
-Type 2: Cracks in the connections between column members and arch ribs ([[Fig 4>#fig4]]).
&br;
&br;
CENTER:&aname(fig4);&attachref(deckty16.gif);&br;
&br;
CENTER:Fig.4 Type 2 crack.&br;
&br;
&br;
>In 1982, temporary repairing works were performed.&br;
-For [[type 1 cracks>#fig3]]: Stop holes, splicing and installing bracket ([[Fig 5>#fig5]]).
&br;
&br;
CENTER:&aname(fig5);&attachref(deckty17.gif);&br;
&br;
CENTER:Fig.5 Repairing works for type 1 crack.&br;
&br;
&br;
-For [[type 2 cracks>#fig4]]:Improving gusset details([[Fig 6>#fig6]]).
&br;
&br;
CENTER:&aname(fig6);&attachref(deckty18.gif);&br;
&br;
CENTER:Fig.6 Repairing works for type 2 crack.&br;
&br;
&br;
>In 1982-1983, investigations including field measurements and FEM analysis were carried out.
&br;
>The results indicated that followings are the causes of fatigue damage.
-high stress concentrations due to the coped flange detail at the end of side span girders ([[type 1 cracks>#fig3]]).
-relative movement between arch ribs and main girders which results fix end moment at the connection ([[type 2 cracks>#fig4]]).
-high stress concentration at the end of gusset plates ([[type 2 cracks>#fig4]]).
&br
&br
>In 1984, retrofitting works for [[type 2 cracks>#fig4]] were performed.
-In order to restraint the horizontal movement of main girders, horizontal shoes with visco-dampers were installed([[Fig.7>#fig7]]).
&br;
&br;
CENTER:&aname(fig7);&attachref(deckty19.gif);&br;
&br;
CENTER:Fig.7 Horizontal restrainer with visco-damper &br;
&br;
&br;
-Strengthening gusset plates were added in 11 connections among 24 damaged connections.
&br;
>In 1991, some amount of fatigue crack propagation was observed at the connection of column members which were remained as cracked conditions.&br;
>Strengthening gusset plates with improved detail were installed at these details as retrofitting.&br;
>In 1995, some fatigue cracks initiated at the end of strengthening gusset plates.&br;
>These cracks were re-welded and TIG dressing was applied.&br;
&br;
&br;
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