51.4 Bridge
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*51.4 Bridge [#z48a3320]
**1.Field of application [#dd017b57]
>51.5 Bridge in the Windermere zone of Canadian Pacific railway over Dutch River in a suburb of Ottawa, Ontario.
**2.Circumstances of repair [#w3728de7]
>Fatigue cracks were found in the stringer web copes at the stringer-floor beam connections in Nov. 1975 after 5 years of service.
**3.Types of structure [#fefd86df]
>This bridge is two simple through plate girders with single line. The plan and side views are shown in [[figure 1>#fig1]]. The welded plate girders are 2.8m deep and support the floor system which is composed of the floor beams and the stringers ([[Fig.2>#fig2]]). The floor beams are rolled sections of W33 by 130 and the stringers are rolled sections of W24 by 76 ([[Fig.3>#fig3]]). The bottom flanges of the stringers were coped in order to connect to the floor beams. The structural steel is B-grade of G40.11 in CSA (A588).
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CENTER:&aname(fig1);&attachref(514Br_1.gif);&br;
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CENTER:Fig.1 Plan and side views.
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CENTER:&aname(fig2);&attachref(514Br_2.gif);&br;
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CENTER:Fig.2 Cross section of the girder.
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CENTER:&aname(fig3);&attachref(514Br_3.gif);&br;
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CENTER:Fig.3 Structure of the floor beam-stringer.
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**4.Details of loading [#y24850b6]
>Fluctuating loads due to freight trains live load.
**5.Description of damage [#z573588b]
>Fatigue cracks were found in the stringer web (bottom flange) copes at the stringer-floor beam connections ([[Fig.4>#fig4]]).
&br;
>Cause of fatigue cracks was as follows:
-Coped structure of the stringer flanges which caused stress concentration.
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CENTER:&aname(fig4);&attachref(514Br_4.gif);&br;
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CENTER:(a) Cope of the stringer bottom flange.
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CENTER:&aname(fig4);&attachref(514Br_5.gif);&br;
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CENTER:(b) Cracking initiated from the coped web.
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CENTER:Fig.4 Crack initiated from the stringer coped web.
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**6.Repair method applied [#vd44b14f]
>As the primary repair, the 24mm diameter holes were drilled at the crack tips in order to prevent the crack propagation.
>Strengthening of parts subjected to cracking was recommended as follows ([[Fig.5>#fig5]]).
The crack from the coped end to stop hole was gouged and the gouged area was filled in by welding.
Part of the stringer flange and web plates of the cope were cut off and the 229 by 12.7mm plate was bent along the cut web face. This plate was groove welded connected to the stringer bottom flange and fillet weld connected to the stringer web.
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CENTER:&aname(fig5);&attachref(514Br_6.gif);&br;
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CENTER:Fig.5 Detail of the strengthening.
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終了行:
*51.4 Bridge [#z48a3320]
**1.Field of application [#dd017b57]
>51.5 Bridge in the Windermere zone of Canadian Pacific railway over Dutch River in a suburb of Ottawa, Ontario.
**2.Circumstances of repair [#w3728de7]
>Fatigue cracks were found in the stringer web copes at the stringer-floor beam connections in Nov. 1975 after 5 years of service.
**3.Types of structure [#fefd86df]
>This bridge is two simple through plate girders with single line. The plan and side views are shown in [[figure 1>#fig1]]. The welded plate girders are 2.8m deep and support the floor system which is composed of the floor beams and the stringers ([[Fig.2>#fig2]]). The floor beams are rolled sections of W33 by 130 and the stringers are rolled sections of W24 by 76 ([[Fig.3>#fig3]]). The bottom flanges of the stringers were coped in order to connect to the floor beams. The structural steel is B-grade of G40.11 in CSA (A588).
&br;
CENTER:&aname(fig1);&attachref(514Br_1.gif);&br;
&br;
CENTER:Fig.1 Plan and side views.
&br;
&br;
CENTER:&aname(fig2);&attachref(514Br_2.gif);&br;
&br;
CENTER:Fig.2 Cross section of the girder.
&br;
&br;
CENTER:&aname(fig3);&attachref(514Br_3.gif);&br;
&br;
CENTER:Fig.3 Structure of the floor beam-stringer.
&br;
**4.Details of loading [#y24850b6]
>Fluctuating loads due to freight trains live load.
**5.Description of damage [#z573588b]
>Fatigue cracks were found in the stringer web (bottom flange) copes at the stringer-floor beam connections ([[Fig.4>#fig4]]).
&br;
>Cause of fatigue cracks was as follows:
-Coped structure of the stringer flanges which caused stress concentration.
&br;
CENTER:&aname(fig4);&attachref(514Br_4.gif);&br;
&br;
CENTER:(a) Cope of the stringer bottom flange.
&br;
&br;
CENTER:&aname(fig4);&attachref(514Br_5.gif);&br;
&br;
CENTER:(b) Cracking initiated from the coped web.
&br;
CENTER:Fig.4 Crack initiated from the stringer coped web.
&br;
**6.Repair method applied [#vd44b14f]
>As the primary repair, the 24mm diameter holes were drilled at the crack tips in order to prevent the crack propagation.
>Strengthening of parts subjected to cracking was recommended as follows ([[Fig.5>#fig5]]).
The crack from the coped end to stop hole was gouged and the gouged area was filled in by welding.
Part of the stringer flange and web plates of the cope were cut off and the 229 by 12.7mm plate was bent along the cut web face. This plate was groove welded connected to the stringer bottom flange and fillet weld connected to the stringer web.
&br;
CENTER:&aname(fig5);&attachref(514Br_6.gif);&br;
&br;
CENTER:Fig.5 Detail of the strengthening.
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&br;
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