Deck-type Langer bridge on roadway bridge
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開始行:
* Deck-type Langer bridge on roadway bridge [#cc882148]
**1.Field of application [#n1c05136]
>Deck-type Langer bridge on roadway bridge, Japan.&br;
**2.Circumstances of Repair [#p3c9bd23]
>Fatigue cracks were found at the top and bottom ends of the stringers and the floorbeams in 1976 after 21 years of service.&br;
**3.Types of structure [#vaa7cf1e]
>The outline of the bridge structure is as follows.
-Bridge length : 48.0 m
-Structure : Deck-type Langer bridge.
-Deck : Reinforced concrete deck (16.0 cm thickness)
-pavement: concrete (5.0 cm thickness) + asphalt (5.0 cm thickness)
&br;
&br;
>Elevation and framing plan are shown in [[figure 1>#fig1]]. The main girders are spaced at 8.5 m and are 1.5 m deep. The floor system is composed of eleven floorbeams, which are spaced at 4.8 m, and five stringers, which are spaced at 1.55 m. The stringers were rivet connected to the floorbeams. However, the flanges of the stringers were coped at the end of the stringers ([[Fig.2>#fig2]]).
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&br;
&br;
CENTER:&aname(fig1);&attachref(Langer18.jpg);&br;
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CENTER:Fig.1 Elevation and framing plan.&br;
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&br;
CENTER:&aname(fig2);&attachref(Langer19.jpg);&br;
&br;
CENTER:Fig.2 Connection detail between the stringers and floorbeam.&br;
&br;
&br;
**4.Details of loading [#b19c92a1]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#q7c47e3f]
>Fatigue cracks were found at the top and bottom ends of the stringers and the floorbeams ([[Fig.1>#fig1]]). Fatigue cracks originated from the flange cope and the web-flange boxings of the beam ends ([[Fig.3>#fig3]]). At the stringer ends, the cracks over 30mm length were observed at seven locations. In two locations of them (G1,G3), the stringers had fractured ([[Fig.4>#fig4]],[[5>#fig5]]). The crack distribution of the stringers ends is shown in [[figure 6>#fig6]] and the floorbeam ends is shown in [[figure 7>#fig7]].
>Cause of fatigue cracks was thought as follows:
-Stress concentration due to the cope.
&br;
&br;
CENTER:&aname(fig3);&attachref(Langer20.jpg);&br;
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CENTER:Fig.3 Crack from the weld toe.&br;
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&br;
CENTER:&aname(fig4);&attachref(Langer21.jpg);&br;
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CENTER:Fig.4 View of the fractured stringer (G3 stringer).&br;
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&br;
CENTER:&aname(fig5);&attachref(Langer22.jpg);&br;
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CENTER:Fig.5 View of the fractured stringer (G2 stringer).&br;
&br;
&br;
CENTER:&aname(fig6);&attachref(Langer23.jpg);&br;
&br;
CENTER:Fig.6 The distribution of the crack at the stringer copes.&br;
&br;
&br;
CENTER:&aname(fig7);&attachref(Langer24.jpg);&br;
&br;
CENTER:Fig.7 The crack length of the floorbeam ends.&br;
&br;
&br;
**6.Repair method applied [#w125ec36]
-Repair of the stringer.
>It was difficult to repair the cracks at the boxing. Removal of the cracks was not recommended. Therefore, repair was performed by bolt-splice and the construction of the knee brace ([[Fig.8>#fig8]]).
-At the deck-pavement joint.
>The original deck and pavement was replaced with the reinforced concrete deck of 26 cm thickness.
&br;
&br;
>After the completion of these repairs, the top flange of the stringers were bolt connected to the top flanges of the floorbeams ([[Fig.9>#fig9]]). The whole of the concrete deck was replaced.
&br;
&br;
CENTER:&aname(fig8);&attachref(Langer25.jpg);&br;
&br;
CENTER:Fig.8 Repair detail.&br;
&br;
&br;
CENTER:&aname(fig9);&attachref(Langer26.jpg);&br;
&br;
CENTER:Fig.9 Connection detail between the stringer and the floorbeam.&br;
&br;
&br;
終了行:
* Deck-type Langer bridge on roadway bridge [#cc882148]
**1.Field of application [#n1c05136]
>Deck-type Langer bridge on roadway bridge, Japan.&br;
**2.Circumstances of Repair [#p3c9bd23]
>Fatigue cracks were found at the top and bottom ends of the stringers and the floorbeams in 1976 after 21 years of service.&br;
**3.Types of structure [#vaa7cf1e]
>The outline of the bridge structure is as follows.
-Bridge length : 48.0 m
-Structure : Deck-type Langer bridge.
-Deck : Reinforced concrete deck (16.0 cm thickness)
-pavement: concrete (5.0 cm thickness) + asphalt (5.0 cm thickness)
&br;
&br;
>Elevation and framing plan are shown in [[figure 1>#fig1]]. The main girders are spaced at 8.5 m and are 1.5 m deep. The floor system is composed of eleven floorbeams, which are spaced at 4.8 m, and five stringers, which are spaced at 1.55 m. The stringers were rivet connected to the floorbeams. However, the flanges of the stringers were coped at the end of the stringers ([[Fig.2>#fig2]]).
&br;
&br;
&br;
CENTER:&aname(fig1);&attachref(Langer18.jpg);&br;
&br;
CENTER:Fig.1 Elevation and framing plan.&br;
&br;
&br;
CENTER:&aname(fig2);&attachref(Langer19.jpg);&br;
&br;
CENTER:Fig.2 Connection detail between the stringers and floorbeam.&br;
&br;
&br;
**4.Details of loading [#b19c92a1]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#q7c47e3f]
>Fatigue cracks were found at the top and bottom ends of the stringers and the floorbeams ([[Fig.1>#fig1]]). Fatigue cracks originated from the flange cope and the web-flange boxings of the beam ends ([[Fig.3>#fig3]]). At the stringer ends, the cracks over 30mm length were observed at seven locations. In two locations of them (G1,G3), the stringers had fractured ([[Fig.4>#fig4]],[[5>#fig5]]). The crack distribution of the stringers ends is shown in [[figure 6>#fig6]] and the floorbeam ends is shown in [[figure 7>#fig7]].
>Cause of fatigue cracks was thought as follows:
-Stress concentration due to the cope.
&br;
&br;
CENTER:&aname(fig3);&attachref(Langer20.jpg);&br;
&br;
CENTER:Fig.3 Crack from the weld toe.&br;
&br;
&br;
CENTER:&aname(fig4);&attachref(Langer21.jpg);&br;
&br;
CENTER:Fig.4 View of the fractured stringer (G3 stringer).&br;
&br;
&br;
CENTER:&aname(fig5);&attachref(Langer22.jpg);&br;
&br;
CENTER:Fig.5 View of the fractured stringer (G2 stringer).&br;
&br;
&br;
CENTER:&aname(fig6);&attachref(Langer23.jpg);&br;
&br;
CENTER:Fig.6 The distribution of the crack at the stringer copes.&br;
&br;
&br;
CENTER:&aname(fig7);&attachref(Langer24.jpg);&br;
&br;
CENTER:Fig.7 The crack length of the floorbeam ends.&br;
&br;
&br;
**6.Repair method applied [#w125ec36]
-Repair of the stringer.
>It was difficult to repair the cracks at the boxing. Removal of the cracks was not recommended. Therefore, repair was performed by bolt-splice and the construction of the knee brace ([[Fig.8>#fig8]]).
-At the deck-pavement joint.
>The original deck and pavement was replaced with the reinforced concrete deck of 26 cm thickness.
&br;
&br;
>After the completion of these repairs, the top flange of the stringers were bolt connected to the top flanges of the floorbeams ([[Fig.9>#fig9]]). The whole of the concrete deck was replaced.
&br;
&br;
CENTER:&aname(fig8);&attachref(Langer25.jpg);&br;
&br;
CENTER:Fig.8 Repair detail.&br;
&br;
&br;
CENTER:&aname(fig9);&attachref(Langer26.jpg);&br;
&br;
CENTER:Fig.9 Connection detail between the stringer and the floorbeam.&br;
&br;
&br;
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