Minato-Shin bridge of R-23
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開始行:
*Minato-Shin bridge of R-23 [#v7c2dd24]
**1.Field of application [#n9c35012]
>Minato-Shin bridge of Route 23, Nagoya, Aichi.&br;
**2.Circumstances of Repair [#beb7f6d9]
>Fatigue cracks were found at the corners of the diaphragms in the box-girders and at the intersection of the ribs on the steel plate floor deck in 1987 after 23 years of service.&br;
**3.Types of structure [#yd0e64b2]
>The outline of the bridge structure is as follows.
-Bridge length : 250.0 m
-Span length : 77.0 + 96.0 + 77.0 m
-Structure : Tree spans continuous two box-girders bridge with steel plate floor.
-Deck : Steel plate floor (12mm thickness)
-Structural steel : SS 41 , SM 50
&br;
&br;
>Elevation and cross section are shown in [[figure 1>#fig1]]. The box girders are spaced at 11.0 m and depth is from 2.5 m to 5.6 m. The interior of the box-girders contain the diaphragms. Diaphragms were composed of the vertical stiffeners and the transverse ribs. In the vertical stiffeners at the diaphragm locations, the flanges had been installed to increase the stiffness. On the other hand no the flange plates existed in the vertical stiffeners at the intermediate transverse rib locations.
&br;
&br;
&br;
CENTER:&aname(fig1);&attachref(Minato27.jpg);&br;
&br;
CENTER:Fig.1 Elevation and cross section.&br;
&br;
&br;
**4.Details of loading [#mc1875aa]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#zfec16cd]
>Fatigue cracks were found at the corners of the diaphragms and at the intersections of the transverse and longitudinal ribs ([[Fig.2>#fig2]],[[3>#fig3]]). The schematic of fatigue cracking in the diaphragm location is shown in figure 4. The degree of the damage in the area "A" as shown in [[figure 2>#fig2]] was more intense than the area "B". Fatigue cracking was observed at most of the diaphragm locations. However, fatigue cracking did not show a tendency in the axial direction of the bridge.
>Cause of fatigue cracks was thought as follows:
-Structural detail that the stress do not transfer smoothly.
>( Strain response and structural analysis indicated that it was effective to construct the additional rib.)
&br;
&br;
CENTER:&aname(fig2);&attachref(Minato28.jpg);&br;
&br;
CENTER:Fig.2 Crack locations.&br;
&br;
&br;
CENTER:&aname(fig3);&attachref(Minato29.jpg);&br;
&br;
CENTER:Fig.3 Crack at the corner of the diaphragm.&br;
**6.Repair method applied [#w333535c]
>The damage at the corners of the diaphragms was such intense that there was much possibility of crack reinitiation in case of the only localized repair. Therefore, strengthening of the structure itself was required with the localized repair.
&br;
&br;
As strengthening of the diaphragms, truss structure was recommended within the diaphragms, between the box-girders and at the bracket locations ([[Fig.4>#fig4]],[[5>#fig5]]).
&br;
&br;
In case it was possible to execute, stop holes were drilled at the crack tips.
&br;
&br;
In the intermediate transverse rib locations, the structure like-cane was recommended and truss structure was partially added.
&br;
&br;
Follow-up inspection have been executed because of confirming the effect of the repair and the strengthening.
&br;
&br;
CENTER:&aname(fig4);&attachref(Minato30.jpg);&br;
&br;
CENTER:Fig.4 Localized repair location.&br;
&br;
&br;
CENTER:&aname(fig5);&attachref(Minato31.jpg);&br;
&br;
CENTER:Fig.5 Truss structure.&br;
終了行:
*Minato-Shin bridge of R-23 [#v7c2dd24]
**1.Field of application [#n9c35012]
>Minato-Shin bridge of Route 23, Nagoya, Aichi.&br;
**2.Circumstances of Repair [#beb7f6d9]
>Fatigue cracks were found at the corners of the diaphragms in the box-girders and at the intersection of the ribs on the steel plate floor deck in 1987 after 23 years of service.&br;
**3.Types of structure [#yd0e64b2]
>The outline of the bridge structure is as follows.
-Bridge length : 250.0 m
-Span length : 77.0 + 96.0 + 77.0 m
-Structure : Tree spans continuous two box-girders bridge with steel plate floor.
-Deck : Steel plate floor (12mm thickness)
-Structural steel : SS 41 , SM 50
&br;
&br;
>Elevation and cross section are shown in [[figure 1>#fig1]]. The box girders are spaced at 11.0 m and depth is from 2.5 m to 5.6 m. The interior of the box-girders contain the diaphragms. Diaphragms were composed of the vertical stiffeners and the transverse ribs. In the vertical stiffeners at the diaphragm locations, the flanges had been installed to increase the stiffness. On the other hand no the flange plates existed in the vertical stiffeners at the intermediate transverse rib locations.
&br;
&br;
&br;
CENTER:&aname(fig1);&attachref(Minato27.jpg);&br;
&br;
CENTER:Fig.1 Elevation and cross section.&br;
&br;
&br;
**4.Details of loading [#mc1875aa]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#zfec16cd]
>Fatigue cracks were found at the corners of the diaphragms and at the intersections of the transverse and longitudinal ribs ([[Fig.2>#fig2]],[[3>#fig3]]). The schematic of fatigue cracking in the diaphragm location is shown in figure 4. The degree of the damage in the area "A" as shown in [[figure 2>#fig2]] was more intense than the area "B". Fatigue cracking was observed at most of the diaphragm locations. However, fatigue cracking did not show a tendency in the axial direction of the bridge.
>Cause of fatigue cracks was thought as follows:
-Structural detail that the stress do not transfer smoothly.
>( Strain response and structural analysis indicated that it was effective to construct the additional rib.)
&br;
&br;
CENTER:&aname(fig2);&attachref(Minato28.jpg);&br;
&br;
CENTER:Fig.2 Crack locations.&br;
&br;
&br;
CENTER:&aname(fig3);&attachref(Minato29.jpg);&br;
&br;
CENTER:Fig.3 Crack at the corner of the diaphragm.&br;
**6.Repair method applied [#w333535c]
>The damage at the corners of the diaphragms was such intense that there was much possibility of crack reinitiation in case of the only localized repair. Therefore, strengthening of the structure itself was required with the localized repair.
&br;
&br;
As strengthening of the diaphragms, truss structure was recommended within the diaphragms, between the box-girders and at the bracket locations ([[Fig.4>#fig4]],[[5>#fig5]]).
&br;
&br;
In case it was possible to execute, stop holes were drilled at the crack tips.
&br;
&br;
In the intermediate transverse rib locations, the structure like-cane was recommended and truss structure was partially added.
&br;
&br;
Follow-up inspection have been executed because of confirming the effect of the repair and the strengthening.
&br;
&br;
CENTER:&aname(fig4);&attachref(Minato30.jpg);&br;
&br;
CENTER:Fig.4 Localized repair location.&br;
&br;
&br;
CENTER:&aname(fig5);&attachref(Minato31.jpg);&br;
&br;
CENTER:Fig.5 Truss structure.&br;
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