Allegheny River Br.
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開始行:
*Allegheny River Br. [#d5061b0c]
**1.Field of application [#e71f5e28]
>Allegheny River Bridge is Pennsylvania Turnpike over Allegheny River on the outskirts of Pittsburgh, Pennsylvania.
**2.Circumstances of repair [#h8755997]
>Fatigue crack was found in the tie plate which was rivet connected with the floorbeam top flange and the cantilever bracket top flange in 1971 after 19 years of service.
**3.Types of structure [#aeb4ee39]
>This bridge consist of four spans of Gerber bridge and five spans of truss bridge ([[Fig.1>#fig1]]). The structure is composed of two main girders, floorbeams, twelve stringers supporting the reinforced concrete deck, cantilever brackets. The plane, elevation views and typical cross section are shown in [[figure 2>#fig2]],[[3>#fig3]]. The top flange of the floorbeams are rivet connected to the top flanges of the brackets by the tie plate ([[Fig.4>#fig4]]). The tie plates were A7 steel.
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CENTER:&aname(fig1);&attachref(Allegh7.gif);&br;
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CENTER:Fig.1 Allegheny River Bridge.
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CENTER:&aname(fig2);&attachref(Allegh8.gif);&br;
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CENTER:Fig.2 Plan and elevation views.
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CENTER:&aname(fig3);&attachref(Allegh9.gif);&br;
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CENTER:Fig.3 Cross section (A-A section shown in figure 2.)
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CENTER:&aname(fig4);&attachref(Allegh10.gif);&br;
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CENTER:Fig.4 Detail of the tie plate.
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**4.Details of loading [#n4f46cf1]
>Fluctuating loads due to highway live load.
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**5.Description of damage [#nb1828be]
>Fatigue cracks were found in the tie plate which was rivet connected to the floorbeam top flange and the cantilever bracket top flange ([[Fig.5>#fig5]]). These cracks initiated from the rivet connection holes of the tie plates.
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>Cause of fatigue cracks was as follows:
-In-plane-distortion of the tie plates which was caused by the longitudinal displacement of the main girder top flanges.
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CENTER:&aname(fig8);&attachref(Allegh10.gif);&br;
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CENTER:Fig.5 Cracked tie plate.
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**6.Repair method applied [#l1c3ff99]
>Repair of the tie plates subjected to cracking was performed by groove welding. The strengthening plates were bolt connected on the repaired tie plate ([[Fig.6>#fig6]]).
However, significant cyclic stresses, which were caused by the displacement, have been acting in the repaired tie plates and the reinforcing plates. Therefore, there was possibility that crack reinitiate after 10 or 20 years.
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CENTER:&aname(fig6);&attachref(Allegh11.gif);&br;
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CENTER:Fig.6 The reinforcing plate.
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終了行:
*Allegheny River Br. [#d5061b0c]
**1.Field of application [#e71f5e28]
>Allegheny River Bridge is Pennsylvania Turnpike over Allegheny River on the outskirts of Pittsburgh, Pennsylvania.
**2.Circumstances of repair [#h8755997]
>Fatigue crack was found in the tie plate which was rivet connected with the floorbeam top flange and the cantilever bracket top flange in 1971 after 19 years of service.
**3.Types of structure [#aeb4ee39]
>This bridge consist of four spans of Gerber bridge and five spans of truss bridge ([[Fig.1>#fig1]]). The structure is composed of two main girders, floorbeams, twelve stringers supporting the reinforced concrete deck, cantilever brackets. The plane, elevation views and typical cross section are shown in [[figure 2>#fig2]],[[3>#fig3]]. The top flange of the floorbeams are rivet connected to the top flanges of the brackets by the tie plate ([[Fig.4>#fig4]]). The tie plates were A7 steel.
&br;
CENTER:&aname(fig1);&attachref(Allegh7.gif);&br;
&br;
CENTER:Fig.1 Allegheny River Bridge.
&br;
&br;
CENTER:&aname(fig2);&attachref(Allegh8.gif);&br;
&br;
CENTER:Fig.2 Plan and elevation views.
&br;
&br;
CENTER:&aname(fig3);&attachref(Allegh9.gif);&br;
&br;
CENTER:Fig.3 Cross section (A-A section shown in figure 2.)
&br;
&br;
CENTER:&aname(fig4);&attachref(Allegh10.gif);&br;
&br;
CENTER:Fig.4 Detail of the tie plate.
&br;
**4.Details of loading [#n4f46cf1]
>Fluctuating loads due to highway live load.
&br;
**5.Description of damage [#nb1828be]
>Fatigue cracks were found in the tie plate which was rivet connected to the floorbeam top flange and the cantilever bracket top flange ([[Fig.5>#fig5]]). These cracks initiated from the rivet connection holes of the tie plates.
&br;
>Cause of fatigue cracks was as follows:
-In-plane-distortion of the tie plates which was caused by the longitudinal displacement of the main girder top flanges.
&br;
CENTER:&aname(fig8);&attachref(Allegh10.gif);&br;
&br;
CENTER:Fig.5 Cracked tie plate.
&br;
**6.Repair method applied [#l1c3ff99]
>Repair of the tie plates subjected to cracking was performed by groove welding. The strengthening plates were bolt connected on the repaired tie plate ([[Fig.6>#fig6]]).
However, significant cyclic stresses, which were caused by the displacement, have been acting in the repaired tie plates and the reinforcing plates. Therefore, there was possibility that crack reinitiate after 10 or 20 years.
&br;
CENTER:&aname(fig6);&attachref(Allegh11.gif);&br;
&br;
CENTER:Fig.6 The reinforcing plate.
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