Dan Ryan Express
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開始行:
*Dan Ryan Express [#dd02b438]
**1.Field of application [#l3ed32eb]
>Dan Ryan elevated bridge of the Lake-Dan Ryan express line in Chicago, Illinois.
**2.Circumstances of repair [#jdd6e7be]
>Fatigue crack was found in the transverse box beam cap of the rigid-frame steel pier in Jan. 1978 after 9 years of service. After finding this crack, repair was immediately recommended.
**3.Types of structure [#j83b307a]
>This bridge is curved and elevated structure ([[Fig.1>#fig1]],[[2>#fig2]]). The superstructure is composed of four continuous plate-girders and field-placed concrete deck ([[Fig.3>#fig3]]). The transverse beams of the rigid-frame steel pier which support four plate-girders and columns are box sections ([[Fig.4>#fig4]]). The girder bottom flanges pass through the slot-holes, which were formed near the box beam lower web, and is partial penetration groove weld connected to the box beam webs. The welded girder members, which corresponded to 0.9~1.22mm length from both side of the transverse beam, was fabricated with the pier and was pin-link or bolt connected to the adjacent girder members. The structural steel was applied to the quality of A36 steel as a result of the tensile test and so on.
&br;
CENTER:&aname(fig1);&attachref(DanRya7.gif);&br;
&br;
CENTER:Fig.1 Complete view.
&br;
CENTER:&aname(fig2);&attachref(DanRya8.gif);&br;
&br;
CENTER:Fig.2 Pier and superstructure view.
&br;
CENTER:&aname(fig3);&attachref(DanRya9.gif);&br;
&br;
CENTER:Fig.3 Plan and cross section.
&br;
CENTER:&aname(fig4);&attachref(DanRya10.gif);&br;
&br;
CENTER:Fig.4 Pier view and crack location.
&br;
**4.Details of loading [#xf35a68d]
>Fluctuating loads due to rail live load.
**5.Description of damage [#c8b09665]
>Fatigue cracks was found in the groove weld at the box beam web connection with the girder bottom girder flange ([[Fig.5>#fig5]]). In the fabrication, the slot holes were firstly opened to the box beam webs by frame-cutting in order to permit the penetration of the girder flanges. Secondly , the girder bottom flanges were inserted in the slot hole and were groove weld connected to the box beam webs.
>Causes of fatigue crack were as follows:
-Lack of fusion in the groove weld which connected the girder bottom flange to the transverse box beam cap of the pier.
-Detail of the weld joint indicating the low fatigue strength.
&br;
CENTER:&aname(fig5);&attachref(DanRya1.gif);&br;
&br;
CENTER:Fig.5 Crack occurred in pier 26.
&br;
**6.Repair method applied [#m67844b0]
>After the discovery of the crack, temporary supports were immediately constructed and stop holes were drilled at the crack tips as a emergency repair.
>Strengthening was recommended to lessen the high stress concentration and residual stress at the girder flange-box beam web connections where fatigue crack did not initiate yet.
Two 64mm diameter holes were drilled on side of the box beam web adjacent to up-and-down girder flange termination. The two holes were connected by a vertical saw cut ([[Fig.6>#fig6]]).
&br;
CENTER:&aname(fig6);&attachref(DanRya17.gif);&br;
&br;
CENTER:Fig.6 Repair method for pier 26.&br;
&br;
&br;
終了行:
*Dan Ryan Express [#dd02b438]
**1.Field of application [#l3ed32eb]
>Dan Ryan elevated bridge of the Lake-Dan Ryan express line in Chicago, Illinois.
**2.Circumstances of repair [#jdd6e7be]
>Fatigue crack was found in the transverse box beam cap of the rigid-frame steel pier in Jan. 1978 after 9 years of service. After finding this crack, repair was immediately recommended.
**3.Types of structure [#j83b307a]
>This bridge is curved and elevated structure ([[Fig.1>#fig1]],[[2>#fig2]]). The superstructure is composed of four continuous plate-girders and field-placed concrete deck ([[Fig.3>#fig3]]). The transverse beams of the rigid-frame steel pier which support four plate-girders and columns are box sections ([[Fig.4>#fig4]]). The girder bottom flanges pass through the slot-holes, which were formed near the box beam lower web, and is partial penetration groove weld connected to the box beam webs. The welded girder members, which corresponded to 0.9~1.22mm length from both side of the transverse beam, was fabricated with the pier and was pin-link or bolt connected to the adjacent girder members. The structural steel was applied to the quality of A36 steel as a result of the tensile test and so on.
&br;
CENTER:&aname(fig1);&attachref(DanRya7.gif);&br;
&br;
CENTER:Fig.1 Complete view.
&br;
CENTER:&aname(fig2);&attachref(DanRya8.gif);&br;
&br;
CENTER:Fig.2 Pier and superstructure view.
&br;
CENTER:&aname(fig3);&attachref(DanRya9.gif);&br;
&br;
CENTER:Fig.3 Plan and cross section.
&br;
CENTER:&aname(fig4);&attachref(DanRya10.gif);&br;
&br;
CENTER:Fig.4 Pier view and crack location.
&br;
**4.Details of loading [#xf35a68d]
>Fluctuating loads due to rail live load.
**5.Description of damage [#c8b09665]
>Fatigue cracks was found in the groove weld at the box beam web connection with the girder bottom girder flange ([[Fig.5>#fig5]]). In the fabrication, the slot holes were firstly opened to the box beam webs by frame-cutting in order to permit the penetration of the girder flanges. Secondly , the girder bottom flanges were inserted in the slot hole and were groove weld connected to the box beam webs.
>Causes of fatigue crack were as follows:
-Lack of fusion in the groove weld which connected the girder bottom flange to the transverse box beam cap of the pier.
-Detail of the weld joint indicating the low fatigue strength.
&br;
CENTER:&aname(fig5);&attachref(DanRya1.gif);&br;
&br;
CENTER:Fig.5 Crack occurred in pier 26.
&br;
**6.Repair method applied [#m67844b0]
>After the discovery of the crack, temporary supports were immediately constructed and stop holes were drilled at the crack tips as a emergency repair.
>Strengthening was recommended to lessen the high stress concentration and residual stress at the girder flange-box beam web connections where fatigue crack did not initiate yet.
Two 64mm diameter holes were drilled on side of the box beam web adjacent to up-and-down girder flange termination. The two holes were connected by a vertical saw cut ([[Fig.6>#fig6]]).
&br;
CENTER:&aname(fig6);&attachref(DanRya17.gif);&br;
&br;
CENTER:Fig.6 Repair method for pier 26.&br;
&br;
&br;
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