Gulf Outlet Br.
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開始行:
*Gulf Outlet Bridge, Louisiana. [#o2a36f9a]
**1.Field of application [#r0e44263]
>
Gulf Outlet Bridge cross canal in the mouth of a Mississippi River near New Orleans, Louisiana.
<
**2.Circumstances of Repair [#r337d610]
>
Right-angled directional fatigue cracks were found in the fillet welds (corner joints) of the box-section tie girder web-flange connections in 1978 after 13 years of service.
Most of these cracks did not propagate on the surface of the fillet weld. However, the surfaces of all the manual welded areas were needed to be etched and the dye penetrate testing was required.
<
**3.Types of structure [#hec6a8e5]
>
The structure is three spans truss bridge which suspended spans of the tied arch [[(Fig.1)>#fig1]]. The plan and typical cross section are shown in [[figure 2>#fig2]]. The tie girders are box sections with internal diaphragms. The corner joints of the tie girder were fillet weld connected. Each tie girder was connected near center span by Pin-Link [[(Fig.3)>#fig3]]. The tie girder web plate thickness was 19mm except at the Pin-Link connection where it was 89mm and the web plate thickness at the tie girder -floorbeam locations was 25.4mm.The tie girder flange plate thickness was 16mm.
The tie girder flange and web plates are A514 steel.&br;
&aname(fig1);
CENTER:&attachref(GulfOu12.gif);&br;
CENTER:Fig.1 Complete view.&br;&br;
&aname(fig2);
CENTER:&attachref(GulfOu13.gif);&br;
CENTER:Fig.2 Plan and cross section views.&br;&br;
&aname(fig3);
CENTER:&attachref(GulfOu14.gif);&br;
CENTER:Fig.3 Pin-Link connection near the center span.&br;
<
**4.Details of loading [#dcec85cd]
>
Fluctuating loads due to vehicles live load.
<
**5.Description of damage [#k4bb2dc4]
>
Right-angled fatigue cracks were found in the fillet welds (corner joints) of the tie girder web-flange connections near the Pin-Link connection ([[Fig.4>#fig4]]). These cracks occurred in the area where the layer of the manual weld had been added to the submerged arc welded area in order to increase in the weld size. Additional layer by the manual weld existed in the inside and outside corner welds of the tie girder near the Pin connection and in the bolt spliced locations of the tie girder. Analysis of failure Surfaces and Examination of the metal tissue indicated that these cracks had occurred during fabrication.
Cause of fatigue cracks was as follows: Inclusion of slag and void which had existed in high tension residual stress regions due to the weld contraction.&br;
&aname(fig4);
CENTER:&attachref(GulfOu15.gif);&br;
CENTER:&attachref(GulfOu16.gif);&br;
CENTER:Fig.4 Etching face of the crack.&br;
<
**6.Repair method applied [#h6612149]
>
All the right-angled directional cracks were ground out and were removed by hole-drilling or core-drilling ([[Fig.5>#fig5]]).
The ground areas were checked by dye penetration. It was verified that no the crack tips remained.
CENTER:&attachref(GulfOu17.gif);&br;
CENTER:Fig.5 Repair part.&br;
終了行:
*Gulf Outlet Bridge, Louisiana. [#o2a36f9a]
**1.Field of application [#r0e44263]
>
Gulf Outlet Bridge cross canal in the mouth of a Mississippi River near New Orleans, Louisiana.
<
**2.Circumstances of Repair [#r337d610]
>
Right-angled directional fatigue cracks were found in the fillet welds (corner joints) of the box-section tie girder web-flange connections in 1978 after 13 years of service.
Most of these cracks did not propagate on the surface of the fillet weld. However, the surfaces of all the manual welded areas were needed to be etched and the dye penetrate testing was required.
<
**3.Types of structure [#hec6a8e5]
>
The structure is three spans truss bridge which suspended spans of the tied arch [[(Fig.1)>#fig1]]. The plan and typical cross section are shown in [[figure 2>#fig2]]. The tie girders are box sections with internal diaphragms. The corner joints of the tie girder were fillet weld connected. Each tie girder was connected near center span by Pin-Link [[(Fig.3)>#fig3]]. The tie girder web plate thickness was 19mm except at the Pin-Link connection where it was 89mm and the web plate thickness at the tie girder -floorbeam locations was 25.4mm.The tie girder flange plate thickness was 16mm.
The tie girder flange and web plates are A514 steel.&br;
&aname(fig1);
CENTER:&attachref(GulfOu12.gif);&br;
CENTER:Fig.1 Complete view.&br;&br;
&aname(fig2);
CENTER:&attachref(GulfOu13.gif);&br;
CENTER:Fig.2 Plan and cross section views.&br;&br;
&aname(fig3);
CENTER:&attachref(GulfOu14.gif);&br;
CENTER:Fig.3 Pin-Link connection near the center span.&br;
<
**4.Details of loading [#dcec85cd]
>
Fluctuating loads due to vehicles live load.
<
**5.Description of damage [#k4bb2dc4]
>
Right-angled fatigue cracks were found in the fillet welds (corner joints) of the tie girder web-flange connections near the Pin-Link connection ([[Fig.4>#fig4]]). These cracks occurred in the area where the layer of the manual weld had been added to the submerged arc welded area in order to increase in the weld size. Additional layer by the manual weld existed in the inside and outside corner welds of the tie girder near the Pin connection and in the bolt spliced locations of the tie girder. Analysis of failure Surfaces and Examination of the metal tissue indicated that these cracks had occurred during fabrication.
Cause of fatigue cracks was as follows: Inclusion of slag and void which had existed in high tension residual stress regions due to the weld contraction.&br;
&aname(fig4);
CENTER:&attachref(GulfOu15.gif);&br;
CENTER:&attachref(GulfOu16.gif);&br;
CENTER:Fig.4 Etching face of the crack.&br;
<
**6.Repair method applied [#h6612149]
>
All the right-angled directional cracks were ground out and were removed by hole-drilling or core-drilling ([[Fig.5>#fig5]]).
The ground areas were checked by dye penetration. It was verified that no the crack tips remained.
CENTER:&attachref(GulfOu17.gif);&br;
CENTER:Fig.5 Repair part.&br;
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