Platte-Winner Br.
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*Platte-Winner Br. [#l1dc1502]
**1.Field of application [#be38ddfd]
>The Platte-Winner Bridge of Route 44 crosses Lake Francis Case between Platte and Winner, South Dakota.
**2.Circumstances of repair [#b88bfda4]
>This bridge was designed in November 1961.In 1986,cracking was found in the girder web gaps between the transverse connection plate ends and the girder tension flange in the positive moment regions. In 1987, many locations were found with cracking in the web gaps in the positive moment regions and also in the negative moment regions.
>Therefore, the girder web gaps adjacent to the tension flange required strengthening.
>In 1987,Small surface cracks were also observed on the girder flanges at the fillet weld ends of the lateral gusset plates and in the girder web gaps at the longitudinal and vertical stiffener intersections.
>The stress range there were low such that peening the weld ends would provide the sufficient retrofits.
**3.Types of structure [#lba15077]
>The structure is welded construction consisting of two longitudinal girders, two longitudinal stringers, floorbeams, and lateral cross bracing. The general plan and elevation views are as shown in [[Fig.1>#fig1]],[[2>#fig2]].The girder webs of 10mm thickness contain longitudinal stiffeners 10 by 150mm and vertical stiffeners 16 by 200mm.Web gaps exist at the longitudinal and the vertical stiffener intersections or transverse connection plate intersections. The floorbeams are bolt connected to the transverse connection plates which are welded to the girder web and the girder compression flange. The transverse connection plate is cut short of the girder tension flange.
>The structural steel of the girder flanges and webs over the piers was ASTM A441 and the remainder of the structural steel was A36.
&br;
CENTER:&aname(fig1);&attachref(Platte16.gif);&br;
&br;
CENTER:Fig.1 General plan and elevation of portion of the Platte-Winner Bridge.
&br;
CENTER:&aname(fig2);&attachref(Platte17.gif);&br;
&br;
CENTER:Fig.2 General elevation and cross section
&br;
**4.Details of loading [#da3d81f9]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#ye6c0aa7]
>Fatigue cracks were found in the girder web gaps in the positive moment regions and also in the negative moment regions.
&br;
>Causes of fatigue cracks were as follows:
-The out-of-plane distortion which resulted from differential displacement of the girders transferred by the floorbeams and transverse connection plates.
-No positive attachment between the girder tension flange and the transverse connection plate.
**6.Repair method applied [#nf10c885]
>Repair and strengthening of the web gap parts subjected to cracking were performed by hole-drilling([[Fig.3>#fig3]],[[5>#fig5]]) and snugly fit by bars between the transverse connection plate end and the lateral gusset plates or the tension flange as shown in [[figure 4>#fig4]],[[5>#fig5]],[[6>#fig6]].
>At the welded terminations of the longitudinal stiffeners, the retrofit consisted of drilling two 13mm diameter holes between the longitudinal weld terminations and vertical stiffener weld toe. The two holes were connected by a vertical saw cut , referred to as the dog-bone retrofit, as shown in [[figure 7>#fig7]].Increasing the 13mm diameter holes to 19mm minimum was recommended for the final dog-bone retrofit.
&br;
CENTER:&aname(fig3);&attachref(Platte18.gif);&br;
&br;
CENTER:Fig.3 Retrofit hole at a crack tip.&br;
&br;
CENTER:&aname(fig4);&attachref(Platte19.gif);&br;
&br;
CENTER:Fig.4 Plan view of the before and after retrofit of the girder inside web gap adjacent to the bottom tension flange.
&br;
CENTER:&aname(fig5);&attachref(Platte20.gif);&br;
&br;
CENTER:Fig.5 Elevation of the before and after retrofit of the girder inside web gap adjacent to the bottom tension flange.
&br;
CENTER:&aname(fig6);&attachref(Platte21.gif);&br;
&br;
CENTER:Fig.6 Before and after retrofit of the girder inside web gap adjacent to the top tension flange.
&br;
CENTER:&aname(fig7);&attachref(Platte22.gif);&br;
&br;
CENTER:Fig.7 Before and after retrofit of intersecting vertical and longitudinal stiffeners.
&br;
&br;
終了行:
*Platte-Winner Br. [#l1dc1502]
**1.Field of application [#be38ddfd]
>The Platte-Winner Bridge of Route 44 crosses Lake Francis Case between Platte and Winner, South Dakota.
**2.Circumstances of repair [#b88bfda4]
>This bridge was designed in November 1961.In 1986,cracking was found in the girder web gaps between the transverse connection plate ends and the girder tension flange in the positive moment regions. In 1987, many locations were found with cracking in the web gaps in the positive moment regions and also in the negative moment regions.
>Therefore, the girder web gaps adjacent to the tension flange required strengthening.
>In 1987,Small surface cracks were also observed on the girder flanges at the fillet weld ends of the lateral gusset plates and in the girder web gaps at the longitudinal and vertical stiffener intersections.
>The stress range there were low such that peening the weld ends would provide the sufficient retrofits.
**3.Types of structure [#lba15077]
>The structure is welded construction consisting of two longitudinal girders, two longitudinal stringers, floorbeams, and lateral cross bracing. The general plan and elevation views are as shown in [[Fig.1>#fig1]],[[2>#fig2]].The girder webs of 10mm thickness contain longitudinal stiffeners 10 by 150mm and vertical stiffeners 16 by 200mm.Web gaps exist at the longitudinal and the vertical stiffener intersections or transverse connection plate intersections. The floorbeams are bolt connected to the transverse connection plates which are welded to the girder web and the girder compression flange. The transverse connection plate is cut short of the girder tension flange.
>The structural steel of the girder flanges and webs over the piers was ASTM A441 and the remainder of the structural steel was A36.
&br;
CENTER:&aname(fig1);&attachref(Platte16.gif);&br;
&br;
CENTER:Fig.1 General plan and elevation of portion of the Platte-Winner Bridge.
&br;
CENTER:&aname(fig2);&attachref(Platte17.gif);&br;
&br;
CENTER:Fig.2 General elevation and cross section
&br;
**4.Details of loading [#da3d81f9]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#ye6c0aa7]
>Fatigue cracks were found in the girder web gaps in the positive moment regions and also in the negative moment regions.
&br;
>Causes of fatigue cracks were as follows:
-The out-of-plane distortion which resulted from differential displacement of the girders transferred by the floorbeams and transverse connection plates.
-No positive attachment between the girder tension flange and the transverse connection plate.
**6.Repair method applied [#nf10c885]
>Repair and strengthening of the web gap parts subjected to cracking were performed by hole-drilling([[Fig.3>#fig3]],[[5>#fig5]]) and snugly fit by bars between the transverse connection plate end and the lateral gusset plates or the tension flange as shown in [[figure 4>#fig4]],[[5>#fig5]],[[6>#fig6]].
>At the welded terminations of the longitudinal stiffeners, the retrofit consisted of drilling two 13mm diameter holes between the longitudinal weld terminations and vertical stiffener weld toe. The two holes were connected by a vertical saw cut , referred to as the dog-bone retrofit, as shown in [[figure 7>#fig7]].Increasing the 13mm diameter holes to 19mm minimum was recommended for the final dog-bone retrofit.
&br;
CENTER:&aname(fig3);&attachref(Platte18.gif);&br;
&br;
CENTER:Fig.3 Retrofit hole at a crack tip.&br;
&br;
CENTER:&aname(fig4);&attachref(Platte19.gif);&br;
&br;
CENTER:Fig.4 Plan view of the before and after retrofit of the girder inside web gap adjacent to the bottom tension flange.
&br;
CENTER:&aname(fig5);&attachref(Platte20.gif);&br;
&br;
CENTER:Fig.5 Elevation of the before and after retrofit of the girder inside web gap adjacent to the bottom tension flange.
&br;
CENTER:&aname(fig6);&attachref(Platte21.gif);&br;
&br;
CENTER:Fig.6 Before and after retrofit of the girder inside web gap adjacent to the top tension flange.
&br;
CENTER:&aname(fig7);&attachref(Platte22.gif);&br;
&br;
CENTER:Fig.7 Before and after retrofit of intersecting vertical and longitudinal stiffeners.
&br;
&br;
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