2680 Br.
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開始行:
*2680 Br. [#n46ca1ae]
**1.Field of application [#v3088e1f]
>The 2680 bridges on I-79 cross Big Sandy Creek 26 miles (42km) north of Charleston, West Virginia.
**2.Circumstances of repair [#vb8560e3]
>Fatigue cracking was found in the intermediate transverse stiffener end and along the girder web-flange welds in May 1984 after 12 years of service.
>Inspection of bridge structures indicated that the cracked locations required repair.
**3.Types of structure [#a8d98161]
>The structure consists of multiple continuous curved girders which are spliced by field bolting, transverse cross bracing, and lateral bracing. The girder elevation and framing plan are shown in [[figure 1>#fig1]]. Transverse cross bracing is connected to the transverse connection plates which are weld connected to the girder webs. No positive attachment exists between the transverse connection plates and the girder top or bottom flanges. Transverse web stiffeners exist on both sides of the girders.
>The structural steel was ASTM A36.
&br;
CENTER:&aname(fig1);&attachref(2680%20B44.jpg);&br;
&br;
CENTER:Fig.1 Framing Plan and girder elevation, northbound.
&br;
**4.Details of loading [#gb82482c]
>Fluctuating loads due to vehicles live load. This resulted in large cyclic stresses at the web-flange weld toe and the transverse connection plate weld termination.
**5.Description of damage [#we6dd771]
>Initially, fatigue cracks were found in the bottom web gaps at the web stiffener ends near the field splices Additional crack indications were later detected in the girder top web gaps at the transverse connection plate end and along the web-flange weld toe ([[Fig.2>#fig2]]).
>Causes of fatigue crack were as follows:
-The cyclic stress due to shipping and handling.
-The web vibration resulting in the paint breaking.
-Out-of-plane bending in the top web gaps.
&br;
CENTER:&aname(fig2);&attachref(2680%20B45.jpg);&br;
&br;
CENTER:Fig.1 Schematic of fatigue cracking in the girder top web gaps.
&br;
**6.Repair method applied [#tb1a3c59]
>The repairs of parts subjected to cracking were performed by hole-drilling at the tips of all cracks and positively bolt-connecting with an angle at the girder web and flange.
>The repairs for the top web gap were performed by drilling 51mm holes on each side of the transverse connection plate adjacent to the girder top flange.
&br;
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終了行:
*2680 Br. [#n46ca1ae]
**1.Field of application [#v3088e1f]
>The 2680 bridges on I-79 cross Big Sandy Creek 26 miles (42km) north of Charleston, West Virginia.
**2.Circumstances of repair [#vb8560e3]
>Fatigue cracking was found in the intermediate transverse stiffener end and along the girder web-flange welds in May 1984 after 12 years of service.
>Inspection of bridge structures indicated that the cracked locations required repair.
**3.Types of structure [#a8d98161]
>The structure consists of multiple continuous curved girders which are spliced by field bolting, transverse cross bracing, and lateral bracing. The girder elevation and framing plan are shown in [[figure 1>#fig1]]. Transverse cross bracing is connected to the transverse connection plates which are weld connected to the girder webs. No positive attachment exists between the transverse connection plates and the girder top or bottom flanges. Transverse web stiffeners exist on both sides of the girders.
>The structural steel was ASTM A36.
&br;
CENTER:&aname(fig1);&attachref(2680%20B44.jpg);&br;
&br;
CENTER:Fig.1 Framing Plan and girder elevation, northbound.
&br;
**4.Details of loading [#gb82482c]
>Fluctuating loads due to vehicles live load. This resulted in large cyclic stresses at the web-flange weld toe and the transverse connection plate weld termination.
**5.Description of damage [#we6dd771]
>Initially, fatigue cracks were found in the bottom web gaps at the web stiffener ends near the field splices Additional crack indications were later detected in the girder top web gaps at the transverse connection plate end and along the web-flange weld toe ([[Fig.2>#fig2]]).
>Causes of fatigue crack were as follows:
-The cyclic stress due to shipping and handling.
-The web vibration resulting in the paint breaking.
-Out-of-plane bending in the top web gaps.
&br;
CENTER:&aname(fig2);&attachref(2680%20B45.jpg);&br;
&br;
CENTER:Fig.1 Schematic of fatigue cracking in the girder top web gaps.
&br;
**6.Repair method applied [#tb1a3c59]
>The repairs of parts subjected to cracking were performed by hole-drilling at the tips of all cracks and positively bolt-connecting with an angle at the girder web and flange.
>The repairs for the top web gap were performed by drilling 51mm holes on each side of the transverse connection plate adjacent to the girder top flange.
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