Steel girder interstate highway bridge
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*Steel girder interstate highway bridge [#xdbadbc6]
**1.Field of application [#abdc34e7]
>Steel bridge is located on I-40 near Weatherford, Oklahoma.
**2.Circumstances of repair [#wc21aabe]
>Fatigue cracks were found in the coped ends of the diaphragms at the girder connections after approximately 20 years of service.
**3.Types of structure [#x0088449]
>The bridge is steel girder bridge with diaphragms ([[Fig.1>#fig1]]). A photograph showing several diaphragms on the bridge is presented in [[Fig.2>#fig2]]. Each diaphragm is coped top and bottom on both ends. Field observation and strain measurements indicated that the diaphragms were acting compositely with the concrete deck.
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CENTER:&aname(fig1);&attachref(Oklaho57.jpg);&br;
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CENTER:Fig.1 Elevation view.
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CENTER:&aname(fig2);&attachref(Oklaho58.jpg);&br;
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**4.Details of loading [#q6bcfc6d]
>Fluctuating loads due to highway live load.
**5.Description of damage [#h790359c]
>Many diaphragms were cracked ([[Fig.3>#fig3]]) and some of them have experienced a total section loss ([[Fig.4>#fig4]]). [[Fig.5>#fig5]] shows typical crack positions along the diaphragms. The crack began at the root of the cope and extend vertically up through the web toward the top flange.
>Causes of fatigue crack were as follows:
-A high degree of restraint at the diaphragm-to-girder connection.
-High stress concentration of the bottom-flange cope at the diaphragm-to-girder connection due to differential deflections of the longitudinal girders.
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CENTER:&aname(fig3);&attachref(Oklaho59.jpg);&br;
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&br;
CENTER:&aname(fig3);&attachref(Oklaho60.jpg);&br;
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CENTER:&aname(fig4);&attachref(Oklaho61.jpg);&br;
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**6.Repair method applied [#bfae1b00]
>Three modified diaphragms were analyzed and tested to evaluate their suitability as repair options.
>The first : uncoped diaphragm.
>The second : diaphragm with a tapered cope.
>The third : Removing the bolts from the lower half of the diaphragm-to-girder connection.
>All modifications succeed in reducing stress at the cope.
>Based on the research presented, it was recommended to the Oklahoma Department of Transportation that for uncracked diaphragms and for diaphragms with cracks shorter than 25.4, the bottom two bolts in the diaphragm-to-girder connection be removed. It was further recommended that diaphragms containing.
>Cracks longer than 25.4mm should be removed and replaced with diaphragms not coped at the bottom flange. To encourage a smooth flow of stress from one diaphragm to the next, the bottom two bolts should also be omitted from these uncoped diaphragms.
**Reference [#z758ff9f]
>Zwerneman F. J. Fatigue damage to steel bridge diaphragms, '''Journal of Performance of Constructed Facilities''', vol. 7, No.4, 1993.
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終了行:
*Steel girder interstate highway bridge [#xdbadbc6]
**1.Field of application [#abdc34e7]
>Steel bridge is located on I-40 near Weatherford, Oklahoma.
**2.Circumstances of repair [#wc21aabe]
>Fatigue cracks were found in the coped ends of the diaphragms at the girder connections after approximately 20 years of service.
**3.Types of structure [#x0088449]
>The bridge is steel girder bridge with diaphragms ([[Fig.1>#fig1]]). A photograph showing several diaphragms on the bridge is presented in [[Fig.2>#fig2]]. Each diaphragm is coped top and bottom on both ends. Field observation and strain measurements indicated that the diaphragms were acting compositely with the concrete deck.
&br;
CENTER:&aname(fig1);&attachref(Oklaho57.jpg);&br;
&br;
CENTER:Fig.1 Elevation view.
&br;
&br;
CENTER:&aname(fig2);&attachref(Oklaho58.jpg);&br;
&br;
**4.Details of loading [#q6bcfc6d]
>Fluctuating loads due to highway live load.
**5.Description of damage [#h790359c]
>Many diaphragms were cracked ([[Fig.3>#fig3]]) and some of them have experienced a total section loss ([[Fig.4>#fig4]]). [[Fig.5>#fig5]] shows typical crack positions along the diaphragms. The crack began at the root of the cope and extend vertically up through the web toward the top flange.
>Causes of fatigue crack were as follows:
-A high degree of restraint at the diaphragm-to-girder connection.
-High stress concentration of the bottom-flange cope at the diaphragm-to-girder connection due to differential deflections of the longitudinal girders.
&br;
CENTER:&aname(fig3);&attachref(Oklaho59.jpg);&br;
&br;
&br;
CENTER:&aname(fig3);&attachref(Oklaho60.jpg);&br;
&br;
&br;
CENTER:&aname(fig4);&attachref(Oklaho61.jpg);&br;
&br;
**6.Repair method applied [#bfae1b00]
>Three modified diaphragms were analyzed and tested to evaluate their suitability as repair options.
>The first : uncoped diaphragm.
>The second : diaphragm with a tapered cope.
>The third : Removing the bolts from the lower half of the diaphragm-to-girder connection.
>All modifications succeed in reducing stress at the cope.
>Based on the research presented, it was recommended to the Oklahoma Department of Transportation that for uncracked diaphragms and for diaphragms with cracks shorter than 25.4, the bottom two bolts in the diaphragm-to-girder connection be removed. It was further recommended that diaphragms containing.
>Cracks longer than 25.4mm should be removed and replaced with diaphragms not coped at the bottom flange. To encourage a smooth flow of stress from one diaphragm to the next, the bottom two bolts should also be omitted from these uncoped diaphragms.
**Reference [#z758ff9f]
>Zwerneman F. J. Fatigue damage to steel bridge diaphragms, '''Journal of Performance of Constructed Facilities''', vol. 7, No.4, 1993.
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