No. 28 County road Br.
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開始行:
*No. 28 County road Br. [#ac1ffc29]
**1.Field of application [#v5e5d2b2]
>No.28 County road Bridge over I-57 in Fayette County, north of Farina , Illinois.
**2.Circumstances of repair [#df397552]
>Large fatigue crack was found in the main girder web at the core refilled by welding, which was drilled in the main girder web by mistake, in March 1977 after 9 years of service. These cracks had connected each other and had caused the brittle fracture of the girder flange and web. Therefore, repair was required.
**3.Types of structure [#m1872c1a]
>This bridge consists of four continuous spans skewed structure. The plane and elevation views are shown in [[figure 1>#fig1]]. A cross section is shown in [[figure 2>#fig2]]. The five main girders are W36×H150 of ASTM A36-97 steel. The reinforced concrete deck forms composite action with girders.
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CENTER:&aname(fig1);&attachref(No_28B11.gif);&br;
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CENTER:Fig.1 Plan and elevation views.
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CENTER:&aname(fig2);&attachref(No_28B12.gif);&br;
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CENTER:Fig.2 Cross section.
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**4.Details of loading [#qc43cc77]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#vcf973c1]
>Fatigue cracks originated from two cores refilled by welding, which were drilled in the main girder web by mistake([[Fig.3>#fig3]]). The sharp cracks due to fatigue connected each other and occurred in the brittle fracture under low temperature. As a result, the girder bottom flange was fractured.
>Fatigue cracks horizontally had propagated in the middle girder web([[Fig.4>#fig4]]).
&br;
>Cause of fatigue cracks was as follows:
-Inclusion of slag and void which had existed in the refilling weld.
&br;
CENTER:&aname(fig3);&attachref(No_28B13.gif);&br;
&br;
CENTER:Fig.3 Crack initiated from the weld-refilling holes.
&br;
CENTER:&aname(fig4);&attachref(No_28B14.gif);&br;
&br;
CENTER:Fig.4 Crack propagation in the 2B2 girder web.
&br;
**6.Repair method applied [#jce9a91e]
>Replacement of the damaged parts ([[Fig.5>#fig5]]).
>The repair procedure is as follow.
>Total length of the girder web between the splice parts was frame-cut below the 254mm from the bottom face of the girder top flange. The T-shaped steel which consisted of the same form as the removal girder was horizontally field-welded. After that, this T-shaped steel was bolt connected to the adjacent girders by using the connection plate which had been used before repair.
>As a result of repairing, new weld joint was located near the girder neutral axis. No the outstanding cyclic stress could produced there. Therefore, it was supported that no the crack reinitiate from the repaired member.
CENTER:&aname(fig5);&attachref(No_28B15.gif);&br;
&br;
CENTER:Fig.5 Detail of repair.
&br;
&br;
終了行:
*No. 28 County road Br. [#ac1ffc29]
**1.Field of application [#v5e5d2b2]
>No.28 County road Bridge over I-57 in Fayette County, north of Farina , Illinois.
**2.Circumstances of repair [#df397552]
>Large fatigue crack was found in the main girder web at the core refilled by welding, which was drilled in the main girder web by mistake, in March 1977 after 9 years of service. These cracks had connected each other and had caused the brittle fracture of the girder flange and web. Therefore, repair was required.
**3.Types of structure [#m1872c1a]
>This bridge consists of four continuous spans skewed structure. The plane and elevation views are shown in [[figure 1>#fig1]]. A cross section is shown in [[figure 2>#fig2]]. The five main girders are W36×H150 of ASTM A36-97 steel. The reinforced concrete deck forms composite action with girders.
&br;
CENTER:&aname(fig1);&attachref(No_28B11.gif);&br;
&br;
CENTER:Fig.1 Plan and elevation views.
&br;
CENTER:&aname(fig2);&attachref(No_28B12.gif);&br;
&br;
CENTER:Fig.2 Cross section.
&br;
**4.Details of loading [#qc43cc77]
>Fluctuating loads due to vehicles live load.
**5.Description of damage [#vcf973c1]
>Fatigue cracks originated from two cores refilled by welding, which were drilled in the main girder web by mistake([[Fig.3>#fig3]]). The sharp cracks due to fatigue connected each other and occurred in the brittle fracture under low temperature. As a result, the girder bottom flange was fractured.
>Fatigue cracks horizontally had propagated in the middle girder web([[Fig.4>#fig4]]).
&br;
>Cause of fatigue cracks was as follows:
-Inclusion of slag and void which had existed in the refilling weld.
&br;
CENTER:&aname(fig3);&attachref(No_28B13.gif);&br;
&br;
CENTER:Fig.3 Crack initiated from the weld-refilling holes.
&br;
CENTER:&aname(fig4);&attachref(No_28B14.gif);&br;
&br;
CENTER:Fig.4 Crack propagation in the 2B2 girder web.
&br;
**6.Repair method applied [#jce9a91e]
>Replacement of the damaged parts ([[Fig.5>#fig5]]).
>The repair procedure is as follow.
>Total length of the girder web between the splice parts was frame-cut below the 254mm from the bottom face of the girder top flange. The T-shaped steel which consisted of the same form as the removal girder was horizontally field-welded. After that, this T-shaped steel was bolt connected to the adjacent girders by using the connection plate which had been used before repair.
>As a result of repairing, new weld joint was located near the girder neutral axis. No the outstanding cyclic stress could produced there. Therefore, it was supported that no the crack reinitiate from the repaired member.
CENTER:&aname(fig5);&attachref(No_28B15.gif);&br;
&br;
CENTER:Fig.5 Detail of repair.
&br;
&br;
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