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*Steel bridge on Hanshin Expressway (at corner plate weld) [#e252b19a] **1.Field of application [#g7353f0c] >Steel bridge on Hanshin Expressway , Japan.&br; **2.Circumstances of Repair [#rb0ddb5a] >Fatigue cracks were found in the corner plate welds at the diaphragm locations in Jul. 1984 after 16 years of service. **3.Types of structure [#j2a6b924] >This bridge is box girder bridge with steel plate floor composed of three continuous spans. The plan at the crack location of Kobe-Nishinomiya line is shown in [[figure 1>#fig1]]. The corner plates were fillet weld connected to the girder flanges, the webs and the diaphragms ([[Fig.2>#fig2]]).&br; &br; &br; CENTER:&aname(fig1);&attachref(Hanko61.jpg);&br; &br; CENTER:Fig.1 Plan at the crack location.&br; &br; &br; CENTER:&aname(fig2);&attachref(Hanko62.jpg);&br; &br; CENTER:Fig.2 Connections of the corner plate. &br; &br; &br; **4.Details of loading [#l386e90f] >Fluctuating loads due to highway live load. **5.Description of damage [#h6675c82] >Fatigue cracks occurred in the welds of the corner plates at the diaphragm locations ([[Fig.3>#fig3]]). The cracks grew along the weld roots and some of them propagated into the girder bottom flanges. The maximum length of the crack which propagated into the girder bottom flange was beyond 280mm.&br; &br; &br; >Causes of fatigue cracks were as follows: -Restraint of the distortion at the diaphragm locations. -Small weld size and the thickness corner plate which were designed as secondary members. &br; &br; CENTER:&aname(fig3);&attachref(Hanko518.gif);&br; CENTER:&aname(fig3);&attachref(Hanko63.jpg);&br; &br; CENTER:(I-section girder) (Box section girder)&br; CENTER:Fig.3 Crack location.&br; CENTER:Fig.3 Crack at the corner plate connection with the diaphragm.&br; &br; &br; CENTER:&aname(fig4);&attachref(Hanko519.jpg);&br; &br; CENTER:(Girder outside flange) (Girder inside flange)&br; CENTER:Fig.4 Crack which propagated into the girder web and flange ( In case of I section girder ). &br; &br; CENTER:&aname(fig5);&attachref(Hanko520.jpg);&br; &br; CENTER:Fig.5 Crack which propagated into the girder web and flange ( In case of Box section girder ).&br; &br; &br; **6.Repair method applied [#w64e3f12] -In case of I-section girder. >Because it was difficult to replace the sole plate, repair was performed by gouging, groove welding and plate welding. >In order to release the restrained stress, a part of the corner plates at the diaphragm locations was removed ([[Fig.4>#fig4]]). Removal area was sealed by new plates, 250 by 300 by 2mm, in order to prevent corrosion ([[Fig.5>#fig5]]). >Retrofit procedure is as follows. >For the cracks which propagated into the girder bottom flanges, repair was performed by gouging, grinding and re-over welding ([[Fig.6>#fig6]]). >1.16mm diameter stop hole were drilled at the crack tip. >2.After jacking up the girder, a scallop was constructed in the girder web. >3.After gouging the crack and groove welding ([[Fig.6>#fig6]]), the new plates were weld connected on the girder flange and were bolt spliced at the scallop area which corresponded to the stop hole location of the girder web ([[Fig.7>#fig7]],[[8>#fig8]]). &br; &br; -In case of box girder. >The original sole plate was replaced with a new one by bolting ([[Fig.9>#fig9]],[[10>#fig10]]). CENTER:&aname(fig4);&attachref(Hanko64.jpg);&br; &br; CENTER:Fig.4 Removal of the corner plate.&br; &br; CENTER:&aname(fig6);&attachref(Hanko521.jpg);&br; &br; CENTER:Fig.6 Gouging the crack.&br; CENTER:&aname(fig5);&attachref(Hanko65.jpg);&br; &br; CENTER:Fig.5 Sealing by a new plate.&br; &br; CENTER:&aname(fig7);&attachref(Hanko522.jpg);&br; &br; CENTER:Fig.7 Repair method for I section girder.&br; CENTER:&aname(fig6);&attachref(Hanko66.jpg);&br; &br; CENTER:Fig.6 Gouging and re-welding of the crack at the girder bottom flange connection.&br; &br; CENTER:&aname(fig8);&attachref(Hanko523.jpg);&br; &br; CENTER:Fig.8 Complete view.&br; &br; &br; CENTER:&aname(fig9);&attachref(Hanko524.jpg);&br; &br; CENTER:Fig.9 Repair method for Box section girder.&br; &br; &br; CENTER:&aname(fig10);&attachref(Hanko525.jpg);&br; &br; CENTER:Fig.10 Complete view.&br; &br; &br;
