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*Sozuka-Ohhashi (at suspension member) [#vca49e3e] *Mashita Bridge [#i0a7d8c9] **1.Field of application [#i599a773] >Sozuka-Ohhashi over dam lake which is located between Ohtsu and Uji, Shiga-prefecture, Japan.&br; >Through-type Langer bridge on the roadway bridge, Japan.&br; **2.Circumstances of Repair [#u882a38e] >Fatigue fractures were found at the weld of the suspension members, which connected the lower lateral bracing with the stringer, in 1981 after 15 years of service. >Fatigue cracks were found at the joint of the vertical member and the tie girder. >This type of damage cases can be often seen at the arch, truss bridge and through-type deck girder bridge which have the same detail. The lower lateral bracing of these bridges are almost rivet or weld connected to the stringers as same as Sozuka-Ohhashi. Generally, the damage occurs in the rivet connection or weld connection. For such kinds of damage, repair is frequently performed by replacing the original joints to the high strength bolts. **3.Types of structure [#c0ce81ce] >This bridge is the 2-hinge rib arch through bridge of which arch span length is 106m long. The structure of the bridge can be seen in case of "Sozuka-Ohhashi, Ohtsu, Shiga-prefecture (at member connection)". The suspension members were weld connected to the stringer bottom flanges in order to support the lower lateral members. >This bridge is the through-type Langer bridge of which arch span length is 66m ([[Fig.1>#fig1]]). The vertical members were H-type section and were weld connected to the top flange of the tie girders. &br; &br; CENTER:&aname(fig1);&attachref(Mashit26.gif);&br; &br; CENTER:Fig.1 Through-type Langer bridge.&br; **4.Details of loading [#z09b72b6] >Fluctuating loads due to vehicles live load. >Fluctuating loads due to wind load. **5.Description of damage [#id2681d9] >Fatigue fracture initiated from the weld beads of the suspension members at the lower lateral bracing connections with the stringer ([[Fig.1>#fig1]]). There were some cases that the damage occurred in the rivet locations of the suspension members. Cause of fatigue cracks is as follows. Differential displacement between the main girder and the floor system. >Fatigue cracks occurred in the joint of the vertical member and tie girder ([[Fig.2>#fig2]]). The vertical members at the middle part of the bridge suffered the vibration due to wind of which speed was about 15 m/s. Cause of fatigue cracks is as follows. Vibration of the vertical members which was caused by Kerman's vortex. &br; &br; CENTER:&aname(fig1);&attachref(Sozuka23.gif);&br; CENTER:&aname(fig2);&attachref(Mashit27.gif);&br; &br; CENTER:Fig.1 Fatigue fracture of the suspension member.&br; CENTER:&aname(fig2);&attachref(Mashit28.gif);&br; &br; CENTER:Fig.2 Crack which occurred in the joint of the vertical member and tie girder.&br; &br; &br; **6.Repair method applied [#p649a511] >Before repairing, the removal of the original members was carried out by frame-cutting and weld area remained was ground smooth ([[Fig.2>#fig2]]). Repair of parts subjected to damaging was to replace to the new members by using high strength bolts ([[Fig.3>#fig3]]). -Emergency repair >Fracture part were pulled back by wire rope. To prevent the vibration of the vertical members, each vertical member were connected to the adjacent members by making use of logs. -Permanent repair >The modification of connection detail was performed so that the stress transfers smoothly to the web plate of the tie girder ([[Fig.3>#fig3]]). &br; &br; CENTER:&aname(fig2);&attachref(Sozuka24.gif);&br; CENTER:&aname(fig3);&attachref(Mashit29.gif);&br; &br; CENTER:Fig.2 Grinding area.&br; CENTER:Fig.3 Retrofit work.&br; &br; &br; CENTER:&aname(fig3);&attachref(Sozuka25.gif);&br; &br; CENTER:Fig.3 Replacement of the suspension member.&br; &br; &br; **Reference [#c6c99da1] >Takada H. and Mizumoto M.,Report on Strengthening Construction of Sozuka-Ohhashi. '''Yokogawa Bridge Works Technical Report''', No.19,1990 &br; &br;
