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*Two hinges arch bridge on roadway bridge (Part 2) [#h58082e2] **1.Field of application [#re242e97] >Two hinges arch bridge on roadway bridge (Part 2), Japan.&br; **2.Circumstances of Repair [#g6d4997d] >Fatigue cracks were found at the connections between the vertical member and the floor system member 1989 after 20 years of service.&br; **3.Types of structure [#l534c6cc] >The outline of the bridge structure is as follows. -Bridge length : The up bound line : 240 m, The down bound line : 216 m -Span length : The up bound line : (30 + 180 + 30)m, The down bound line : (27 + 167 + 27)m -Structure : Two hinge arch deck bridge -Deck : Reinforced concrete deck (18.0 cm thickness) -Structural steel : SS 41, SM 50, SM58 &br; &br; >Elevation and cross section are shown in [[figure 1>#fig1]]. The number of the main girders are two, which are spaced at 8.0m. The floor system is composed of one stringer and two added stringers.&br; &br; &br; CENTER:&aname(fig1);&attachref(Twohin10.jpg);&br; &br; CENTER:Fig.1 Elevation and cross section.&br; &br; &br; **4.Details of loading [#t1c3e3a8] >Fluctuating loads due to vehicles live load. **5.Description of damage [#c7d1527e] >Fatigue cracks were found at the vertical member weld connections with the arch ribs and the stiffening girders ([[Fig.2>#fig2]],[[3>#fig3]]). The length of the cracks was almost over 10mm except that the maximum length of about 80mm. Fatigue cracks occurred in both the weld toe and the weld root. >Cause of fatigue cracks was thought as follows: -Out-of-plane deformation having acted on the stiffening girder flanges and the arch rib flanges at the vertical member connections. &br; &br; >Fatigue crack was found in the boxing of the gusset plate end which connected the lateral bracing to the end floorbeam. >Cause of fatigue crack was thought as follows. -Out-of-plane distortion of the floorbeam web which resulted from the differential deflection of the main girders and the stringers. &br; &br; CENTER:&aname(fig2);&attachref(Twohin11.jpg);&br; &br; CENTER:Fig.2 Crack location at the vertical member ends.&br; &br; &br; CENTER:&aname(fig3);&attachref(Twohin12.jpg);&br; &br; CENTER:Fig.3 Crack occurring in the boxing of the gusset plate end.&br; &br; &br; **6.Repair method applied [#j1dea2d5] -The vertical member connection. >Localized repair and strengthening were performed for parts subjected to cracking because fatigue cracks initiated locally. >Ⅰ.Parts subjected to cracking. >Repair of parts subjected to cracking was performed by removal of crack and re-welding (full penetration). After that, TIG dressing was performed on the re-weld toe. For parts where were not subjected to cracking, TIG dressing was passed on the boxing toe of the gusset plate. >Ⅱ.The improvement of the structural detail. >For the vertical members near the intermediate span, L-type plates were spliced by high strength bolt in order to lessen the stress concentration of the gusset plate end ([[Fig.4>#fig4]]). -Floor system >Repair of parts subjected to cracking was performed by removal of crack, padding of weld, finishing of the weld toe by grinding. CENTER:&aname(fig4);&attachref(Twohin13.jpg);&br; &br; CENTER:Fig.4 Bolt splice.&br; &br; &br;
