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*Shemimaru Bridge of Meishin Expressway [#x3342dba] **1.Field of application [#qc0a4a79] >Shemimaru bridge between Kyoto-Higashi interchange and Otsu interchange of Meishin expressway. &br; **2.Circumstances of Repair [#f6772d15] >Fatigue cracks were found in the floor system members 1984 after 21 years of service. Further, fatigue cracks were found in the top and bottom ends of the vertical member in 1987 after 24 years of service.&br; **3.Types of structure [#ae54ef73] >The outline of the bridge structure is as follows. -Bridge length : 62..2 m -Span length : The stiffening girder 61.6 m, Between the arch ribs 54.0 m -Skewed degree : 62 degree -Structure : 2 hinge arch deck bridge -Deck : Reinforced concrete deck (16.0 cm thickness) -Structural steel : SS 41, SM 50 &br; &br; >Elevation and plan are shown in [[figure 1>#fig1]]. This bridge is composed of two main girders and two arch ribs. No the cross bracing existed between the arch ribs. The top and bottom ends of the vertical members are weld connected to the base plates which are rivet connected to the arch ribs and the stiffening girders.&br; &br; &br; CENTER:&aname(fig1);&attachref(Shemim5.jpg);&br; &br; CENTER:Fig.1 Elevation and plan views.&br; &br; &br; **4.Details of loading [#s24a1c95] >Fluctuating loads due to highway live load. **5.Description of damage [#fcd62002] >Fatigue cracks were found in the vertical member ends and the stringer webs ([[Fig.2>#fig2]],[[3>#fig3]]). These cracks of the vertical member ends occurred along the weld beads at the vertical members' connections with the base plates. Some of them propagated in the vertical member webs. >Cause of fatigue cracks was thought as follows: -Peculiar structure that showed the complicated in-plane and out-of-plane deformation. &br; &br; CENTER:&aname(fig2);&attachref(Shemim6.jpg);&br; &br; CENTER:Fig.2 Crack locations.&br; &br; &br; CENTER:&aname(fig3);&attachref(Shemim7.jpg);&br; &br; CENTER:Fig.3 Crack at the vertical member ends.&br; &br; &br; **6.Repair method applied [#g885c195] >As the strengthening, the improvement of the structural detail and the whole stiffness were performed. -The improvement of the gusset detail. >The fillet members were installed on the vertical member flanges near the end connections in order to lessen the localized stress concentration ([[Fig.4>#fig4]]). -The improvement of the whole stiffness. >The measure of the improvement of the whole stiffness is shown in [[figure 5>#fig5]]. Strengthening is to spandrel braced arching. The deck and all the members such as the vertical member and the stiffening girders were replaced. The diagonal members, the cross bracings and the arch lateral bracings were added ([[fig.5>#fig5]]).&br; &br; &br; **Outcome [#g885c195] >In the inspection after completion of the strengthening work, fatigue cracking was not found. Further, periodic inspection will be continued from now on. &br; &br; CENTER:&aname(fig4);&attachref(Shemim8.jpg);&br; &br; CENTER:Fig.4 The improvement of the gusset detail.&br; &br; &br; CENTER:&aname(fig5);&attachref(Shemim9.jpg);&br; &br; CENTER:Fig.5 The improvement of the whole stiffness.&br; &br; &br; **Outcome [#g885c195] >In the inspection after completion of the strengthening work, fatigue cracking was not found. Further, periodic inspection will be continued from now on. &br; &br;
