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*Steel bridge of The Tomei Expressway [#q6084129] **1.Field of application [#r87c45b5] >Steel bridge of The Tomei Expressway near Hamamatsu, Japan.&br; **2.Circumstances of Repair [#t8888481] >Fatigue cracks were found in the top ends of the connection plates at the transverse cross bracing locations in 1983 after 15 years of service.br; >Fatigue cracks were found in the top ends of the connection plates at the transverse cross bracing locations in 1983 after 15 years of service.&br; **3.Types of structure [#xb0d9d90] >The outline of the bridge structure is as follows.&br; -Bridge length : three spans : (28.6 + 29.0 + 28.6 )m , four spans : (28.6 + 29.0 + 29.0 + 28.6 )m -Structure : Three spans and four spans continuous I-beam girder bridge -Deck : Reinforced concrete deck ( 19 cm thickness ) -Structural steel : SM50 , SS41 &br; &br; >Framing plan and cross section were shown in [[figure 1>#fig1]]. The number of the main girders which are spaced at 4.0m is three. The floor system is composed of two stringers and transverse cross bracings.&br; &br; &br; CENTER:&aname(fig1);&attachref(TomeiE1.jpg);&br; &br; CENTER:Fig.1 Framing plan and cross section.&br; &br; &br; **4.Details of loading [#bfa00819] >Fluctuating loads due to highway live load. **5.Description of damage [#u9900afd] >Fatigue cracking were found in the weld toes of the connection plate end at the transverse lateral locations ([[Fig.2>#fig2]]).&br; &br; &br; >Cause of fatigue cracks was as follows:&br; -Out-of-plane distortion which resulted from the differential deflection between the girders. &br; &br; CENTER:&aname(fig2);&attachref(TomeiE2.jpg);&br; &br; CENTER:Fig.2 Crack location.&br; &br; &br; **6.Repair method applied [#ob390316] >Repair of parts subjected to cracking was performed by crack-removing, re-welding and weld toe finishing (Grinding or TIG dressing) in order to improve the weld bead and reduce the localized stress concentration at the weld toe, because most of cracks occurred in the fillet weld toe. This repair method is effective in case the occurring stress is not severe.&br; &br; >However the occurring stress is high in this bridge, crack reinitiated.&br; &br; >Therefore, strengthening was performed by addition of the transverse cross bracing or addition of the reinforced concrete deck. It was verified that these strengthening were enough effective to reduce the stress.&br; &br; >Periodic inspection of the strengthened procedures will be continued.&br; &br; &br;
