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*Aquasabon River (defects in the short groove weld in the web) [#pd94628f] **1.Field of application [#za046185] **2.Circumstances of repair [#aa95dbd7] -Location of transformation >main girder of haunch **3.Types of structure [#t81916f6] >The structure is continuous for three spans and the reinforced concrete deck forms composite action ([[Fig.1>#fig1]]). The superstructure is composed of four main girders , which hunched at the piers and abutments, and the floor beams. These hunching procedures were fabricated as follow. The bottom flanges which had been fillet weld connected to the girder web are cut off and the parabolic insert plates of 16mm thickness are butt welded to the cutting girder web and flange ([[Fig.2>#fig2]]). CENTER:&aname(fig1);&attachref(aquasa10.jpg);&br; &br; CENTER:Fig.1 Plan view of Aquasabon Bridge.&br; &br; CENTER:&aname(fig2);&attachref(aquasa11.jpg);&br; &br; CENTER:Fig.2 Detail of the joint and hunched structure.&br; &br; **4.Details of loading [#g5e4708f] >opened in 1948, cracks were found in 1963, 15yeres **5.Description of damage and Repair method applied [#wa29cf7c] -Detail of fatigue transformation >Some fatigue cracks were originated in wide flange of rolled main girder. These cracks were originated at transverse short groove weld which is located at the end of insert with parabolic shape of the main girder ([[Fig.3>#fig3]]). One of the cracks crossed transverse groove weld and reached web plate with the length of 178mm. And it broke about 65% of the lower flange. &br; CENTER:&aname(fig3);&attachref(aquasa12.jpg);&br; &br; CENTER:&aname(fig3);&attachref(aquasa13.jpg);&br; &br; CENTER:Fig.3 Vertical cracking in the butt weld of the hunched girder web.&br; -Cause >Causes of fatigue cracks were as follows: >Big flaws in short transverse groove weld is the cause of cracks. The length of weld was not long enough for good connection. >There is no influence of temperature and environment when cracks are originated. From the inspection of face of crack, it was found that those cracks were stable fatigue cracks ([[Fig.4>#fig4]]). It was not broken by brittle fracture even though cracks reached the web plate because dead load. Stress is low and the maximum stress is low at an inflection points. CENTER:&aname(fig4);&attachref(aquasa15.jpg);&br; CENTER:&aname(fig4);&attachref(aquasa15.gif);&br; &br; CENTER:Fig.4&br; -Maintenance and reinforcement >The cover plate was welded and an insertplate was welded to holes for cracks found in 1963. Welding part was cut off and an insert plate was welded for cracks found in 1973. Clacks in the lower flange were gouged and welded again. >Inspection done late, cracks were generated after maintenance, they were reinforced by splice plates and bolts at all the haunches ([[Fig.5>#fig5]]). -Repair procedure and the effect >The recommended retrofit for improving the cover plate girder in span 10 was peening the weld ends and Gas Tungsten re-weld ([[Fig.8>#fig8]],[[9>#fig9]]). The retrofits of the fatigue cracking which are more than 38mm in length along the weld toe were bolt spliced ([[Fig.10>#fig10]]) and hole-drilling in the girder webs just above the cracking. CENTER:&aname(fig5);&attachref(aquasa17.gif);&br; &br; CENTER:&aname(fig8);&attachref(yellow7.jpg);&br; CENTER:Fig.5&br; &br; CENTER:Fig.8 Weld toe re-welded by Gas Tungsten arc.&br; &br; CENTER:&aname(fig9);&attachref(yellow8.jpg);&br; &br; CENTER:Fig.9 Weld toe peened.&br; &br; CENTER:&aname(fig10);&attachref(yellow9.jpg);&br; &br; CENTER:Fig.10 Detail of the bolt splice.&br; &br; &br;
