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*Thomas Br. [#l370268a] **1.Field of application [#c4bc71a3] >The Thomas bridge of U.S. Route 219 crosses the Blackwater River in Tucker County, West Virginia. **2.Circumstances of repair [#ocdc6a7e] >This bridge was designed in 1979. In 1986, fatigue cracks were found in the top and bottom un-stiffened girder web gaps. Therefore, retrofit procedures were recommended. **3.Types of structure [#t158cd91] >The structure consists of multiple longitudinal girders which support a reinforced concrete deck and transverse cross bracing. The plan and elevation views are shown in [[figure 1>#fig1]],[[2>#fig2]]. The span 1 girders are kinked at the splice to permit a curved roadway. The transverse cross bracing exist between the girders and offset in span 1([[Fig.1>#fig1]]).The transverse cross bracing is bolt connected to transverse connection plates which are fillet weld connected to the girder webs and the girder compression flanges. The transverse connection plates are cut short of the girder tension flanges creating 64mm girder web gaps in the positive and the negative moment regions([[Fig.3>#fig3]]). At the inflection joints, the transverse connection plates are not attached to the girder top and bottom flanges. The structural steel is ASTM A36. &br; CENTER:&aname(fig1);&attachref(i95_ht83.gif);&br; CENTER:&aname(fig1);&attachref(Thomas1.gif);&br; &br; CENTER:Fig.1 Schematic of the exterior web face of fascia girders.&br; CENTER:Fig.1 Framing plan and girder elevation.&br; &br; CENTER:&aname(fig2);&attachref(Thomas3.gif);&br; &br; CENTER:Fig.2 Elevation view and transverse connection plate (or stiffener) layout. &br; CENTER:&aname(fig3);&attachref(Thomas2.gif);&br; &br; CENTER:Fig.3 Transverse cross bracing and transverse connection plates. &br; **4.Details of loading [#w2df67b8] >Fluctuating loads due to vehicles live load. **5.Description of damage [#c4990c2f] >The crack occurred in the butt connection groove weld of a continuous tension-side longitudinal stiffener, continued through the web between the stiffener and bottom flanges, and penetrated the bottom flange. &br; >Fatigue cracks were found in the top and the bottom un-stiffened web gaps at the transverse connection plate ends. >Cause of fatigue crack was as follows: -Separational discontinuities in the butt connection groove weld of the continuous tension longitudinal stiffener. -Out-of-plane distortion which resulted from the differential displacement between the girders. -The kink structure in the span 1 roadway. -No positive attachment near the inflection points between the transverse connection plate ends and the girder flanges. **6.Repair method applied [#u4789b36] >The fatigue cracked girder web and bottom tension flange were bolt spliced ([[Fig2>#fig2]]). >Repair of parts subjected to cracking were performed by hole-drilling at the crack tips and positive attachment between the transverse connection plates and the girder flanges in span1 and the negative moment regions of the other spans. &br; CENTER:&aname(fig2);&attachref(i95_ht84.gif);&br; &br; CENTER:Fig.2 Bolt splice repair of fatigue cracked girder web and bottom flange.&br; > The possibility existed for fatigue crack growth in the butt connection groove welds of other tension longitudinal stiffeners. Therefore, from the exterior of the fascia girder web, small hole was drilled through the girder web at the top of the fillet weld toe centered over the tension groove weld. >A 51mm diameter holes were trepanned from the interior of the fascia girder web centered on the longitudinal stiffener groove weld ([[Fig.3>#fig3]]).The holes extended through the web into the longitudinal stiffener a maximum 3mm past the stiffener fillet weld toe. &br; CENTER:&aname(fig3);&attachref(i95_ht85.gif);&br; &br; CENTER:Fig.3 Retrofit of tension longitudinal stiffeners.&br; &br; &br;
