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*Woodrow Wilson Memorial Br. [#oe9f3a15] **1.Field of application [#e57d1511] >The Woodrow Wilson Memorial Bridge on the Capital Beltway , Route I-95, spans the Potomac River at the State borders of Maryland and Virginia. **2.Circumstances of repair [#f5e69470] >Fatigue cracks were reported in 1982 after 20 years of service. Many types of fatigue cracks existed in this bridge. Therefore, repair was required and periodic inspection of the floorbeams was required. **3.Types of structure [#f69c8199] >The structure is composed of four continuous longitudinal girders, stringers, and floorbeams ([[Fig.1>#fig1]]). At the floorbeam-main girder connection , the floorbeam top and bottom flanges are coped by flame-cutting with only the web bolted to a transverse connection plate which is welded to the longitudinal main girder web. At the stringer-floorbeam connection, the stringer bottom flange is bolted to the floorbeam top flange. >The prestress concrete deck, which replaced on and after 1982-1983, is in bearing with exterior girders G1 and G4 via bearing pads and the stringers via bearing pads or bearing pads with hold down ears. The structural steel is ASTM A36. &br; CENTER:&aname(fig1);&attachref(Woodro14.gif);&br; &br; CENTER:&aname(fig1);&attachref(Woodro15.gif);&br; &br; CENTER:Fig.1 Plan and elevation views of the structure. &br; **4.Details of loading [#f8a42608] >Fluctuating loads due to vehicles live load. **5.Description of damage [#mb4eb4d7] >1. In the floorbeam, Horizontal cracks were found under the stringers along the fillet weld connecting floorbeam web to floorbeam top flange. >2. Vertical fatigue cracks were found at either the top flange cope or the bottom flange cope of the floorbeam webs ([[Fig.2>#fig2]]). >3. At the floorbeam-main girder connection of exterior girders G1 and G4, horizontal cracking were found in the main girder web gap along the fillet weld connecting main girder web to main girder top flange. &br; >Causes of fatigue crack were as follows: &br; &br; >1. Flexibility of the structure by deck replacement. >2. Detail of flame cut coping the top and bottom floorbeam flanges resulted in high tensile residual stresses and stress concentration at the cut edges. >3. In case of the floorbeam-main girder connection. -Out-of-plane distortion resulted from relative deformation between the exterior girder and the adjacent interior girder transferred via the floorbeams. -Two major design differences between the exterior and the interior girders. -The structure flexibility increased by replacing the original deck. &br; CENTER:&aname(fig2);&attachref(Woodro16.gif);&br; &br; CENTER:(a) &br; CENTER:&aname(fig2);&attachref(Woodro17.gif);&br; &br; CENTER:(b) &br; CENTER:Fig.2 Floorbeam web crack at top and bottom flange cope. &br; **6.Repair method applied [#h12cc3e1] -In case of the horizontal cracks in the floorbeams. >The initial retrofit was 25mm hole-drilling at the crack tips and gouging the cracks and fillet welding along the crack length, and fillet welding the transverse connection plate to the main girder top flange. However, cracks in the new flange-to-web weld had occurred. The final retrofit was to strengthening of these cracked floorbeam fillet welds ([[Fig.3>#fig3]]). &br; CENTER:&aname(fig3);&attachref(Woodro18.gif);&br; &br; CENTER:Fig.3 Retrofit for floorbeams located on the far side of abutments and expansion joints relative to the direction of traffic. &br; &br; -In case of the vertical cracks in the floorbeams. >The 25mm hole-drilling and grounding smooth. The hole was bolted with 22mm diameter high strength bolt with washers under both head and nut (Fig.4,5). >The 25mm hole-drilling and grounding smooth. The hole was bolted with 22mm diameter high strength bolt with washers under both head and nut ([[Fig.4>#fig4]],[[5>#fig5]]). >The addition of a splice plate for strengthening the corroded floorbeam web (Fig.5). >The addition of a splice plate for strengthening the corroded floorbeam web ([[Fig.5>#fig5]]). &br; -In case of the horizontal cracks in the main girder web gap. >The retrofit procedure used for fatigue cracking greater than 13mm in length is shown in [[figure 6>#fig6]],[[7>#fig7]] (in case of the not-horizontal cracks). >The retrofit procedure used for fatigue cracking less than 13mm in length is shown in [[figure 8>#fig8]] and 25mm hole-drilling at the crack tips. &br; &br; CENTER:&aname(fig4);&attachref(Woodro19.gif);&br; &br; CENTER:Fig.4 Retrofit of floorbeam web at flange cope to prevent fatigue cracking. &br; CENTER:&aname(fig5);&attachref(Woodro20.gif);&br; &br; CENTER:Fig.5 Repair procedures for cracking up to 4 in (101.6mm) in length in floorbeam web at top or bottom flange cope. &br; CENTER:&aname(fig6);&attachref(Woodro23.gif);&br; &br; CENTER:Fig.6 Repair procedure for cracking greater than 1/2 in (12.7mm) in length in upper web gap at main girder-floorbeam connection. &br; CENTER:&aname(fig7);&attachref(Woodro21.gif);&br; &br; CENTER:Fig.7 Repair procedure for exterior girder buckled webs. &br; CENTER:&aname(fig8);&attachref(Woodro22.gif);&br; &br; CENTER:Fig.8 Retrofit to prevent exterior girder upper web gap cracking at main girder-floorbeam connection. &br;
