![[PukiWiki]](image/pukiwiki.png "[PukiWiki]")
*Walt Whitman Br. [#o5f3bf52] **1.Field of application [#i4d28d2d] >Walt Whitman Suspension Bridge over Delaware River between Philadelphia and Gloucester, New Jersey. **2.Circumstances of repair [#m2c67651] >Fatigue cracks were found in the stringer web gaps between the tie stringers and the horizontal suspended brackets in Oct. 1968 after 11 years of service. Repair method was decided due to the studies on the improvement of the horizontal suspended structure between the transverse truss and the stringers. **3.Types of structure [#jafc2506] >A typical plan and side views are shown in [[figure 1>#fig1]].The transverse trusses which are spaced at 6.15m supports sixteen stringers. The stringers are six span continuous. The cross section in the transverse truss location is shown in [[figure 2>#fig2]]. The stringers supported the steel lattice deck plate which was filled with the concrete. The brackets which played the role of supporting the horizontal motion had been connected to the stringer webs. The structural steel of the stringer is A36. &br; CENTER:&aname(fig1);&attachref(i95_ht83.gif);&br; CENTER:&aname(fig1);&attachref(WaltWh3.gif);&br; &br; CENTER:Fig.1 Schematic of the exterior web face of fascia girders.&br; CENTER:Fig.1 Plan and elevation views. &br; CENTER:&aname(fig2);&attachref(WaltWh11.gif);&br; &br; CENTER:Fig.2 Typical cross section. &br; **4.Details of loading [#tf466ec8] >Fluctuating loads due to vehicles live load. >Fluctuating loads due to vehicles live load. **5.Description of damage [#hf5dadb0] >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 along the stringer web-flange fillet welds and in the stringer webs at the bracket connections ([[Fig.3>#fig3]],[[4>#fig4]]). All the cracks were observed at the road expansion joints where the stringers and the deck are discontinuous. At the locations where the cracks occurred in the bracket-stringer connection angles, gaps had existed between the stringer bottom flanges and the bearing pads on the transverse trusses. >Cause of fatigue crack was as follows: -Separational discontinuities in the butt connection groove weld of the continuous tension longitudinal stiffener. **6.Repair method applied [#fee0a77d] >The fatigue cracked girder web and bottom tension flange were bolt spliced ([[Fig2>#fig2]]). >Cause of fatigue cracks was as follows: -Out-of-plane distortion of the stringer web gap which resulted from the relative displacement between the stringer and the transverse truss. &br; CENTER:&aname(fig2);&attachref(i95_ht84.gif);&br; CENTER:&aname(fig3);&attachref(WaltWh12.gif);&br; &br; CENTER:Fig.2 Bolt splice repair of fatigue cracked girder web and bottom flange.&br; CENTER:Fig.3 Crack occurred in the stringer web. &br; CENTER:&aname(fig4);&attachref(WaltWh13.gif);&br; &br; CENTER:Fig.4 Crack occurred in the bracket angle. &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. **6.Repair method applied [#fee0a77d] >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. >The primary repair was to filling the gaps by the caulking pads between the stringer bottom flanges and the bearing pads. As a result of the various improvements of the structure, the improvement of the brackets were performed. The bracket plates which were located in the road expansion joints and on the adjacent transverse trusses were cut off. As a result, the connections between the stringer webs and the transverse trusses was removed. &br; CENTER:&aname(fig3);&attachref(i95_ht85.gif);&br; &br; CENTER:Fig.3 Retrofit of tension longitudinal stiffeners.&br; &br; &br;
