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*Poplar Street Br. [#yafb0039] **1.Field of application [#oecf1bc6] >Poplar Street Bridge Approach on east shore of Mississippi River in East St. Louis, Illinois. **2.Circumstances of repair [#u03523e8] >Some types of fatigue cracks were found in 1973 after 2 years of service. **3.Types of structure [#w5d8e066] >This bridge is multiple span continuous structures with two longitudinal girders and is composed of elevated structure and some ramps ([[Fig.1>#fig1]],[[2>#fig2]]). The transverse floorbeams exist between the girders. The transverse floorbeams support stringers and a reinforced concrete deck ([[Fig.3>#fig3]]). The web plate thickness of the longitudinal girders was 12.7mm. The vertical connection plates which connected the transverse floorbeams were fit with the girder tension flange and were weld connected to the girder compression flange at the positive moment regions. >12.7 to 25.4 mm web gaps existed between the weld termination of the vertical connection plate end and the girder web-flange weld. The vertical stiffeners were weld connected to the girder outside webs and cut short (16mm) of the girder tension flange. At the transverse floorbeam end stiffener connection, both up-and-down sides of the end stiffeners were not weld connected to the girder flanges. &br; CENTER:&aname(fig1);&attachref(Poplar1.gif);&br; &br; CENTER:Fig.1 Arrangement of Poplar Street Bridge Approach. &br; &br; CENTER:&aname(fig2);&attachref(Poplar2.gif);&br; &br; CENTER:Fig.2 Plan and elevation views. &br; &br; CENTER:&aname(fig3);&attachref(Poplar3.gif);&br; &br; CENTER:Fig.3 Typical cross section. &br; **4.Details of loading [#p72fb147] >Fluctuating loads due to vehicles live load. **5.Description of damage [#m8ce24d1] >Fatigue cracks were classified into the three types as follows. >Type I : Fatigue cracking which occurred in the girder bottom web gaps between the girder bottom flange and the cut short ends of the vertical connection plates near the girder support ([[Fig.4>#fig4]]). >The cracks originated in the vertical connection plate ends and propagated in both ways along the girder web-flange weld. >Type II : Fatigue cracking which occurred in the girder top web gaps between the girder top flanges and the top ends of the vertical connection plates at the negative moment regions ([[Fig.5>#fig5]]). >Type III : Fatigue cracking which occurred in the end stiffener termination doubling as the connection plate connected to the transverse floorbeam. >The cracks were observed in the top ends of the end stiffeners which were not weld connected to the girder top flanges. &br; &br; &br; >Cause of fatigue cracks was as follows: -Out-of-plane deformation at the connection plate ends which resulted from the rotation of the transverse floorbeam ends. &br; CENTER:&aname(fig4);&attachref(Poplar4.gif);&br; &br; CENTER:&aname(fig4);&attachref(Poplar5.gif);&br; &br; CENTER:Fig.4 Crack occurred in the girder bottom web gap. &br; &br; CENTER:&aname(fig5);&attachref(Poplar6.gif);&br; &br; CENTER:&aname(fig5);&attachref(Poplar7.gif);&br; &br; CENTER:Fig.5 Crack occurred in the girder top web gap. **6.Repair method applied [#p4013bc9] >Repair of parts subjected to cracking was performed as follow. -At the end of the girder. >1. The floorbeam connection plates were weld connected to the girder top-and-bottom flanges in order to prevent the relative displacement between the girder flanges and both ends of the connection plate (Fig.6) >1. The floorbeam connection plates were weld connected to the girder top-and-bottom flanges in order to prevent the relative displacement between the girder flanges and both ends of the connection plate ([[Fig.6>#fig6]]) >2. For cracking along the girder web-flange weld and at the stiffener end, the 13mm holes were drilled at the crack tips. >3. Fatigue cracks were removed by gouging. The gauged area were full penetration welded to the drilling-hole. -At the negative moment region. >For cracking along the web-flange weld and at the vertical stiffener end, the holes were drilled at the crack tips ([[Fig.7>#fig7]]). -Other case &br; &br; >Strengthening procedure for the girder ends is shown in [[figure 8>#fig8]]. >Repair for cracking as shown in [[figure 9>#fig9]] is shown in [[figure 10>#fig10]]. &br; CENTER:&aname(fig6);&attachref(Poplar8.gif);&br; &br; CENTER:Fig.6 Stop holes at the crack tips. &br; CENTER:&aname(fig7);&attachref(Poplar9.gif);&br; &br; CENTER:Fig.7 Strengthening for cracking. &br; CENTER:&aname(fig8);&attachref(Poplar10.gif);&br; &br; CENTER:Fig.8 The strengthened girder. &br; CENTER:&aname(fig9);&attachref(Poplar11.gif);&br; &br; CENTER:Fig.9 Large cracks in the intermediate support. &br; CENTER:&aname(fig10);&attachref(Poplar12.gif);&br; &br; CENTER:Fig.10 Bolt-splice for the large cracks. &br; &br;
