![[PukiWiki]](image/pukiwiki.png "[PukiWiki]")
*Chamberlain Br. [#a7d5a4c7] **1.Field of application [#iad952e1] >Chamberlain Bridge over the Missouri River near Chamberlain, South Dakota. **2.Circumstances of repair [#o0131d7d] >Fatigue cracks were found in the intermittent fillet weld of the vertical stiffener at the diaphragm locations in Sep. 1973 after 21 years of service. Further fatigue cracks were found in the girder web gaps of the girder-diaphragm connections near the girder compression flanges of the positive moment regions in 1973 after 21 years of service. **3.Types of structure [#l999b01c] >Span length of this bridge is 610.8m. Five spans truss bridge is connected to continuous plate girders approach. West approach is three spans continuous composite plate girder (Fig.1) and east is two spans continuous plate girder. The plate girders were spaced at 2.75m and supported the reinforced concrete deck of 150mm thickness. The cross section of this plate girder bridge and view of internal diaphragms are shown in figure 2. Transverse cross bracings as internal diaphragms were composed of angles, 126 by 126 by 8mm, and weld connected to the vertical connection stiffeners, 126 by 8mm. All the vertical stiffeners were only connected to the girder webs by the intermittent fillet welding. >Span length of this bridge is 610.8m. Five spans truss bridge is connected to continuous plate girders approach. West approach is three spans continuous composite plate girder ([[Fig.1>#fig1]]) and east is two spans continuous plate girder. The plate girders were spaced at 2.75m and supported the reinforced concrete deck of 150mm thickness. The cross section of this plate girder bridge and view of internal diaphragms are shown in [[figure 2>#fig2]]. Transverse cross bracings as internal diaphragms were composed of angles, 126 by 126 by 8mm, and weld connected to the vertical connection stiffeners, 126 by 8mm. All the vertical stiffeners were only connected to the girder webs by the intermittent fillet welding. &br; CENTER:&aname(fig1);&attachref(i95_ht83.gif);&br; CENTER:&aname(fig1);&attachref(Chambe1.gif);&br; &br; CENTER:Fig.1 Schematic of the exterior web face of fascia girders.&br; CENTER:Fig.1 Plan and elevation views of the approach spans. &br; &br; CENTER:&aname(fig2);&attachref(Chambe2.gif);&br; &br; CENTER:Fig.2 Typical cross section. &br; **4.Details of loading [#w5867d56] >Fluctuating loads due to vehicles live load. >Fluctuating loads due to vehicles live load. **5.Description of damage [#vfe15f0c] >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 girder web gaps of the girder-diaphragm connections near the girder compression flanges of the positive moment regions ([[Fig.3>#fig3]]). >Cause of fatigue crack was as follows: -Separational discontinuities in the butt connection groove weld of the continuous tension longitudinal stiffener. >The 1976 inspection indicated that fatigue cracks were classified in three types as follows. **6.Repair method applied [#x4d34a6a] >1. Fatigue cracking along the girder web-flange weld. >The fatigue cracked girder web and bottom tension flange were bolt spliced ([[Fig2>#fig2]]). >2. Fatigue cracking which occurred in the girder web at the top end of the intermittent fillet weld. The cracks propagated parallel to the girders ([[Fig.4>#fig4]]). >3. Fatigue cracking which occurred in the intermittent fillet weld which attached the vertical connection stiffeners to the main girder webs. This type of the cracks showed the growth through the weld throat and the propagation along the weld toe of the girder web side ([[Fig.4>#fig4]]). >Causes of fatigue cracks were as follows: -Out-of-plane displacement of the girder web gaps of the girder-diaphragm connection which resulted from the relative vertical displacement between the girders. -Discontinuity at the intermittent fillet weld roots of the vertical stiffener ([[Fig.5>#fig5]]) &br; CENTER:&aname(fig2);&attachref(i95_ht84.gif);&br; CENTER:&aname(fig3);&attachref(Chambe3.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 girder web gap. &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. &br; CENTER:&aname(fig4);&attachref(Chambe4.gif);&br; &br; CENTER:Fig.4 Typical cracking pattern. &br; >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; CENTER:&aname(fig5);&attachref(Chambe5.gif);&br; &br; CENTER:Fig.3 Retrofit of tension longitudinal stiffeners.&br; CENTER:Fig.5 General view of the intermittent fillet weld. &br; **6.Repair method applied [#x4d34a6a] >Retrofit holes were drilled at the crack tips in order to prevent the crack propagation. The top and bottom ends of the diaphragm connection stiffeners were connected to the girder top and bottom flanges by fillet welding of 75mm length and 8mm leg length. &br;
