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*Deck-type curved-chord warren truss bridge [#q2131dbf] **1.Field of application [#u6a62a8e] >Two hinges arch bridge on roadway bridge (Part 2), Japan.&br; >Through-type curved-chord warren truss bridge on roadway bridge, Japan.&br; **2.Circumstances of Repair [#g59b704a] >Fatigue cracks were found in the floor beam top web gaps at the bottom chord member connections after 1989 after 21 years of service.&br; **3.Types of structure [#rd71239f] >The outline of the bridge structure is as follows. -Bridge length : 69.3 m -Structure : Through-type curved-chord warren truss. -Deck : Reinforced concrete deck (17.0 cm thickness) -Structural steel : SS 41, SM 50 &br; &br; >Elevation and plan views are shown in [[figure 1>#fig1]]. The main girders are spaced at 9.3m and are 11.0m deep at the center span. The floor system is composed of eight floorbeams, which are spaced at 9.9 m, and four stringers, which are spaced at 2.3 m. The deck was located from the floorbeam top flange end to end. The webs of the floorbeams were connected to the bottom chord member webs and the top flanges of the floorbeams were not connected.&br; &br; &br; CENTER:&aname(fig1);&attachref(curved14.jpg);&br; &br; CENTER:Fig.1 Elevation and plan views.&br; &br; &br; **4.Details of loading [#p257b470] >Fluctuating loads due to vehicles live load. **5.Description of damage [#uec9e6d6] >Fatigue cracks were found in the floorbeam top web gaps at the bottom chord member connections ([[Fig.2>#fig2]]). These cracks initiated from the web weld toes at the floorbeam web-flange connections. The cracks horizontally propagated along the web-flange weld. Propagating over the width of the connection plates which connected the floorbeams to the main girders, the cracks diagonally propagated down ([[Fig.3>#fig3]]). The crack of the web gap at and near the end floorbeam locations propagated more than the crack at the center span. >Cause of fatigue cracks was thought as follows: -Out-of-plane deformation which resulted from the horizontal relative displacement between the bottom chord member and floor system. &br; &br; CENTER:&aname(fig2);&attachref(curved15.gif);&br; &br; CENTER:Fig.2 Crack at the floorbeam top web gap.&br; &br; &br; CENTER:&aname(fig3);&attachref(curved16.gif);&br; &br; CENTER:Fig.3 Crack location.&br; **6.Repair method applied [#x360313d] >The original deck at the warping was separated from the floorbeam. The floorbeam top flanges were bolt spliced to the main girder top flanges ([[Fig.4>#fig4]]). &br; &br; >Repair of parts subjected to cracking was performed by re-welding. Filled by welding, the finishing was performed by grinding. &br; &br; CENTER:&aname(fig4);&attachref(curved17.jpg);&br; &br; CENTER:Fig.4 Connection detail between the floorbeam top flange and the chord member to flange.&br; &br; &br;
