Railway Track & Structures 12/07

near a bearing pad, and bent and broken anchor bolts near lateral restrainers. No repairs have been necessary since the bridges were installed. Both of the 30foot concrete box girders were damaged during transport from the precasting plant. The damage was mainly at the girder ends. The concrete was repaired at FAST using Sikadur High Mod 33 (twopart epoxy) mixed with dried masonry sand. The repairs have performed well, with no deterioration of the repaired areas noted. These bridges provide a challenging environment for track ties and fasteners, with significant degradation noted in less than 300 mgt. Broken ties, broken tie plates, and loose screw spikes have been noted. Rail welding Thermite welds are widely used to join rails in the field because of their utility. However, thermite welds fail at higher rates than the adjoining rail or electric flash butt welds. Improvements in thermite weld performance or development of viable alternatives could improve safety while reducing track maintenance costs. Two new weld tests began in 2006. In January, two rail strings containing a total of 10 gas pressure welds (GPW) produced by Jinzhou Institute (now merged with Shengyang Institute) were installed in a five-degree curve. The GPW welds are intended to be a lower cost alternative to electric flash butt welding. Fourteen Hollink Slot Welds were installed in the same curve by the Holland Company in June. The Hollink process removes head defects from the rail, leaving the web and base intact. A robotic gas metal arc welder then repairs the railhead. The GPW welds have accumulated 263 mgt. Three welds had to be removed due to subsurface shells on the gauge face at 150, 193 and 216 mgt. Another weld failed at 165 mgt due to web cracking that originated at a rail manufacturer’s stamp located in the weld heat affected zone. Three welds required maintenance at 84 mgt due to weld batter (approximately 0.065 inch). Rails adjacent to the welds were taper ground to minimize impacts on the welds. The slot welds were successfully installed in track at four-inch superelevation (earlier slot welds tests at FAST had to be installed in nonsuperelevated track). Average weld installation time was less than 25 minutes. This included milling the slot, preheating, and welding, but not cooling time or post-weld grinding. Three welds had failed in 190 mgt. Two were from horizontal fractures in the railhead after 124 and 127 mgt. One was from shelling of the gauge corner after 171 mgt. Several types of improved thermite welds were installed early in 2007. These welds, produced by Orgo-Thermit, Inc., include head-hardened high-performance welds, 1.5-inch gap welds, and improved collar geometry 1.5-inch gap welds. Results will be reported in 2008. Other experiments at FAST Other major experiments at FAST include special trackwork, and steel bridge. Both will be reported on in later articles. www.rtands.com Railway Track & Structures December 2007 25 http://www.rtands.com

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Railway Track & Structures - December 2007 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Hand-Held Tools Provide the Power to Get Big Jobs Done AREMA C&S Update Striving to Solve the Riddle of Wheel Climb RTA Stages Warm Gathering in Sunny Florida in October Products and Literature People Calendar Website Directory Advertisers Index Sales Representatives Professional Directory Classified Advertising Chicago Perspective

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