Railway Track & Structures 12/07

TTCI R&D Figure 2, left, are examples of broken tie plates and screw spikes. Figure 3 is a concrete bridge at FAST. of high-hardness premium rail have been evaluated at FAST since 2003. A six-degree test curve is divided into three test sections, representing two different grinding practices, as well as unground rail. There are three types of rail in each section: two of approximately 395 Brinell hardness number (Bhn) and one approximately 370 Bhn. By the spring of 2007, 515 mgt of traffic had accumulated on the rails. The following results, which are typical of FAST (revenue service conditions may differ), provide insights into the effects of wheel/rail contact conditions and rail mechanical properties on rail performance. • Grinding tests at FAST indicated that state-of-the-art high-hardness rail required little or no grinding. Unground rail in 515 mgt of traffic exhibited less wear, developed only minor, isolated rolling contact fatigue (RCF), and had no internal railhead defects under 315,00-pound car operations than rail ground using various grinding strategies. Because wheels on the test train at FAST tend to wear to a shape conformal with the rail in the High Tonnage Loop and both gauge faces of high rail and the top of the low rail are lubricated, contact stresses remained acceptable throughout the test. • Compared to the unground rail, total metal loss in the preventive grinding zone was about 77 percent higher on the high rail and about 240 percent higher on the low rail. The metal removed by preventive grinding was the primary reason for the increase; wear rates were similar. • The 370 Bhn rail wore and deformed more than the 395 Bhn rails. The difference in wear was about 15 percent. The wheel/rail contact conditions at FAST may not be achievable in revenue service. They do, however, point the way toward reduced rail maintenance and increased rail life when optimum wheel/rail profile match is achieved and sustained under controlled conditions. Concrete bridges Concrete is the material of choice when railroads replace older timber bridges. The concrete spans have provided reliable service, but continuing evaluation of the structures and the performance of the track on the structures is needed. Two new precast concrete bridges were installed in five-degree curve in 2003. One bridge features a 15-foot slab span, a 42foot high-performance concrete double voided box girder, and a 30-foot double voided box girder (Figure 3). The second bridge has 24- and 32-foot double-cell box spans. The bridges have accumulated 517 mgt to date. All of the spans have performed well structurally. Deterioration and maintenance issues have been noted, but have not been critical in nature. Deterioration thus far includes cracking in ballast curbs, wear at lateral restrainers, a cracked end corner 24 Railway Track & Structures December 2007 www.rtands.com http://www.aar.com 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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