Railway Track & Structures - July 2008 - (Page 21)

Special trackwork report Selecting a turnout design Selecting turnout design depends on the operation conditions by LLC assessment by Miodrag Budisa, transit/rail project manager DMJM Harris | AECOM R ailroading will always be railroading, but its life time can be inﬂuenced with the methods used to create it. Profound understanding of the geometrical relationships of railway patterns is crucial in order to create a turnout with the highest performance. This understanding could be building or maintaining a high-speed passenger line or designing a 40-mph coal line. In order to determine vehicle response, conventional EU turnout methods apply kinematic forces rather than dynamic forces. Calculations used in conventional EU turnouts are based on a geometric projection of the length and the relative direction at the points where the connections are made. The projection methods are used to create essential equations. Figure 1 shows the damage and wear that can occur on a turnout. Four sensitive areas in turnouts are the straight point of switch and intersection point of switch (both represent outdated design), tangential point of switch and tangential point of switch with sunk point. For high-speed passenger operations, UIC utilizes the clothoidal turnout, with an allowable diverging speed up to 143 mph (230 km/h). This type of turnout minimizes lateral acceleration and jerk at key turnout locations. This complements car body features such as automatic tilting to maximize speeds through the curve. Figure 2 illustrates the use of this type of turnout. The frog number for this turnout is #40.154, which corresponds to an angle of one-degree 12-feet 7.5 inches. The sinusoidal curvature of the blade (points) minimizes the impact felt at the point of switch as compared to the very large impact felt in conventional North American turnouts Sensitive areas in turnouts nents in line with expected loads; • Employ optimum materials, in particular for those parts of the turnouts subjected to highest loads. In today’s cost-conscious environment, all organizations are placing great importance on life-cycle cost. The maintenance cost, in addition to the price of a product, makes a great impact on life-cycle costs. Optimized life-cycle cost turnouts are ensured by the following measures: • Reduce the forces and acceleration forces acting on turnouts; • Apply low-maintenance components in order to reduce maintenance and repair work; • Using ﬁnite element calculations, design turnout compowww.rtands.com Life-cycle cost of optimized turnout Crossings with a movable point have a ﬂexibly moving point and splice rails, along with a special bolting between the point and splice rails, which permits relative displacement that enables longitudinal compensation during setting to take place. Therefore, an expansion joint in the closure rail is not required. The use of standard rail selection means that a wide selection of material is possible. Advantages of crossings with movable point are: • Continuous wheel over running area. This makes it suitable for high-speed and heavy-haul trafﬁc and mixed operation (different vehicles and wheel set types). • High-speed trafﬁc is able to run faster because checks are not required. Crossings with movable point Special trackwork supplier reports from: Cleveland Track Material, Inc. L.B. Foster Nortrak-DAMY Progress Rail Services VAE Nortrak Railway Track & Structures July 2008 21 http://www.rtands.com

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Railway Track & Structures - July 2008 On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Products and Literature People Calendar Sales Representatives Website Directory Advertisers Index Professional Directory Classified Advertising Chicago Perspective Extending Service Life for Costly Special Trackwork Rail Welding Gets Act Together Premium Fasteners, Rail Steels Help Meet Strain of Heavy Haul

Railway Track & Structures - July 2008

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