Use of Guard/Girder/Restraining Rail (2007) / Chapter Skim
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Research Results Digest 82 April 2007 USE OF GUARD/GIRDER/RESTRAINING RAILS This digest summarizes the results of TCRP Project D-7/Task 12, "Restraining/ Guard Rail." The digest was prepared by the Transportation Technology Center, Inc.
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2• Three-dimensional W/R contact effects are significant at AOA larger than 58 mrad (corresponding to curves with a radius of about 100 ft)
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The tasks of this project were the following: • Conducting a survey of the current uses of guard/restraining rail in transit systems, as well as examining and evaluating present guidelines; • Investigating the effect of guard/restraining rail parameters on wheel/rail (W/R) forces and wear through NUCARS® simulation and analysis; and • Providing preliminary guidelines for guard/ restraining rail design and maintenance based on the survey results and NUCARS® simulation and analysis.
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and wheel gages, rail sections, alignments, speeds, and track moduli. The Transportation Technology Center, Inc.
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Figure 2 shows, are referred to as restraining rails. According to this definition, the horizontal mounted rail with low height in Figure 3 is modeled as a guard rail because its contact angle, δ, on the wheel flange back is less than 90 degrees.
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Table 1 shows the current practices used by several different transit systems. It would be desirable to provide guidelines based on the track and vehicle information instead of periodic inspection because the decision to use or not use a guard/restraining rail has to be made during the design and test stage, and it is impractical for periodic inspection to occur at that time.
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Wharton Diagram," a graphical method developed about 100 years ago. A modified version of the Filkins-Wharton Diagram, referred to as the Nytram Plot, was developed in for TCRP Report 57 (4)
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the installation height of the restraining rail should also take into account the optimization of flangeway width. 2.5 Rail Lubrication It is a common practice for transit systems to lubricate rails or apply other friction modifiers.
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right wheel with different yaw angles onto the rail, XR = 100-in. plane.
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For the three-dimensional contact model, the threedimensional wheel contour for different yaw angles must be generated before performing the simulation. Even though the wheel contour is not changed with the wheelset yaw angle during the simulation, the longitudinal shift of the contact point on the wheel caused by the yaw angle is calculated based on a simplified three-dimensional contact algorithm in NUCARS® for both the two-dimensional and threedimensional W/R contact models (7 )
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can't decrease the lateral force on an axle; however, the distribution of the lateral W/R forces between high rail and guard rail can be controlled by the guard rail installation position. W/R wear can also be controlled by the guard rail installation position because it is proportional to W/R forces.
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4.3 Guard Rail In this section, the results of NUCARS® simulations to investigate the effect of various guard rail parameters on the W/R lateral forces are discussed. 4.3.1 Effect of Flangeway Width Table 4 lists the basic W/R parameters used for guard rail simulations.
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back contacts on the guard rail at the same time. Even though the lateral forces and wear are almost in balance between the high rail and guard rail (as Figures 14 and 15 show)
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own applied vertical load. The lateral creep force, F, generated by the wheelset AOA is large enough to resist the fall of the wheel and forces the flange tip to climb on top of the rail.
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AOA/track curvature if the three-dimensional flange back fattening effect is larger than that on the max flange angle face (this situation applies to most W/R contact cases)
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higher than that of the left wheel, which climbs onto the guard rail at the flange tip, as Figure 24 (a) shows.
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height, the clearance between the wheel flange back and guard rail decreases. Correspondingly, the optimal flangeway width has to increase to keep the same flange front clearance and flange back clearance.
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mu = 0.1) and no lubrication on the high rail (high-rail flange mu = 0.5)
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stops further climbing on the high rail under the lateral load that was shown in Figure 13; the left wheel doesn't contact the guard rail if the flangeway width is wider than 1.6 in., as Figure 33 shows. For cases without lubrication (W/R friction coefficient mu = 0.5 for all contact points)
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• The optimal flangeway width makes the flange front W/R clearance between the wheel flange face and the high rail equal to the flange back clearance between the wheel flange back and the guard rail (see Figure 1)
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• The three-dimensional W/R contact effect is significant at AOA higher than 58 mrad (corresponding to curves with about 100-ft radius)
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width is 1.61 in., with a 63.9-degree contact angle on the high rail and a 77.2-degree contact angle on the girder, as Figure 41 (c) shows.
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23 (a) Flangeway width 1.433 in.
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-5.E+03 0.E+00 5.E+03 1.E+04 2.E+04 1.4 1.5 1.6 1.7 1.8 1.9 2 1.4 1.5 1.6 1.7 1.8 1.9 2 Flangeway Width (inch)
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25 0.E+00 2.E+03 4.E+03 6.E+03 8.E+03 1.E+04 1.64 1.66 1.68 1.7 1.72 1.74 1.76 1.64 1.66 1.68 1.7 1.72 1.74 1.76 Flangeway Width (inch)
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tact wheel back fattening effect is usually larger than that on the flange. Because the restraining rail contacts on the wheel back, as described in Section 2.4, the threedimensional contact effect increases significantly with increasing restraining rail height, but increases insignificantly for guard rails and girder rails.
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imately linearly with increasing restraining rail height (see Figure 53)
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flange angle wheel, its contact points, longitudinal shift (L) , and rolling radius increase with the wheel back radius (R2)
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cle simulations with a 75-degree flange angle wheel contacting guard/girder/restraining rails are presented in this section. The vehicle modeled is a typical articulated lowfloor light rail transit vehicle.
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5.2 Vehicle Negotiating a Curve with a Girder Rail As Figure 61 shows, the vehicle simulation predicts the optimal flangeway width for the girder rail is about 1.61 in., which is consistent with the optimized value predicted by the single wheelset simulation in Figure 40. The wheelset AOA in the equilibrium position is about 20.3 mrad.
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The vehicle simulation results show that the wheelset AOA is mainly determined by the truck and curve geometry. For most transit vehicle trucks without severe wear on the components, the wheelset steering effect on AOA is relatively small, unless a very soft primary suspension or a forced steering suspension is used.
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ratio and climb distance safety criteria as proposed in TCRP Report 71: Track-Related Research -- Volume 5: Flange Climb Derailment Criteria and Wheel/Rail Profile Management and Maintenance Guidelines for Transit Operations (1)
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These rail damage functions also provide evidence for the concept of guard rail parameter optimization, which uses the strategy of mitigating the excessive wear on high rails and sharing the wear between high rails and guard rails. 6.2.2 Run Matrix and Results Four types of hypothetical transit cars representing two types of heavy rail and two types of light rail transit vehicles with the 63- and 75-degree flange angle wheel profiles have been modeled using NUCARS®.
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34 0 50 100 150 200 250 0 500 1,000 1,500 2,000 Radius (feet)
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optimized guard/girder/restraining rail installation and design can be drawn from this work: • The optimal guard/girder/restraining rail installation, leading to a balance of lateral W/R forces as well as a balance of wear between the high rail and the guard/girder/restraining rail, can be achieved through the control of flangeway width and W/R friction coefficients. • The optimal flangeway width depends on the wheel profile shape including flange back profile, wheel back-to-back distance, track gage, guard/girder/restraining rail profile shapes, installation height, and wheelset AOA or the track curvature.
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high friction coefficients on the contact patches in the presence of low contact angles. • The wear for wheels with higher flange angles is more severe than those with lower flange angles under the same running and load conditions.
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37 for the flangeway widths could be relaxed because of the dynamic balance characteristics (see Figure 66)
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Transportation Research Board 500 Fifth Street, NW Washington, DC 20001 These digests are issued in order to increase awareness of research results emanating from projects in the Cooperative Research Programs (CRP)
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