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3 CHAPTER 1 Introduction In 2005, Transportation Technology Center, Inc. (TTCI) only rail head wear. Philosophy II can be accomplished by conducted research for TCRP Project D-7/Task 12, "Guard/ simply widening the track gage. Restraining Rail Study" to develop guidelines for the application The following (based on the Research Needs Statement for of guard/restraining rails in transit systems. Optimizing the Check Gauge of Restraining Guard Rail1) are TCRP Research Results Digest 82: Use of Guard/Girder/ reasons for installing guard rails using Philosophy II: Restraining Rails was published in 2007 (1) as a result of this study, and it recommended simultaneous contact between · Because of the variations in the wheel mounting back-to- the guard and high rails, which would result in the sharing of back dimensions, wheel flange wear, rail gage face wear, and lateral forces. The optimal flangeway clearances needed to track gage variations, it is impossible to have shared contact achieve this were included in the report. A general guideline with both the high rail and the guard/restraining rail in any based on a wheel lateral-to-vertical force (L/V) ratio and flange reliable manner. This can result in contact that is shared climb distance criteria was also proposed. Subsequently, TRB intermittently, and adverse steering forces are introduced Committee AP080, Rail Transit Systems Design, suggested into the trucks, resulting in rapid oscillation and in signif- that the two guard rail installation philosophies described in icantly increased nosing forces. These forces can damage the following sections be compared. the track, such as gouging wear of both the high rail and the guard/restraining rail and breaking the bolts holding the guard/restraining rail. The sudden, adverse steering forces 1.1 Philosophy I also are likely to result in a lurching and an uncomfortable The "shared contact" methodology will be referred to as ride in the vehicles, especially for standing passengers. guard rail installation Philosophy I (illustrated in Figure 1). · Contacting the back of the flange on only the guard/ The optimization methodology proposed in the previous restraining rail reduces curving noise, since only one rail study (1) for optimal flangeway clearance clearly belongs to and one wheel are involved as opposed to two. This results Philosophy I. With equal rates of wear, it is expected that the in less bell-ringing and wheel squeal and significantly reduces high rail and the guard/girder/restraining rail will wear out at wear on the high rail so that the high rail has a considerably the same time and be replaced during the same track mainte- extended life, roughly equal to that of the low rail. nance period, minimizing service interruptions. Even though the wheel/rail (W/R) contact of these two philosophies starts in two significantly different situations, they 1.2 Philosophy II ultimately end with the same situation as Philosophy I, because There is a different guard rail installation philosophy used the high-rail contact will eventually occur for Philosophy II by transit systems that will be referred to as Philosophy II as the guard/restraining rail gradually wears in. (illustrated in Figure 2). The methodology of Philosophy II is The obvious question is this: Is Philosophy I or II the cor- to increase the check gage dimension and track gage so that rect way of installing a guard rail? It is an important question no flange contact with the high rail will occur under any com- because it could lead to operating safety issues, premature bination of wear and tolerances. As a result, the guard/girder/ restraining rail resists all the curving forces and therefore 1 Research Needs Statements: Optimizing the Check Gauge of Restraining Guard experiences all the gage face wear, while the high rail experiences Rail, http://rns.trb.org/dproject.asp?n=13826.
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4 Low Rail High Rail Figure 1. Guard rail installation Philosophy I. Low Rail High Rail Figure 2. Guard rail installation Philosophy II. wear, or damage to the track that increases the maintenance Lateral forces developed (implying damage on rail and requirements, poor ride quality, and additional noise. fastening system); Consequently, in 2008, TTCI conducted research for TCRP Rolling resistance (implying energy consumption); under TCRP Project D-07/Task 16, "Guard/Restraining Rail Wear index (including wear of both the flange face and Study--Phase II" with the following three tasks: flange back); and Axle angle-of-attack (implying axle steering capability). · Task 1: Conduct a literature review of guard/restraining rail · Task 3: Develop guard rail installation guidelines based on installation guidelines and the philosophies behind them. track curvature, vehicle type, and operation condition. · Task 2: Quantify the performance/benefits of both philoso- phies and recommend a preferred method through model- This report presents the results of the work done in support ing using the following key results as a basis for comparison: of these three tasks.