Allan M Zarembski

The response equations for a cross-tie track

SummaryEarly analyses of the lateral response of cross-tie railroad tracks are based on the assumption that the rail-tie structure responds like a beam in bending. Because of the difficultiese encountered in determining the lateral bending stiffnes of a cross-tie track, a more recent approach is to model the rail-tie structure as a beam in bending that is also subjected to continuous resistance moments, transmitted to the rails by the fasteners. Also this approach exhibits a number of shortcomings. To date there no generally accepted equations for the lateral response of the cross-tie track. The main purpose of the present paper is to derive such equations. Since the rail-tie structure consists of a repeated pattern of identical units, the correspondingdifference equations are derived first. Then, by a limiting process, in which the tie spaces tend to zero, the difference equations are reduced todifferential equations. This approach yields equations with well-defined coefficients, in terms of the geometrical and mechanical parameters of the track structure. Difference and differential equations are derived for the track response in the lateral, as well as the vertical plane. The derived equations are then discussed and compared with those suggested by other investigators.ZusammenfassungFrühe Untersuchungen der Querverschiebungen von Eisenbahngleisen bauen auf der Annahme, daß sich das System Schiene-Schwelle wie ein Biegebalken verhält. Wegen der bei der Bestimmung der Querbiegesteifigkeit eines Querschwellengleises entstehenden Schwierigkeiten formuliert eine neuere Näherung das System Schiene-Schwelle als einen Biegebalken mit kontinuierlichen Reaktionsmomenten, welche auf die Schienen durch die Befestigungen übertragen werden. Auch dieser Vorgang zeigt eine Anzahl von Unzulänglichkeiten. Es gibt heutzutage keine allgemein akzeptierten Gleichungen für die Querverschiebungen von Queschwellengleisen. Es ist der Hauptzweck dieser Arbeit, solche Gleichungen herzuleiten. Da das System Schiene-Schwelle aus wiederholten Abscnitten identischer Einheiten besteht, werden zuerst die entsprechendenDifferenzengleichungen hergeleitet. Dann, mittels eines Grenzübergangs, in welchem der Schwellenabstand gegen Null geht, werden die Differenzengleichungen zuDifferentialgleichungen reduziert. Diese Vorgangsweise liefert Gleichungen mit wohldefinierten Koeffizienten, ausgedrückt durch geometrische und mechanische Parameter des Gleises. Differenzen- und Differentialgleichungen werden sowohl für die Ausschläge des Gleises in der Querebene als auch in der vertikalen Ebene hergeleitet. Die hergeleiteten Gleichung werden anschließend besprochen und mit denen vorgeschlagen in anderen Untersuchungen verglichen.

Estimating Maintenance Costs for Mixed Higher Speed Passenger and Freight Rail Corridors

In order to reduce the cost of new intercity passenger rail corridors, the operation of higher speed passenger networks on existing freight corridors is being examined and considered. The issues to be addressed in such operations include the one-time upgrade of the track to allow for this higher speed passenger traffic and the ongoing maintenance costs necessary to maintain this track for the mixed higher speed passenger and freight operations. This latter issue is usually addressed in the access agreements for the corridor, and must include how these costs are to be shared. A recent US Federal Railroad Administration study specifically addressed the issue of “steady state” maintenance costs for mixed use corridors consisting on this class of higher speed passenger operations and concurrent freight operations, to include heavy axle load freight operations. The result of that study was a “planner’s handbook” for estimating these track maintenance costs, as part of the overall analysis of the feasibility and cost of operating higher speed passenger traffic on existing freight corridors. This paper presents the methodology used in the development of the methodology for estimating maintenance costs for mixed higher speed passenger and freight rail corridors (Classes 4, 5 and 6). Specifically, it addresses the estimation of these “steady state” infrastructure maintenance costs for a range of operating scenarios with different combination of passenger and freight traffic densities and operating speeds. These infrastructure costs include track, bridge and building (B&B), and communications and signal (C&S) costs. The resulting costs are presented as a set of cost matrices both in terms of a total cost per track mile and in terms of cost per passenger train mile. The cost matrices cover a range of combinations of traffic and track configuration, with minimum and maximum costs developed for each cell in the cost matrices. The minimum costs are based on maintenance standards geared to typical Class I freight railroad practice, such as where passenger trains currently operate on a freight railroad right of way, while the maximum costs reflect maintenance practices on existing high speed railroad track. This paper provides a description of the analytic models used to generate the costs, and the process by which those models were calibrated to actual cost data to develop costs for a wide range of traffic and track combinations. Sample application of the methodology to include several proposed mixed use corridors is also presented.Copyright

Increasing Speeds Through the Diverging Route of a Turnout Without Increasing Lead Length

Presented are the results of Phase I of an FRA-sponsored study on low-cost means to increase safe speeds through turnouts by way of a retrofit or upgrade. Turnout lead length and frog angle were considered fixed, eliminating costs in relocating the frog or switch points. After in-depth research and dynamic simulation testing, it was determined that the best approach was to optimize existing American Railway Engineering and Maintenance of Way Association (AREMA) turnout geometry. This required a new diverging switch rail and reshaping both the curved stock and closure rails. This low-cost modification applies to most existing turnouts and is expected to improve ride quality and decrease wear without detriment to current maintenance practices. The optimization of a conventional AREMA #20 turnout with straight switch points is discussed as an example. The best vehicle performance in simulations was achieved by a design having a very low entry angle. Vehicle behavior at a speed of 51 mph was significantly improved over the AREMA straight point design at its speed limit of 36 mph, as well as that of the AREMA curved point design at its limit of 50 mph. Also, simulated vehicle performance was nearly as good as for a #20 tangential turnout that has a 20 ft longer lead length. Finally, there was improved performance at speeds as high as 60 mph without exceeding any established safety limits. From these results, a turnout with the reshaped geometry has been constructed and is scheduled for installation on New Jersey Transit.

Estimation of Investment in Track and Structures Needed to Handle 129 844-kg (286,000-lb) Railcars on Short-Line Railroads

Ownership of the U.S. rail industry is divided between eight Class I railroads (those with more than

Shared Corridors, Shared Interests

258.5 million in annual revenue) and about 550 regional and short-line railroads. The eight large railroads own about 70 percent of the 273 700 track-km (170,000 track-mi) and account for about 90 percent of industry revenues. The remaining 30 percent of track kilometers belongs to the regional and short-line railroads, which must operate and maintain them with 10 percent of industry revenues. U.S. railroads function as an integrated network; freight originating on a short-line railroad can be delivered anywhere in the United States, Canada, or Mexico. Equipment is freely interchanged, so the small railroads must handle the same heavy cars as the Class I railroads even though maximum freight car weights have increased in recent years, with cars of 129 844 kg (286,000 lb) becoming common. Many of the smaller railroads own trackage that had been branchlines belonging to the larger companies, and track components and condition are often marginal or inadequate to handle the heavier loads. Yet, if short lines cannot handle heavier cars, they face a loss of revenue and ultimately business failure. ZETA-TECH conducted a survey of short-line and regional railroads to determine the quantities of track materials, bridge repairs, and replacements needed to handle heavier cars. Using standard railroad industry unit costs, ZETA-TECH estimated the cost of this work at

Economics of Wayside Inspection Systems

6.86 billion in 1999 dollars.

AUTOMATED TURNOUT INSPECTION

What are some of the practical obstacles to a “shared interests” between a freight railway business and the proposed new higher speed passenger entity? This paper discusses the real “tension” between the two business interests that fund freight trains versus those that support and fund higher speed passenger trains as they attempt to share the same tracks in a safe manner. There are fundamental laws of physics that have to be addressed as the two different sets of equipment are “accommodated” on a shared corridor. This may not always be an easy accommodation between the two commercial parties. One real tension between the two commercial interests involves the physical problem of accommodating two radically different train sets on areas of curved track. For one example, what will be the passenger train required future higher speeds and how will these speeds be accommodated in existing main line tracks with curves varying from 1% to 6% in degrees? How much super elevation will need to be put back into the heretofore freight train tracks? How will the resulting super elevation affect the operation of so called drag or high tonnage slow speed bulk cargo trains? Accommodating such differences in train set types, axle loadings, freight versus passenger train set speeds, requires making detailed choices at the engineering level. These may be shared interests, but they are also variables with far different outcomes by design for the two different business types. The freight railways have spent the last few decades “taking the super elevation out” because it is not needed for the modern and highly efficient freight trains. Now the requirements of the passenger trains may need for it to be replaced. What are the dynamics and fundamental engineering principles at work here? Grade crossings have a safety issue set of interests that likely require such things as “quad” gates and for the highest passenger train speeds even complete grade separation. Track accommodating very high speed passenger trains requires under federal regulations much closer physical property tolerances in gauge width, track alignment, and surface profile. This in turn increases the level of track inspection and track maintenance expenses versus the standard freight operations in a corridor. Fundamentally, how is this all going to be allocated to the two different commercial train users? What will be the equally shared cost and what are examples of the solely allocated costs when a corridor has such different train users? In summary, this paper provides a description of these shared issues and the fundamental trade-offs that the parties must agree upon related to overall track design, track geometry, track curvature, super elevation options, allowed speeds in curves, more robust protection at grade crossings, and the manner in which these changes from the freight only corridors are to be allocated given the resulting much higher track maintenance costs of these to be shared assets.Copyright

EFFECT OF RAIL SECTION AND TRAFFIC ON RAIL FATIGUE LIFE

The use of wayside load measurement sites to monitor vertical and/or lateral wheel/rail forces has been in active use in North America for many years. Recently interest has increased in establishing a network of such sites to allow for the monitoring of railway cars that generate excessive levels of vertical and/or lateral loads. This would potentially allow for the identification of these high load level vehicles and the ability to take them out of service to investigate the cause of these high levels of loading. This paper addresses the issue of the economics of such a site or series of sites. Specifically the benefits associated with both vertical and lateral load detection wayside sites are identified to include both safety related benefits (e.g. derailment reduction) and maintenance (non-safety) related benefits. These latter benefits include reduced track maintenance, reduced equipment maintenance, reduction in fuel consumption, reduction in lading damage, and reduced inspection costs. Likewise the costs to set up and operate these sites, to include capital and operating costs, as well as costs associated with “false alarms” and associated unnecessary removal and inspection of cars are defined and quantified. The resulting overall system economics, and the associated sensitivity of these costs and benefits to key operating parameters are presented and discussed.© 2003 ASME