Design and performance evaluation of railway sleeper baseplate hold-down system for timber sleeper elastic fasteners
Khan, Rahat Mahmud
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https://hdl.handle.net/2142/122180
Description
Title
Design and performance evaluation of railway sleeper baseplate hold-down system for timber sleeper elastic fasteners
Author(s)
Khan, Rahat Mahmud
Issue Date
2023-12-07
Director of Research (if dissertation) or Advisor (if thesis)
Dunn, Alison C.
Committee Member(s)
Dersch, Marcus S.
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Railway engineering
timber sleeper
elastic fastener
tie plate
hold-down method
spring washer
stress relaxation.
Abstract
The adoption of timber sleeper elastic fasteners to mitigate rail-rollover derailments in the North American freight network has led to the failure of spikes which, in-turn, have caused at least 13 derailments in past two decades. Previous spike-failure investigations have determined that the loss of friction at the plate-sleeper interface (caused by the wave action of the rail) is a driving factor of these failures because it causes additional load (i.e., lateral and especially longitudinal) to transfer to the spikes, thus triggering the spike stress levels to exceed their endurance limit. Previous studies have also identified that a feasible mitigation method is the application of a vertical hold-down force to the plate, thus reducing the spike stress (e.g., a 4.5 kN (1,000 lbs.) hold-down load per spike can lead to a 70% reduction in spike stresses). This load has historically been applied using spring washers with screw spikes. However, there are currently no specifications (performance or design) for these spring washers. This has in turn led to insufficiently resilient washers being installed at load magnitudes that exceed the timber strength which has, in-turn, caused a reduction of hold-down force over time and a loss of benefit of the system. In response to this, a review of the limitations of the systems and a suite of laboratory experiments have been executed to help establish recommendations for a spring for this application. The laboratory experiments characterized the static performance (i.e., resiliency) of various spring washers as well as the time-dependent behavior of the sub-system (i.e., stress relaxation of the sleeper-screw spike-washer). Results of this work are intended to aid the railroad industry in the development of hold-down method recommendations.
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