Dynamic factor evaluation method calculation methods outlined by Eisenmann (DAF_Eisenmann) and the American Railway Engineering Association (DAF_Area) are used to calculate the dynamic factor during design and for trackside measurement, respectively, in nations where the construction of concrete track structures is relatively new. In this situation, dynamic factor calculation methods may be incorrect, and this is demonstrated by comparison of the respective track types’ total spring constant. A finite element analysis of a standard design railway track is conducted, and the design total spring constant (TSC, or K) obtained from the time history function analysis is compared to the TSC of existing tracks through trackside measurement results. The comparison result shows that TSC obtained by finite element analysis result is 22% higher than that of the trackside measurement value, indicating that the TSC is conservative in the current track design. Considering the proportional relationship between TSC and dynamic factor, it is estimated that the dynamic factor currently being applied in track design is also conservative. Based on these findings, an assessment of the applicability of different dynamic factors (DAF_Eisenmann and DAF_Area), theoretical calculation and field measurement (DAF_Field) using the probabilistic analysis of wheel loads from the field measurement data is conducted. A correlative analysis between DAF_Eisenmann and DAF_Area shows that DAF_Eisenmann and DAF_Area were estimated to be higher by 33% and 27% in ballasted track and by 39% and 30% in concrete track than the dynamic factor derived from field measurement, respectively, which indicates that the dynamic factor currently in use can potentially lead to over-estimation in track design and maintenance.

Track impact factor (TIF) is a coefficient for estimating the increase of train dynamic load and is a major factor for the evaluation of dynamic stability of railway tracks. Many kinds of TIF in ballasted and ballast-less slab tracks consider only speed as a variable in different regions of the world. Because of this lack of clarification, nations such as Korea and those in the Middle East, and South East Asia are implementing overly simplified calculation methods for TIF, resulting in inconsistent maintenance of different railway track types. A comparative analysis of theoretically track support stiffness (TSS) and trackside measurement calculated TSS at wheel-rail contact point shows different values (depending on speed) between ballasted and ballast-less slab tracks. Based on this finding, this paper investigates a TIF formulation method that considers both dynamic wheel load and speed as variables, and a separate application of TIF formulation depending on track types is proposed. A clarified distinction of how these parameters (TSS and TIF) interact differently between ballasted and ballast-less slab track structures can be an important factor in case of track designing and maintenance aspects.

A joint- or crack-opening resistance evaluation method for the selection of optimal waterproofing material for a railroad bridge deck is proposed. The joint opening range (mm) for the evaluation, and a typical load case of a high-speed double-track railroad bridge structure deck, is analyzed through the finite element method (FEM) and the results of analysis are used to calculate the minimum opening range. The evaluation method is then demonstrated with 4 commonly used waterproofing types of cementitious membrane system: a polyurethane coating system, self-adhesive asphalt sheet system and synthetic polymerized rubber gel composite asphalt sheet system. Five specimens of each type are subjected to continuous joint opening under 4 different joint width range conditions (1.5, 3.0, 4.5, and 6.0 mm), and the joint-opening resistance performance is compared. The proposal for the evaluation criteria and the specimen test results demonstrate how the evaluation method is pertinent for future selection of waterproofing membranes for the sustainability of high-speed railroad bridge deck structures.

Countries such as Korea adopt design codes, evaluation criteria and specifications from standards originating abroad; this leads to a lack of distinction of the separate applications of dynamic stability evaluation parameters between various track structures of different track moduli. This paper discusses the applicability of the dynamic stability evaluation method of railway track structures by assessing 10 different types of railway track sections of a newly constructed railway operation line (5 ballasted and 5 concrete type track structures) by field instrumentation testing. Parameters of track support stiffness (TSS), wheel load fluctuation, derailment coefficient, and rail displacement are measured. The respective results are first compared to the standard criteria (design specification) and comparisons between the different track types are presented as ratios. Findings show that while all of the tracks satisfy the design specification requirements, each track type measurement result varies by a noticeable degree, particularly when comparing between concrete and ballast type track structures. Results of the study demonstrate that using the same dynamic stability evaluation criteria can lead to an incorrect assessment of the track performance evaluation of track structure, and a separate evaluation parameter for ballasted and concrete track structures is required.