RISK ANALYSIS BASED CWR TRACK BUCKLING SAFETY EVALUATIONS.
As part of the Federal Railroad Administration’s (FRA) track systems research program, the US DOT’ Volpe Center is conducting analytic and experimental investigations to evaluate track lateral strength and stability limits for improved safety and performance. This paper deals with a part of this research addressing the development of a comprehensive CWR buckling safety analysis which includes a risk analysis based approach for prediction of probable number of buckles on a given track. These risk based buckling evaluations are particularly useful for dealing with statistical variability in the track parameters. The risk approach can provide economic options for track maintenance to achieve the desirable buckling strength. The buckling risk methodology and the statistical parametric descriptors are discussed and a buckling risk analysis model is presented with illustrative examples. The model also provides a computational scheme for the determination of buckling probability as a function of maximum rail temperature when the key influencing parameters of track lateral resistance, lateral alignment defect and rail neutral temperature are given as statistical variables. The risk based approach as well as the previously developed deterministic approaches in CWR-BUCKLE and CWR-INDY are all being integrated in a single new computer program called CWR-SAFE. CWR-SAFE is a Windows based software analysis package for a comprehensive buckling safety evaluation for use by both the railroad industry and the research community.
Mechanism and Application of a New Guard Rail for Improving the Stability of Small Radius Curve Tracks with Continuous Welded Rails
This paper studied an effect of a new guard rail on the stability of curve tracks with CWR, and revealed a mechanism of the new guard rail for improving the stability of small radius curve tracks with CWR, and also analyze the degree of the new guard rail for enlarging the pave range of small radius curve tracks with CWR. In order to achieve these, an improved load-deformation method for calculating the stability of tracks with continuous welded rails (CWR) is suggested and verified. The results indicate that the improved load-deformation method not only has the same accuracy as the improved unified formula in specification, but also has the same clear and simple characteristics as the original load-deformation method. The mechanism of the new guard rail for improving the stability of small radius curve tracks with CWR is that the CWR stability can be greatly improved by increasing the stiffness of the track framework under conditions of maintaining the same cross-sectional area of the rails. The CWR with the new guard rail can allow the minimum laying radius from 300 m down to 230 m, i.e. the current specification limit can be relaxed 23.3%. If combined with the roadbed strengthening measures, the new guard rail can allow the minimum laying radius from 300 m down to 140 m, i.e. the current specification limit can be further relaxed 53.3%.
Analysis of thermal track buckling in the lateral plane
SummaryThe determination of the safe temperature increase in the rails of a continuously welded track, to prevent lateral buckling is presented. The criterion used is based on the post-buckling equilibrium branches of the track. The range of safe temperature increases is defined asT0<TL, whereTL is the smallest value of the temperature rise at which a deformed state of equilibrium (thus, a buckled state) becomes possible. The post-buckling equilibrium states are determined analytically. To obtain a consistent formulation of the problem use is made of the principle of virtual displacements and the variational calculus for variable matching points. The obtained formulations are nonlinear, but can be solved exactly. Solutions are presented for four buckled configurations. The results are presented graphically for a typical railroad track presently in use on main lines. The obtained results are compared with the corresponding results of other investigators.ZusammenfassungDer zulässige Temperaturanstieg in den Schienen eines kontinuierlich geschweißten Gleises wird bestimmt, um seitliches Ausbeulen zu verhindern. Das verwendete Kriterium basiert auf Nachbeulgleichgewichtskurven des Geleises. Der Bereich des zulässigen Temperaturzuwachses wird definiert mitT0<TL, wobeiTL der kleinste Wert des Temperaturanstieges ist, bei dem ein verformter Gleichgewichtszustand (im ausgebeulten Zustand) möglich ist. Die Nachbeulgleichgewichtslagen werden analytisch bestimmt. Für eine klare Formulierung des Problems wird das Prinzip der virtuellen Verschiebungen und die Variationsrechnung für variable Endpunkte verwendet. Die erhaltenen Gleichungen sind nichtlinear, können aber exakt gelöst werden. Lösungen werden für vier Beulformen angegeben. Die Ergebnisse sind für eine typische Eisenbahnschiene, wie sie gegenwärtig auf den Hauptlinien verwendet wird, graphisch dargestellt. Die erhaltenen Ergebnisse werden mit entsprechenden Ergebnissen anderer Untersuchungen verglichen.