Measuring the track radius in degrees Celsius

On the shoulders of CWR giants

In 1994 UIC (the International Union of Railways) and ERRI (the European Railway Research Institute) set up a committee of specialists – D202 – to develop an international standard code for laying and maintenance of continuous welded rail track.

Various research institutions and national railway administrations provided a complex set of data which was used in the development of the said code.

The committee produced in three years a set of 10 reports, covering the basic aspects of CWR, presenting the results of existing or new tests undertaken by various UIC members, two calculation models for the behaviour of CWR, and proposed the first issue of the UIC leaflet 720 – Laying and Maintenance of CWR, which, after further research, was published in 2005.

Their work deserves not to be forgotten. Names like Dr. Coenraad Esveld, Andrew Kish, Gopal Samavedeam deserve not to be forgotten.

All the countries involved in this research, and not only them, ended up after 2000 with revised and more documented standards on CWR maintenance and installation.

I would like to spend more time describing the work of this committee and their precious findings … but I’m forced to leave that for another time and focus now on a very particular subject.

What’s the connection between D202 and the title of this post – measuring the track radius in degrees Celsius?

Critical Rail Temperature and Radius

One of the things the committee worked on was to establish the influence the track radius has on the behaviour of CWR, and how much the critical rail temperatures decrease from its value for straight track.

The graph below presents their findings for well consolidated track.

Interesting to notice that the decrease in CRT relative to straight is matching the degree of curvature, D°. The degree of curvature is matching the decrease in CRT.

D° = °C

So, we can say based on this research, that for CRT management purposes, we can measure the radius in degrees Celsius.

For example a radius of 500m is 3.5°C or 250m is 7°C.

Or the difference between a track with radius of 500m and one of 250m, in CRT terms, is 3.5°C. The 250m radius curve needs 3.5 degrees less to buckle compared to a 500m radius.

That’s in brief the very much simplified and incomplete story of the radius measured in degrees Celsius.

Before running away, I note that several things shown in this graph deserve for sure some attention on this blog.

For example, with some significant amount of vulgarisation (?), in the graph above