60E1 railway rail — properties of a real published profile

A rolled steel beam is a handful of dimensions — depth, flange width, two thicknesses, two radii — so the Section Calculator can build one from the published table. A rail is not like that. Its head is three different radii blended together, its web is a curve rather than a straight line, and its foot tapers at 1:20. There is no short list of numbers that reconstructs it.

So this example does what you would do in practice, and what we did to build it:

1. Open the manufacturer’s datasheet PDF for the rail.
2. Extract the DRAWING, not the dimension labels — the profile is vector art in the file, and the outline itself is the data. On Linux, pdftocairo -svg rail.pdf rail.svg.
3. Scale it by ONE published dimension (here the 172 mm height) and check a second one falls out right.
4. Type the outline in as a polyline, or open a .scsection that already holds it.

The Try it button at the foot of this page loads the finished profile, so you can measure it, dimension it, and change it without typing 89 coordinates.

The rail is 171.8 mm tall, so mid-height is about 86 mm. The centroid sits at ȳ = 80.85 mm — close, but the closeness is a coincidence of this particular profile, not a rule.

A rail is monosymmetric: symmetric left-to-right, and not at all symmetric top to bottom. A heavy head, a thin web, a wide flat foot. The centroid lands where the areas balance:

Published EN 13674-1 gives 80.92 mm. The tool computes 80.85 mm — -0.08%.

Because the centroid is not at mid-height, the head and the foot are different distances from it. The section therefore has two different elastic moduli about the same axis:

Here Z_top = 332825 mm³ and Z_bot = 374538 mm³ — the foot’s modulus is about 13% larger, because the foot is closer to the centroid than the head is.

The tool reports the governing as the smaller of the two — 332825 mm³ — because that is the fiber that reaches its limit first under a sagging moment.

Turn on PNA and a second horizontal line appears, at 82.94 mm rather than the centroid’s 80.85 mm. They are different axes answering different questions:

• The elastic centroid is where the first moment of area vanishes — the axis the section bends about while it stays elastic.
• The plastic neutral axis divides the section into two equal AREAS — the axis it bends about once the whole section has yielded.

They coincide only on a doubly symmetric section. On this rail they are 2.091 mm apart, which is why 452639 mm³ is not simply times a tidy shape factor.