What it is called, by market
One concept, four markets. Where a name means something else locally, the card says so rather than leaving you to find out on site.
United Kingdom
Same word, different thinguniversal beam (UB)
also RSJ, universal column (UC), I-beam
"RSJ" strictly means the older rolled steel joist with tapered flanges, largely superseded by UB and UC — but it survives in speech for any steel beam, which is why it is an unreliable word in a specification.
Australia
Close, not identicaluniversal beam (UB)
also UC, universal column
The naming convention follows the British one, but the available section sizes are the Australian range and the designations are not interchangeable with British ones.
United Statesyours
Same word, different thingW-shape
also wide flange, W12x26, I-beam
A W designation gives nominal depth and WEIGHT PER FOOT, where a UB designation gives depth, width and mass per metre — the numbers encode different things.
Canada
Close, not identicalW-shape
also wide flange
As the United States for the naming, with the designations stated in metric — so a Canadian W section number is not the same number as the American one for the same member.
The governing standard, by market
United Kingdom
BS EN 1993 (Eurocode 3)
Design of steel structures.
United States
AISC 360
Specification for structural steel buildings, with the section property tables.
Australia
AS 4100
Steel structures.
Calculators for this
Each works in either measurement system, and the terminology on the page follows whichever market you have selected.
Frequently asked questions
- Is an RSJ the same as a universal beam?
- Strictly no, though the words are used as though they were. A rolled steel joist is an older section with TAPERED flanges, and it has largely been superseded in British practice by the universal beam and universal column, which have parallel flanges — a shape that is easier to connect to, easier to bolt through and more efficient in bending. The word survived the product: in everyday British site and domestic use, any steel beam over an opening is called an RSJ. That is harmless in conversation and unhelpful in a specification, because a fabricator asked for an RSJ has to decide whether a genuine tapered-flange section is meant or whether the ordinary UB is intended.
- What do the numbers in a designation mean?
- Different things in each system, which is why they cannot be compared directly. An American W designation gives a nominal depth followed by the weight per foot, so the second number is a mass rather than a dimension and two sections of the same nominal depth can have quite different actual depths. A British or Australian universal beam designation gives the serial size — depth and width — followed by the mass per metre. So a designation carries depth-and-mass in one system and depth-width-and-mass in the other, and the nominal depth in the American system is not necessarily the actual depth. Reading either across requires the section tables rather than arithmetic.
- What is the difference between a beam and a column section?
- Proportions, chosen for the job. A universal beam is deep relative to its width, because bending stiffness grows with depth and a beam's job is to resist bending over a span. A universal column is closer to square, because a column resists buckling about BOTH axes and a deep narrow section is weak about its minor axis. The American W range covers both duties within one designation family rather than splitting the names, so the distinction there is made by choosing proportions rather than by the prefix. Using a beam section as a column, or the reverse, is a real error rather than a preference, and it is easier to make when reading a designation from an unfamiliar system.