For most of us, this may seem like a silly question. A hollow structural steel pipe, or HSS, is the same thing as tube steel, or TS, right? Actually, I’ve been asked this very question, so I feel a short explanation may be necessary. Steel tubing, or tube steel, is what we used to use in the U.S. to describe a closed steel section — whether of rectangular, square or round shape. These sections are commonly made in the U.S. in accordance with the ASTM A500 specification. In Canada, the typical specification is CSA G40. You can even see the history of the term in the name of the organization created to promote steel tubing: the Steel Tube Institute.
Now, a carbon steel pipe is something completely different (because it’s produced to a different specification), but that is a subject for another day.
In Canada, Europe and Asia, the typical nomenclature for these closed steel sections or tubes has always been some variation ofhollow structural section. In some places, there exist the variations of SHS (square hollow section), RHS (rectangular hollow section) and CHS (circular hollow section).
In the early 1990s, the American Institute of Steel Construction (AISC) decided to transition from TS to HSS in order to align with the rest of the world. Starting with the second edition of AISC’s LRFD Steel Construction Manual (the silver two-volume set), the designation of hollow structural section was established as the correct way to call out steel tubes. This also coincided with the publication of the black HSS Connections Manual, published jointly by AISC and the Steel Tube Institute.