ASTM A500

Standard Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes

This specification covers the majority of the HSS used in construction, including round, rectangular and square shapes used for “welded, riveted or bolted construction of bridges and buildings, and for general structural purposes” (ASTM 2021a). The HSS conforming to A500 are cold-formed carbon steel tubes that are made with either a welded or seamless process. When welded, each HSS is made from a flat steel sheet with the opposite two edges welded together by the electric-resistance-welding (ERW) process, which involves simultaneously applying pressure and a strong electric current to melt and forge the steel together.

The 2021 version of the A500 standard has made important revisions affecting the strengths and sizes of the HSS covered by the standard, which are reflected in this description. Grade C is the predominant material available with a yield strength of 50ksi and a tensile strength of 62ksi for all HSS shapes, including round. Most HSS produced domestically is dual-graded for both grades B and C. Thus, STI recommends using grade C as the default for structural notes on a project.

A500 encompasses tubes up to a maximum total perimeter of 88 inches. As an example, this means the maximum square HSS size would be 22 inches x 22 inches. Domestically produced HSS is available in sizes up to 22 inches for square shapes, 34 inches for rectangular shapes, and 28 inches for round shapes with wall thicknesses up to 1-inch nominal. For current availability of HSS sizes, including producer contact information for each size, see STI’s HSS Capability Tool.

Per A500, the maximum nominal thickness is 1 inch, but due to the thickness tolerance of 10%, AISC 360-16 Section B4.2 requires calculations involving the thickness be multiplied by a factor of 0.93 times the nominal thickness. The maximum corner radius for rectangular and square shapes is 3*t, but the section properties are calculated based on different values depending on the property type to account for averages. As an example, slenderness values for b/t and h/t are based on a corner radius of 1.5*t while the workable flat is based on 2.25*t.

Section properties and design tables are available for A500, A1065 and A1085 in STI Design Guide Volume 1 and 2A and 2B.

Section properties for A500 rounds, squares and rectangles from 1″ to 22″ can be found in the ASTM A500 brochure. For more information on this and other HSS ASTM standards, see our HSS Insider article “Understanding HSS Material Specifications: Which ASTM Should I Specify for HSS?“