# Round Steel Tube Dimensions

Round steel tube dimensions are also part of structural steel tube in addition to rectangular steel structural tubing and square tube steel sections, These round hollow structural steel tube are industry standard steel tube sizes but must be differentiated from steel pipes.

The difference between HSS round sections and steel pipes according to AISC are as follows:

Steel pipe: ASTM A53 grade B Fy = 35 ksi; often designated as Std., x-strong, and xx-strong

Round HSS: ASTM A500 grade B Fy = 42 ksi or grade C Fy = 46 ksi

Since round tubes are for structural application, they are measured by their outside diameter (OD). This will allow the inside diameters (ID) to vary depending on the strength necessary to transfer the load required. The higher the strength required the thicker the thickness of the wall.

Pipes on the other hand are vessel and therefore identified by the inside diameters. By maintaining a consistent inside diameter will allow outside diameter to be as big as needed.

The design of round hollow structural sections are very similar to rectangular tubes sections. Let's take a look at a 16 feet long round HSS10x.250, section properties shown in figure 35. The section designation reads 10 inches outside diameter with 1/4 inch wall thickness.

Moment equation M=wL^2/8

Section Modulus S=M/.66Fy

Substituting M into the S equation and solve for w (applied load) yield w = 8*.66*Fy*S/L^2 = 8*.66*46*17.1/(16*12^2) = .113 kip/in = 1352 lbs/ft.

The weight of the circular tube is 26.06 lbs/ft taken from the applied load the result is 1326 lbs/ft. The 16 feet long HSS10x.250 has the capacity to carry 1326 pounds per foot total load or 21,216 pounds.