Rectangular Tube Sections: Mass of 1 m, Dimensions and Section Properties

Rectangular tubes to GOST 8645-68

A rectangular hollow section has two unequal sides, so its stiffness differs in the two directions. For every size the table gives the dimensions, the section area, the mass of 1 m and the properties about both axes.

Rectangular steel tubes · ГОСТ 8645-68

h and b are the longer and the shorter side, s is the wall thickness, all in millimetres. A is the section area; Jy, Wy, iy are the moment of inertia, section modulus and radius of gyration about the y–y axis (the strong axis); Jz, Wz, iz are the same about the z–z axis. Moments of inertia are in cm⁴, section moduli in cm³, radii of gyration in cm.

RHS tubes to EN 10219

The European RHS range covers cold-formed welded tubes. The table lists five sizes with sides of 200×100 and 200×150 mm.

The axes are named differently here: the strong axis is x–x and the weak one is y–y. So Jx in the RHS table corresponds to Jy in the GOST table, and Jy of the RHS to Jz of the GOST.

Rectangular hollow sections (RHS) · EN 10219:2006

h and b are the sides, s is the wall thickness, in millimetres. Jx, Wx, ix refer to the strong axis x–x; Jy, Wy, iy to the weak axis y–y. Moments of inertia are in cm⁴, section moduli in cm³, radii of gyration in cm.

What 80×40×3 means

The first number is the longer side h, the second is the shorter side b and the third is the wall thickness s, all in millimetres. An 80×40×3 tube has an 80 by 40 mm section with a 3 mm wall.

The mass is the mass per metre times the length. An 80×40×3 tube weighs 5.25 kg/m, so a six-metre piece is 31.5 kg, and a tonne of this tube is 190.5 m long. For 100×50×4 (8.7 kg/m) a tonne is about 115 m.

In the RHS range a 200×150×8 tube has a mass of 41.1 kg/m, and a tonne of it is 24.3 m.

Which way to place the tube: on edge or flat

Jy in the table is larger than Jz because, in bending in the plane of the longer side, the wall material lies farther from the neutral axis. Take an 80×40×3 tube: with the 80 mm side vertical, Jy = 53.46 cm⁴ and Wy = 13.36 cm³. Laid flat, it has only Jz = 17.84 cm⁴ and Wz = 8.92 cm³.

The moment of inertia differs threefold, and it is what governs deflection: under the same load and over the same span, a tube laid flat deflects about three times as much. So a purlin or a beam is set with its longer side along the load.

If the load acts in both planes, as on a frame column, look at the lower of the two stiffnesses. The radii of gyration iy and iz serve this purpose.

Where rectangular tubes are used

Rectangular tubes go into roof and wall purlins, truss chords and web members, frame beams and columns, canopy and fence frames. When the load acts mostly in one plane, the longer side is placed along it.

Calculator and ordering

How much a batch of tubes of the length you need will weigh is shown by the rolled metal calculator. Other kinds of rolled metal are collected in the rolled metal handbook. A frame, truss or portal from such tubes is made by the POLYGONAL company: send a drawing or a specification. It makes steel structures to the customer’s drawings, prepares KM and KMD drawings and galvanizes the products.