Home / For Designers / Rolled Metal Handbook: Sections, Mass of 1 m, Metres per Tonne / Steel Section Selector by Section Modulus and Moment of Inertia
Rolled Metal Handbook: Sections, Mass of 1 m, Metres per Tonne
Steel Section Selector by Section Modulus and Moment of Inertia
If you know the required section modulus W or moment of inertia I, the calculator finds the sections that meet the condition and lists them from the lightest. The data come from the steel section handbook tables: I-beams, channels, equal-leg angles, and square, rectangular and round tubes.
Contents
Selecting a section by W or I
Choose the type of section and the axis, and enter the required W or I. Each section shows its mass per metre and its margin over the required value.
Values from the steel section handbook tables. The selection is preliminary: strength, stability and deflection are checked in the design to the applicable codes.
Get a cost estimateHow to use the selector
- choose the type of section: I-beam, channel, angle, square, rectangular or round tube, roll-formed channel;
- choose the axis: Wx and Ix about the axis of greatest stiffness, Wy and Iy about the axis of least stiffness;
- enter the required section modulus W, moment of inertia I or both; limit the mass per metre if needed;
- in the results table the sections are sorted by mass per metre, and the margin shows by what percent a section exceeds the required value.
What section modulus and moment of inertia are
The moment of inertia I (cm⁴) describes the stiffness of a section: the larger it is, the less a beam deflects. The section modulus W (cm³) equals the moment of inertia divided by the distance from the axis to the farthest point of the section, and it relates to strength: it is used to estimate bending stress.
The x axis in the tables is the one about which the section is stiffest (for an I-beam and a channel in the DSTU tables it is labelled y). The y axis is always weaker. For an equal-leg angle and a square tube the axes are equivalent.
A selection example
Suppose an I-beam with a section modulus Wx of at least 100 cm³ is needed. In the handbook table I-beam No. 14 has Wx = 81.7 cm³, so it does not suit, while I-beam No. 16 with Wx = 109 cm³ suits with a 9% margin. The calculator gives the same result and compares sections by mass per metre.
What to keep in mind
Selecting by W and I does not replace a calculation. Strength, stability, deflection and connections are checked in the design to the applicable codes; the calculator only helps find candidates quickly. All the tables and dimensions are in the steel section handbook, and the mass of a length or a batch can be worked out in the steel weight calculator.
We make structures from the selected sections to order: custom steel fabrication, with calculations and drawings under steel structure design.
Updated:
Frequently asked questions about section selection
What is the section modulus W?
It is a section property in cm³ used to assess bending strength: the larger W is, the greater the bending moment a beam can carry at the same stress.
What is the moment of inertia I?
It is a stiffness property of the section in cm⁴: the larger I is, the less a beam deflects under load.
How do Wx and Wy differ?
Wx is about the axis of greatest stiffness, Wy about the axis of least stiffness. A beam is usually oriented so that bending falls on the x axis.
How do I find the lightest section?
Enter the required W or I: the results table is sorted by mass per metre, and the lightest section that meets the condition comes first.
Does the selection replace a structural calculation?
No. It is a quick search for candidates from the tables; strength, stability and deflection are checked in the design.
Related products: Custom steel fabrication · Steel structure design (structural and detail drawings)
More on this topic: I-beam Sections: Mass of 1 m, Dimensions and Section Properties · Rebar Sections: Mass of 1 m, Section Area and Metres per Tonne · Round, Square and Hexagon Bar Sections: Mass of 1 m and Sizes · Sheet and Flat Bar Sections: Mass of 1 m² and 1 m · Channel Sections: Mass of 1 m, Dimensions and Section Properties · Equal-leg Angle Sections: Mass of 1 m and Section Properties
Get a quote for your requirements
Send us your requirements — we will calculate the price and lead time.