Common Section Types
Structural sections fall into open and closed shapes. Open shapes include H-beams, I-beams, channels and angles; closed shapes are mainly square and rectangular tubes. The shape sets the difference between strong and weak axes, and therefore whether a member is better in bending, in compression, or as bracing and connection material.
How Each Section Behaves
| Section | Character | Typical use |
|---|---|---|
| H-beam | Wide, straight flanges; small two-axis difference | Beams, columns, portal frames |
| I-beam | Narrower flanges; efficient in strong-axis bending | Members loaded mainly in bending |
| Channel | Single-symmetric; weaker in torsion | Purlins, bracing, secondary members |
| Angle | Two legs ease connections | Bracing, connection parts, truss webs |
| Rectangular tube | Closed section; better torsion and appearance | Columns, trusses, exposed members |
The table shows general behaviour. Real selection depends on span, load, connection method and fire or corrosion requirements.
Reading a Section Designation
Taking a common H-beam notation, H400×200×8×13 gives section height, flange width, web thickness and flange thickness in order. These four numbers indicate bending capacity and connection detailing. Angles and channels use different conventions, usually leg width and thickness, so confirm the notation used before quoting.
What Drives Selection
- Load path: bending-dominated or compression-dominated, and whether loading is biaxial.
- Span and load: longer spans generally demand greater depth and stiffness.
- Connections: joint detailing feeds back into section choice.
- Environment and appearance: exposed or corrosive settings affect shape and surface treatment.
Hot-Rolled Sections vs Welded Built-Up Sections
Hot-rolled sections are limited to standard series, and lead time and availability follow stock. Where a design falls outside the standard series, or needs tapered sections, openings or special lengths, plate is assembled and welded instead. The two routes differ in connections, inspection and lead time, so decide early.
Buying and Fabrication Notes
For a quotation, supply at once: grade, section size, quantity and length, cutting or drilling requirements, surface treatment, and delivery destination. If members are spliced or welded, also state weld grade and inspection requirements. Complete inputs make quotations and process plans comparable.
Common Questions
Is a bigger section always safer? Not necessarily. Section and grade together must satisfy strength and stability; an oversized section adds self-weight and cost.
Can you cut and process to drawing? Cutting, drilling and end preparation can be reviewed against approved drawings, with the final scope confirmed by drawing and equipment review.
To confirm section supply and supporting processing, see Structural Steel Materials, custom built-up H-beams and steel girders; fabrication scope is on structural steel fabrication. Send your list or drawings for review.