5.1 Structural steel sections

Structural steel is rolled into a variety of shapes and sizes. The shapes are designated by the shape and size of their cross-section. Following are various types of rolled structural steel sections commonly used:

Rolled steel beam sections (I-section)

Rolled steel channel sections

Rolled steel angle sections

Rolled steel T-sections

Rolled steel bars

Rolled steel plates

Rolled steel sheets and strips

Mild steel flats

Figure 5.1 Rolled steel I beam

Rolled steel beam section (Figure 5.1)

ISI Hand Book for Structural Engineers Vol 1: Structural steel sections gives five series of beam section

Junior beams, designated as ISJB (Indian Standard Junior Beams)

Light Beams designated as ISLB (Indian Standard Light Beams)

Medium Beams, designated as ISMB (Indian Standard Medium Weight Beams)

Wide Flange Beams, designated as ISWB (Indian Standard Wide-Flange Beams)

H-Beams or column beams designated as ISHB (Indian Standard H-Beams)

Each beam section is designated by the series to which it belongs followed by the depth (in

of the section. For example, ISMB 400 means a beam section of medium weight and of depth equal to 400 mm. In some cases of wide flange beams and H-beams, more than one

section is available for the same depth. For example, more than one section is available for the same depth. For example, there are two sections of ISWB600; these two sections are differentiated by writing the mass of the beams per m run. Thus we have ISWB 600 @133.7 kg/m and ISWB 600@145.1 kg/m both of these being two different sections having different properties. Similarly we have ISHB 300@58.8 kg/m and ISHB 300@63.0 kg/m giving two different sections having different geometrical properties.

  1. Rolled Steel Channel Sections (Figure 5.2)

ISI hand book gives the following four series of channel sections:

Junior channels designated by ISJC (Indian Standard Junior Channels)

Light Channels designated by ISLC (Indian Standard Light Channels)

Medium channels designated by ISMC (Indian Standard Medium Weight Channels)

Special channels designated by ISSC (Indian Standard Special Channels)

Each rolled steel section is designated by the series to which it belongs, followed by its depth (in mm) and then its mass per metre length. Thus we have ISLC 400@45.7 Kg/m, meaning thereby that it is a light channel, having depth equal to 400 mm and mass equal to 45.7 kg/m. A channel section has only one axis of symmetry. Due to this, it is subjected to twisting or torsion, along with bending, when used as a beam.

Figure 5.2 Rolled steel channel

Rolled Steel Angle Sections (Figure 5.3) ISI hand book gives three series of angle sections:

Equal angles section designated by ISA (Indian Standard Equal Angles)

Unequal angles section designated by ISA (Indian Standard Unequal Angles)

Bulb angle section designated by ISBA (Indian Standard Bulb angles) (Figure 5.4) Since the equal angle section and unequal angle section are designated by the same series, the width and height of the legs of the angle are also mentioned along with the series. Thus, ISA

4040 will mean an equal angle section, having width and depth equal to 40 mm. Similarly ISA 4025 will mean an unequal angle section having depth equal to 40 mm and width equal to 25 mm. A bulb angle has unequal legs and hence only its depth is mentioned along with the series designation. Thus we have ISBA 300 meaning there by that it is a bulb angle section having its depth equal to 300 mm. However, there may be two bulb sections of the same depth, and these are differentiated by mentioning their mass per metre length. Thus we have ISBA 300 @ 47.5 kg/m and ISBA 300 @52.6 kg/m giving two sections which have different properties. It should be noted that the angle sections mentioned above do not have any axis of symmetry and hence the principal axes u-u and v-v are inclined to x-x and y-y axes.

Figure 5.3 Rolled steel angle

  1. Rolled Steel T-sections (Figure 5.5)

Normal Tee designated by ISNT, having width of flange, equal to the depth of section

H-Tee or wide flange tee, designated by ISHT, having width of flange equal to twice the depth of the section.

Short-Tee designated by ISST, having the width of flange shorter than the depth of the section

Light-Tee, designated by ISLT, having light weight

Junior Tee designated by ISJT

Each T-section is designated by the series to which it belongs followed by the depth in mm. Thus we have ISNT 100, meaning there by that it is a normal Tee section, having its depth equal to 100 mm. Similarly ISLT 100 will mean a light Tee section having depth of section equal to 100 mm. It is always preferable to mention the mass per metre length also such as ISNT 100 @ 15.0 kg/m or ISST 200 @ 28.4 kg/m etc.

  1. Rolled Steel Bar Sections (Figure 5.6)

ISI Hand book gives rolled steel bars of two types:

Round bars designated by ISRO

Square bars designated by ISSQ

Each bar section is designated by the series to which it belongs along with the diameter or the width in mm. Thus ISRO 100 will mean a round bar having 100 mm diameter. Similarly ISSQ 80 will mean a square bar of size 80 mm.