I-beam — 56.82 kg per metre, 72.4 cm² cross-sectional area. IS 808 Table 2 - Light/Junior Beams.
Light & Junior Beams (LB, JB). Reproduced as printed in IS 808 Table 2 - Light/Junior Beams.
A radius of gyration here disagrees with this row’s own I and A
As printed in IS 808 Table 2 - Light/Junior Beams. 400 mm deep, 165 mm wide. Units are shown on every row, because the two standards on this site use different ones for the radius of gyration.
| Depth of section D | 400 | mm |
|---|---|---|
| Width of flange B | 165 | mm |
| Thickness of web t | 8 | mm |
| Thickness of flange T | 12.5 | mm |
| Flange slope | 98 | ° |
| Root radius R1 | 16 | mm |
| Toe radius R2 | 8 | mm |
| Mass per metre M | 56.82 | kg/m |
|---|---|---|
| Sectional area A | 72.4 | cm² |
| Second moment of area Izz | 19,300 | cm⁴ |
|---|---|---|
| Radius of gyration rzz | 16.3 | mm |
| Elastic section modulus Zzz | 965 | cm³ |
| Plastic section modulus Zpz | 1,090 | cm³ |
| Second moment of area Iyy | 716 | cm⁴ |
|---|---|---|
| Radius of gyration ryy | 3.14 | mm |
| Elastic section modulus Zyy | 86.8 | cm³ |
| Plastic section modulus Zpy | 151 | cm³ |
| Torsion constant (St Venant) It | 41.2 | cm⁴ |
|---|---|---|
| Warping constant Iw | 3,51,000 | cm⁶ |
Total weight is the mass per metre multiplied by the length and the number of pieces. Ten pieces of LB 400 at six metres each is 56.82 × 6 × 10 = 3,409 kg. There is nothing else to it — the standard publishes the mass, so no one needs to compute it from the area.
You can check that mass against the area on this page: 72.4 cm² of steel at 7 850 kg/m³ is 56.83 kg/m. Every row in this dataset was checked that way, which is how the contradictions flagged on some of these pages were found.
Work it out for your own lengths and quantities →
IS 808 : 2021 gives LB 400 a mass of 56.82 kg per metre. Its printed cross-sectional area of 72.4 cm² agrees: 72.4 cm² of steel at 7 850 kg/m³ works out at 56.83 kg per metre.
340.92 kg. Mass per metre times length: 56.82 × 6. Ten such pieces come to 3409 kg.
It is the same section under the name IS 808 : 2021 gives it — the 2021 revision of IS 808 dropped the "IS" prefix, so a drawing saying ISLB 400 means this section. Check the edition before assuming the figures match, though: this page publishes the current tables, and a great many tables in circulation were copied from the 1989 edition.
400 mm deep and 165 mm wide, with a 8 mm web and 12.5 mm flanges.
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