2. Dimensions of sections
2.1 Masses
The masses per metre have been calculated assuming that the density of steel is 7850 kg/m3.
In all cases, including compound sections, the tabulated masses are for the steel section alone and no allowance has been made for connecting material or fittings.
2.2 Ratios for local buckling
The ratios of the flange outstand to thickness (b/T) and the web depth to thickness (d/t) are given for I, H and channel sections. The ratios of the outside diameter to thickness (D/t) are given for circular hollow sections. The ratios d/t and b/t are also given for square and rectangular hollow sections. All the ratios for local buckling have been calculated using the dimensional notation given in Figure 5 of BS 5950-1: 2000 and are for use when element and section class are being checked to the limits given in Tables 11 and 12 of BS 5950-1: 2000.
2.3 Dimensions for detailing
The dimensions C, N and n have the meanings given in the figures at the heads of the tables and have been calculated according to the formulae below. The formulae for N and C make allowance for rolling tolerances, whereas the formulae for n make no such allowance.
2.3.1 Universal beams, universal columns and bearing piles
| N |
= (B - t) /2 + 10 mm |
(rounded to the nearest 2 mm above) |
| n |
= (D - d) /2 |
(rounded to the nearest 2 mm above) |
| C |
= t /2 + 2 mm |
(rounded to the nearest mm) |
2.3.3 Parallel flange channels
| N |
= (B – t) + 6 mm |
(rounded up to the nearest 2 mm above) |
| n |
= (D - d) /2 |
(taken to the next higher multiple of 2 mm) |
| C |
= t + 2 mm |
(rounded up to the nearest mm) |
