BS5950-8 provides two tables for columns, tension members and beams. The use of the tables depends on the section types, as summarised below:

The design temperatures are given in Table 1 for columns and tension members and 10 of Table 2 for beams. Note that the design temperatures refer to steel temperatures at section flanges directly exposed to the furnace fire. For web temperatures, they can conservatively be determined from the tables by replacing the flange thickness with the web thickness. For fire resistance ratings greater than 60 min, the steel temperature can conservatively be assumed to be the same as the furnace temperature used in the standard fire test.

Table 1 Design temperatures for columns and tension members (BS5950-8: 2003) Flange thickness [mm] Design temperature [°C] for fire resistance period of 15 min 30 min 45 min 60 min 6 672 821 895 941 7 654 811 894 940 8 635 799 893 939 9 615 786 891 938 10 596 772 889 938 11 577 760 886 937 12 558 750 883 936 13 540 743 879 935 14 523 738 874 934 15 507 735 868 933 16 491 732 861 931 17 476 728 853 930 18 462 722 844 928 19 449 716 835 926 20 436 708 825 923 22 413 692 804 917 24 391 674 784 909 26 372 657 766 899 28 355 639 752 887 30 339 622 743 874 32 325 605 737 859 34 312 589 734 844 36 300 574 729 828 38 289 559 723 812 40 279 545 714 797 45 256 512 690 764 50 237 482 663 744 55 221 456 637 735 60 208 432 612 728 65 196 410 589 714 70 185 390 567 697 75 176 373 547 679 80 168 356 527 661

Table 2 Design temperatures for beams (BS5950-8: 2003) Flange thickness [mm] Design temperature [°C] for fire resistance period of 15 min 30 min 45 min 60 min 6 672 820 895 940 7 654 810 894 940 8 634 798 887 939 9 615 785 892 938 10 596 772 891 938 11 577 760 889 937 12 560 750 887 936 13 542 743 884 935 14 526 739 879 934 15 511 736 875 933 16 496 733 869 932 17 482 730 863 930 18 468 725 856 928 19 457 720 847 927 20 445 714 840 925 22 423 699 831 920 24 401 683 812 913 26 385 668 793 905 28 370 654 778 897 30 354 638 764 886 32 342 624 752 875 34 328 609 744 862 36 318 596 738 850 38 307 583 736 837 40 300 574 730 827

Composite Slabs

BS5950-8 provides the tabulated design temperature profiles for unprotected composite slabs with profiled steel sheeting as given in Table 3. The temperatures of the reinforcement or concrete of a slab can be determined from the table according to their depths normal to the surface of the profiled steel sheeting. The information in this table was taken from the Reference by Cooke, Lawson & Newman (1988). Comparison with the temperatures recorded in fire tests has shown these values to be reasonably conservative for design purposes (Newman 1991).

Shelf Angle Floor Beams

Annex C (normative) of BS5950-8 (2003) provides a tabular method of for determining the temperature distribution of shelf angle floor beams.

A shelf angle floor beam normally consists of an I-section with angles connected to the webs. Precast concrete slabs are then positioned on the angles, with the void around the I-beam filled by in-situ concrete. Basically, the concrete floor will protect the upper part of the steel beam from a fire beneath the floor. The fire resistance would be improved if the shelf angles were placed with their legs pointing upwards and embedded in the concrete.

A number of standard fire resistance tests have been carried out on shelf angle floor beams. They showed that the floor beams can achieved a fire resistance up to 90 minutes without the need for fire protection of the lower parts of the beams (Wainman & Kirby 1988; Lawson & Newman 1990). The temperature data recorded from the tests have formed the basis of the tabular method of BS5950-8.

Basically, as shown in Figure 1, the temperature profile of the beam is divided into different temperature blocks and BS5950-8 provides the block temperatures for a fire resistance period of 30 min, 60 min or 90min. For the exposed steelwork, the temperature θ₁ of the lower flange (block 1) should be determined from 8.4.3 of BS5950-8 (see the table in Figure 1). The temperatures of the lower web θ₂, and the angle legs θ₃ and root θ_R are determined according to the aspect ratio D_e/B_e of the beam, where D_e is the overall exposed depth of the steel section and B_e is the width of the exposed bottom flange.

Aspect ratio	Block temperature [°C] for a fire resistance period of:
	30 min			60 min			90 min
	θ2	θ3	θR	θ2	θ3	θR	θ2	θ3	θR
De/B ≤ 0.6	θ1 - 140	475	350	θ1 - 90	725	600	θ1 - 60	900	775
0.6 < De/B ≤ 0.8	θ1 - 90	510	385	θ1 - 60	745	620	θ1 - 30	910	785
0.8 < De/B ≤ 1.1	θ1 - 45	550	425	θ1 - 30	765	640	θ1	925	800
1.1 < De/B ≤ 1.5	θ1 - 25	550	425	θ1	765	640	θ1	925	800
De/B > 1.5	θ1	550	425	θ1	765	640	θ1	925	800

The embedded steelwork is divided into three blocks: 4, 5 and 6 according to the position of the 300°C line x₃₀₀, as defined in Figure 2. The temperatures of blocks 4, 5 and 6 are given by:

with

where

θR	is the temperature at location x [°C];
G	is the temperature gradient [°C/mm];
x	is the distance from angle root as shown in Figure 2 [mm].

Figure 2 Definition of blocks 4, 5 and 6 for shelf angle beams (BS5950-8: 1990)