Steel Buildings in Europe

Part 4: Detailed Design 4 – 10 Table 2.1 Limiting stress on the gross cross-section of the bracing members Stress limit on the gross cross-section of the bracing member due to horizontal forces equal to 0.025 V Angle of bracing to the horizontal  (degrees) Top storey of 30 m building Top storey of 20 m building Bottom storey of building 15   < 20 65 N/mm 2 80 N/mm 2 100 N/mm 2 20   < 30 70 N/mm 2 95 N/mm 2 135 N/mm 2 30   < 40 55* N/mm 2 110 N/mm 2 195 N/mm 2 40   < 50 75 N/mm 2 130 N/mm 2 225 N/mm 2 * This value is lower than the rest due to the way in which the forces are distributed Note: The maximum stresses in Table 2.1 are limited in application to a building of a maximum height of 30 m, storey height  3 m, with 5 m  b  12 m. The maximum permissible axial stress on the gross cross-section of the columns and beams (from horizontal loads of 2,5% of vertical loads) is 30 N/mm 2 . 2.7 The effects of imperfections Four types of imperfections influence the behaviour and design of multi-storey frames and their components. The references listed below relate to EN 1993-1-1.  Overall sway imperfections (§ 5.3.2 (1) to (4))  Sway imperfections over a storey (§ 5.3.2 (5))  Imperfections at splices (§ 5.3.3 (4))  Individual bow imperfections of members (§ 5.3.4). EN 1993-1-1 provides comprehensive guidance on the treatment of all four types of imperfection. 2.7.1 Overall sway imperfections The global sway imperfections to be considered are shown in EN 1993-1-1 Figure 5.2, reproduced below as Figure 2.4.   h h Figure 2.4 Equivalent sway imperfections (taken from EN 1993-1-1 Figure 5.2)