Steel Buildings in Europe

Part 3: Actions 3 - 29  Multispan roofs : Figure 7.10 and the coefficients c pe are derived from Tables 7.3 to 7.4. Figure 8.4 of this guide shows the zones for duopitch roofs. b e /10 G F 1 e /10 F H J I 2 4 e /4 e /4 3 b e /10 G F 1 e /2 F H I I 2 e /4 e /4 G H Wind on the long side (perpendicular to the ridge line) 1 Wind direction 2 Ridge line 3 Upwind face 4 Downwind face Wind on the gable (parallel to the ridge line) e = min( b ; 2 h ) b is the crosswind dimension Figure 8.4 Zones for duopitch roofs 8.2.5 Internal pressure coefficients The internal pressure coefficient c pi depends on the size and distribution of the openings in the building envelope. When in at least two sides of the building (façades or roof) the total area of openings in each side is more than 30 % of the area of that side, the structure should be considered as a canopy roof and free-standing walls. A face of a building should be regarded as dominant when the area of openings in that face is at least twice the area of openings in the remaining faces of the building considered. Where an external opening would be dominant when open but is considered to be closed in the ultimate limit state, during severe windstorms (wind used for the design of the structure), the condition with the opening open should be considered as an accidental design situation. For a building with a dominant face, the internal pressure should be taken as a fraction of the external pressure at the openings of the dominant face:  Area of the openings on the dominant face = 2  area of openings in the remaining faces: c pi = 0,75 c pe  Area of the openings in the dominant face = 3  area of openings in the remaining faces: c pi = 0,90 c pe