(1) Applicable values of external pressure coefficients, Cp, are provided in,
(a) Sentences (2) to (5), and
(b) Article 4.1.7.6. for certain shapes of low buildings.
(2) For the design of the main structural system, the value of Cp shall be established as follows,where H is the height of the building and D is the width of the building parallel to the wind direction:
(a) on the windward face,
Cp =0.6 for H/D < 0.25
=0.27(H/D + 2) for 0.25 ≤ H/D < 1.0
=0.8 for H/D ≥ 1.0,
(b) on the leeward face,
Cp =–0.3 for H/D < 0.25
=–0.27(H/D + 0.88) for 0.25 ≤ H/D < 1.0
=–0.5 for H/D ≥ 1.0, and
(c) on the walls parallel to the wind,
Cp = –0.7.
(3) For the design of roofs, the value of Cp shall be established as follows, where x is the distance from the upwind edge of the roof:
(a) for H/D ≥ 1.0,
Cp = –1.0,
and
(b) for H/D <1.0,
Cp =–1.0 for x ≤ H
=–0.5 for x > H
(4) For the design of the cladding and of secondary structural elements supporting the cladding, the value of Cp shall be established as follows,where W and D are the widths of the building:
(a) on walls, Cp shall be taken as ±0.9, except that within a distance equal to the larger of 0.1D and 0.1W from a building corner the negative value of Cp shall be taken as –1.2,
(b) on walls where vertical ribs deeper than 1 m are placed on the facade, Cp shall be taken as ±0.9, except that within a distance equal to the larger of 0.2D and 0.2W from a building corner the negative value of Cp shall be taken as –1.4, and
(c) on roofs, Cp shall be taken as –1.0, except that,
(i) within a distance equal to the larger of 0.1D and 0.1W from a roof edge, Cp shall be taken as –1.5,
(ii) in a zone that is within a distance equal to the larger of 0.2D and 0.2W from a roof corner, Cp shall be taken as –2.3 but is permitted to be taken as –2.0 for roofs with perimeter parapets that are higher than 1 m, and
(iii) on lower levels of flat stepped roofs, positive pressure coefficients established for the walls of the steps apply for a distance b as shown in Figure 4.1.7.6.D.
(5) For the design of balcony guards, the internal pressure coefficient, Cpi, shall be taken as zero and the value of Cp shall be taken as ±0.9, except that within a distance equal to the larger of 0.1D and 0.1W from a building corner, Cp shall be taken as ±1.2.