(1) For all arch roofs, curved roofs and domes, the full and partial load cases defined in Article 4.1.6.3. shall be considered.
(2) For arch roofs, curved roofs and domes with rise-to-span ratio h/b > 0.05 as shown in Figure 4.1.6.10.A., the load cases provided in Sentences (3) to (7) shall also be considered.
(3) For arch roofs with a slope at the edge αe ≤ 30° as shown in Figure 4.1.6.10.A. and as described in Table 4.1.6.10., Ca shall be,
(a) taken as 0 on the upwind side of the peak, and
(b) on the downwind side of the peak, taken as,
C_a = (x h) / (0.03 C_b b^2) for 0.05 < h/b ≤ 0.12, and C_a = (4 x) / (C_b b) for h/b > 0.12
where,
x =horizontal distance from the roof peak,
h =height of arch, and
b =width of arch.
(4) For arch roofs with slope at the edge αe > 30° as shown in Figure 4.1.6.10.A. and as described in Table 4.1.6.10., Ca, shall be,
(a) taken as 0 on the upwind side of the peak, and
(b) on the downwind side of the peak,
(i) for the part of the roof between the peak and point where the slope α = 30°, taken as,
C_a = (x · h) / (0.06(C_b x_{30})b) for 0.05 < h/b ≤ 0.12
and
C_a = (2 x) / (C_b x_{30}) for h/b > 0.12
where,
x, h, b =as specified in Sentence (2), and
x30 =value of x where the slope α = 30°, and
(ii) for the part of the roof where the slope α >30°, taken as,
C_a = h / (0.06 · C_b · b) for 0.05 < h/b ≤ 0.12, and C_a = 2 / C_b for h/b > 0.12
(5) Except as provided in Sentence (6), Ca for curved roofs shall be determined in accordance with the requirements for arch roofs stated in Sentences (3) and (4).
(6) Where the slope, α, of a curved roof at its peak is greater than 10°, Ca shall be determined in accordance with the requirements for gable roofs described in Article 4.1.6.9. using a slope equal to the mean slope of the curved roof.
(7) For domes of circular plan form as shown in Figure 4.1.6.10.B., Ca shall,
(a) along the central axis parallel to the wind, vary in the same way as for an arch roof with the same rise-to-span ratio, h/b, and
(b) off this axis, vary according to,
C_a(x, y) = C_a(x, 0) · (1 − y / r)
where,
Ca(x,y) =value of Ca at location (x,y),
Ca(x,0) =value of Ca on the central axis parallel to the wind,
x =distance along the central axis parallel to the wind,
y =horizontal coordinate normal to the x direction, and
r =radius of dome.
(8) For all arch roofs, curved roofs and domes, the slope factor, Cs, shall be as prescribed in Sentences 4.1.6.2. (5) and (6).
(9) For all arch roofs, curved roofs and domes, the wind exposure factor, Cw, shall be as prescribed in Table 4.1.6.10.