4.1.6.10.Arch Roofs, Curved Roofs and Domes

(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 (See 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° (See Figure 4.1.6.10.-A and 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 xh h Ca = 2 for 0.05 < ≤ 0.12 and 0.03Cb b b 4x h Ca = for > 0.12 Cb b b where x = horizontal distance from the roof peak, h = height of arch, and b = width of arch. Figure 4.1.6.10.-A Accumulation Factors for Arch Roofs and Curved Roofs Forming Part of Sentences 4.1.6.10.(2) to (4) Notes to Figure 4.1.6.10.-A: (1) Refer to Table 4.1.6.10. for applicable values of Cw and Sentences 4.1.6.2.(5) and (6) for applicable values of Cs. Table 4.1.6.10. Load Cases for Arch Roofs, Curved Roofs and Domes Forming Part of Sentences 4.1.6.10.(3), (4) and (9) Factors Arch Roofs, Range of Curved Roofs Arch and Curved Roofs Domes Load Case Application and Domes Ca Ca Ca Cw Upwind Side Downwind Side Downwind Side As stated in Case I All values of h/b 4.1.6.2.(3) 1.0 1.0 1.0 and (4) xh h Slope at edge ≤ 30° Ca = 2 for ≤ 0.12 0.03Cb b b h/b > 0.05 1.0 0.0 all values of x 4x h Ca = for > 0.12 Cb b b xh h Slope at edge > 30° Ca = for ≤ 0.12 0.06Cb x30 b b y Case II h/b > 0.05 1.0 0.0 Ca (x, y) = Ca (x, 0) (1 − ) 0 < x < x30 2x h r Ca = for > 0.12 Cb x30 b h h Slope at edge > 30° Ca = for ≤ 0.12 0.06Cb b b h/b > 0.05 1.0 0.0 x ≥ x30 2 h Ca = for > 0.12 Cb b (4) For arch roofs with a slope at the edge αe > 30° (See Figure 4.1.6.10.-A and 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, xh h Ca = for 0.05 < ≤ 0.12, and 0.06Cb x30 b b 2x h Ca = for > 0.12 Cb x30 b 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, h h Ca = for 0.05 < ≤ 0.12, and 0.06Cb b b 2 h Ca = for > 0.12 Cb b (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 stated 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 (see 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 y Ca (x, y) = Ca (x, 0) (1 − ) 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. Figure 4.1.6.10.-B Unbalanced Snow Accumulation Factor on a Circular Dome Forming Part of Sentence 4.1.6.10.(7) Notes to Figure 4.1.6.10.-B: (1) Refer to Table 4.1.6.10. for applicable values of Cw and Sentences 4.1.6.2.(5) and (6) for applicable values of Cs. (2) Refer to Sentences 4.1.6.10.(3) and (4) for the calculation of Ca(x,0). (8) For all arch roofs, curved roofs and domes, the slope factor, C s, 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, C w, shall be as prescribed in Table 4.1.6.10.