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 α_e ≤ 30° (See Figure 4.1.6.10.-A and Table 4.1.6.10.), C_a shall be

(a)

taken as 0 on the upwind side of the peak, and

(b)

on the downwind side of the peak, taken as

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 C_w and Sentences 4.1.6.2.(5) and (6) for applicable values of C_s.

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)

(4)

For arch roofs with a slope at the edge α_e > 30° (See Figure 4.1.6.10.-A and Table 4.1.6.10.), C_a 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,

where x, h, b = as specified in Sentence [[b-4.1.6.10.#^2hplca|(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,

(5)

Except as provided in Sentence (6), C_a 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°, C_a 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), C_a 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

where C_a (x,y) = value of C_a at location (x,y), C_a (x,0) = value of C_a 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 C_w and Sentences 4.1.6.2.(5) and (6) for applicable values of C_s.

(2) Refer to Sentences 4.1.6.10.(3) and (4) for the calculation of C_a (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.