Loading According to EN 1991-1-4 and Safety Against Overturning of Circular Cylinders

Factor of safety against overturning The structural component is at risk of overturning.
Factor of safety against overturning = 1: The stability moment and the overturning moment are equal. The model is unstable and it cannot be ruled out that it is overturning.
Factor of safety against overturning 1: The model is not at risk of overturning.

Example

As an example, there is a circular cylinder with a diameter of 2.5 m and a height of 6 m. It is located in the wind load zone 2 with the terrain category 3.

Wind Loading

Fundamental value of the basic velocity:
v_b0 = 25.0 m/s

Directional factor:
c_dir = 1

Season coefficient:
c_season = 1

Air density at the atmospheric pressure of 1,013 hPa and T = 10° C:
ρ = 1.25 kg/m³

Kinematic viscosity of the air:
ν = 15 ∙ 10 ^-6 m ²/s  

Basic velocity:
v_b = c_dir ∙ c_season ∙ v_b0 = 25.0 m/s

Basic velocity pressure:
q_b = 1/2 ∙ ρ ∙ v_b² = 0.391 kN/m²

Peak velocity pressure:
q_p = 1.5 ∙ q_b = 0.586 kN/m²

Peak velocity:

Equivalent surface roughness:
k = 0.2 mm (galvanized steel)

Ratio of equivalent surface roughness and width:
k / b = 8 ∙ 10^-5

Reynolds number:

Force coefficient of cylinders without free-end flow:

Effective slenderness:
λ = l / b = 2.4

End-effect factor:
ψ_λ = 0.65

Structure coefficient:
c_sc_d = 1

Reference area:
A_ref = l ∙ b = 15 m²

Force coefficient:
c_f = c_f0 ∙ ψ_λ = 0.498

Wind force:
F_w = c_sc_d ∙ c_f ∙ q_p ∙ A_ref = 4.377 kN

Surface load due to the wind:
F_w = F_w / A_ref = 0.29 kN/m²

Stability Factor Due to Overturning

Height of circular cylinder:
h = 6 m

Distance between supports:
a = 1.35 m

Self-weight:
F_G = 18.495 kN

Overturning moment:
M_K = F_w ∙ h / 2 = 13.13 kNm

Stability moment:
M_S = F_G ∙ a / 2 = 12.48 kNm

Factor of safety against overturning:
η = M_S / M_K = 0.95

If you use RFEM for the calculation, you can recognize from the position of the resultants that they are within its extension behind the overturning edge of the circular cylinder. Thus, the model would be unstable if the supports were not additionally secured against pulling out.

Position of Resultants