Lateral & Axial Loads

The wind force to a given post will be based on:

• The Wind Pressure, q_w
• The Velocity Pressure Exposure Coefficient, K_z
• The Topographic Factor, K_zt
• The Elevation Factor, K_e
• The Inverted Fence Opening Reduction Factor for wind loading, R_1w
• The Force Height Adjustment Factor for wind loading, F_hw
• The Wind Force Coefficient, C_fw
• The solid height of the fence, s (ft)
• The spacing of the fence posts, L (ft)
• The Solidity Ratio, ε
• For open fencing, you will also need:
  • The diameter or width of the expected post size, Ø_p (in) – this may change after post selection. For solid or mostly solid fencing, Ø_p = 0
  • The diameter or width of the top rail, Ø_r (in) – if not applicable, Ø_r = 0. For solid or mostly solid fencing, Ø_r = 0
  • The diameter or width of the mid rail, Ø_m (in) – if not applicable, Ø_m = 0. For solid or mostly solid fencing, Ø_m = 0
• The wind area tributary to the post, A_w = ε s L
  • For open fencing, add (Ø_p /12) × h + (Ø_r / 12) × 2 × L + (Ø_m / 12) × L to account for the exposed post and rails if applicable.

The wind force, f_w (lbs) to be applied to the post is:

f_w = q_w K_z K_zt K_e R_1w F_hw C_fw A_w

As the axial load on the post affects the bending strength, the following is also needed:

• The Axial Load supported by the post, p_w = D_w s L
• 5 × the p_w value for a stability check

For wind on ice forces, additional variables are required.

• The Wind on Ice Pressure, q_i
• The Inverted Fence Opening Reduction Factor for wind on ice loading, R_1i
• The Force Height Adjustment Factor for wind on ice loading, F_hi
• The Wind on Ice Force Coefficient, C_fi
• The Iced Solidity Ratio, ε’
• The wind area tributary to the post in the iced condition, A_i = ε’ s L

The Wind on Ice force, f_i (lbs) applied to the post is:

f_i = q_i K_z K_zt K_e R_1i F_hi C_fi A_i

As the axial load on the post affects the bending strength, the following is also needed:

• The Axial Load supported by the post, p_i = (D_w + D_i) s L
• 5 × the p_i value for a stability check

Next – Post Selection