Figure 1 - Tip Load Components


The total tip load force on pole is the vector sum of the following components: 


e.g.  


In a no wind condition, only longitudinal conductor forces will contribute to the tip load of pole.


Wind Load on Conductor

Transverse Wind Force on Conductor


The transverse wind force on conductor is calculated as follows:



Where: 

Fc = load on structure from wind on projected wind area of conductor

qz = design wind pressure on conductor (kPa)

Cd = drag coefficient of conductor. This is defaulted to 1 in the  absence of more accurate information.  

L = conductor span length (m)

d = conductor diameter (m)

SRF = span reduction factor. Default to 1.

α = angle between wind direction and the normal to the conductor (°)


In Directionless Tip Load Calculation method, the wind angle is taken as the worse case for each conductor , i.e.α = 0°

In Direction Sampling Calculation method, the wind angle is sampled at a discrete number of times around the pole, as defined by user, i.e.α = 5°, 10°, 15°, 20° etc


Longitudinal Conductor Force 


The longitudinal conductor force H, can be derived from the following principal:



Where:

T = tangential or axial conductor tension (N)

H = horizontal component of conductor tension (N)

V = vertical component of tension (N)


H can be derived with the MacLaurin's series approximation of the catenary equation:





Wind Load on Pole

The wind force on a cylindrical pole is calculated as follows:




Where:

Fpole = Wind load on pole (kN)

P = design wind pressure on pole (kPa)

OD = average outter diameter of pole (m)

h = height of pole above ground (m)


Reference:

AS/NZS 7000:2016 Overhead Line Design


See also:

Sag Tension Calculation

Pole Plant Calculation