Calculation of Crippling (Ultimate Transverse) Load on Electrical Pole
- Wind Speed = 89 Mile/Hr.
- Height of Pole=10 Meter
- Type of Pole =RCC
- Height of Pole in Ground=1.5 Meter.
- Pole Section on Bottom of Pole (Length x Width)=400mm x 150mm
- Pole Section on Top of Pole (Length x Width)=127mm x 150mm
- Conductor Mounting from top of Pole(g)=0.5 Meter.
- Distance between Two Pole(s) =20 Meter.
- No of Conductor on Pole(n)=3No’s
- Size of Conductor(r)= 30mm
Calculations:
- Wind Pressure = 00256 x 2x Wind Speed
- Wind Pressure = 00256 x 2x 90 = 20.506 Pound /Sq.Foot
- Wind Pressure(Wp) =4.882×20.506 = 100 Kgf/M2
- Wind Load on Conductor/Span(ws)=2/3 x Wp x s x r x n
- Wind Load on Conductor/Span(ws)=2/3 x 100 x 20 x 30 x 3 =120 Kg———–(I)
- Height of Pole Above Ground (h)= 10-1.5 =8.5 Meter
- Total Bending Movement at Ground Level due to Wind Load on All Conductor=ws x h
- Total Bending Movement at Ground Level due to Wind Load on All Conductor(b)=120 x 8.5= 960 Kg.Mt
- Equivalent Safe Working Load at said Meter from TOP of The Pole corresponding to Wind Load on All Conductors =b / (h- g) = 960 / 8.5-0.5 =120 Kg
- Wind Load on Pole Surface above Ground Level (p1)=Wp x h /((l1+w1)/(2×1000))
- Wind Load on Pole Surface above Ground Level (p1)=100×8.5/(400+150/2×1000) =233.75 Kg
- Centre of Gravity of Tapering rectangular section of Pole(p2)= (h/3)x((l2+(l1*2))/(l1+l2))
- Centre of Gravity of Tapering rectangular section of Pole(p2)= (5/3)x((127+(400×2)) /(127+400))=4.98Mt
- Bending Movement at Ground Level due to Wind Load on Pole(p) =p1 x p2
- Bending Movement at Ground Level due to Wind Load on Pole(p) =233.75×4.98=1164.98 Kg.Mt
- Equivalent Safe Working Load at said meter from Top of The Pole corresponding to Wind Load on Pole(wt) = p /(h-g) =1164.98 / (8.5-0.5) = 62 Kg——————————(II)
- Total Transverse Load at said meter from Top of The Pole (Due to wind Load on Conductors + Wind Load on Pole Surface) (T)=Ws + Wt = 120+145.62 =256.62 Kg
| Type of Pole | Safety Factor |
| Wooden Pole | 3.5 |
| RCC Pole | 2.5 |
| PCC Pole | 2.5 |
| Steel Tubular Pole | 2 |
| Rail/RSJ Pole | 2 |
| Struts (Steel Pole) | 2.5 |
| Struts (RCC/PCC) | 3 |
| PCC Pole for 33 KV | 2 |
- From Above Table Safety Factor=2.5
- Total Transverse Load (Crippling Load) of Pole = T x Safety Factor
- Total Transverse Load (Crippling Load) of Pole = 256 x 2.5 =664 Kg.
- Total Transverse Load (Crippling Load) of Pole=664 Kg
| Max. Length of Pole (Meter) | Min. Ultimate Transverse Load from 0.6meter from Top (Kg) |
| 17 | 3000 |
| 17 | 2300 |
| 17 | 2000 |
| 17 | 1400 |
| 16 | 1100 |
| 15 | 1050 |
| 14 | 1050 |
| 13 | 1000 |
| 12 | 800 |
| 11 | 600 |
| 10 | 500 |
| 9 | 300 |
| 8 | 200 |
| 7 | 200 |
| 6 | 200 |
| 5 | 150 |
| 4 | 150 |
| 3 | 150 |
- From Above Table Min. Ultimate Transverse Load for 10 Meter Pole = 500 Kg and as per our calculation it is 664 Kg hence Selection of Pole if O.K
Results:
- Calculated Transverse Load (Crippling Load) of Pole = 664 Kg
View more at https://electricalnotes.wordpress.com/2020/07/19/calculation-of-crippling-ultimate-transverse-load-on-electrical-pole/.
Published by Department of EEE, ADBU: tinyurl.com/eee-adbu
