Poles
Poles are used largely because of their practicality, simplicity and strength. Poles are commonly used to support transmission lines or as structural members in pole frame construction. The latter is a derivative of post and beam construction, and has wide-spread application. It may be used in houses, industrial buildings, churches, restaurants, tourist resorts and rural sheds.

Timber poles have advantages such as:

• Minimising site disturbance.
  
• Reducing construction requirements in highly reactive soils, i.e. by embedding the poles in the ground.
  
• Offering design flexibility.
  
• Harmonising with the natural environment.
  
• Suiting steeply sloping sites.
  
• Providing ductility and flexibility where high wind loads and earthquakes are a concern.

Pole Sizes

• Pole diameters are 150mm, 200mm, 250mm, 300mm, 350mm (based on the butt end (larger) or ground line),
  
• Lengths can be ordered at 300mm increments,
  
• Lengths typically fall in the range of 1.8m to 15.0 metres – and may be available up to 20m in length,
  
• Longer lengths are limited to larger diameter poles (250mm or greater),
  
• Check size and length availability with suppliers before specifying.

Natural Characteristics
Natural characteristics for poles are described in AS2209 (see note 2) which limits the ovality, straightness, knot size, allowable checks, end splits and permissible visual defects. This standard is for power poles but can also be used for pole construction.
 

Structural Properties
Structural properties such as strength group, stress grade and durability parameters are provided in Table 2. This information can be used in conjunction with Section 6 of AS1720.1 (see note 3) to create design requirements for round timber products. Care should be taken to account for bending strength reduction factors brought about by immaturity, shaving and processing factors. When calculating the effective cross section of the timber, untreated round timber should be reduced so as to disregard any values for sapwood content. It is also important to make the general design assumption that all parts of piles or poles within 1.0m of the ground and anywhere below are permanently in an unseasoned condition.



Notes
1. AS2209 timber power poles for overhead lines, Standards Australia, Homebush, 1994
2. AS1720.1 Timber Structures - Design Methods, Standards Australia, Homebush, 1997