The Total Combined Sail Weight of the lighting, camera, artwork or other equipment including its headframe mounted on the pole and the impact of wind on this total area. This can be increased by the sail offset if objects mounted on the pole are not uniformly distributed on the pole or mast such as they are located on one side only.
The Mounting Height of the lighting or other equipment on the column. The height at which a light, camera or other equipment is mounted on the pole will impact the engineering requirements for its manufacture. The higher that an object is mounted on the pole the greater the load will be on the pole or mast.
The Location of its Installation as wind speeds vary throughout Australia the location of a pole in either in a Wind Region A, B, C or D will effect its design. Below is a map of the various wind regions in throughout Australia.
The Terrain Category of the installation site. The terrain category rating indicates permanent obstructions of a particular area, which will have a direct effect on the wind loading on the column. Typically, the larger the obstacles surrounding the installation site will reduce wind speed within a certain area. Poles and masts located in open spaces will experience greater winds speed that that located behind a mountain or in a valley.
|1||Exposed open terrain with few or no obstructions and water surfaces at serviceability wind speeds.|
|2||Water surfaces, open terrain, grassland with few, scattered obstructions having heights generally from 1.5m to 10m. For example airports, harbours and areas with scattered trees.|
|3||Terrain with numerous closely spaced obstructions 3m to 5m high such as areas of suburban housing and level forested country.|
|4||Terrain with numerous large, high (10m to 30m high) and closely spaced obstructions such as large central business districts and densely-developed industrial areas.|
Topographical Multiplier – Wind velocities increase by up to 70% in the vicinity of mountains and hills. The topographic multiplier takes into account the angle of the land, the height of an obstacle such as hill or mountain and the distance from the obstacle and the direction of the prevailing wind. Subsequently when poles are shielded by wind from other large permanent structures a Shielding Multiplier can be calculated.
Directional Multiplier – In non-cyclonic regions prevailing wind direction is taken into account in conjunction with the positioning of any fittings mounted on the pole or mast. In areas of cyclones this is not calculated as the wind direction is not from a consistent direction as a cyclone passes wind can come from the exact opposite direction.
Annual Probability Of Exceedance – This is the probability that a wind speed will be exceeded in any one year and is the inverse of the “Wind Return Period” or the average recurrence interval. The wind speed for a long wind return period (such as 100 years) will be significantly higher than the wind speed for a short wind return period (such as ten years). Australian Standards give guidance on the selection of a return period for wind loading based on the importance of the structure and its design life. An important structure with a long design life will be designed for a longer return period and thus higher wind speed.
The Soil Type of the installation location The soil type and condition has to be taken into account when engineering the design of the footings for a pole or mast. Areas where the soil is sandy and free running or clay based will require a larger footing than a pole location where the soil loamy, gravelly and course.
The Design Life of the product. This is the length of time of the intended useful life of the pole or mast before its replacement or a structural repair.
Operational Parameters of mounting equipment, such as. Cameras and communication equipment and includes maximum oscillation of the pole where vibrations from wind can reduce the effectiveness of the equipment mounted on the pole or mast.
The Frangibility requirement of the Pole of Mast. Where the poles or masts are located near roads or paths the potential impact with a vehicle is taken into account and can be either manufactured into the pole or mast or the footing on which it is mounted. In the event of collision with the pole it is important the pole is not too rigid or strong, which increases the damage to the vehicle and people.