CEMENT & CONCRETE
Precast pole durability
T THE BENEFITS OF CONCRETE POLES • An optimised design enables the use of standardised fittings and ease of installation • They are maintenance-free, while being a cost-effective, long-term, durable solution • Superior fire rating compared to wooden poles • Less prone to theft and vandalism – hardened concrete has no resale value
he days of using wooden poles for electrification projects have long passed with the advent of superior concrete products that provide greater longevity, and cost efficiencies. Rocla, part of the IS Group of companies, recently underscored this by subjecting one of its precast poles to 11 m/8 kN of force testing at its Roodepoort plant. “Our cast pole is manufactured using the conventional concrete casting method,” explains civil engineer Mohammad Bodhania. “It is essential that we continually conduct quality checks to ensure the concrete pole stands up to the required standard, and the results of the recent test show that our concrete poles easily reach the required SANS 470 concrete pole code. In fact, the final test result showed that our poles reached a load of 10 kN without collapse.”
Ultimate load The recent 8 kN force testing means that the pole should be able to support a load of 8 kN applied at 300 mm from the tip. This is known as the ultimate load of the pole. The pole has a safety factor of 2.5, meaning that – in practice – the pole might be subject to a maximum load of 2.5 times less than the ultimate load. This is known as the working load. The proof load of the pole is 10% higher than the working load. At proof, the load must comply with the deflection, crack width and permanent set criteria stipulated in the SANS 470 concrete pole code. “We loaded our concrete pole to proof. At proof, the deflection and maximum crack width were measured. The load at which the first hair crack appears was also noted. After loading the pole to proof, the load was released and the permeant set was measured. We then loaded the pole again to ultimate and achieved the 10 kN without collapse,” Bodhania concludes.
