precast reinforced concrete street lighting poles
1986 Edition

IS 1332 permits the use of mild and medium tensile steel bars adhering to IS 432 (Part 1)-1982, deformed steel bars complying with IS 1786-1985, and structural steel bars as per IS 226-1975. The reinforcement must meet quality and mechanical property standards, with welding and lap splices designed to ensure joint strength at least equal to the base steel. Laps should be staggered following IS 456-1978 to guarantee proper load transfer and ductility.

According to IS 1332 Clause 5.3, the minimum embedment depth depends on the pole's mounting height. For poles 4.0 to 6.0 meters tall, the depth is approximately one twentieth of the height, rounded preferably to 0.5 m increments. Poles between 6.5 and 7.5 meters require a minimum depth of 1.50 meters, and those from 8.0 to 9.0 meters should be embedded at least 1.80 meters. Adjustments may be made based on soil conditions, and additional reinforcement is mandated for poles exceeding 7.5 meters to improve impact resistance.

Poles must be subjected to transverse strength testing per IS 2905-1966, applying a load 60% higher than the working load. The permanent deformation after load removal should not exceed 15% of the test deflection, and no cracks larger than 0.1 mm should appear before the design transverse load at first crack. Dimensional checks and uprightness inspections are also required. Brackets undergo strength tests in their mounted position. Sampling and acceptance criteria are established based on lot size, ensuring that defective units remain within permissible limits.

IS 1332 Clause 7.7 prescribes two methods for earthing poles: (a) embedding a galvanized iron wire or equivalent copper cable inside the concrete, with 100 mm projections at 215 mm from the top and 150 mm below ground level, or (b) providing holes at these locations through the hollow pole to allow passage of the earthing conductor. Exact details should be agreed upon between manufacturer and purchaser to ensure a reliable grounding path for safety and lightning protection.

The standard recommends initial curing by covering freshly cast concrete with absorbent materials such as sacking or hessian and keeping it continuously moist until sufficient strength is attained. After demoulding, poles should be watered periodically to prevent surface cracking. Steam curing is also allowed as an alternative to accelerate strength development. Daily compressive strength testing on concrete cubes is advised to monitor quality, with a minimum concrete grade of M20 and adequate reinforcement cover for durability.