That at design working load the stresses and strains

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Unformatted text preview: as not to cause any harmful cracking in the pole. bars and wires 5.3.1 The surface of all reinforcement shall be free from loose scale, loose rust, oil, grease, clay or other material that may have deteriorating effect on the bond between the reinforcement and the concrete. 6.4.1 The strength of the pole in the direction of the line shall not be less than one-quarter of the strength required in the transverse direction. 5.4 Admixture 6.4.2 The load factor on transverse strength for reinforced concrete poles shall not be less than 2. Admixtures if used shall conform to IS 9 103. 5.5 Concrete 6.4.3 Poies intended to be fitted with stays or struts shall be designed accordingly, and if required by the purchaser, they shall be appropriately tested. Minimum grade of concrete used for the mamrfacture of reinforced concrete poles shall be M 25. 6.5 Method of selection of reinforced concrete pole in any given situation shall be as specified in IS7321. 5.6 Water The requirement of water used for mixing and curing shall conform to the requirements given in IS 456. Sea water shall not be used. 7MANUpACI’URE 7.1 All reinforcement shall be accurately placed and maintained in position during manufacture. All buttons or chairs or other devices used to obtain the necessary cover shall be of corrosion-resistant material. 6 DESIGN 6.1 The poles shall be so designed that they do not fail owing to failure initiated by compression in concrete. 7.2 Cover 6.2 Loading The cover of concrete overall reinforcement shall be atleast equal to the maximum size of aggregate plus 2 mm but in no case less than 20 mm. The maximum wind pressure to be assumed for compuringthe&signworkingloadshallbeasspecified by the State Governments, who are empowered in this behalf under the Indian Electricity Rules, 1956. Wind pressure may also be determined as specified in IS 875 (Part 3). 7.3 Welding and Lapping of Reinfomement Welding and lapping of reinforcement shall be as given in IS 456. 7.4 Forms 6.3 Depth of Planting 7.4.1 Forms shall be of the shape required and shall be so constructed as to maintain their shape during the placing and compaction of the concrete. They shall be sufliciently tight to prevent loss of liquid from the concrete. Themi m.mum depth ofplanting of a pole below ground level shall be in accordance with Table 1, the actual depth being determined on the basis of ground conditions. 2 IS 785 : 19Y8 7.42 Removal of Forms dia galvanized iron wire embedded in concrete during manufacture and the ends of the strip or cable left projecting from the pole to a length of 50 mm at 2 15 mm from top and 1%)111111 be1011 ground level (see Fig. 1). Forms shall not be removed until the concrete has hardened sufficiently so that the surface is not marred by the removal of the forms. Poles shall not be moved until the concrete has attained sufficient strength to withstand the stresses introduced during demoulding. 7.5 Placing, Compaction b) By providing two holes of suitable dimensions...
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This document was uploaded on 10/01/2013.

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