REQUIREMENTS GOVERNING REINFORCEMENT AND DETAILING (IS:456-1978)

Reinforcing steel of same type and grade shall be used as the main reinforcement in a structural member . However, simultaneous use of two different types or grades of steel for main and secondary reinforcement respectively is permissible.(2) Bars may be arranged singly , or in pairs in contact ,or in groups of three or four bars bundled in contact. Bundles shall not be used in a members without stirrups . Bundled bars shall be tied together to ensure the bars remaining together .Bars larger than 36 mm diameter shall not be bundled, except in the column.(3) The Recommendations for detailing for earthquake-resistant construction given in IS:4326-1976 should be taken into consideration,where applicable.(4) Development of stress in reinforcement is required to be calculated in tension or compression in any bar at any section shall be developed on each side of the section by an appropriate development length or end encourage or by a combination thereof.(5) In the case of bars bundled in contact the development length of the each bar of bundled bars shall be that for the individual bar , increased by 10 percent for two bars in contact,20 percent for three bars in contact and 33 percent for four bars in contact.(6) Stirrups--- Not withstanding any of the provisions of this standard,in case of secondary reinforcement,such as stirrups and the transverse ties ,complete development lengths and anchorage shall be deemed to have been provided when the bar is bent through of an angle atleast 90 degree round a bar of atleast its own diameter and is continued beyond the end of the curve for a length of atleast eight diameters, or when the bar is bent through an angle of 135 degree and is continued beyond the end of the curve for a length of atleast six bars dia or when the bar is bent through an angle of 180 degree and is continued beyond the end of the curve for a length of atleast four bars diameter.