Reinforcing steel of same type and grade shall be used as 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.
Bars may be arranged singly, or in pairs, in contact, or in groups of three or four bars bundled in contact. Bundled bars shall be closed within stirrups or ties. Bundled bars shall be tied together to ensure the bars remains together. Bars larger than 32 mm diameter shall not be bundled except in columns.
The calculated 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 anchorage or by a combination thereof.
Development Length of Bars: The development length Ld is given by Ld = (ǿσs)/4τbd
Where ǿ = nominal diameter of the bar,
σs = stress in bar at the section considered at design load, and
Ƭhd = design bond stress
The anchorage length of straight bar in compression shall be equal to the development length of bars in compression as specified in. The projected length of hooks, bends and straight lengths beyond bends if provided for a bar in compression, shall only be considered for development length.
For the purpose of this clause the diameter of a round bar shall be its nominal diameter and in the case of bars which are not round or in the case of deformed bars or crimped bars, the diameter shall be taken as the diameter of the circle given an equivalent effective area. Where spacing limitations and minimum concrete cover are based on the diameter. A group of ban bundled in contact shall be treated as a single bar of diameter derived from the total equivalent area.
Nominal cover is the design depth of concrete cover to all steel reinforcements, including links. It is the dimension used in design and indicated in the drawings. It shall be not less than the diameter of the bar.
|Column Dimension (b or D)||Minimum Wall Thicknt.u|
|Fire Resistance (h)||Maximum Beam Width(b)||Rib Width of Slubs (b)||Minimum Thickness of Floors (D)||Fully Exposed||50% Exposed||one Face Exposed||p < 0.4%||0.4% < p < 1%||p > 1%|