In any member subjected to bending, every reinforcing bar should extend, except at end supports, beyond the point at which it is no longer needed, for a distance equal to the effective depth of the member or 12 times the diameter of the bar, whichever is the greater. The point at which reinforcement is theoretically no longer needed is where the design resistance moment of the section, considering only the continuing bars, is equal to the applied design moment. However, reinforcement should not be curtailed in a tension zone unless at least one of the following conditions is satisfied for all arrangements of design load considered:
a) Reinforcing bars extend at least the anchorage
length appropriate to their design strength from the point at which they are no longer required to resist bending;
b) Design shear capacity at the section where the reinforcement stops is greater than twice the shear force due to design loads, at that section;
c) Continuing reinforcing bars at the section where the reinforcement stops provide double the area required to resist the bending moment at that section.
Where there is little or no end fixity for a member in bending, at least 25 percent of the area of the tension reinforcement required at mid-span should be carried through to the support. This reinforcement may be anchored in accordance with 10.5.5.4, or by providing,
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an effective anchorage length equivalent to 12 times the bar diameter beyond the centre line of the support, where no bend or hook begins before the centre of the support, or
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an effective anchorage equivalent to 12 times the bar diameter plus d/2 from the face of the support, where d is the effective depth of the member, and no bend begins before d/2 inside the face of the support.
Where the distance from the face of a support to the nearer edges of a principal load is less than twice the effective depth, all the main reinforcement in a member subjected to bending should continue to the support and be provided with an anchorage equivalent to 20 times the bar diameter.
