Bar Curtailment (Reinforcement Curtailment)

Bar curtailment is the practice of terminating (cutting off) tension reinforcement at the points along a member where the bending moment has reduced enough that the bar is no longer required, instead of running every bar full length — a major steel economy in beams and slabs. However, a bar cannot simply stop at the theoretical cut-off point: IS 456 Cl. 26.2.3 requires it to extend beyond that point by the effective depth d or 12 times the bar diameter (whichever is greater), and to satisfy development-length, shear-at-cut-off and detailing rules to avoid premature diagonal cracking.

Additional rules: not more than the permitted fraction of bars should be curtailed at one section; at least one-third (simply supported) or one-fourth (continuous) of the mid-span steel must continue into the support; and curtailment in a tension zone must meet the extra shear/anchorage conditions of Cl. 26.2.3.2. Poorly detailed curtailment (stopping bars exactly at the BMD cut-off) is a recurring cause of cracking near mid-span/quarter-span.