Moment Redistribution

Moment redistribution is the design technique of modifying the bending-moment diagram obtained from elastic analysis of a continuous beam/frame to take advantage of the ductility of under-reinforced RCC: as the most-stressed section yields and forms a plastic hinge (without collapsing), it sheds moment to less-stressed sections, so the structure's real collapse load is higher than first yield. IS 456 Cl. 37.1.1 permits redistributing the elastic moments by up to 30% (limit-state design), subject to equilibrium being maintained and the neutral-axis depth at the redistributed section being limited to preserve ductility.

Its practical value is at heavily reinforced beam-over-support regions of continuous frames: reducing the (negative) support moment and increasing span moments evens out and declutters the reinforcement, easing congestion and bar-fixing while keeping the design safe and economical. It must not be combined unsafely with seismic/ductile detailing requirements, and the percentage used is limited and tied to the section's rotation capacity per the code.