The procedure for limit analysis involves the following:

  1. Elastic analysis for ultimate (factored) loads.
  2. Redistribution of moments subject to following conditions:
  • Equilibrium shall always be maintained i.e. the sum of the support moments and the span moment shall never be less than the maximum span moment for a simply supported beam. In brief, a reduction in support moment must be accompanied by corresponding increase in the mid-span moment.
  • Amount of redistribution shall not exceed 30% in limit state design and 10% in case of multistory frames in which design is governed by horizontal loads.
  • Nowhere, the design moment shall be less than 0,7 times the elastic moment at ultimate state.
  • The depth of neutral axis shall be limited. This is required for satisfying the requirement of rotation capacity at a point where redistribution of moment is done.