36.1 Analysis of Structure
Method of analysis as in 21 shall be used. The material strength to be assumed shall be characteristic values in the determination of elastic properties of members irrespective of the limit state being considered. Redistribution of the calculated moments may be made as given in 36.1.1.
36.1.1 Redistribution of Moments in Continuous Beams and Frames
The redistribution of moments may be carried out satisfying the following conditions:
a) Equilibrium between the internal forces and the external loads is maintained.
b) The ultimate moment of resistance provided at any section of a member is not less than 70 percent of the moment at the section obtained from an elastic maximum moment diagram covering all appropriate combinations of loads.
c) The elastic moment at any section in a member due to a particular combination of loads shall not be reduced by more than 30 percent of the numerically largest moment given anywhere by the elastic maximum moments diagram for the particular member, covering all appropriate combination of loads.
d) At sections where the moment capacity after redistribution is less than that from the elastic maximum moment diagram, the following relationship shall be satisfied:
where
depth of neutral axis,
effective depth, and
percentage reduction in moment.
e) In structures in which the structural frame
modulus of elasticity of steel.
provides the lateral stability, the reduction in moment allowed by condition given in 36.1.1 (c) shall be restricted to 10 percent for structures over 4 storeys in height.
36.1.2 Analysis of Slabs Spanning in Two Directions at Right Angles
Yield line theory or any other acceptable method may be used. Alternatively the provisions given in Annex D may be followed.