In plastic analysis and design of a structure, the ultimate load of the structure as a whole is regarded as the design criterion. The term plastic has occurred due to the fact that the ultimate load is found from the strength of steel in the plastic range. This method is rapid and provides a rational approach


In elastic-plastic materials, stress is proportional to strain up to the yield stress, σy. The yield moment, My is the bending moment corresponding to a bending stress distribution in which the stress equals the yield stress only at the

