Moment redistribution in steel continuous beam according to limited plasticity concept

Conventional approach to elastic-plastic analysis of steel continuous beam, according to which it is assumed that two plastic hinges occur in an edge span at the ultimate limit state, not always gives safe evaluations of real member resistance. The reason is mainly the possibility of unlimited accumulation of permanent strains. Therefore some limitations of moment redistribution should be defined. Two of them are proposed and discussed by the author . It is accepted that the first plastic hinge arises in the cross-section in which maximum elastic bending moment is induced; however, in the second critical cross-section its appearance is not admissible. Only elastic in the first case, or limited elastic-plastic ultimate moment in the second example is there considered. The design methodology presented in the article is connected with the reduction of member redundancy and transformation of the whole beam into unstable mechanism is not allowable.