ABSTRACT
An elastic analysis of a structure is important to study its performance, especially with regard to serviceability, under the service loading for which the structure is designed. However, if the load is increased until yielding occurs at some locations, the structure undergoes elastic-plastic deformations and, on further increase, a fully plastic condition is reached, at which a sufficient number of plastic hinges are formed to transform the structure into a mechanism. The chapter considers the principles of plastic analysis of plane frames in which buckling instability is prevented and fatigue or brittle failure is not considered possible. In most cases, the calculation of the collapse load involves trial and error, which may become tedious in large structures. The collapse load of the beam and this applies also to statically indeterminate structures can be calculated by equating the external and internal work during a virtual movement of the collapse mechanism.
