Why we perform plastic analysis for structures?

 Plastic analysis

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 for the analysis of the structure. It also provides striking economy as regards the weight of steel since the sections required by this method are smaller in size than those required by the method of elastic analysis. Plastic analysis and design has its main application in the analysis and design of statically indeterminate framed structures. 

Plastic analysis is based on the idealization of the stress-strain curve as elastic-perfectly-plastic. It is further assumed that the width-thickness ratio of plate elements is small so that local buckling does not occur- in other words the sections will classify as plastic. With these assumptions, it can be said that the section will reach its plastic moment capacity and then undergo considerable rotation at this moment.

Plastic analysis is defined as the analysis in which the criterion for the design of structures is the ultimate load.

ANSWER FOR YOUR QUESTION: To check the Performance of structure under ultimate loads.

1. Ultimate loads check structure also verify utmost capcity of element.

 .We conduct plastic analysis of the structure to verify its quality