Chapter 7 - Factors Affecting Plastic Collapse

Abstract

Plastic analysis has been used traditionally to assess the collapse behavior of structures on the basis of yielding of cross-sections under proportionally increasing loading. There are materials that may not be able to sustain plastic moment throughout the loading history because of lack of ductility in the materials. In this case, it may be necessary to limit the plastic rotation in the plastic hinges instead of allowing for indefinite plastic rotation capacity. In other cases, instead of increasing the loading, it may be more realistic to increase some prescribed displacements proportionally, such as foundation settlements, in order to realize the effect of settlements on failure behavior of the structure. For structures under increasing temperature, such as those in fires, it is more relevant to calculate the failure temperature, rather than the failure load, for the assessment of the safety of the structure under high temperature. In this case, proportionally increasing prescribed temperatures may be a better way to assess the collapse behavior of the structure. This chapter discusses the influence of these factors on the failure of structures and describes ways of analyzing the structures.