This chapter discusses the structural limits in Section III NB and Section VIII Div 2 as related to specific structural failure modes considered applicable to pressure vessel and piping design. The rules and requirements for Section III NB and Section VIII Div 2 are based on design by analysis philosophy addressing specific structural failure modes of structural collapse, rupture, instability, fatigue, and progressive deformation. Beam, plate, and shell theory have been used in the past to develop design analysis methods. These methods are giving way to finite element analysis (FEA) methods that are commonplace in engineering practice today. This chapter...