In many discussions, with colleagues and with students, I realized that many misunderstandings and problems are related to different, or just fuzzy usage of designations and definitions of terms. Even frequently used terms, like shakedown, structural stress/strain, are used and defined differently in the very same context by experts of different schools .

At the same time, terms and definitions that are appropriate for simple calculations of simple structures under simple loads are carried over to modern detailed analyses of complex structures subject to complex actions, where these outdated terms and definitions are not appropriate (anymore), because they do not possess the required flexibility.

Therefore, emphasis is on definitions and on usage of designations as general and as clear as possible without a too strong interference with easy reading. To keep the main text clear, most of the terms and definitions are put together in Section 2.2. A definition can then be found via the subject index, where the relevant number of the page containing the definition is in bold face.

Implicit definitions and definitions of more local usage are given in the text, with the designations in bold face.

Direct, unchanged or only editorially changed, citations from legal documents and from harmonized standards are in italics, followed by an abbreviated designation of the source.

The whole book follows strictly the Pressure Equipment Directive (PED) [1] and Annex B of EN 13445-3 [2], without any intentional deviation, but, in cases of doubt, it is the text of the PED and of...