PSI - Issue 46

Tamás Fekete et al. / Procedia Structural Integrity 46 (2023) 189–196 Tamás Fekete / Structural Integrity Procedia 00 (2021) 000–000

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LSPS should remain tolerant of damage and dynamic overloads at least until the end of its DSL . Design Safety Calcu lations ( DSCs ) form the core of the ‘ design by analysis ’ phase of a design project, with the aim to justify that the LSPS will be safe to operate at least up to DSL . DSCs for an LSPS simulate the long-term behaviour of the planned system, including the effects of cracks in its load bearing walls through fracture mechanics calculations, as well as the effects of its expected normal operation and the potential accidents in a variety of low to very low probability scenarios. DSC s are nowadays based on internationally recognized design standards and/or guidelines; materials properties, the infor mation describing ageing of structural materials and the stability conditions of the structural materials are also based on standards and/or guidelines –see e.g., ASME (2021), PNAE (1989)–. As mentioned, the TAL of an LSPS is the time-period, from the date of commissioning, over which it can safely perform its intended functions, i.e., without significant risk of its structural integrity abruptly being lost. The TAL of the system is predicted by SICs , which also follow the DDOT concept. Therefore, SICs of an LSPS simulate the long term behaviour of a functioning system; fracture mechanics calculations are used to track the effects of cracks in load bearing walls, while the temporal behaviour of the system is investigated based on the past operating history of the system, supplemented with information on the subsequent load history, including the effects of expected continued normal operation and possible accidents under various low to very low probability scenarios. Today, the SIC method ology is generally based on the respected design standards and guidelines –see e.g., ASME (2021), PNAE (1989)–, while material properties used in the calculations and the necessary information describing the ageing of structural materials are based on materials testing results conducted on site. Typically, for a system, DSL ≤ TAL . With a knowledge of both the standards and the standards-based methodologies of DSCs and SICs , it is claimed that the methodology carries the imprint of continuum physics from the second half of the 19 th century. This is mani fested in the nearly exclusive use of isotropic, homogeneous, and time-independent constitutive models in the theoretic description –see Maugin (2009)–. It is not surprising therefore that the ageing of structural materials in this method ology is described almost exclusively through empirical correlations. So, a deeper understanding of the concept of SI is needed to significantly improve the methodology of SICs with a view to future developments. 3. Sketch of a Generalized Conceptual Framework for Structural Integrity of Large-Scale Pressure Systems 3.1. A Generalized Conceptual Framework for Structural Integrity and its Philosophical Basics Under the previous section, a bird's-eye view of the methodological issues of SICs was given and some comments on the methodology were made. It was found that SICs for LSPSs are engineering calculations that aim to justify the safe operation of technologies that meet the requirements of everyday life and practice in modern society. It was also shown that the SICs of an LSPS are intertwined with DSCs of the system, and their methodology is inherently based on the methodology of DSCs . However, the methodology for DSCs is composed of theoretical models that can be traced back to the historical development of related physical and engineering disciplines –see above and in more detail in Fekete (2018)–. Considering the current international good practice on the methodology of SICs , it can also be concluded that, for some reason, the evolution of these engineering methodologies is still behind the progress achieved in the scientific background of the relevant domains. Thus, when developing a Generalized Concept of SI for LSPSs , it is reasonable to pay careful attention to the metaphysical and scientific foundations of this conceptual framework, so that the resulting one will eventually be a plausible and coherent concept based on the best available knowledge. First, by explaining the objectives assigned to each area, an overview of the areas in which the term Structural Integrity applies is presented as follows.  Structural Integrity of an in-service LSPS is understood to be a coordinated set of activities, intended to provide a realistic assessment of the margin between its fail-safe operation and failure, using SICs and appropriate practical methods for their verification (e.g., a system of specific measurements and other experiment-based monitoring programs and systems).  Structural Integrity of LSPSs is understood primarily as research and development activities aimed at maintaining and improving the methodological framework for the safe operation of these systems, and at developing the sci entific and technological basis for assessing the border zone between safe operation and potential failure.