Committee IV.1: Design Principles and Criteria
Authors: Collette Matthew , Caridis Piero , Georgiev Petar , Hørte Torfinn , Jeong Han Koo , Kurt Rafet emek , Ilnytskiy Igor , Okada Tetsuo , Randall Charles , Sekulski Zbigniew , Sidari Matteo , Zhan Zhihu , Zhu Ling 
Published: April 2023

Committee Mandate
Concern for the quantification of general sustainability criteria in economic, societal and environmental terms for marine structures and for the development of appropriate principles for rational life-cycle design using these criteria. Special attention should be given to the issue of Goal-Based Standards as concerns their objectives and requirements and plans for implementation. Possible differences with the safety requirements in existing standards developed for the offshore, maritime and other relevant industries and of the current regulatory framework for ship structures shall be considered. Role of reliability-based design codes and requirements as well as their calibration to established safety levels.

Introduction
Design principles and criteria form the framework for assessing marine structures against societal sustainability goals for economic, social, and environmental performance. Design principles and criteria seek to link the analytic tools and data sources discussed in other ISSC committees into a framework for practical evaluation, comparison, and decision-making for proposed marine structures. Similar to other committees, the work on principles and criteria is largely evolutionary. After a burst of development surrounding the introduction of goal-based standards and increased use of risk in the approval process in the 2003-2015 timeframe, recent developments in principles and criteria have occurred over a broader range of topics. For the current mandate period, the committee chose a report structure that extended on several themes from the 2018 report, as well as exploring some areas of our mandate that have not received significant attention recently.
The committee report begins with an introduction to principles and criteria, followed by an extensive discussion of sustainability criteria, including the growing push to decarbonize the maritime industry. While further structural design improvements appear to have limited impact on decarbonization, understanding these developments is critical to planning future structural systems and accommodating potential green fuels which may impose their own unique material, structural, and risk assessments. Work on Goal Based Standards and international regulations has been largely evolutionary in the mandate period. To provide an overview of the activities at IMO and with class societies, we departed from past convention and structured the overview to mirror the other sections in our report.
Three areas of continuity were selected from the 2018 report, based on rapid developments in these areas or a desire to extend beyond what the 2018 report was able to cover. The growing use of digital twin monitoring systems is reviewed, with a focus on systems for wave climate reconstruction. While direct integration of these systems into criteria is still in development, this field is moving quickly in this direction, and we felt it was essential to continue to chronicle its growth. Work on accidental limit states was also highlighted. Recent ISSC reports from both technical and specialist committees have highlighted technical developments in modelling such limit states. In this work, we have highlighted the extensions of these methods into practical criteria. The 2018 report explored the concept of human factors applied to the engineering process itself, instead of the operational phase. The 2018 chapter revealed that little work was ongoing in this area, but the feedback from the 2018 report suggested that a broader focus on human factors would be welcome, which is presented in our penultimate chapter.
Finally, in reviewing the past IV.1 reports, it was clear that the portion of the mandate covering structural reliability has only received passing treatment for several cycles. In this cycle, the committee returned to a deeper focus on reliability, covering both recent developments in publication, along with example calculations. As digital twins and in-service monitoring proliferate, updatable reliability calculations may become more common, reliability approaches continue to be an important part of the principles and criteria landscape. Principles and criteria are inherently linked to both algorithmic formulations and computation tools. Thus, our report should be read in conjunction with several additional ISSC reports which cover fundamental developments in related fields. The work on digital twins is complemented by the work of specialist committee V.7 on Structural Longevity. The work on accidental loading is complemented by specialist committee V.1. Finally, owing to the tight coupling between design principles and design tools, the report of committee IV.2 also complements the work here.