Committee Mandate

Concern for accidental limit states (ALS) of ships and offshore structures and their structural components under accidental conditions. Types of accidents considered shall include collision, grounding, dropped objects, explosion, and fire. Attention shall be given to hazard identification, accidental loads and nonlinear structural consequences including residual strength together with related risks. Uncertainties in ALS models for design shall be highlighted. Consideration shall be given to the practical application of methods and to the development of ISSC guidance for quantitative assessment and management of accidental risks.


Ships and offshore structures may be subject to accidental actions during their operation. Design for preventing or minimizing the effects of accidents is termed accidental limit states (ALS) design and is characterized by preventing/minimizing loss of life, environmental damage, and loss of the structure. Collision, grounding, dropped objects, explosion, and fire are traditional accident categories. ALS design seeks to improve the outcomes of accidents by designing in flexibility/redundancy/durability that will permit the operator & crew to deal with the accident more effectively. Mitigations such as redundant systems, fault tolerant systems, and structural-system-level ductility will tend to improve accident outcomes. ALS design is inherently a scenario-driven exercise. Different structures may be subject to different accident scenarios depending on the type of structure and its intended purpose. Determination of appropriate accident scenarios for a particular structure for a particular operation is typically performed via hazard and risk assessment.

In general, this committee report discusses newer publications (from approximately 2017 to mid-2021) and references older publications as required for clarity. Chapter 1 introduces the basic terminology, definitions and background information required to discuss ALS. Chapter 2 presents an overview of rule and code design for ALS. Chapter 3 discusses accident hazard and risk analysis. Chapter 4 discusses recent publications relating to analytical, experimental, and numerical modeling of ALS. Chapter 5 discusses ALS related publications for new and emerging research areas. Chapter 6 presents a summary and the recommendations of this committee report. Finally, the appendix contains a benchmark study examining the capability of commercially available finite element analysis software to predict fracture for structures subject to an evolving state of stress. The benchmark study models novel large-pendulum impact experiments on full-scale ship structures.

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