Civil Engineering Association

This part of ISO 19901 gives general requirements for the determination and use of meteorological and oceanographic (metocean) conditions for the design, construction and operation of offshore structures of all types used in the petroleum and natural gas industries. The requirements are divided into two broad types:
a) those that relate to the determination of environmental conditions in general, together with the metocean parameters that are required to adequately describe them;
b) those that relate to the characterization and use of metocean parameters for the design, the construction activities or the operation of offshore structures.
The environmental conditions and metocean parameters discussed comprise
⎯ extreme and abnormal values of metocean parameters that recur with given return periods that are considerably longer than the design service life of the structure,
⎯ long-term distributions of metocean parameters, in the form of cumulative, conditional, marginal or joint statistics of metocean parameters, and
⎯ normal environmental conditions that are expected to occur frequently during the design service life of the structure.
Metocean parameters are applicable to
⎯ the determination of actions and action effects for the design of new structures,
⎯ the determination of actions and action effects for the assessment of existing structures,
⎯ the site-specific assessment of mobile offshore units,
⎯ the determination of limiting environmental conditions, weather windows, actions and action effects for pre-service and post-service situations (i.e. fabrication, transportation and installation or decommissioning and removal of a structure), and
⎯ the operation of the platform, where appropriate.
NOTE Specific metocean requirements for tension leg platforms are to be contained in ISO 19904-2[1], for sitespecific assessment of jack-ups in ISO 19905-1[2], for arctic structures in ISO 19906[3] and for topsides structures in ISO 19901-3[4].

This part of ISO 19901 contains requirements for defining the seismic design procedures and criteria for offshore structures; guidance on the requirements is included in Annex A. The requirements are applicable to fixed steel structures and fixed concrete structures. The effects of seismic events on floating structures and partially buoyant structures are also briefly discussed. The site-specific assessment of jack-ups in elevated condition is only covered in this part of ISO 19901 to the extent that the requirements are applicable. Only earthquake-induced ground motions are addressed in detail. Other geologically induced hazards such as liquefaction, slope instability, faults, tsunamis, mud volcanoes and shock waves are mentioned and briefly discussed. The requirements are intended to reduce risks to persons, the environment, and assets to the lowest levels that are reasonably practicable. This intent is achieved by using:
a) seismic design procedures which are dependent on the platform's exposure level and the expected intensity of seismic events;
b) a two-level seismic design check in which the structure is designed to the ultimate limit state (ULS) for strength and stiffness and then checked to abnormal environmental events or the accidental limit state (ALS) to ensure that it meets reserve strength and energy dissipation requirements. For high seismic areas and/or high exposure level fixed structures, a site-specific seismic hazard assessment is required; for such cases, the procedures and requirements for a site-specific probabilistic seismic hazard analysis (PSHA) are addressed. However, a thorough explanation of PSHA procedures is not included. Where a simplified design approach is allowed, worldwide offshore maps are included in Annex B that show the intensity of ground shaking corresponding to a return period of 1 000 years. In such cases, these maps may be used with corresponding scale factors to determine appropriate seismic actions for the design of a structure.
NOTE For design of fixed steel offshore structures, further specific requirements and recommended values of design parameters (e.g. partial action and resistance factors) are included in ISO 19902, while those for fixed concrete offshore structures are contained in ISO 19903. Specific seismic requirements for floating structures are to be contained in ISO 19904[2], for site-specific assessment of jack-ups and other MOUs in ISO 19905[3], for arctic structures in ISO 19906[4] and for topsides structures in ISO 19901-3[1].

This part of ISO 19901 contains requirements and recommendations for those aspects of geoscience and foundation engineering that are applicable to a broad range of offshore structures, rather than to a particular structure type. Such aspects are
 site characterization,
 soil and rock characterization,
 design and installation of foundations supported by the seabed (shallow foundations), and
 identification of hazards.
Aspects of soil mechanics and foundation engineering that apply equally to offshore and onshore structures are not addressed. The user of this part of ISO 19901 is expected to be familiar with such aspects.
NOTE 1 Particular requirements for the design of piled foundations, which have a traditional association with fixed steel structures, are given in ISO 19902.
NOTE 2 Particular requirements for the design of shallow gravity foundations, which have a traditional association with fixed concrete structures, are detailed in ISO 19903.
NOTE 3 Particular requirements for the anchor points of mooring systems of floating structures are detailed in ISO 19901-7 [65].
NOTE 4 Particular requirements for the design of spud can foundations, which have a traditional association with jackup mobile offshore units (MOUs), are detailed in ISO 19905 (all parts).

This part of ISO 19901 provides requirements and guidance for the planning and engineering of marine operations, encompassing the design and analysis of the components, systems, equipment and procedures required to perform marine operations, as well as the methods or procedures developed to carry them out safely.
This part of ISO 19901 is applicable to marine operations for offshore structures including
⎯ steel and concrete gravity-base structures (GBS);
⎯ piled steel structures and compliant towers;
⎯ tension leg platforms (TLP);
⎯ deep-draught floaters (DDF), including spars or deep-draught caisson vessels (DDCV);
⎯ floating production semi-submersibles (FPSS);
⎯ floating production, storage and offloading vessels (FPSO);
⎯ other types of floating production systems (FPS);
⎯ mobile offshore units (MOU);
⎯ topsides and components of any of the above;
⎯ subsea templates and similar structures;
⎯ gravity, piled, drag-embedded and suction or other anchors;
⎯ tendon foundations;
⎯ associated mooring systems.
This document is also applicable to modifications of existing structures, e.g. installation of additional topsides modules.
This part of ISO 19901 is not applicable to the following marine operations:
a) construction activities, e.g. in a fabrication yard onshore, where there is no exposure to the marine environment;
b) drilling, processing and petrochemical activities;
c) routine marine activities during the service life of the structure;
d) drilling from mobile offshore drilling units (MODU);
e) installation of pipelines, flowlines, risers and umbilicals (but the interface between them and the structure is considered);
f) diving.