General Requirements, Design Criteria, the Environment, and Loads
This is the third edition of CSA S471, General requirements, design criteria, the environment, and loads. It supersedes the second edition, published in 1992, and the preliminary edition, published in 1989.
It is the first of five CSA Standards that form the Code for the design, construction, and installation of offshore structures. The others are
(a) CAN/CSA-S472-92, Foundations;
(b) CSA S473-04 (under preparation), Steel Structures;
(c) CSA S474-04 (under preparation), Concrete Structures;
(d) CAN/CSA-S475-03, Sea Operations.
The Code was developed in the 1980s and 1990s at the request of the petroleum industry and regulatory authorities, which recognized that hydrocarbon production structures would likely become common in Canada’s offshore regions. In 1984, CSA formed a special Executive Management Committee to establish a program for developing offshore engineering standards. This evolved into the Strategic Steering Committee on Offshore Structures and the Technical Committees responsible for producing the Code’s five Standards. The Standards were developed with the participation of representatives from government, regulatory authorities, industry, classification societies, universities, and research and other institutions.
Although this Standard specifies minimum requirements for the design of offshore structures, it is intended as a guide to current practice in the context of a limit states design format and is not meant to inhibit the development and application of new engineering concepts. The proper exercise of engineering judgment is essential to good design, and it is the designers who are ultimately responsible for the soundness of their structures; the provisions of this Standard do not diminish that responsibility in any way.
The load and resistance factors in this Standard have been evaluated with the objective of providing consistent levels of safety for offshore structures. These levels have been related to target annual reliability levels. To provide flexibility, two safety classes have been incorporated. The first is concerned with situations in which the possible consequences could result in a great risk to life or a great potential for environmental damage; the second is concerned with a small risk to life and a small potential for environmental damage. A greater degree of safety is required in the first case than in the second.
The current edition of this Standard incorporates the results of expert review and comment since the publication of the second edition. Although this Standard originally applied to fixed offshore structures only, this edition has been generalized to apply to floating offshore structures as well. Where floating offshore structures are concerned, however, the information in this Standard does not provide a complete set of design requirements and should be supplemented by information obtainable from other documents. In addition, users of this Standard are advised to consult the other four Standards in the Code to ensure that significant details concerning both fixed and floating offshore structures are not overlooked.
This Standard was prepared by the Technical Committee on General Requirements (S471), Foundations (S472), and Sea Operations (S475), under the jurisdiction of the Strategic Steering Committee on Offshore Structures, and has been formally approved by the Technical Committee. It will be submitted to the Standards Council of Canada for approval as a National Standard of Canada.
This Standard specifies minimum requirements for and provides guidance on design principles, safety levels, and loads in connection with the design, construction, transportation, installation, and decommissioning of offshore structures.
This Standard is intended to cover all offshore structures and all parts of offshore structures (including the main deck and topside structures), whether they are of steel, reinforced concrete, composite, hybrid, or earth-filled construction. Although this Standard may be applied to floating offshore structures, it does not provide a complete set of design requirements for floating offshore structures. Users are strongly advised to seek additional guidance from publicly available international standards regarding the design of floating offshore structures.
(1) This Standard does not provide specific requirements for the operation, maintenance, service-life inspection, or repair of offshore structures.
(2) Mechanical and electrical equipment and any specialized equipment associated with offshore operations are not covered by this Standard except insofar as offshore structures must be able to safely sustain the loads imposed by the installation, housing, and operation of such equipment.
1.2 Alternative design method
An alternative design method based on theoretical analysis and recognized engineering practice may be used in lieu of the design method provided in this Standard. The alternative design method is to provide levels of safety and serviceability that are at least equal to those provided by the requirements of this Standard.
Note: The intent of this clause is to allow design methods that are not totally in accordance with the requirements of the Standard, but can be justified by proven performance or by theory and analysis based on special investigations.
Such investigations might include
(a) evaluation of a full-scale structural element or a prototype structure by a loading test, supplemented by calculations as required;
(b) studies of a scale model or a combination of model tests and calculations; or
(c) observed behaviour of existing structures similar to the one being designed.
The key point of this clause is that the levels of safety and serviceability required by the Standard must be achieved by whatever design method is used.
Novel or special structural elements may be used if they are designed using analytical and engineering principles and reliable test data that demonstrate that the levels of safety and serviceability provided are at least equal to those provided by the requirements of this Standard.
Each investigation, analysis, design activity, construction activity, inspection, and monitoring activity described in this Standard is to be performed by or under the supervision of one or more competent persons who have demonstrated experience relevant to the activity and are professionally licensed in Canada as engineers, geologists, or geophysicists.
1.4 Mandatory language
In CSA Standards, “shall” is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; “should” is used to express a recommendation or that which is advised but not required; and “may” is used to express an option or that which is permissible within the limits of the standard. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Legends to equations and figures are considered requirements.