OS-C501

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Offshore Standard DNV-OS-C501, November 2013 Sec.2 Design philosophy and design principles – Page 24 4.3 Component testing 4.3.1 The purpose of this approach is to define the characteristic strength of the finished and complete structure under relevant load conditions. If deemed relevant, the resistance may be found by testing scaled models or parts of the finished structure. 4.3.2 Details about component testing are given in Sec.10 and Sec.7. 4.3.3 A sufficiently large number of tests shall be carried out in order to be able to define the characteristic strength of the structure with a confidence level at least as large as required for the data used with the analytical approach. 4.3.4 The failure mode(s), failure mechanism(s) and location(s) of failure shall be verified during and or after the tests. 4.4 Analyses combined with updating 4.4.1 Analyses of the structure may be complicated and a conservative bias may have to be introduced in the analyses. The reasons for such biases may be: — Scaling effects. — Uncertainties in the relevance of the design rules, e.g. in areas with large stress gradients. — The analytical models for analysing the stress level in the structure. — The effect of the environment on the mechanical properties. — Etc. 4.4.2 In such cases the analyses that have been carried out may be combined with the procedure for updating given in Sec.10 [3]. The purpose of this approach is to update the predicted resistance of the structure with the results from a limited number of tests in a manner consistent with the reliability approach of the standard. 4.4.3 It is a basic assumption that that all biases are handled in a conservative way, i.e. that the bias lead to a conservative prediction of the resistance of the structure. 5 Requirements to documentation 5.1 Design Drawings and Tolerances 5.1.1 Design drawings shall be provided according to general standards. 5.1.2 Tolerances shall be indicated. 5.2 Guidelines for the design report 5.2.1 The design Report should contain the following as a minimum: — Description of the entire structure and of its components. — Design input as described in Sec.3, including design life, environmental conditions. — Relevant design assumptions and conditions including applicable limitations. — Description of analysis from design phase, evaluation of problem areas, highly utilised and critical areas of the structure and highlighting points that require special attention during subsequent phases. — Reference to accepted calculations and other documents verifying compliance with governing technical requirements for all phases. — Fabrication procedures giving a concentrated description of the manufacturing/ fabrication history, reference to specifications, drawings etc., discussion of problem areas, deviations from specifications and drawings, of importance for the operational phase identification of areas deemed to require special attention during normal operation and maintenance. — Reference to documentation needed for repair and modification. 5.2.2 All failure modes and failure mechanisms shall be clearly identified and listed in a systematic way, preferably in a table. It shall be shown that each combination of identified failure modes and mechanisms was addressed in the design. DET NORSKE VERITAS AS
Offshore Standard DNV-OS-C501, November 2013 Sec.3 Design input – Page 25 1 Introduction 1.1 SECTION 3 DESIGN INPUT 1.1.1 This section identifies the input needed for the analysis of the structure. The material properties are addressed separately in Sec.4 for laminates and Sec.5 for sandwich structures. 1.1.2 The Design Input of this section (Sec.3) and Sec.4 and Sec.5 for Material Properties, form the basis of the Design Premises. 2 Product specifications 2.1 General function or main purpose of the product 2.1.1 The general function or the main purpose of the product and its main interactions with other components and the environment shall be specified in the product specifications. 2.1.2 The design life in service should be specified in the product specifications. Guidance note: E.g. the product is a gas pressure bottle for diving activities. The filling pressure will be 200 bars, the volume 100 l and the lifetime in service 20 years. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 3 Division of the product or structure into components, parts and details 3.1 3.1.1 The following levels of division of the product or structure are used in this standard: — structure / product — sub-structure / sub-product — components — parts — details. 3.1.2 The term product or structure designates in this standard the entity being designed. 3.1.3 The product or structure can be divided into sub-products or sub-structures, each of which may belong to different safety and service classes. 3.1.4 The structure or product can be divided into components corresponding to the same Safety Class but may be subject to different functional requirements. 3.1.5 Each component can be divided into parts and each part into details. Guidance note: For example: Structure = pipeline Sub-structure = the pipeline portion close to human activity should be classed under high safety class, whereas the rest of the pipeline can be classed under low or normal safety class. The pipeline can be divided into to sub-structures corresponding to different safety classes Components = the pipeline could be constituted of an inner liner and an outer shell. The liner’s function is to keep the pipeline tight, whereas the shell’s function is to hold the pressure loads. The two components have different functional requirements Parts and details = the pipeline can be divided into pipe body, couplers and fittings. Different design approaches and design solutions may be used for the different parts and details ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 3.1.6 A structure or substructure is an independent part for which a safety class can be defined. Components, parts and details are part of a structure or substructure. Failure of any of these components, parts or details shall be seen in combination with each other. See also Sec.8 [4]. 3.1.7 The interfaces between parts, components or structures shall be considered carefully. Interfaces shall be analysed as a part itself if they belong to a continuous structure. If the interfaces are physical interfaces, the requirements of Sec.7 [4] shall be considered. DET NORSKE VERITAS AS
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