The electronic pdf version of this document found through is the officially binding version. OFFSHORE STANDARD. DNV-OS-C If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall. DNV GL rules for classification: High speed and light craft (RU-HSLC) Maritime > DNV GL offshore standards (OS) > Document code: DNVGL-OS-C
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DNV GL rules and standards
DNV undertakes classification, certification, and other verification and consultancy services relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carries out research in relation to these functions.
DNV Offshore Codes consist of a three level hierarchy of documents: Provide principles and procedures of DNV classification, certification, verification and consultancy services. Provide technical provisions and acceptance criteria for general use by the offshore industry as well as the technical basis for DNV offshore services.
Provide proven technology and sound engineering practice as well as guidance for the higher level Offshore Service Specifications and Offshore Standards.
DNV Offshore Codes are offered within the following areas: The changes are incorporated in the Web, CD and printable pdf versions. The amendments are shown in red colour in the Web and CD versions. All changes affecting DNV Offshore Codes that have not been reprinted, are published separately in the current Amendments and Corrections, issued as a printable pdf file.
Comments may be sent by e-mail to rules dnv. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the prior written consent of Det Norske Veritas. If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such person for his proved direct loss or damage.
However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million. In this provision “Det Norske Veritas” shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of Det Norske Veritas.
General Application and Assumptions Hull Girder Longitudinal Strength Turret and Moonpool Areas Topside Facilities Structural Support Fore and Aft Ship Structural Details and Stress Concentration Factors Design Loads and Calculation of Stress Ranges Design Loads for Minimum Structural Capacity Calculation of Fatigue Damage Loss of Heading Control Collision and Accidental Flooding Structure in Way of a Fixed Mooring System A Permanently Installed Units General A Area of application for Ch.
The design wave bending moments and shear forces at an annual probability of year return period are determined by means of direct calculations based on a site specific wave scatter diagram. The requirements given in Ch. This implies that the unit shall comply with the main class requirements for the midship section modulus. These requirements are based on the wave bending moments for the North Atlantic at an annual probability of Benign waters is in this context defined as the environments where required hull girder capacity calculated according to the LRFD method is less than the minimum section modulus calculated according to the main class requirements.
A Objectives The objectives of this standard are to: General Application and Assumptions B General It is assumed that the units will follow the normal class survey periods including regular dry-docking for inspection and maintenance. Units intended to stay on location for prolonged periods shall also comply with the requirements given in Appendix A. The turret may be of significant size and will affect the distribution of hull girder bending stresses — units designed with a submerged disconnectable turret buoy normally located in the foreship or bow region — units designed with spread mooring system, or similar solutions.
Such solutions are normally restricted to benign environments. A Classification C. Definitions C Floating storage and offloading units A floating production, drilling, storage and offloading unit can be relocated, but is generally located on the same location for a prolonged period of time. The units normally consist of a hull, with turret, and production and drilling equipment on the deck.
The unit is equipped for crude oil storage.
The crude oil may be transported to shore by shuttle tankers via an offloading arrangement. C Floating production, storage and offloading units A floating production storage and offloading unit can be relocated, but is generally located on the same location for a prolonged period of time. The units normally consist of a hull, with turret, and production equipment on the deck.
C Drilling vessels A drilling vessel is generally operating on the same location for a limited period of time. The unit follows the normal class survey program. The unit is normally equipped with dynamic positioning system with several thrusters. The units normally consist of a hull with moonpool and drilling equipment on the deck.
The unit may also be equipped for limited oil storage for testing. C Well stimulation or intervention vessel A well stimulation vessel or well intervention vessel is generally operating on the same location for a limited period of time.
The unit is normally equipped with a dynamic positioning system with several thrusters. The units normally consist of a hull with moonpool and equipment for well stimulation or maintenance e. C Symbols General symbols and definition of terms applicable for offshore units are given in the Rules for Classification of Ships Pt. Selection of Material A General A material specification shall be established for all structural materials. The materials shall be suitable for their intended purpose and have adequate properties in all relevant design conditions.
With reference to the application of material classes as given in the Rules for Classification of Ships Pt. The requirements are based on the consideration of fatigue damage and general fabrication quality. A Special category – typical locations The following locations are considered special category: Design Basis A Operational modes A unit shall be designed for all relevant modes of operation. Typically, the assessment of the unit shall be based on the following operational modes: A Still water load conditions All relevant still water loading conditions shall be considered to determine the limit curves for maximum permissible bending moments and shear forces.
A Environmental loads Environmental conditions shall in principle be described using relevant data for the period and areas in which the unit is to operate. A Prolonged survey periods Units intended to stay on location for a prolonged survey period, i. Fore and aft unit is normally areas outside 0. The hull girder will typically comprise the following elements: This will normally be the extreme full load and ballast condition.
The effect of topside facilities shall be included in the hull girder assessment for these load conditions. B Local strength assessment Local strength assessment shall be carried out for typical elements like: Strength Assessment B Compliance with main class requirements The requirements given in this standard are supplementary to the requirements for main class.
The wave load analysis shall in such cases be based on an annual probability of exceedance of The extent of the supporting structure is limited to the structural members affected by the local loads from the topside structure. Both global and local response of the turret shall be considered.
In addition the local structure shall be considered for the special load cases as defined in Sec. Hull deformations shall be considered. Fatigue Assessment C General principles Fatigue capacity shall be carried out according to Clas- sification Note The different methods given in Classification Note Applicable method can also be selected depending on the results from a screening process to identify fatigue critical details. Examples of such requirements may be: Design Loads for Minimum Structural Capacity B General principles To define the minimum design basis, the design sea pressures and pressures from liquid in tanks according to the Rules for Classification of Ships Pt.
DNV-OS-C Structural Design of Offshore Ships_百度文库
The acceptance criteria for these elements shall be as given in the Rules for Classification of Ships Pt. The shear force limit curves shall be corrected for actual load condition and structural arrangement as given in the Rules for Classification of Ships Pt.
Loads used in the global check shall be consistent. This implies that the longitudinal stresses based on global load conditions in D and E shall be combined with transverse stresses based on sea pressures and tank pressures as defined in DNV-OS-C Environmental Loads E General Environmental loads are loads caused by environmental phenomena. The characteristic value of an environmental load is the maximum or minimum value whichever is the most unfavourable corresponding to a load effect with a prescribed probability of exceedance.
Information on the joint probability of the various environmental loads may be taken into account if such information is available and can be adequately documented. Strip theory may be used provided: Three-dimensional effects in fore and aft ship will reduce the drag force compared to a strip theory approach. Each mooring system configuration will impose loads on the hull structure. These loads shall be considered in the structural design of the unit, and combined with other relevant load components.
E Sloshing loads in tanks In partly filled tanks sloshing occurs when the natural periods of the tank fluid is close to the periods of the motions of the unit. Factors governing the occurrence of sloshing are: The Rules for Classification of Ships differentiate between ordinary sloshing loads non-impact and sloshing impact loads.
The positions shall include the areas where the maximum vertical bending moment and shear force occur and at the turret position. The roll damping shall be evaluated for the return period in question.
E Mooring loads A unit may be kept on location by various methods. E Green water The green water is the overtopping by water in severe wave conditions. The forward part of the deck and areas aft of midship will be particularly exposed to green water.