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DNV-OS-C102 Structural Design of Offshore Ships [Table of Contents] Sec.2: cture and elements not covered by Rules for

DNV-OS-C102 Structural Design of Offshore Ships

[-] Sec.1: Topside stru

SECTION 1
Topside stru

Sec.1
A. General

Sec.1
A 100   General

Sec.1 A
101   This standard comprises sections with provisions applicable to all types of offshore floating ship shaped units, and sections with provisions for specific types of units such as well intervention/drilling units and FPSOs.

Sec.1 A
102   This standard is based on the principles of the Working Stress Design (WSD). In WSD the target component level is achieved by keeping the calculated stress for different load combinations equal to or lower than the maximum stress. The maximum permissible stress is defined by multiplication of the capacity, of the structural member with permissible usage factors.

Sec.1
A 200   Objectives

Sec.1 A
201   The objectives of this standard are to:
—provide an internationally acceptable standard for design of offshore ship-shaped units
—serve as a technical reference document in contractual matters between purchaser and manufacturer
—serve as a guideline for designers, purchaser, contractors and regulators
—specify procedures and requirements for units subject to DNV classification services
—base the design of the hull and topside on the same principles and methodology for all transit and operational scenarios
—provide, as far as possible, consistent loads for both topside and hull design.

Sec.1
A 300   Classification

Sec.1 A
301   Classification principles, procedures and applicable class notations related to classification services of offshore units are specified in the DNV Offshore Service Specifications given in Table A1.

Sec.1 A
Table A1 DNV Offshore Service Specifications  
Reference Title 
DNV-OSS-101  Rules for Classification of Offshore Drilling and Support Units  
DNV-OSS-102 Rules for Classification of Floating Production, Storage and Loading Units 



Sec.1 A
302   Documentation for classification shall be in accordance with the NPS DocReq (DNV Nauticus Production System for documentation requirements) and DNV-RP-A201.

Sec.1
B. Assumptions and Applications

Sec.1
B 100   General

Sec.1 B
101   It is assumed that the units will comply with the requirement for retention of the Class as defined in the DNV-OSS-101 or DNV-OSS-102.

Sec.1 B
102   This standard is applicable to hull and topside of ship-shaped offshore units, such as well intervention units, drilling units, floating production and storage units, constructed in steel for both non-restricted and restricted operations.

Sec.1 B
103   The environmental loads used for the longitudinal strength calculations for the survival conditions is based on the 10-2 annual probability of exceedance (100 year return period).

Sec.1 B
104   Shelf State requirements are not covered by this standard.

Sec.1 B
105   Requirements concerning mooring and riser system are not considered in the standard.

Sec.1
C. Definition

Sec.1
C 100   Verbal forms

Sec.1 C
101   Shall: Indicates a mandatory requirement to be followed for fulfilment or compliance with the present standard. Deviations are not permitted unless formally and rigorously justified, and accepted by all relevant contracting parties.

Sec.1 C
102   Should: Indicates a recommendation that a certain course of action is preferred or particularly suitable. Alternative courses of action are allowable under the standard where agreed between contracting parties but shall be justified and documented.

Sec.1 C
103   May: Indicates a permission, or an option, which is permitted as part of conformance with the standard.

Sec.1
C 200   Terms

Sec.1 C
201   Standard terms are given in DNV-OS-C101.

Sec.1 C
202   Drilling vessel: A unit used for drilling in connection with exploration and/or exploitation of oil and gas. The unit is generally operating on the same location for a limited period of time and is normally equipped with dynamic positioning system with several thrusters. The unit follows the normal class survey program.

Sec.1 C
203   Well intervention vessel: A unit equipped for performing wire-line intervention (without riser) of subsea wells and or coiled tubing of subsea. The unit is generally operating on the same location for a limited period of time and is normally equipped with dynamic positioning system with several thrusters. The unit follows the normal class survey program.

Sec.1 C
204   Floating production and offloading unit: A unit used for the production of oil with arrangement for offloading to a shuttle tanker. The units normally consist of a hull, with turret or spread mooring arrangement, and production facilities above the main deck. The unit can be relocated, but is generally located on the same location for a prolonged period of time.

Sec.1 C
205   Floating storage and offloading unit: A unit used for storage of oil with arrangement for offloading to a shuttle tanker. The units normally consist of a hull, with turret or spread mooring system. The unit is equipped for crude oil storage. The unit can be relocated, but is generally located on the same location for a prolonged period of time.

Sec.1 C
206   Floating production, storage and offloading unit: A unit used for the production and storage of oil with arrangement for offloading to a shuttle tanker. The unit is equipped for crude oil storage. The unit is normally moored to the seabed with production facilities on the main deck. The unit can be relocated, but is normally located on the same location for a prolonged period of time.

Sec.1 C
207   Floating production, drilling, storage and offloading unit: A unit used for drilling, storage and production of oil with arrangement for offloading to a shuttle tanker. The unit is equipped for crude oil storage.

Sec.1 C
208   LNG/LPG Floating Production and Storage units: A unit with facilities for oil and gas production and storage. The unit is typically permanently moored. Due to the complexity of the unit more comprehensive safety assessment are typically carried out. The unit is normally equipped with solutions for quick disconnection of mooring lines between the shuttle tanker and the oil and gas producing and storage unit.

Sec.1 C
209   Turret: A device providing a connection point between the unit and the combined riser- and mooring- systems, allowing the unit to freely rotate (weather vane) without twisting the risers and mooring lines.

Sec.1 C
210   Temporary mooring: Anchoring in sheltered waters or harbours exposed to moderate environmental loads.

Sec.1 C
211   Structural design brief: A document providing criteria and procedures to be adopted in the initial stages of the design process. The structural design brief should include analytical methods, procedures and methodology used for the structural design taking all relevant limiting design criteria into account. Owner's additional specification, if any, should be clearly described in the structural design brief.

Sec.1 C
212   Service life: The expected life time of the unit

Sec.1 C
213   Fatigue life: Service life ´ Design Fatigue Factor (DFF)

Sec.1 C
214   Probability of exceedance:
10-4: Appr. daily return period
10-8: Appr. 20 years return period
10-8.7: Appr. 100 years return period


Sec.1 C
215   Annual probability:
10-1: 10 years return period
10-2: 100 years return period

Sec.1
C 300   Symbols

Sec.1 C
301   The following Latin characters are used in this standard:

Sec.1 C
Table C1 Latin characters used  
V  Speed in knots  
CW Wave coefficient as given in DNV Rules for Classification of Ships Pt.3 Ch.1 Sec.4  
av Vertical acceleration 
at Transverse acceleration 
al Longitudinal acceleration 
Mwv Vertical wave bending moment 
Mwh Horizontal wave bending moment 
Qwv Vertical wave shear force 



Sec.1 C
302   The following Greek characters are used in this standard:

Sec.1 C
Table C2 Greek characters used  
h0 Basic usage factor 
b Coefficient depending on type of structure 
hp Permissible usage factor 

Sec.1
C 400   Abbreviations

Sec.1 C
401   The abbreviations given in Table C3 are used in this standard. Definitions are otherwise given in DNV-OS-C101 'Design of Offshore Steel Structures, General' (LRFD method).

Sec.1 C
Table C3 Abbreviations  
Abbreviation In full 
DFF  Design fatigue factor  
NDT  Non-destructive testing  
SCF  Stress concentration factors  
WSD  Working stress design  

Sec.1
D. References

Sec.1
D 100   DNV Offshore Standards, Rules and Classification Notes

Sec.1 D
101   The offshore standards and rules given in Table D1 are referred to in this standard.

Sec.1 D
Table D1 DNV Offshore Standards, Rules, Classification Notes and Recommended Practice 
Reference Title 
DNV-OS-C101  Design of Offshore Steel Structures, General (LRFD method)  
DNV-OS-C201  Structural Design of Offshore Units (WSD method)  
DNV-OS-C401  Fabrication and Testing of Offshore Structures  
DNV-OS-B101  Metallic Materials  
DNV-OS-C301 Stability and Watertight Integrity 
DNV-RP-C201  Buckling Strength of Plated Structures  
DNV-RP-C202  Buckling Strength of Shells  
DNV-RP-C205 Environmental Conditions and Environmental Loads  
Classification Note 30.7  Fatigue Assessment of Ship Structures  
DNV-RP-C203  Fatigue Strength Analysis of Offshore Steel Structures  
DNV-RP-C206 Fatigue Methodology of Offshore Ships 

DNV-OS-C102 Structural Design of Offshore Ships [Table of Contents] Sec.2: cture and elements not covered by Rules for