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Sec.1: Introduction [Table of Contents] B: References

DNV-OS-C103 Structural Design of Column Stabilised Units (LRFD method)

[-] Sec.1: Introduction
[-] A: General

Sec.1
A. General

Sec.1
A 100   General

Sec.1 A
101   This offshore standard provides requirements and guidance for the structural design of column-stabilised units, constructed in steel.

Sec.1 A
102   The standard has been written for general world-wide application. Governmental regulations may include requirements in excess of the provisions given by this standard depending on the size, type, location and intended service of an offshore unit or installation.

Sec.1
A 200   Objectives

Sec.1 A
201   The objectives of this standard are to:
—provide an internationally acceptable standard of safety by defining minimum requirements for design of column-stabilised units
—serve as a contractual reference document between suppliers and purchasers
—serve as a guideline for designers, suppliers, purchasers and regulators
—specify procedures and requirements for column-stabilised units subject to DNV verification.

Sec.1
A 300   Assumptions and applications

Sec.1 A
301   The requirements and guidance documented in this standard are generally applicable to all configurations of column-stabilised units, including those with:
—ring pontoons
—twin pontoons.


Sec.1 A
302   A column-stabilised unit is a floating structure that can be relocated. A column-stabilised unit normally consists of a deck box with a number of widely spaced, large diameter, supporting columns that are attached to submerged pontoons.

Sec.1 A
303   Column-stabilised unit may be kept on station by either a passive mooring system, e.g. anchor lines, or an active mooring system, e.g. thrusters, or a combination of these methods.

Sec.1 A
304   Requirements concerning mooring and riser systems are not considered in this standard.

Sec.1 A
305   A column-stabilised unit may be designed to function in a number of modes, e.g. transit, operational and survival. Limiting design criteria modes of operation shall be clearly established and documented. Such limiting design criteria shall include relevant consideration of the following items:
—intact condition, structural strength
—damaged condition, structural strength
—air gap
—watertight integrity and hydrostatic stability.


Sec.1 A
306   For novel designs, or unproved applications of designs where limited or no direct experience exists, relevant analyses and model testing, shall be performed to clearly demonstrate that an acceptable level of safety is obtained.

Sec.1
A 400   Classification

Sec.1 A
401   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 Drilling and Support Units 
DNV-OSS-102 Rules for Classification of Production and
Storage Units 



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

Sec.1 A
403   Technical requirements given in DNV-OS-C101, section 8, related to Serviceability Limit States, are not mandatory as part of classification.

Sec.1: Introduction [Table of Contents] B: References