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DNV-OS-C502 Offshore Concrete Structures
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SECTION 2
Safety philosophySec.2
A. General
Sec.2
A 100 Objective
Sec.2 A
101 The purpose of this section is to present the safety philosophy
and corresponding design format applied in this standard.
Sec.2 A
102 This section applies to Offshore Concrete Structures which
shall be built in accordance with this standard.
Sec.2 A
103 This section also provides guidance for extension of this standard
in terms of new criteria etc.
Sec.2 A
104 The integrity of an Offshore Concrete Structures designed
and constructed in accordance with this standard is ensured through
a safety philosophy integrating different parts as illustrated in
Figure 1.
Sec.2 A
105 An overall safety objective shall be established, planned and
implemented, covering all phases from conceptual development until
abandonment.
Fig. 1 Safety Philosophy structure
Sec.2
A 200 Systematic review
Sec.2 A
201 As far as practical, all work associated with the design, construction
and operation of the Offshore Concrete Structure shall be such as
to ensure that no single failure will lead to life-threatening situations
for any person, or to unacceptable damage to the Structure or the
environment.
Sec.2 A
202 A systematic review or analysis shall be carried out for all
phases in order to identify and evaluate the consequences of single
failures and series of failures in the Offshore Concrete Structure,
such that necessary remedial measures can be taken. The extent of
the review or analysis shall reflect the criticality of the Offshore
Concrete Structure, the criticality of a planned operation, and
previous experience with similar systems or operations.Guidance note:
A methodology for such a systematic review is quantitative
risk analysis (QRA). This may provide an estimation of the overall risk
to human health and safety, environment and assets and comprises:| - | hazard identification,| - | assessment of probabilities of failure events,| - | accident developments, and | - | consequence and risk assessment. | | | |
It should be noted that legislation in some countries requires
risk analysis to be performed, at least at an overall level to identify critical
scenarios that might jeopardise the safety and reliability of the
Structure. Other methodologies for identification of potential hazards
are Failure Mode and Effect Analysis (FMEA) and Hazard and Operability
studies (HAZOP).---e-n-d---o-f---G-u-i-d-a-n-c-e---n-o-t-e---
Sec.2
A 300 Safety class methodology
Sec.2 A
301 The Offshore Concrete Structure is classified into the safety
class 3 based on failure consequences. For definition see Table
A1.Sec.2 A
| Table A1 - Safety
Classes |
| Class for consequences of failure | Safety Class | Minor seriousness | 1 | | Serious | 2 | | Very Serious | 3 | |
Sec.2
A 400 Quality assurance
Sec.2 A
401 The safety format within this standard requires that gross
errors (human errors) shall be controlled by requirements for organisation
of the work, competence of persons performing the work, verification
of the design, and quality assurance during all relevant phases.
Sec.2 A
402 For the purpose of this standard, it is assumed that the owner
of the Offshore Concrete Structure has established a quality objective.
The owner shall, in both internal and external quality related aspects,
seek to achieve the quality level of products and services intended
in the quality objective. Further, the owner shall provide assurance
that intended quality is being, or will be, achieved.
Sec.2 A
403 The quality system shall comply with the requirements of ISO
9000 and specific requirements quoted for the various engineering
disciplines in this Standard.
Sec.2 A
404 All work performed in accordance with this standard shall
be subject to quality control in accordance with an implemented
Quality Plan. The Quality Plan should be in accordance with the
ISO 9000 series. There may be one Quality Plan covering all activities,
or one overall plan with separate plans for the various phases and
activities to be performed.
Sec.2 A
405 The Quality Plan shall ensure that all responsibilities are defined.
An Interface Manual should be developed that defines all interfaces
between the various parties and disciplines involved, and ensure
that responsibilities, reporting and information routines as appropriate
are established.Sec.2
A 500 Health, safety and environment
Sec.2 A
501 The objective of this standard is that the design, materials,
fabrication, installation, commissioning, operation, repair, re-qualification,
and abandonment of the Offshore Concrete Structure are safe and
conducted with due regard to public safety and the protection of
the environment.Sec.2
A 600 Qualifications of personnel
Sec.2 A
601 All activities that are performed in the design, construction,
transportation, inspection and maintenance of offshore structures
according to this Standard shall be performed by skilled personnel
with the qualifications and experience necessary to meet the objectives
of this Standard. Qualifications and relevant experience shall be
documented for all key personnel and personnel performing tasks
that normally require special training or certificates.
Sec.2 A
602 National provisions on qualifications of personnel such as
engineers, operators, welders, divers, etc. in the place of use apply.
Additional requirements may be given in the project specification.Sec.2
B. Design Format
Sec.2
B 100 General
Sec.2 B
101 The design format within this standard is based upon a limit
state and partial safety factor methodology, also called Load and
Resistance Factor Design format (LRFD). The design principles are specified in Sec.2 of DNV-OS-C101.
The design principle is based on LRFD, but design may additionally
be carried out by both testing and probability based design.
The aim of the design of the Offshore Concrete Structure and its
elements are to:
| — | sustain loads liable to occur
during all temporary operating and damaged conditions if required |
| — | maintain acceptable safety for personnel and environment |
| — | have adequate durability against deterioration during
the design life of the Offshore Concrete Structure. |
Sec.2 B
102 The design of a structural system, its components and details
shall, as far as possible, account for the following principles:| — | resistance against relevant
mechanical, physical and chemical deterioration is achieved |
| — | fabrication and construction comply with relevant, recognised
techniques and practice |
| — | inspection, maintenance and repair are possible. |
Sec.2 B
103 Structures and elements there of, shall possess ductile resistance
unless the specified purpose requires otherwise.
Sec.2 B
104 Requirements to materials are given in Sec.4, Loads and Analyses
Requirements in Sec.5, Detailed Design of Offshore Concrete Structures
in Sec.6, Construction in Sec.7 and In-service Inspection, Maintenance
and Conditioned Monitoring in Sec.8.
Sec.2 B
105 Additionally, in Appendices A to F, guidelines are given for:| — | environmental loading (A) |
| — | structural analysis - modelling (B) |
| — | structural analyses (C) |
| — | seismic analyses (D) |
| — | use of alternative design standard (E) |
| — | crackwidth calculation (F). |
Sec.2
C. Identification of Major Accidental
Hazards
Sec.2
C 100 General
Sec.2 C
101 The Standard identified common accidental hazards for an Offshore
Concrete Structure. The designer shall ensure itself of its completeness
by documenting through a hazard identification and risk assessment
process that all hazards which may be critical to the safe operation
of the Offshore Concrete Structure have been adequately accounted
for in design. This process shall be documented.
Sec.2 C
102 Criteria for the identification of major accident hazards shall
be:| — | significant damage to the asset |
| — | significant damage to the environment. |
There should be a clear and documented link between major accident
hazards and the critical elements.
Sec.2 C
103 The following inputs are normally required in order to develop
the list of critical elements:
| — | description of Structure and
mode(s) of operation, including details of the asset manning |
| — | equipment list and layout |
| — | hazard identification report and associated studies |
| — | safety case where applicable. |
Sec.2 C
104 The basic criteria in establishing the list of critical elements
is to determine whether the system, component or equipment which - should they fail - have
the potential to cause, or contribute substantially to, a major
accident. This assessment is normally based upon consequence of
failure only, not on the likelihood of failure.
Sec.2 C
105 The following methodology should be applied for confirming
that prevention, detection, control or mitigation measures have
been correctly identified as critical elements:| — | identify the major contributors
to overall risk, |
| — | identify the means to reduce risk, |
| — | link the measures, the contributors to risk and the
means to reduce risk to the assets' systems - these
can be seen to equate to the critical elements of the asset. |
Sec.2 C
106 The record of critical elements typically provides only a list
of systems and types of equipment or structure etc. In order to
complete a meaningful list, the scope of each element should be
clearly specified such that there can be no reasonable doubt as
to the precise content of each element.
Sec.2 C
107 The above processes should consider all phases of the lifecycle
of the Structure.
Sec.2 C
108 The hazard assessment shall consider, as a minimum the following
events:| — | damage to the primary structure
due to:| — | extreme weather | | — | ship collision | | — | dropped objects | | — | helicopter collision | | — | exposure to unsuitable cold/warm temperature | | — | exposure to high radiation heat. |
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| — | fire and explosion |
| — | loss of Primary Liquid Containment (duration shall be determined
based on an approved contingency plan) |
| — | oil/gas leakage |
| — | release of flammable or toxic gas to the atmosphere
or inside an enclosed space |
| — | loss of stability |
| — | loss of any single component in the Station Keeping/Mooring
system |
| — | loss of ability to offload oil/gas |
| — | loss of any critical component in the process system |
| — | loss of electrical power. |
Sec.2 C
109 The results of the Hazard Identification and Risk Assessment
shall become an integrate part of the structural design of the Offshore
Concrete Structure.
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