**2.2 Potential hazards characterization in the technical area when developing the sea shelf**

With the progress and complication of engineering of technogenic aspects in the field of sea shelf development the analysis of man-caused (technogenic) offshore accidents and disasters becomes one of the most vital tasks of fundamental, interdisciplinary research; applied scientific and technical developments; development of diagnostic and monitoring systems; and designing of barriers and protection means. The ultimate purpose of such research works and development becomes the problem of evidence-based assessment of comprehensive risks and adjusting these risks to acceptable levels by use of expressions (1)–(9).

The analysis and generalization of the numerous data (in the most developed countries, such data bases amount thousands and tens of thousands facts) make it possible to carry out certain classification of technogenic and natural and manmade accidents and disasters [3]. Classification of accidents can be performed on scales of the countries and territories affected by them, on number of the victims and injured persons and on economic and ecological damage; in such classification, seven general groups can be identified: planetary, global, national, regional, local, object-based and local emergency and catastrophic situations (**Figure 4**).

The events resulting in similar serious accidents within technogenic field can also be classified by potential hazard and in this line can be named objects of the nuclear, chemical, metallurgical and mining industry, unique engineer

*Hybrid Modeling of Offshore Platforms' Stress-Deformed and Limit States… DOI: http://dx.doi.org/10.5772/intechopen.88894*

#### **Figure 4.**

Based on (1)–(7), actions to provide enhancement of safety and security with the corresponding economic expenses Z(t) shall be developed. The actions directed to reduction of risks R(t) value to the level [R(t)] have to be effective and correlate

where *mz* is the performance factor of economic costs for reduction of economic

The general expression for the analysis and the sea platforms safety provision as

ð8Þ

ð9Þ

with the levels of estimated risks R(t)

*Probability, Combinatorics and Control*

per risks criteria based on Eqs. (1)–(8) is the following:

• justification of acceptable risks [*R*(*t*)];

risks to acceptable levels by use of expressions (1)–(9).

margins *nR*; and

factor *mZ*.

**the sea shelf**

**78**

In the Eq. (9), practically are represented all set above main:

• scientific risks *R*(*t*) analysis via its basic components *P*(*t*)*, U*(*t*);

• scientific-methodological justification of risks' tolerance *Rс*(*t*) and risks'

**2.2 Potential hazards characterization in the technical area when developing**

acceptable level [R(t)] providing optimal expenses Z(t) with the set efficiency

With the progress and complication of engineering of technogenic aspects in the field of sea shelf development the analysis of man-caused (technogenic) offshore accidents and disasters becomes one of the most vital tasks of fundamental, interdisciplinary research; applied scientific and technical developments; development of diagnostic and monitoring systems; and designing of barriers and protection means. The ultimate purpose of such research works and development becomes the problem of evidence-based assessment of comprehensive risks and adjusting these

The analysis and generalization of the numerous data (in the most developed countries, such data bases amount thousands and tens of thousands facts) make it possible to carry out certain classification of technogenic and natural and manmade accidents and disasters [3]. Classification of accidents can be performed on scales of the countries and territories affected by them, on number of the victims and injured persons and on economic and ecological damage; in such classification, seven general groups can be identified: planetary, global, national, regional, local,

The events resulting in similar serious accidents within technogenic field can also be classified by potential hazard and in this line can be named objects of the

object-based and local emergency and catastrophic situations (**Figure 4**).

nuclear, chemical, metallurgical and mining industry, unique engineer

• development of methodological recommendations on formation and implementation of the actions directed to risks R(t) reduction to the

risks (*mz* ≥ 1).

*Losses (damages) and frequency of natural and man-made accidents and disasters.*

constructions (dams, platforms), offshore development objects (sea platforms, hydrocarbons storage tanks, LNG plants), the transport systems (airspace, surface and underwater, on-land) that provide transportation of dangerous cargos, large number of people, main gas-, oil pipelines and product lines. In this line, the hazardous objects of defense industry also shall be mentioned.

At the same time, a majority of accidents and disasters are followed by infringement of stress conditions and depletion of lifetime of the most loaded components in routine situations or in emergencies. The probabilities P(t) characterizing frequency of disaster accidents occurrence in peace time ranges from (2–3)<sup>10</sup><sup>2</sup> up to (0.5–1) 10<sup>1</sup> per year, while damages (losses) U(t) ranges from 1011 to 109 dollars per accident. At the same time, their risks R(t) vary in the limits from 104 dollars per year to 1010 dollars per year ranging from 104 dollars/year up to 1010 dollars/year.

In view of said above, the new fundamental and applied scientific tasks needed to be set at national and international levels, for instance:


Based on the level of potential hazard, according to the legislation requirements and taking into account accidents occurrence risks, the abovementioned objects of a technosphere can be split in four (4) main groups (**Figure 5**) for each of which corresponding safety requirements are provided:

Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Structures in Ice Environments, АРI Recommended Practice 2N (RP

CAN CAN/CSA-S473-92, "Offshore Structures", A National Standard of Canada, 1992 CAN CAN/CSA-S16.1-94, "Limit States Design of Steel

DnV, "Structural Reliability Analysis of Marine Structures", 1992. DnV, Offshore Standard OS-C101, Design of Offshore Steel Structures, General, 2001; ISO 19906, 2010 (ISO/DIS 19906 "Petroleum and natural gas industries - Arctic

Above documentation was used for definition of the main basic specified characteristic load during design of the sea platforms intended for use at a sea

Implementation of the proposed recommendations and norms covers the structures with vertical and inclined sides, monopods and multicolumn constructions. In the documents, the rules of definition of the main loads conditioned by action of all potentially dangerous ice features subject to consideration are given. In **Figure 6**,

**Global conventional and extreme loads on conical and vertical**

**constructions:** sheet and rafted ice; ice ridge compression; ultimate moving force (ice field crowding force); global (abnormal loads); ice islands (stopped

**Local ice pressure (for vertical and inclined surfaces):** solid ice area; and ice

**Ice loads dynamics:** shock actions and interaction "ice—construction" (selfexcited); ice load change in time; fatigue ice impact; ice grinding impact; and

*Types of sea platforms dependent on the sea depth (for standard soil conditions): (a) the artificial pad, depth is up to 5 m; (b) the caisson-island fixed along contour, depth up to 15–20 m; (c) the monopod or monokone, depth is up to 25–30 m; (d) shell support; and (e) the truss-shell type supports, depth 25–30 m and more.*

DnV, "Structural Design, General", Rules for classification of Fixed Offshore

Structures", A National Standard of Canada, 1992, Toronto;

*Hybrid Modeling of Offshore Platforms' Stress-Deformed and Limit States…*

CAN/CSA-S471-92, "General Requirements, Design Criteria, the Environment, and Loads", A National Standard of Canada, 1992; Toronto; Commentary to CSA Standard CAN/CSA-S471-92, "General Requirements, Design Criteria, the

2N), 1995, Washington;

*DOI: http://dx.doi.org/10.5772/intechopen.88894*

Installations, 1993;

by a construction).

fragments area.

regelation.

**Figure 6.**

**81**

offshore structures", 2010).

depth from 20 to 70 m to 200–250 m.

the various structures design versions are presented. The following loads are subject to analysis:

**2.3 Types, design diagrams and cases**

Environment, and Loads", 1992, Toronto;


For the continental shelf infrastructures, the number of the objects to be analyzed is reduced by one or two orders.

In the system of initial standards, specifications and guidelines used for design and calculations of SPs were included the following documents:

• Russian regulations database:

GOST 27751-88 "Reliability of structural units and foundations. Basic calculations methodology.", 1988; SNiP 2.01.07-85 "Loads and impacts", 1996; SNiP 2.06.04-82\*, "Loads and impacts on hydrotechnical structures (waves, ice and sea vessels)", 1995 & 1983; Marine Registry. FDR/OFR Guidelines, 2001; VSN 41-88, "Industry Specific Code of Practice for design of offshore iceresistant fixed platform (OIRFP)", М., 1988;

• Foreign regulations database:

Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms – Load and Resistance Factor Design, АРI Recommended Practice 2A-LRFD, 1993, Washigton;

**Figure 5.** *Diagram of analysis of potentially hazardous objects of the technosphere.*

*Hybrid Modeling of Offshore Platforms' Stress-Deformed and Limit States… DOI: http://dx.doi.org/10.5772/intechopen.88894*

Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Structures in Ice Environments, АРI Recommended Practice 2N (RP 2N), 1995, Washington;

CAN/CSA-S471-92, "General Requirements, Design Criteria, the Environment, and Loads", A National Standard of Canada, 1992; Toronto; Commentary to CSA Standard CAN/CSA-S471-92, "General Requirements, Design Criteria, the Environment, and Loads", 1992, Toronto;

CAN CAN/CSA-S473-92, "Offshore Structures", A National Standard of Canada, 1992 CAN CAN/CSA-S16.1-94, "Limit States Design of Steel Structures", A National Standard of Canada, 1992, Toronto; DnV, "Structural Design, General", Rules for classification of Fixed Offshore Installations, 1993;

DnV, "Structural Reliability Analysis of Marine Structures", 1992. DnV, Offshore Standard OS-C101, Design of Offshore Steel Structures, General, 2001; ISO 19906, 2010 (ISO/DIS 19906 "Petroleum and natural gas industries - Arctic offshore structures", 2010).

Above documentation was used for definition of the main basic specified characteristic load during design of the sea platforms intended for use at a sea depth from 20 to 70 m to 200–250 m.
