Offshore Structures: Design, Construction and Maintenance

Cover
Offshore Structures: Design, Construction and Maintenance
Copyright
Dedication
Contents
About the author
Preface
1 Introduction to offshore structures
	1.1 Introduction
	1.2 History of offshore structures
	1.3 Overview of field development
		1.3.1 Field development cost
		1.3.2 Multicriteria concept selection
	1.4 Front end engineering design requirements
	1.5 Types of offshore platforms
		1.5.1 Drilling/well-protected platform
		1.5.2 Tender platforms
		1.5.3 Self-contained platforms
		1.5.4 Production platform
		1.5.5 Quarters platform
		1.5.6 Flare jacket and flare tower
		1.5.7 Auxiliary platform
		1.5.8 Bridges
		1.5.9 Heliport
	1.6 Different types of offshore structures
		1.6.1 Concrete gravity platform
		1.6.2 Floating production, storage, and offloading
		1.6.3 Tension-leg platform
	Reference
	Further reading
2 Offshore structure loads and strength
	2.1 Introduction
	2.2 Gravity load
		2.2.1 Dead load
		2.2.2 Live load
		2.2.3 Impact load
		2.2.4 Design for serviceability limit state
			Vibrations
			Deflections
		2.2.5 Helicopter landing loads
			Loads for helicopter landing
			Loads for helicopters at rest
				Helicopter static loads
				Area load
				Helicopter tie-down loads
				Wind loading
				Installation motion
			Safety net arms
			Design load conditions
			Example of helicopter load
		2.2.6 Crane support structure
	2.3 Wind load
	2.4 Example for stair design
		2.4.1 Gravity loads
		2.4.2 Wind loads
	2.5 Offshore loads
		2.5.1 Wave load
			Comparison between wind and wave calculations
			Conductor shielding factor
		2.5.2 Current force
			Design current profiles
				Current profile
		2.5.3 Earthquake load
			Strength requirements
			Ductility requirements
			Topsides appurtenances and equipment
		2.5.4 Ice loads
		2.5.5 Other loads
			Marine growth
			Scour
	2.6 Design for ultimate limit state
		2.6.1 Load factors
		2.6.2 Extreme environmental situation for fixed offshore platforms
		2.6.3 Operating environmental situations—fixed platforms
		2.6.4 Partial action factors
	2.7 Collision events
		2.7.1 Accidental impact energy
			Total kinetic energy
		2.7.2 Dropped objects
	2.8 Fires and explosions
	2.9 Material strength
		2.9.1 Steel groups
		2.9.2 Steel classes
			Structural steel pipe
			Selection for conditions of service
			Cement grout
	References
	Further reading
3 Offshore structure platform design
	3.1 Introduction
	3.2 Preliminary dimensions
		3.2.1 Approximate dimensions
	3.3 Bracing system
	3.4 Jacket design
	3.5 Structure analysis
		3.5.1 Global structure analysis
		3.5.2 The loads on piles
		3.5.3 Modeling techniques
			Joint coordinates
			Local member axes
			Member effective lengths
			Joint eccentricities
		3.5.4 Dynamic structure analysis
			Natural frequency
		3.5.5 In-place analysis according to ISO 19902
	3.6 Cylinder member strength
		3.6.1 Cylinder member strength calculation according to ISO 19902
			Axial tension
			Axial compression
			Column buckling
			Local buckling
			Bending
			Shear
			Torsional shear
			Hydrostatic pressure
			Hoop buckling
			Tubular members subjected to combined forces without hydrostatic pressure
				Axial tension and bending
				Axial compression and bending
			Tubular members subjected to combined forces with hydrostatic pressure
				Axial tension, bending, and hydrostatic pressure
				Axial compression, bending, and hydrostatic pressure
			Effective lengths and moment reduction factors
		3.6.2 Cylinder member strength calculation
			Axial tension
			Axial compression
			Local buckling
				Elastic local buckling stress
				Inelastic local buckling stress
			Bending
			Shear
			Torsional shear
			Pressure on stiffened and unstiffened cylinders
			Design hydrostatic head
			Hoop buckling stress
				Elastic hoop buckling stress
				Critical hoop buckling stress
			Combined stresses for cylindrical members
				Combined axial compression and bending
				Member slenderness
			Combined axial tension and bending
			Axial tension and hydrostatic pressure
			Axial compression and hydrostatic pressure
			Safety factors
	3.7 Tubular joint design
		3.7.1 Simple joint calculation API RP2A (2007)
			Joint classification and detailing
			Simple tubular joint calculation
			Strength factor Qu
				Chord load factor Qf
				Joints with thickened cans
				Strength check
				Overlapping joints
				Grouted joints
		3.7.2 Joint calculation according to API RP2A (2000)
			Punching shear
			Allowable joint capacity
			Tubular joint punching failure
		3.7.3 Fatigue analysis
			Stress concentration factors
			SCFs in grouted joints
			S–N curves for all members and connections
			S–N curves for tubular connections
				Thickness effect
			Fatigue design for a jacket
	3.8 Topside design
		3.8.1 Grating design
		3.8.2 Handrails, walkways, stairways, and ladders
	3.9 Boat landing design
		3.9.1 Boat landing calculation
			Cases of impact load
		3.9.2 Riser guard design
			Cases of impact load
		3.9.3 Boat landing design using the nonlinear analysis method
		3.9.4 Boat impact methods
		3.9.5 Tubular member denting analysis
			Simplified method for denting limit calculation
			Nonlinear finite element method analysis
	3.10 Riser guard
	3.11 On-bottom stability
	3.12 Bridges
	3.13 Crane loads
	3.14 Lift installation loads
	3.15 Vortex-induced vibrations
	3.16 Helideck design
	3.17 Structure analysis and design quality control
	References
	Further Reading
4 Geotechnical data and pile design
	4.1 Introduction
	4.2 Investigation procedure
		4.2.1 Performing an offshore investigation
		4.2.2 Drilling equipment and method
		4.2.3 Wire-line sampling technique
		4.2.4 Offshore soil investigation problems
	4.3 Soil tests
	4.4 In situ testing
		4.4.1 Cone penetration test
			Equipment requirements
			CPT testing procedure
			Calibration requirements
			CPT results
		4.4.2 Field vane test
			Testing procedure
	4.5 Soil properties
		4.5.1 Strength
		4.5.2 Soil characteristics
	4.6 Pile foundations
		4.6.1 Pile capacity for axial loads
			Skin friction and end bearing in cohesive soils
			Shaft friction and end bearing in cohesionless soils
		4.6.2 Foundation size
			Pile penetration
		4.6.3 Axial pile performance
			Static load-deflection behavior
			Cyclic response
			Axial load-deflection (t–z and Q–z) data
			Axial pile capacity
			Laterally loaded pile reactions
			Lateral bearing capacity for soft clay
			Lateral bearing capacity for stiff clay
			Lateral bearing capacity for sand
			Alternative methods for determining pile capacity
			Establishing design strength and effective overburden stress profiles
			Time affects changes in the axial capacity in clay soil
		4.6.4 Pile capacity calculation methods
			Simplified ICP-05
			Offshore UWA-05
			Fugro-05
			NGI-05
			Application of CPT
		4.6.5 Pile capacity under cyclic loadings
			Cyclic loading effects
			Analytical models
			Discrete element models
			Continuum models
	4.7 Scour
	4.8 Pile wall thickness
		4.8.1 Pile stresses
		4.8.2 Stresses due to the hammer effect
		4.8.3 Minimum wall thickness
		4.8.4 Driving shoe and head
		4.8.5 Pile section lengths
	4.9 Pile drivability analysis
		4.9.1 Evaluation of soil resistance drive
		4.9.2 Unit shaft resistance and unit end bearing for uncemented materials
		4.9.3 Upper- and lower-bound soil resistance drive
		4.9.4 Results of wave equation analyses
		4.9.5 Results of drivability calculations
		4.9.6 Recommendations for pile installation
	4.10 Soil investigation report
	4.11 Conductor support platform
	References
	Further Reading
5 Fabrication and installation
	5.1 Introduction
	5.2 Construction procedure
	5.3 Engineering of execution
	5.4 Fabrication
		5.4.1 Joint fabrication
		5.4.2 Fabrication based on international standards organization
			Tubular members and joints
			Slotted members
			Grouted pile to sleeve connections
			Heat straightening
			Rat-holes, penetrations, and cut-outs
			Movement, erection, and roll-up of subassemblies
			Fabrication tolerances
				Legs spacing tolerance
				Vertical level tolerance
				Tubular member tolerance
				Tolerance of leg alignment and straightness
				Tubular joint tolerance
				Stiffener tolerances
				Conductor guides and piles tolerances
				Dimensional control
	5.5 Jacket assembly and erection
	5.6 Weight control
		5.6.1 Weight calculation
			Classification of weight accuracy
			Allowances and contingencies
			Management contingency
			Operating contingency
			Weight engineering procedures
	5.7 Loads from transportation, launch, and lifting operations
	5.8 Lifting procedure and calculation
		5.8.1 Lifting calculation
			Calculated weight
			Hook load
			Skew load factor
			Resolved padeye load
			Sling force
			Crane lift factors
			Part sling factor
			Termination efficiency factor
			Bending efficiency factor
			Grommets
			Shackle safety factors
			Consequence factors
		5.8.2 Structural calculation for lifting
		5.8.3 Lift point design
		5.8.4 Clearances
			Clearances around the lifted object
			Clearances around the crane vessel
		5.8.5 Lifting calculation report
			The crane vessel
		5.8.6 Bumpers and guides
			Module movement
	5.9 Loadout process
	5.10 Transportation process
		5.10.1 Supply boats
		5.10.2 Anchor-handling boats
		5.10.3 Towboats
		5.10.4 Towing
		5.10.5 Drilling vessels
		5.10.6 Crew boats
		5.10.7 Barges
		5.10.8 Crane barges
		5.10.9 Offshore derrick barges (fully revolving)
		5.10.10 Jack-up construction barges
	5.11 Transportation loads
	5.12 Launching and upending forces
	5.13 Installation and pile handling
	References
	Further reading
6 Corrosion protection
	6.1 Introduction
		6.1.1 Corrosion in seawater
		6.1.2 Steel corrosion in seawater
		6.1.3 Choice of system type
		6.1.4 Geometric shape
	6.2 Coatings and corrosion protection of steel structures
	6.3 Corrosion stresses due to the atmosphere, water, and soil
		6.3.1 Classification of environments
			Categories for water and soil
		6.3.2 Mechanical, temperature, and combined stresses
	6.4 General cathodic protection design considerations
		6.4.1 Environmental parameters affecting cathodic protection
		6.4.2 Design criteria
		6.4.3 Protective potentials
		6.4.4 Detrimental effects of cathodic protection
		6.4.5 Galvanic anode materials
		6.4.6 Cathodic protection design parameters
			Design life
			Design current densities
			Coating breakdown factors for cathodic protection design
			Galvanic anode material design parameters
			Anode resistance formulas
			Seawater and sediment resistivity
			Anode utilization factor
			Current drain design parameters
		6.4.7 Cathodic protection calculation and design procedures
			Current demand calculations
			Selection of anode type
			Anode mass calculations
			Calculation of anode number
			Calculation of anode resistance
			Anode design precaution
			Distribution of anodes
	6.5 Design example
	6.6 General design considerations
	6.7 Anode manufacture
	6.8 Installation of anodes
	6.9 Anode dimension tolerance
		6.9.1 Internal and external inspection
	Reference
	Further Reading
7 Assessment of existing structures and repairs
	7.1 Introduction
	7.2 American Petroleum Institute RP2A historical background
		7.2.1 Environmental loading provisions
			Morison’s equation
			Wave theories
			Selection of design condition
			Deck clearance or air gap
			The latest editions of RP2A working stress design and load resistance factor design
		7.2.2 Regional environmental design parameters
		7.2.3 Member resistance calculation
		7.2.4 Joint strength calculation
		7.2.5 Fatigue
		7.2.6 Foundation design
	7.3 Historical review of Department of Energy/Health and Safety Executive guidance notes
		7.3.1 Environmental loading provisions
		7.3.2 Joint strength equations
		7.3.3 Fatigue
		7.3.4 Foundations
		7.3.5 Definition of design condition
		7.3.6 Currents
		7.3.7 Wind
		7.3.8 Waves
		7.3.9 Deck air gap
		7.3.10 Historical review of major North Sea incidents
	7.4 Historical assessment of UK environmental loading design practice
		7.4.1 Design environmental parameters
		7.4.2 Fluid loading analysis
	7.5 Development of American Petroleum Institute RP2A member resistance equations
	7.6 Allowable stresses for cylindrical members
		7.6.1 Axial tension
		7.6.2 Axial compression
		7.6.3 Bending
		7.6.4 Shear
		7.6.5 Hydrostatic pressure
		7.6.6 Combined axial tension and bending
		7.6.7 Combined axial compression and bending
		7.6.8 Combined axial tension and hydrostatic pressure
		7.6.9 Combined axial compression and hydrostatic pressure
		7.6.10 American institute of steel construction historical background
		7.6.11 Pile design historical background
		7.6.12 Effects of changes in tubular member design
	7.7 Failure due to fire
		7.7.1 Degree of utilization
		7.7.2 Tension member design by EC3
		7.7.3 Unrestrained beams
		7.7.4 Example: strength design for steel beam
		7.7.5 Steel column: strength design
		7.7.6 Case study for a deck under fire
	7.8 Platform failure case study
	7.9 Failure mechanism
		7.9.1 Strength reduction
		7.9.2 Environmental load effect
		7.9.3 Structure assessment
	7.10 Assessment of platform
		7.10.1 Nonlinear structure analysis in ultimate strength design
			General purpose nonlinear beam column models
			Plastic hinge beam column models
			Phenomenological models
			Shell FE models
			Modeling the element
			Conductor connectivity
		7.10.2 Structural modeling
			Secondary framework
			Dented beam and cracked joint
		7.10.3 Determine the probability of structural failure
		7.10.4 Establish acceptance criteria
		7.10.5 Reliability analysis
			Limit state function
			First-order reliability method
		7.10.6 Software requirement
	7.11 Offshore platform decommissioning
		7.11.1 Decommissioning methods
			Small pieces
			Large pieces
			Single lift
		7.11.2 Cutting tools
		7.11.3 Case study for platform decommissioning
	7.12 Scour problem
	7.13 Offshore platform repair
		7.13.1 Deck repair
		7.13.2 Reduce the loads
			Marine growth removal
			Vibration monitoring
		7.13.3 Jacket repair
		7.13.4 Dry welding
			Dry welding in topsides
			Dry welding at or below the sea surface
			Hyperbaric welding
			Platform underwater repair
		7.13.5 Platform “shear pups” repair
		7.13.6 Underwater repair for a platform structure
		7.13.7 Case study 2: platform underwater repair
		7.13.8 Clamps
			Stressed mechanical (friction) clamps
			Unstressed grouted clamp connections
			Stressed grouted clamps
			Stressed elastomer-lined clamp
			Drilling platform stabilization post Hurricane Lili
		7.13.9 Grouting
			Joint grouting
			Grout filling of members
			Allowable axial force calculation
			Composite technology
			Reinforced epoxy grout
			Fiber reinforced polymer composites
		7.13.10 Example of using fiber reinforced polymer
		7.13.11 Case study for conductor composite repair
		7.13.12 Fiberglass access decks
		7.13.13 Fiberglass mudmats
		7.13.14 Case study 1: flare repair
		7.13.15 Case study 2: repair of the flare jacket
		7.13.16 Case study 3: repair of the bearing support
	References
	Further Reading
8 Risk-based inspection technique
	8.1 Introduction
	8.2 Structure integrity management methodology
	8.3 Quantitative risk assessment for fleet structures
		8.3.1 Likelihood (probability) factors
			Interactions
			Likelihood calculation for strength
				Design practice
				Number of legs and bracing configuration
				Piles system
				Risers and conductors
				Boat landings
				Grouted piles
				Damaged, missing, and cut members
				Splash zone corrosion and damage
				Flooded members
				CP surveys and anode depletion
				Inspection history
				Remaining wall
			Likelihood calculation for load
				Design loading
				Marine growth
				Scour
				Topside weight change
				Additional risers, caissons, and conductors
				Wave-in-deck
				Earthquake load
			Likelihood categories
			Consequence factors
			Environmental losses
			Business losses
			Safety consequences
			Consequence categories
		8.3.2 Overall risk ranking
	8.4 Underwater inspection plan
		8.4.1 Underwater inspection (according to API SIM 2005)
		8.4.2 Baseline underwater inspection
		8.4.3 Routine underwater inspection scope of work
		8.4.4 Inspection plan based on ISO 9000
		8.4.5 Inspection and repair strategy
			Expected total cost
			Optimization strategy
		8.4.6 Flooded member inspection
			Final inspection reporting
	8.5 Anode retrofit maintenance program
	8.6 Assessment process
		8.6.1 Collecting data
		8.6.2 Structure assessment
			Simple methods
			Design-level method
			Ultimate strength method
				Damage modeling
				Actual yield stress
				Effective length factors
				Soil strength
			Alternative assessment methods
				Historical performance
				Explicit probabilities of survival
			Acceptance criteria
	8.7 Mitigation and risk reduction
		8.7.1 Consequence mitigation
		8.7.2 Reduction probability of platform failure
			Load reduction
				Gravity and hydrodynamic loading
			Raising the deck
			Strengthening
				Member flooding
	8.8 Occurrence of member failures with time
	References
	Further reading
9 Subsea pipeline design and installation
	9.1 Introduction
	9.2 Pipeline project stages
		9.2.1 Pipeline design management
	9.3 Pipeline design codes
		9.3.1 Pipeline route design guidelines
	9.4 Design deliverables
		9.4.1 Pipeline design
			Pipeline bursts
			The collapse
			Buckle propagation
			Buckling
			On-bottom stability
		9.4.2 Near-shore pipeline
		9.4.3 Methods of stabilization
		9.4.4 Combined current and wave in pipeline
		9.4.5 Impact load
		9.4.6 Pipeline free span
	9.5 Concrete coating
		9.5.1 Inspection and testing
	9.6 Installation
		9.6.1 S-lay
		9.6.2 J-lay
		9.6.3 Reel-lay
		9.6.4 Piggyback installation
	9.7 Installation management
	References
	Further reading
Index
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