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Chapter 33. This introductory chapter provides an
overview of the state-of-the-art of offshore platforms.
The chapter highlights the various structural concepts
(such as fixed, gravity, compliant, floating, and subsea platforms) developed during the past 75 years of
active offshore exploration and exploitation. The chapter focuses on the various factors that influence the
choice of structure during project development and
design, and gives an overview of the strength and
weaknesses of various offshore development scenarios.
The chapter concludes by discussing future trends and
developments.
Chapter 34. The Stability of Offshore Systems chapter provides the theoretical background to analyze the
buoyancy and stability of offshore platforms and discusses the regulatory framework, including IMO regulations, which sets standards of stability. Such standards
apply criteria on the righting moment of a floating
structure with appropriate safety factors. They aim at
preventing incidents related to excessive heel or trim,
capsizing, catastrophic loss of buoyancy, or even sinking. Intact stability and damaged stability of floating
structures are considered in this chapter. Methods of
calculating the righting moment are examined. The
spirit and practical application of regulations are discussed in detail.
Chapter 35. The Wave, Current, and Wind Loads
chapter describes various loads on fixed or floating
offshore platforms. Both linear and nonlinear waves
are discussed in deterministic and irregular seas. Wave
loads on large structures are formulated using linear
potential theory in the frequency domain. Morison’s
equation and the associated drag and inertia coefficients
are introduced for slender structures. Also discussed are
wave-current interaction and current-induced forces,
including vortex-induced vibrations. Both steady and
unsteady wind profiles are used to describe wind forces.
Model tests and similarity laws are also discussed.
Chapter 36. The Vortex-Induced Vibrations (VIV)
of Slender Structures chapter reviews the vibrations of
flexible structures placed in a cross-flow, caused by
vortices forming due to flow instability in the wake.
The phenomenon is important for ocean and offshore
applications because of possible fatigue damage and increased drag forces, and spans Reynolds numbers from
as low as 50, reaching the highest Reynolds numbers
recorded. The complex flow-structure interaction mechanisms result in a very rich dynamic behavior, which
has made this a canonical problem of flow-structure
interaction studies. The focus is on the response of flexible risers and cables, and the review of the effectiveness
of vortex cancelation devices.
Chapter 37. The Structural Dynamics chapter
presents the theory that is especially relevant to dynamics of flexible ocean structures. The primary focus
of this chapter is on linear response to regular waves
and random seas, but the extension to nonlinear systems is also discussed. Equations of motion in the time
and frequency domains for a single-degree-of-freedom
system with both viscous and hysteretic damping are
presented. Generalization of these concepts to multidegree-of-freedom systems is then covered. Hydroelasticity, which couples the structural and fluid models,
is presented. Numerical solutions including spatial and
time discretization and integration are presented. Nonlinear hydroelasticity, viz. fluid-structure interaction, is
discussed briefly.
Chapter 38. The Cable Dynamics chapter provides
information associated with the dynamic behavior of
slender cables (e.g., mooring lines) with particular emphasis on marine applications. The scope of the chapter
is to associate the aspect of dynamics, linear and nonlinear, with the most typical practical applications of
cables in the marine and, especially, in the offshore
sector. The chapter first derives a global formulation
for the governing dynamical systems, and then numerical methodologies required for their solutions are
presented.
Chapter 39. The Wave-Seabed-Structure Interactions chapter provides an overview of theoretical models for wave-induced seabed response in marine sediments. This includes the introduction of the existing
three well-known models, a new analytical approximation for the wave-induced pore pressure accumulations,
a new concept for linking oscillatory and residual mechanisms, and the inclusion of currents in the existing
models for wave-seabed interactions. A case of caissontype breakwater is considered as an application of
the proposed numerical models. With the new model,
the liquefaction zones around breakwater with different approximations are compared, and the differences
identified. Finally, three topics are suggested for future
studies in this area.
Chapter 40. The Buoy Technology chapter presents
an introduction to small buoy systems used for oceanographic or other ocean-monitoring purposes. This chapter outlines typical buoy and mooring types and their
applications, buoy and mooring material choices, specialty strength members, and expected dynamic behaviors and specific analysis techniques used to analyze
a coupled buoy/mooring system. Tables of material and
component properties useful to the designer, as well
as a summary of hydrodynamic coefficients for small
cylindrical buoys are included. The chapter concludes
Chapter 33. This introductory chapter provides an
overview of the state-of-the-art of offshore platforms.
The chapter highlights the various structural concepts
(such as fixed, gravity, compliant, floating, and subsea platforms) developed during the past 75 years of
active offshore exploration and exploitation. The chapter focuses on the various factors that influence the
choice of structure during project development and
design, and gives an overview of the strength and
weaknesses of various offshore development scenarios.
The chapter concludes by discussing future trends and
developments.
Chapter 34. The Stability of Offshore Systems chapter provides the theoretical background to analyze the
buoyancy and stability of offshore platforms and discusses the regulatory framework, including IMO regulations, which sets standards of stability. Such standards
apply criteria on the righting moment of a floating
structure with appropriate safety factors. They aim at
preventing incidents related to excessive heel or trim,
capsizing, catastrophic loss of buoyancy, or even sinking. Intact stability and damaged stability of floating
structures are considered in this chapter. Methods of
calculating the righting moment are examined. The
spirit and practical application of regulations are discussed in detail.
Chapter 35. The Wave, Current, and Wind Loads
chapter describes various loads on fixed or floating
offshore platforms. Both linear and nonlinear waves
are discussed in deterministic and irregular seas. Wave
loads on large structures are formulated using linear
potential theory in the frequency domain. Morison’s
equation and the associated drag and inertia coefficients
are introduced for slender structures. Also discussed are
wave-current interaction and current-induced forces,
including vortex-induced vibrations. Both steady and
unsteady wind profiles are used to describe wind forces.
Model tests and similarity laws are also discussed.
Chapter 36. The Vortex-Induced Vibrations (VIV)
of Slender Structures chapter reviews the vibrations of
flexible structures placed in a cross-flow, caused by
vortices forming due to flow instability in the wake.
The phenomenon is important for ocean and offshore
applications because of possible fatigue damage and increased drag forces, and spans Reynolds numbers from
as low as 50, reaching the highest Reynolds numbers
recorded. The complex flow-structure interaction mechanisms result in a very rich dynamic behavior, which
has made this a canonical problem of flow-structure
interaction studies. The focus is on the response of flexible risers and cables, and the review of the effectiveness
of vortex cancelation devices.
Chapter 37. The Structural Dynamics chapter
presents the theory that is especially relevant to dynamics of flexible ocean structures. The primary focus
of this chapter is on linear response to regular waves
and random seas, but the extension to nonlinear systems is also discussed. Equations of motion in the time
and frequency domains for a single-degree-of-freedom
system with both viscous and hysteretic damping are
presented. Generalization of these concepts to multidegree-of-freedom systems is then covered. Hydroelasticity, which couples the structural and fluid models,
is presented. Numerical solutions including spatial and
time discretization and integration are presented. Nonlinear hydroelasticity, viz. fluid-structure interaction, is
discussed briefly.
Chapter 38. The Cable Dynamics chapter provides
information associated with the dynamic behavior of
slender cables (e.g., mooring lines) with particular emphasis on marine applications. The scope of the chapter
is to associate the aspect of dynamics, linear and nonlinear, with the most typical practical applications of
cables in the marine and, especially, in the offshore
sector. The chapter first derives a global formulation
for the governing dynamical systems, and then numerical methodologies required for their solutions are
presented.
Chapter 39. The Wave-Seabed-Structure Interactions chapter provides an overview of theoretical models for wave-induced seabed response in marine sediments. This includes the introduction of the existing
three well-known models, a new analytical approximation for the wave-induced pore pressure accumulations,
a new concept for linking oscillatory and residual mechanisms, and the inclusion of currents in the existing
models for wave-seabed interactions. A case of caissontype breakwater is considered as an application of
the proposed numerical models. With the new model,
the liquefaction zones around breakwater with different approximations are compared, and the differences
identified. Finally, three topics are suggested for future
studies in this area.
Chapter 40. The Buoy Technology chapter presents
an introduction to small buoy systems used for oceanographic or other ocean-monitoring purposes. This chapter outlines typical buoy and mooring types and their
applications, buoy and mooring material choices, specialty strength members, and expected dynamic behaviors and specific analysis techniques used to analyze
a coupled buoy/mooring system. Tables of material and
component properties useful to the designer, as well
as a summary of hydrodynamic coefficients for small
cylindrical buoys are included. The chapter concludes