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A guide to the analysis and design of compliant offshore structures that highlights a new generation of platforms Offshore Compliant Platforms provides an authoritative guideto the analysis and design of compliant offshore structures and puts the focus on a new generation of platforms such as: triceratops, Buoyant Leg Storage and Regasification platforms. Whilst the authors - noted experts on the topic - include basic information on the conceptual development of conventional platforms, the book presents detailed descriptions of the design and development of new deep-water platforms. The book describes the preliminary design of triceratops in ultra-deep waters and presents a detailed analysis of environmental loads that are inherent in offshore locations such as wave, wind and current. The new methodology for the dynamic analysis of triceratops under ice loads, predominantly in ice-covered regions, is also examined with detailed parametric studies. In addition, the book covers the structural geometry and the various methods of analysis for assessing the performance of any other similar offshore platform under the special loads. A discussion of the fatigue analysis and service life prediction is also included. This important book: * Includes the analysis and design of compliant offshore structures with a focus on a new generation of platforms * Examines the preliminary design of triceratops in ultra-deep waters * Covers an analysis of environmental loads that are inherent in offshore locations such as wave, wind and current * Reviews the structural geometry and various methods of analysis for assessing the performance of any other similar offshore platform under special loads * Discusses fatigue analysis and service life prediction Written for engineers and researchers across engineering including civil, mechanical, structural, offshore, ocean and naval architecture, Offshore Compliant Platforms fills the need for a guide to new offshore platforms that provides an understanding of the behaviour of these structures under different loading conditions.

A buoyant leg storage and regasification platform (BLSRP) consists of a deck supported by buoyant legs. These legs are position‐restrained by tethers with high initial pre‐tension. The buoyant legs are subjected to waves and current while the superstructure of the platform is predominantly under the influence of wind. A recent development in offshore deep water platforms is the BLSRP to store and process liquefied natural gas offshore. This chapter presents experimental investigations carried out on a scale model of a BLSRP in the presence of regular waves. Numerical studies carried out on the prototype of the BLSRP with both regular and random waves for different wave approach angles are also discussed in detail. The chapter also presents a detailed numerical analysis carried out for the BLSRP using the Mathieu equation of stability. The very low fatigue life of tethers with Mathieu instability proves the severity of the instability.

Offshore structures need to be analyzed for dynamic effects arising due to ice–structure interactions. Of several ice failure modes, crushing ice failure tends to cause maximum ice force on the structure. This chapter deals with a response analysis of an offshore triceratops under ice load due to continuous ice crushing, impact loads arising due to ship–platform collisions, and fire loads on the deck of the platform. When an ice load acts on two buoyant legs, the complex behavior of the triceratops shows significant responses in both the deck and buoyant legs in all degrees of freedom. The surge and pitch responses in the buoyant legs induce significant tether tension variation in the triceratops. The buoyant legs of the triceratops are prone to accidental impact loads arising from ship–platform collisions. Hydrocarbon fires are among the most severe accidental loads on topside structures in the offshore industry.

While it is a common understanding that structural forms are conceived to counteract the applied loads acting on them, it may not be completely true in the context of offshore structures. This chapter presents details of the structural geometry of compliant offshore platforms while emphasizing the design and development of these platforms rather than of fixed platforms. Offshore structures are grouped as fixed, compliant, and floating types, based on the boundary conditions of their station‐keeping characteristics. Fixed platforms are further categorized as jacket platforms, gravity platforms, and jack‐up rigs. Compliant platforms are further categorized as guyed towers, articulated towers, and tension leg platform. Floating platforms are further categorized as semi‐submersibles, floating production units, floating storage and offloading, floating production storage and offloading, and spar. The chapter also presents various control strategies commonly deployed for response control of structures subjected to lateral loads while presenting detailed applications of tuned mass dampers in offshore structures.

This chapter explains the application of offshore triceratops as support systems for wind turbines. It presents developments in conceptual models of triceratops with different types of buoyant leg configurations. The chapter also presents conceptual models of stiffened and elliptical buoyant legs. In a stiffened triceratops, the buoyant legs of the basic triceratops are modified with cylindrical columns that are interconnected to the central moon pool by a finite number of stiffeners. The response amplitude operator results of the translational response of the deck and buoyant legs of the stiffened triceratops show that the values are directly proportional to the linear displacement of the structure. The natural frequencies of the triceratops given different degrees of freedom are assessed through power spectral density plots. An offshore triceratops derives an advantage from the chosen geometric form in addition to being advantageous for deepwater and ultra‐deepwater applications.

This chapter explains the dynamic response of an offshore triceratops in response to the action of regular and random waves. It also explains the behavior of the triceratops in response to the combined action of wind, wave, and current. Tether tension variation of the triceratops increases with greater severity of the sea conditions. The tether response is predominantly governed by the action of regular waves and the combined responses of the deck and buoyant legs of the triceratops. The compliant offshore platform is monolithic in the translational degrees of freedom (DOF), so the transfer of differential heave from the buoyant legs induces a small pitch response in the deck of the triceratops. The maximum spectral energy in different DOF occurs close to multiples or fractions of the natural frequency of the platform due to the complex behavior of the platform.