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"Chandrasekaran, Srinivasan"
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Offshore Compliant Platforms
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.
eBook
Steel Coped Beam with Functionally Graded Material for Offshore Topside: Numerical Investigations
The use of rolled steel sections is typical in offshore topside, while recent developments are focused on coped sections to accommodate service lines and fire hydrants. Coped beams are better alternatives without compromising the load-bearing capacity and shear strength. On the topside, the use of coped beams is helpful in creating a more orderly, safe, and undisturbed workspace for laying service mains and fire hydrants; otherwise, they pose a general threat to the topside functional safety. Coped beam replaces the stack of service mains without compromising on the strength requirements of the web. Enhanced safety and improved aesthetics of the topside design are additional advantages. The present study investigates a coped beam with functionally graded material (FGM) to accommodate the services mains in a safer mode without losing its strength; corrosion resistance is also investigated as an additional requirement for any leak occurring from the mains. A coped beam of FGM and X52 steel is investigated under conventional loads and compared for their strength and serviceability requirements. Parameters such as cope length and depth are varied as per the design requirements. FGM coped beams showed higher load-carrying capacity even under the larger coped sections. Under deeper web sections, the cope depth and length have a significant impact on the buckling and load-carrying capacity. For all the chosen coped sections, FGM beams registered a significant reduction in buckling stress compared to X52 steel beams in the coped region, indicating the former is a better candidate for such applications.
Journal Article
Advanced steel design of structures
\"Advanced Steel Design of Structures examines the design principles of steel members under special loads and covers special geometric forms and conditions not typically presented in standard design books. It explains advanced concepts in a simple manner using numerous illustrative examples and MATLABھ codes. Features: Provides analysis of members under unsymmetrical bending Includes coverage of structures with special geometry and their use in offshore applications for ultra-deep water oil and gas exploration Presents numerical modeling and analysis of steel members under fire conditions, impact, and blast loads Includes MATLABھ examples that will aid in the capacity building of civil engineering students approaching this complex subject Written for a broad audience, the presentation of design concepts of steel members will be suitable for upper-level undergraduate students. The advanced design theories for offshore structures under special loads will be an attractive feature for post-graduate students and researchers. Practicing engineers will also find the book useful, as it includes numerous solved examples and practical tutorials\"-- Provided by publisher.
Book
Postulated Tendon Failure of Offshore Triceratops
Offshore triceratops is one of the successful manifestations of the form-dominant design approaches deployable in ultra-deepwater oil and gas exploration. The deck’s geometric shape and partial isolation from the legs counteract lateral loads. Legs are position-restrained to the sea bed by taut-moored tendons, while ball joints partially isolate the deck from the buoyant legs. However, compliance in the horizontal plane imposes large displacements, intuiting the necessity to examine tendon failure. Numerical analysis of triceratops under wave and wind combined action is carried out under the postulated conditions of a tendon failure. 10-yr, 100-yr, and 1 000-yr post-Katrina hurricane conditions are assumed as loading to the platform. Results confirm a marginal increase in the natural periods of stiff degrees of freedom even under postulated failure conditions, ensuring good adaptability to ultra-deep water. Under postulated failure, the tension of adjacent tendons varies significantly, causing a shift to the mean position of the platform. Fatigue life is significantly reduced under the postulated failure of tendons, making the platform free-floating without affecting its stability. Results also show that the pitch response of the deck is a clear manifestation of the postulated failure, which is otherwise absent due to the presence of ball joints. The attempted study deliberates on the fatigue life of tendons, assessing the platform’s suitability to ultra-deep waters and identifying the vulnerable legs for the chosen load combinations.
Journal Article
Fatigue Assessment of Offshore Triceratops Restraining System Under Hurricane-driven Metocean Conditions
Compliant offshore platforms use a form-dominant approach to achieve the required compliance in ultra-deep water. They are position-restrained by taut-moored tethers, which undergo considerable stress cycles during their service life, making fatigue assessment essential. The present study investigates triceratops’ restraining system at 2400 m water depth under hurricane-driven Metocean conditions. The fatigue assessment uses two approaches: T–N curve and the S–N curve. As the numerical studies show, the 10-year hurricane return period governs the fatigue life of tethers. In specific terms, peak wave and peak wind cases govern the fatigue life of tether-2, whereas the peak current case governs tether-1 under hurricane conditions. Further, the unfactored fatigue life estimated using the S–N curve is about 60% higher than that of the T–N curves. However, the factored service life estimated using both the approaches with recommended safety factors matches closely. The presented study will aid the offshore engineers in preliminary designing a restraining system for the novel triceratops.
Journal Article
Treatment of dentinal hypersensitivity using propolis varnish: A scanning electron microscope study
Background: Dentin hypersensitivity (DH) affects all age groups in a population and is perceived as pain to any stimuli. From time immemorial, researchers have sought herbal or natural solutions to treat hypersensitivity. Propolis is one such natural, nontoxic resinous substance produced by honey bees, which is useful in various applications in dentistry and effective in treating dentinal hypersensitivity. Aim: The aim of this in vitro study is to assess the effect of propolis varnish on occlusion of dentinal tubules thus aiding in the treatment of dentinal hypersensitivity. The objective is to evaluate the effectiveness of the proposed treatment using scanning electron microscope (SEM) imaging. Materials and Methods: Twenty naturally extracted teeth were collected and stored until in vitro assessment. Discs obtained from each tooth were divided into two groups of 20 each - I (test) and II (control), with each tooth acting as its own control. Propolis varnish was applied only to the acid-etched surface of the exposed dentin of discs in the test group, whereas all the discs were subjected to SEM imaging. Results: Statistical analysis showed a significant reduction in open tubules (P < 0.001) from 160 ± 6.97 before treatment to 61.20 ± 9.10 after propolis varnish application in the test group. Conclusion: This study showed the promise of propolis varnish as a natural treatment modality for DH.
Journal Article
Response control of buoyant leg storage and regasification platform using magnetorheological dampers
The rising demand for liquefied natural gas (LNG) has spurred research into offshore regasification platforms as a reliable solution to meet global energy needs. Buoyant leg storage and regasification platforms (BLSRPs) offer superior positional stability compared to ship-shaped alternatives; however, heave motion needs to be mitigated for safe regasification. This study proposes a semi-active response control mechanism (RCM) employing magnetorheological (MR) dampers to suppress radial buoyant leg displacements, which are directly coupled with deck heave. A baseline numerical model of the BLSRP was developed in AQWA software without an RCM, and a mathematical model incorporating the MR-RCM was formulated to evaluate the controlled system performance. Unlike previous BLSRP studies, we explicitly incorporated combined wave-wind-current environmental loading conditions. Transformation matrices were established to convert radial responses into deck heave, with influence factors calibrated for varying sea states and approach angles. Results indicate that the MR-RCM achieves 30-45% root-mean-square reductions in radial displacements under moderate and high sea conditions, resulting in significant control of deck heave. Even under very high sea states, 8-11% reductions are maintained, preventing uncontrolled escalation. Hysteresis plots validate the nonlinear energy dissipation of MR dampers and their adaptability to broadband excitations. The findings demonstrate that MRRCM improves platform stability, reduces boil-off gas generation, and enhances safety in LNG operations. Overall, the study establishes MR-based semi-active damping as a practical and scalable solution for offshore platforms, bridging the limitations of passive devices and the complexities of fully active systems.
Journal Article