Reliability of Offshore Structures Under Cyclic Application of Environmental Loading PDF Download

Author: Rauf Joseph Ubaji
Publisher:
ISBN:
Category : Impact
Languages : en
Pages : 109

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Author: Rauf Joseph Ubaji
Publisher:
ISBN:
Category :
Languages : en
Pages : 250

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Author: Stanford University. Department of Civil Engineering. Blume Earthquake Engineering Center
Publisher:
ISBN:
Category :
Languages : en
Pages : 216

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Author: George Deodatis
Publisher: CRC Press
ISBN: 1315884887
Category : Technology & Engineering
Languages : en
Pages : 1112

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Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures contains the plenary lectures and papers presented at the 11th International Conference on STRUCTURAL SAFETY AND RELIABILITY (ICOSSAR2013, New York, NY, USA, 16-20 June 2013), and covers major aspects of safety, reliability, risk and life-cycle performance of str

Author: Bao Li Zheng
Publisher:
ISBN: 9780438930551
Category :
Languages : en
Pages :

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Design of offshore foundations can be difficult due to challenging soils that can vary from high plasticity, soft clay to very dense sand, and complex loading conditions from the respective environments (e.g., wind, waves, seismicity), in the form of combinations of monotonic and cyclic load patterns. Understanding the interaction of the soil-foundation-structure system under design loads is critical for reliable operations of offshore structures. This dissertation provides the evaluation of performance and investigation of mechanisms against cyclic loading for: (1) subsea wellhead-pipeline-manifold systems on soft clay; and (2) multi-pile-supported offshore wind turbine structures in dense sand. Commonly, the product from deep gas wells is collected at a central manifold founded on the seabed via jumpers (i.e., pipelines). The connections to the jumpers are relatively stiff, with limited tolerance against shear failure induced from relative displacement. A centrifuge test was conducted on the 9-m centrifuge at the UC Davis Center for Geotechnical Modeling to study the seismic performance of a caisson-supported manifold structure and a deeply-installed wellhead founded on soft clay when subjected to extreme and abnormal level earthquakes. Dynamic response of jumpers connecting the manifold structure and the wellhead was interpreted as the difference between the dynamic displacement time histories between the manifold structure, the wellhead, and the free-field clay surface. Comparison demonstrated that the governing jumper connections lie between the manifold and the wellhead and between the wellhead and the free-field surface, and the wellhead is the more critical component under the specific ground motion. Offshore wind turbine structures (OWTS) are subject to wind and wave loads with varying magnitudes of static and cyclic loads over their design lives. During normal operation, these structures are further loaded by rotor and blade-passing imbalance forces. Cyclic loading can cause significant degradation in the capacity and generate excessive movement, as well as reduction of the soil-pile stiffness and the natural frequency toward resonance with rotor frequencies. A centrifuge program was designed and performed on the 1-m Schaevitz centrifuge at UC Davis to evaluate the performance of tension piles against cyclic loads for multi-pile-supported offshore wind turbines. The potential for obtaining meaningful results using a small centrifuge for this application was demonstrated, and an initial data set from centrifuge testing of piles subjected to one-way and two-way cyclic axial loading was developed. The data set was presented and evaluated within the interaction diagram framework that is commonly used to predict the cyclic stability of piles. Results from the centrifuge tests were generally consistent with predictions from interaction diagrams (e.g., under one-way loading, increase in cyclic load amplitude lowers pile stability). However, inconsistencies were also observed in the comparison, such as a reduction of capacity for combinations of static and cyclic loads where the interaction diagram suggested “stable” behavior, and an increase in capacity for combinations where the diagram suggested “unstable” behavior. Other observations and implications of the centrifuge results are discussed. Inconsistencies between expected and observed response, such as that mentioned above, demonstrated a lack of full understanding on the complex mechanisms concerning the cyclic stability of tension piles. An axisymmetric finite-element model was developed in OpenSees (McKenna et al., 2010) to help understand the mechanisms affecting the evolution of the axial response (i.e., capacity, stiffness, and pullout rate) under different load combinations of static and cyclic loads on tension piles. The 2004 Dafalias and Manzari bounding surface plasticity model was used for the response of the soil. Five loading stages were performed to simulate this axial problem: confinement, installation by cylindrical cavity expansion and downward shear, static tensile shearing, cyclic shearing, and monotonic pullout. Results from the numerical analysis demonstrated the dependence of the evolution of axial response on the magnitudes of the static and cyclic shear stresses, and the number of applied cycles. Specifically, the analysis suggested the possibility for increase in tensile capacity and stiffening of the soil-pile stiffness for some load combinations, which is typically not considered in design. Other mechanisms and observations, as well as practical implication on current design, are presented.

Author: Ashok Gupta
Publisher: Springer Science & Business Media
ISBN: 364282899X
Category : Science
Languages : en
Pages : 312

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and Literature Rev iew Chapter 1 1. INTRODUCTION AND LITERATURE REVIEW The exploration for oil and gas in ever increasing water depths has given an impetus to research efforts on the behaviour of offshore structures under ocean environment. These structures are continuously subjected to environmental loading because of waves, wind and current. A response analysis is required to assess the safety of offshore structure under severe storm conditions as well as for estimation of damage caused by less severe but more frequently occuring sea states. A majority of the reported failures in the life time of offshore structures are in fact fatigue failures. The offshore structures are usually built in the form of welded tubular structures. The joints of these tubular members experience the fatigue damage mainly due to small defects in welding which act as crack initiators, high stress concentrations and the variable loads. The variable loads due to the ocean waves cause cyclic stress variation in the structural members and the accumu lated effect of these stresses results in the fatigue failure.

Author: Srinivasan Chandrasekaran
Publisher: Springer
ISBN: 9811076081
Category : Technology & Engineering
Languages : en
Pages : 344

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This book provides detailed analysis methods and design guidelines for fire resistance, a vital consideration for offshore processing and production platforms. Recent advancements in the selection of various geometric structural forms for deep-water oil exploration and production require a detailed understanding of the design of offshore structures under special loads. Focusing on a relatively new aspect of offshore engineering, the book offers essential teaching material, illustrating and explaining the concepts discussed through many tutorials. It creates a basis for designing new courses for students of ocean engineering and naval architecture, civil engineering, and applied mechanics at both undergraduate and graduate levels. As such, its content can be used for self-study or as a text in structured courses and professional development programs.

Author: Zafarullah Nizamani
Publisher: Springer
ISBN: 3319150510
Category : Technology & Engineering
Languages : en
Pages : 347

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This book presents a study for the determination of environmental load factors for Jacket Platforms in Malaysia and a methodology to determine the life extension of aging platforms. The simplified methods described here could be used for determining not only structural reliability but also safety factors. Its content is particularly interesting to design and maintenance engineers who are working in offshore or onshore industry.

Author: Norman Allyn
Publisher:
ISBN: 9780921652342
Category : Offshore structures
Languages : en
Pages : 86

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Describes work conducted to examine issues related to the CSA/CAN S474 Code for Fixed Offshore Concrete Structures, divided into two phases: examination of the appropriateness of the 1.35 load factor specified for use on the 1 in 100 year iceberg for the design of the concrete strength; and examination of the load combination factors specified in the Code for rare environmental events occurring along with companion frequent environmental events. Sections describing phase I discuss the principles and computer programs used to determine iceberg loadings, the design of a force analysis model and the subsequent force analysis, analyze the structure for the reliability level under iceberg loads, and present an economic analysis for the different load factors. Sections describing phase II discuss methodology and theory used to calculate environmental loads, introduce computer analysis methods, and present analytical results including final calculated environmental loads and resulting calculated load combination factors.

Author: Srinivasan Chandrasekaran
Publisher: Springer
ISBN: 9811060894
Category : Technology & Engineering
Languages : en
Pages : 449

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This book introduces readers to various types of offshore platform geometries. It addresses the various environmental loads encountered by these structures, and provides detailed descriptions of the fundamentals of structural dynamics in a classroom style, helping readers estimate damping in offshore structures and grasp these aspects’ applications in preliminary analysis and design. Basic concepts of structural dynamics are emphasized through simple illustrative examples and exercises. Design methodologies and guidelines, which are FORM based concepts, are explained through a selection of applied sample structures. Each chapter also features tutorials and exercises for self-learning. A dedicated chapter on stochastic dynamics helps students to extend the basic concepts of structural dynamics to this advanced domain of research. Hydrodynamic response of offshore structures with perforated members is one of the most recent research applications, and has proven to be one of the most effective means of retrofitting offshore structures. In addition, the book integrates the concepts of structural dynamics with the FORM-evolved design of offshore structures, offering a unique approach. This new edition is divided into seven chapters, each of which has been updated. Each chapter also includes a section on frequently asked Questions and Answers (Q&A), which enhances understanding of this complex subject through easy and self-explanatory text. Furthermore, the book presents valuable content with respect to new and recent research carried out by the author in structural dynamics. All numeric examples have been re-checked with more additional explanations. New exercises have been added to improve understanding of the subject matter. Computer coding is also included (wherever possible) to aid computer-based learning of the contents of the book. The book can serve as a textbook for senior undergraduate and graduate courses in civil, structural, applied mechanics, mechanical, aerospace, naval architecture and ocean engineering programs. The book can also serve as a text for professional learning and development programs or as a guide for practicing and consulting offshore structural engineers. The contents of this book will be useful to graduate students, researchers, and professionals alike.