Bibliographies thématiques / Very Large Floating Structures

Littérature scientifique sur le sujet « Very Large Floating Structures »

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Publié le 10 mars 2023

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Articles de revues sur le sujet "Very Large Floating Structures"

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Cengiz Ertekin, R., Jang Whan Kim, Koichiro Yoshida et Alaa E. Mansour. « Very large floating structures (VLFS) Part I ». Marine Structures 13, no 4-5 (juillet 2000) : 215–16. http://dx.doi.org/10.1016/s0951-8339(00)00037-x.

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Cengiz Ertekin, R., Jang Whan Kim, Koichiro Yoshida et Alaa E. Mansour. « Very large floating structures (VLFS) Part II ». Marine Structures 14, no 1-2 (janvier 2001) : 3–4. http://dx.doi.org/10.1016/s0951-8339(01)00004-1.

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NAKAHIRA, Tatsuya, Taro KAKINUMA, Ko YAMAMOTO, Kei YAMASHITA et Takahiro MURAKAMI. « Can Very Large Floating Structures Reduce Tsunami Height ? » Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 70, no 2 (2014) : I_911—I_915. http://dx.doi.org/10.2208/kaigan.70.i_911.

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Newman, J. N. « Efficient hydrodynamic analysis of very large floating structures ». Marine Structures 18, no 2 (mars 2005) : 169–80. http://dx.doi.org/10.1016/j.marstruc.2005.07.003.

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Wang, C. M., et Z. Y. Tay. « Very Large Floating Structures : Applications, Research and Development ». Procedia Engineering 14 (2011) : 62–72. http://dx.doi.org/10.1016/j.proeng.2011.07.007.

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Kagemoto, Hiroshi, et Dick K. P. Yue. « Hydrodynamic interaction analyses of very large floating structures ». Marine Structures 6, no 2-3 (janvier 1993) : 295–322. http://dx.doi.org/10.1016/0951-8339(93)90025-x.

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Che, Xiling, Dayun Wang, Minglun Wang et Yingfan Xu. « Two-Dimensional Hydroelastic Analysis of Very Large Floating Structures ». Marine Technology and SNAME News 29, no 01 (1 janvier 1992) : 13–24. http://dx.doi.org/10.5957/mt1.1992.29.1.13.

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We have reached a stage at which we are capable of building very large floating structures to meet the steadily increasing needs of ocean resource utilization or to fulfill some special industrial or civil purpose. When such a structure is large enough, its behavior in waves may be substantially different from that of ordinary offshore structures due to low resonant frequencies of the deformable body, and its analysis may require different techniques. In this paper, a two-dimensional hydroelastic theory is applied to a very large floating structure that may be multimodule and extend in the longitudinal direction. A revised strip theory is employed to analyze the hydrodynamic coefficients, but some modifications are introduced to allow for multibody cross sections. The structure is considered to be a flexible beam responding to waves in the vertical direction. Numerical examples are presented with reference to an integrated system of semisubmersibles. A simple model for engineering estimation is also presented.
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Hadizadeh Asar, Tannaz, Keyvan Sadeghi et Arefeh Emami. « Free Vibration Analysis of Very Large Rectangular Floating Structures ». International Journal of coastal and offshore engineering 2, no 1 (1 juin 2018) : 59–66. http://dx.doi.org/10.29252/ijcoe.2.1.59.

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Ertekin, R. C., H. R. Riggs, X. L. Che et S. X. Du. « Efficient Methods for Hydroelastic Analysis of Very Large Floating Structures ». Journal of Ship Research 37, no 01 (1 mars 1993) : 58–76. http://dx.doi.org/10.5957/jsr.1993.37.1.58.

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The linear hydroelastic response of a very large floating structure (VLFS) consisting of multiple modules is studied theoretically, following a review of the past work on hydroelasticity in fluid-structure interaction. The 3-dimensional Green function method and Morison's equation approach are used to determine the fluid loading in conjunction with two different hydroelastic models. The first method uses a rigid module, flexible connector model in which the hydrodynamic interaction between rigid modules is taken into account. The double composite source distribution method, which is a numerically efficient implementation of the Green function method that exploits double symmetry of the structure in the longitudinal and lateral directions, is used to reduce computations. In the second method, fully elastic modules are considered. In this approach, the fluid loading is obtained by Morison's equation, and the structure is modeled by frame finite elements. The predictions for the rigid-body motions and structural deformations, as well as module-connector loads, obtained by the two different methods are compared. The proposed methods of hydroelasticity have been used to predict the response of a 16-module VLFS, 100 m by 1600 m. Both methods are sufficiently efficient to allow the analysis of even larger VLFS.
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Maeda, Hisaaki, Koichi Masuda, Shogo Miyajima et Tomoki Ikoma. « Hydroelasitic Responses of Pontoon Type Very Large Floating Offshore Structures ». Journal of the Society of Naval Architects of Japan 1996, no 180 (1996) : 365–71. http://dx.doi.org/10.2534/jjasnaoe1968.1996.180_365.

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Thèses sur le sujet "Very Large Floating Structures"

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Carter, Benjamin. « Water-wave propagation through very large floating structures ». Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/12031.

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Proposed designs for Very Large Floating Structures motivate us to understand water-wave propagation through arrays of hundreds, or possibly thousands, of floating structures. The water-wave problems we study are each formulated under the usual conditions of linear wave theory. We study the frequency-domain problem of water-wave propagation through a periodically arranged array of structures, which are solved using a variety of methods. In the first instance we solve the problem for a periodically arranged infinite array using the method of matched asymptotic expansions for both shallow and deep water; the structures are assumed to be small relative to the wavelength and the array periodicity, and may be fixed or float freely. We then solve the same infinite array problem using a numerical approach, namely the Rayleigh-Ritz method, for fixed cylinders in water of finite depth and deep water. No limiting assumptions on the size of the structures relative to other length scales need to be made using this method. Whilst we aren t afforded the luxury of explicit approximations to the solutions, we are able to compute diagrams that can be used to aid an investigation into negative refraction. Finally we solve the water-wave problem for a so-called strip array (that is, an array that extends to infinity in one horizontal direction, but is finite in the other), which allows us to consider the transmission and reflection properties of a water-wave incident on the structures. The problem is solved using the method of multiple scales, under the assumption that the evolution of waves in a horizontal direction occurs on a slower scale than the other time scales that are present, and the method of matched asymptotic expansions using the same assumptions as for the infinite array case.
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Crema, Ilaria [Verfasser], et Hocine [Akademischer Betreuer] Oumeraci. « Oscillating water column wave energy converters integrated in very large floating structures / Ilaria Crema ; Betreuer : Hocine Oumeraci ». Braunschweig : Technische Universität Braunschweig, 2018. http://d-nb.info/1175815357/34.

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Jin, Jingzhe. « A mixed mode function : boundary element method for very large floating structure : water interaction systems excited by airplane landing impacts ». Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/52018/.

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This thesis develops a mixed mode function – boundary element method (BEM) to analyze the dynamics of an integrated airplane – floating structure – water interaction system subject to airplane landing impacts. The airplane and the floating structure are treated as two solid substructures of which the motions are represented by their respective modal functions. The landing gear system of the airplane is modelled with a few linear spring – damper units connecting the airplane and the floating structure. The water is assumed to be inviscid and incompressible and the fluid motion is irrotational. Under a linear potential theory, the motion of the fluid is governed by the Laplace equation and the related boundary conditions. A linearised composite free surface boundary condition and an undisturbed far field (infinity) radiation condition are considered. The Green function, or kernel, of BEM formulation is a fundamental solution of the Laplace equation assuming an infinite fluid domain. The motion of the floating structure and the surrounding fluid are coupled through the wetted surface interface conditions. The coupled equations of the airplane, the floating structure and the surrounding fluid are solved using a step by step time integration procedure based on the Newmark assumptions. A FORTRAN program MMFBEP is written to implement the proposed numerical method. A few examples are completed to validate the mathematical model and the developed computer code. In comparing the available numerical and experimental results reported in the literature, sound agreements are reached. It is hoped that the developed method and computer code may be further improved and modified to provide an engineering tool for the dynamic design of Very Large Floating Structures (VLFS).
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Talamini, Brandon Louis. « Simulation of deformation and fracture in very large shell structures ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103420.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 207-221).
Although advances in computing have increased the limits of three-dimensional computational solid mechanics, structural elements remain essential in the practical design of very large thin structures such as aircraft fuselages, ship hulls, automobiles, submarines, and pressure vessels. In many applications, fracture is a critical design concern, and thus the ability to numerically predict crack propagation in shells is a highly desirable goal. There are relatively few tools devoted to computational shell fracture, and of the existing approaches, there are two main defects: First, the existing methods are not scalable, in the sense of parallel computing, and consequently simulation of large structures remains out of reach. Second, while the existing approaches treat in-plane tensile failure, fracture due to transverse shearing has largely been ignored. In this thesis, a new computational framework for simulating deformation and fracture in large shell structures is presented that is well-suited to parallel computation. The scalability of the framework derives from the combination of a discontinuous Galerkin (DG) finite element method with an interface element-based cohesive zone representation of fracture. This representation of fracture permits arbitrary crack propagation, branching, and merging, without on-the-fly mesh topological changes. Furthermore, in parallel computing, this propagation algorithm is indifferent to processor boundaries. The adoption of a shear-flexible shell theory is identified as a necessary condition for modeling transverse shear failure, and the proposed method is formulated accordingly. Locking is always an issue that emerges in numerical analysis of shear-flexible shells; here, the inherent flexibility afforded by DG methods in the choice of approximation spaces is exploited to prevent locking naturally, without recourse to mixed methods or reduced integration. Hence, the DG discretization elegantly solves both the problems of scalability and locking simultaneously. A stress resultant-based cohesive zone theory is proposed that considers transverse shear, as well as bending and in-plane membrane forces. The theory is quite general, and the specification of particular constitutive relations, in the form of resultant traction-separation laws, is independent of the discretization scheme. Thus, the proposed framework should be extensible and useful for a variety of applications. A detailed description of the implementation strategy is provided, and numerical examples are presented which demonstrate the ability of the framework to capture all of the relevant modes of fracture in thin bodies. Finally, a numerical example of explosive decompression in a commercial airliner is shown as evidence that the proposed framework can successfully perform shell fracture simulations of unprecedented size.
by Brandon Louis Talamini.
Ph. D.
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Gordon, Christal. « An adaptive floating-gate network using action-potential signaling ». Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15683.

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Kucic, Matthew R. « Analog programmable filters using floating-gate arrays ». Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/13755.

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Twigg, Christopher M. « Floating Gate Based Large-Scale Field-Programmable Analog Arrays for Analog Signal Processing ». Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11601.

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Large-scale reconfigurable and programmable analog devices provide a new option for prototyping and synthesizing analog circuits for analog signal processing and beyond. Field-programmable analog arrays (FPAAs) built upon floating gate transistor technologies provide the analog reconfigurability and programmability density required for large-scale devices on a single integrated circuit (IC). A wide variety of synthesized circuits, such as OTA followers, band-pass filters, and capacitively coupled summation/difference circuits, were measured to demonstrate the flexibility of FPAAs. Three generations of devices were designed and tested to verify the viability of such floating gate based large-scale FPAAs. Various architectures and circuit topologies were also designed and tested to explore the trade-offs present in reconfigurable analog systems. In addition, large-scale FPAAs have been incorporated into class laboratory exercises, which provide students with a much broader range of circuit and IC design experiences than have been previously possible. By combining reconfigurable analog technologies with an equivalent large-scale digital device, such as a field-programmable gate array (FPGA), an extremely powerful and flexible mixed signal development system can be produced that will enable all of the benefits possible through cooperative analog/digital signal processing (CADSP).
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Ponchio, Federico [Verfasser]. « Multiresolution structures for interactive visualization of very large 3D datasets / submitted by Federico Ponchio ». [Clausthal-Zellerfeld] : [Univ.-Bibliothek], 2009. http://d-nb.info/997062789/34.

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Gray, Jordan D. « Application of Floating-Gate Transistors in Field Programmable Analog Arrays ». Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7540.

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Floating-gate transistors similar to those used in FLASH and EEPROM can be used to build reconfigurable analog arrays. The charge on the floating gate can be modified to pass or block a signal in a cross-bar switch matrix, or it can be finely tuned to eliminate a threshold difference across a chip or set a bias. By using such a compact and versatile reconfigurable analog memory element, the number of analog circuit components included on an integrated circuit that is field-programmable is significantly higher. As a result, large-scale FPAAs can be built with the same impact on analog design that FPGAs have had on digital design. In my research, I investigate the areas floating-gate transistors can be used to impact FPAA design and implementation. An FPAA can be broken up into two basic components, elements of connection and elements of computation. With respect to connection, I show that a floating-gate switch can be used in a cross-bar matrix in place of a transmission gate resulting in less parasitic capacitance and a more linear resistance for the same size transistor. I illuminate the programming issues relating to injecting a floating-gate for use as a switch, including the drain selection circuitry and rogue injection due to gate induced drain leakage. With respect to computation, I explain how a Multiple-Input Translinear Element, or MITE, can be augmented to fit in an FPAA framework. I also discuss two different MITE implementations compatible with CMOS technology, a subthreshold MOS design and a BJT MITE that uses a lateral BJT. Beyond FPAA components, I present two alternative FPAA systems. The first is a general purpose reconfigurable analog system that uses standard analog design components that have been augmented with floating-gates. The second FPAA is built upon MITE circuits, and is focused on supporting direct system synthesis. I conclude with a discussion of a future large-scale MITE FPAA.
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Che, Xiling. « Techniques for hydroelastic analysis of very large floating structures ». Thesis, 1993. http://hdl.handle.net/10125/10007.

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Livres sur le sujet "Very Large Floating Structures"

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Wang, Chien-ming. Very large floating structures. New York, NY : Taylor & Francis, 2007.

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Japan) International Workshop on Very Large Floating Structures (1996 Hayama-machi. Very large floating structures : [proceedings of International Workshop on Very Large Floating Structures], Hayama, Kanagawa, Japan, November 25-28, 1996. [Kanagawa, Japan] : Ship Research Institute, Ministry of Transport, 1996.

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Japan) International Workshop on Very Large Floating Structures (4th 2003 Tokyo. 4th International Workshop on Very Large Floating Structures : VLF '03, January 28-29, 2003, Tokyo, Japan. [Tokyo] : National Maritime Research Institute, 2003.

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Wang, C. M., et B. T. Wang, dir. Large Floating Structures. Singapore : Springer Singapore, 2015. http://dx.doi.org/10.1007/978-981-287-137-4.

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IEEE Electron Devices Society. Standards Committee., Institute of Electrical and Electronics Engineers. et IEEE-SA Standards Board, dir. IEEE standard definitions and characterization of floating gate semiconductor arrays. New York, N.Y., USA : Institute of Electrical and Electronics Engineers, 1999.

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A VLSI architecture for concurrent data structures. Boston : Kluwer Academic, 1987.

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Indo-Soviet, Workshop on Experiences in Large Canals and Hydraulic Structures in Subsident Swelling and Floating Soils (1986 New Delhi India). Indo-Soviet Workshop on Experiences in Large Canals and Hydraulic Structures in Subsident, Swelling, and Floating Soils, 18-19 September 1986 : Proceedings. New Delhi : The Board, 1986.

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Meinel, Christoph. Algorithms and data structures in VLSI design : OBDD-foundations and applications. Berlin : Springer, 1998.

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International Conference on Very Large Data Bases (17th 1991 Barcelona, Spain). Proceedings of the Seventeenth International Conference on Very Large Data Bases : September 3-6 1991 Barcelona (Catalonia, Spain). Sous la direction de Lohman Guy M, Sernadas Amílcar et Camps Rafael. Hove : Morgan Kaufman, 1991.

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Wang, C. M., E. Watanabe et T. Utsunomiya. Very Large Floating Structures. Taylor & Francis Group, 2020.

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Chapitres de livres sur le sujet "Very Large Floating Structures"

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Fu, Shixiao, Shuai Li et Weicheng Cui. « Very Large Floating Structures (VLFS) : Overview ». Dans Encyclopedia of Ocean Engineering, 2095–103. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-10-6946-8_335.

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Fu, Shixiao, Shuai Li et Weicheng Cui. « Very Large Floating Structures (VLFS) : Overview ». Dans Encyclopedia of Ocean Engineering, 1–8. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-10-6963-5_335-1.

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Ng, ChunWee, et Rongrong Jiang. « Classification Principles for Very Large Floating Structures ». Dans Lecture Notes in Civil Engineering, 235–51. Singapore : Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8743-2_13.

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Sankalp, Aditya, et Yves De Leeneer. « Mooring Systems for Very Large Floating Structures ». Dans Lecture Notes in Civil Engineering, 253–73. Singapore : Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8743-2_14.

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Panduranga, Kottala, et Santanu Koley. « Water Wave Interaction with Very Large Floating Structures ». Dans Lecture Notes in Mechanical Engineering, 531–40. Singapore : Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1769-0_48.

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Lu, Ye, Bei Teng, Yikun Wang, Ye Zhou, Xiaoming Cheng et Enrong Qi. « Structural Design of Hinge Connector for Very Large Floating Structures ». Dans Lecture Notes in Civil Engineering, 197–208. Singapore : Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-4672-3_12.

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Wang, C. M., et Z. Y. Tay. « Hydroelastic Analysis and Response of Pontoon-Type Very Large Floating Structures ». Dans Fluid Structure Interaction II, 103–30. Berlin, Heidelberg : Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14206-2_5.

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Kakinuma, Taro, et Naoto Ochi. « Tsunami-Height Reduction Using a Very Large Floating Structure ». Dans Mathematics for Industry, 193–202. Singapore : Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-6062-0_14.

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Bispo, I. B. S., S. C. Mohapatra et C. Guedes Soares. « A review on numerical approaches in the hydroelastic responses of very large floating elastic structures ». Dans Developments in Maritime Technology and Engineering, 425–36. London : CRC Press, 2021. http://dx.doi.org/10.1201/9781003216582-48.

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Wang, C. M., et B. T. Wang. « Great Ideas Float to the Top ». Dans Large Floating Structures, 1–36. Singapore : Springer Singapore, 2014. http://dx.doi.org/10.1007/978-981-287-137-4_1.

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Actes de conférences sur le sujet "Very Large Floating Structures"

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Suzuki, H., H. R. Riggs, M. Fujikubo, T. A. Shugar, H. Seto, Y. Yasuzawa, B. Bhattacharya, D. A. Hudson et H. Shin. « Very Large Floating Structures ». Dans ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29758.

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Very Large Floating Structure (VLFS) is a unique concept of ocean structures primary because of their unprecedented length, displacement cost and associated hydroelastic response. International Ship and Offshore Structures Congress (ISSC) had paid attention to the emerging novel technology and launched Special Task Committee to investigate the state of the art in the technology. This paper summarizes the activities of the committee. A brief overview of VLFS is given first for readers new to the subject. History, application and uniqueness with regard to engineering implication are presented. The Mobile Offshore Base (MOB) and Mega-Float, which are typical VLFS projects that have been investigated in detail and are aimed to be realized in the near future, are introduced. Uniqueness of VLFS, such as differences in behavior of VLFS from conventional ships and offshore structures, are described. The engineering challenges associated with behavior, design procedure, environment, and the structural analysis of VLFS are introduced. A comparative study of hydroelastic analysis tools that were independently developed for MOB and Mega-Float is made in terms of accuracy of global behavior. The effect of structural modeling on the accuracy of stress analysis is also discussed. VLFS entails innovative design methods and procedure. Development of design criteria and design procedures are described and application of reliability-based approaches are documented and discussed.
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Wang, C. M., Z. J. Yao, A. M. Hee et W. L. Tan. « Optimal Layout of Gill Cells for Very Large Floating Structures ». Dans ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29762.

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This paper is concerned with the optimal layout of gill cells for minimizing the differential deflection of a very large floating structure under a non-uniform load distribution over the surface of the structure. Gill cells are compartments in the floating structure where the bottom surface is perforated to allow water to flow freely in and out. At the locations of these gill cells, the buoyancy forces are eliminated. When placed appropriately, these gill cells are very cost effective in minimizing the differential deflection of the loaded structure. So the optimal layout of the gill cells is a very important design consideration. In this paper, the modeling of a very large floating structure with gill cells is developed and a computational method based on genetic algorithms for seeking the locations of a given number of gill cells is presented. The model and optimization technique are demonstrated on a floating structure which carries a heavy load in its central portion of the structure. Resulting from the non-uniform heavy load on the structure, the differential deflection may cause operational problems for equipments which are sensitive to tilting. Using gill cells that are positioned optimally, it will be shown that the differential deflection can be considerably minimized.
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Srinivasan, Nagan, et R. Sundaravadivelu. « Ocean Space Utilization Using Very Large Floating Semi-Submersible ». Dans ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10458.

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Very Large Floating Structures (VLFS) are highly specialized floating structures with variety of applications in the civil engineering of ocean. Their economic design is based on their hydro-elastic behavior due to wave environmental forces. VLFS are extra large in size and mostly extra long in span in the design feature for their applications. For that reason they are mostly modularized into several smaller structures and joined together in the site. The critical problem is the longitudinal bending moment of the long floating vessel in severe wave environment. With the result of that the present available VLFS designs become not economical for applications in hostile-ocean. This paper presents ocean space utilization using an innovative VLFS with truss pontoon concept. The concept uses a strong deck with strong longitudinal beams to take care of the needed bending moment of the vessel for the survival, standby and operational conditions of the ocean environment. At the submerged bottom just above the keel-tank top, a simple open-frame truss-structure is used instead of a heavy shell type pontoon. The truss-pontoon provides the necessary flow transparency for the reduction of the wave exciting forces and consequently reduces heave amplitude of motions and the vertical acceleration. Each individual columns of the truss pontoon semi-submersible is tuned to have heave-period over 22 sec, independently, such that minimum hydrodynamic-motions are obtained for the overall structure. The VLFS is designed with minimum heave for the extreme storms unlike the conventional column stabilized semi-submersible unit with conventional pontoon. The paper proposes a new VLFS concept which is feasible for applications in harsh environment. Most importantly cost effective VLFS is achieved. This paper presents the details of the VLFS design, stability, motion, and experimental verification from the physical wave-tank with the scaled-down model. At the end of the paper, a few comprehensive example applications are illustrated.
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Utsunomiya, T., et E. Watanabe. « ACCELERATED BEM FOR WAVE RESPONSE ANALYSIS OF VERY LARGE FLOATING STRUCTURES ». Dans Proceedings of the Second International Conference. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812776228_0079.

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Kakinuma, Taro, Kei Yamashit et Keisuke Nakayama. « INTERACTION OF SURFACE AND INTERNAL WAVES WITH VERY LARGE FLOATING STRUCTURES ». Dans Proceedings of the 6th International Conference. WORLD SCIENTIFIC, 2013. http://dx.doi.org/10.1142/9789814412216_0079.

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Cappietti, Lorenzo, Irene Simonetti et Ilaria Crema. « Concept Design of Very Large Floating Structures and Laboratory-Scale Physical Modelling ». Dans ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96259.

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Abstract The use of Very Large Floating Structures, VLFS, may represent a strategic approach in order to cope with some of the future societal challenges arising from the impressive growth of the world population. In this article, the motivations of this perspective are briefly discussed, the main issues for the development of VLFS are summarized and a concept structural design based on building-blocks technology is proposed. A small-scale physical model was manufactured and tested in the wave-current flume of the Laboratory of Maritime Engineering, LABIMA, of the Florence University, Italy. The aim of this study is the assessment of the structural feasibility and the effectiveness of the proposed VLFS concept, in terms of resistance to wave loads and control of floating behavior. The experimental measurements provide a first contribution to the necessary knowledge, about load magnitudes and floating behavior, for sizing some of the key structural components. The results appear to support the feasibility of the system in terms of usage of structural materials, technical components and building technologies, available at present, that can withstand the measured loads. Moreover, the acquired experimental database is fundamental in order to validate numerical models, in the perspective of using also such tools as complementary methodology for further improvement of the knowledge of design issues.
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Muhamed Basheer Naseema, Sibin, et Nilanjan Saha. « Hydroelastic Response of Very Large Floating Structures (VLFS) Connected With Wind Turbines ». Dans ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-61099.

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Very large floating structure (VLFS) technology is a novel idea being introduced in ports and harbors, fishing, land reclamation, petroleum product storage facilities and so on. The flexible nature of VLFS makes the response hydroelastic and it is important to have a reduced response of VLFS. The term hydroelasticity refers to the action of hydrodynamic excitation over elastic body limits. The present study tries to examine the combined effect of horizontal loads of wind turbine tower along with the vertical hydrodynamic loads which question the stability of the performance of VLFS. This would lead to better understanding of the hydroelastic response of integrated wind farm-VLFS configuration. To examine the effect of relevant parameters on the VLFS hydrodynamic responses, motion amplitude transfer functions (RAO) for a wide range of wave frequencies are computed. Pontoon type VLFS are giant platforms resting on the sea surface, which are modeled by very large plates according to the Mindlin thick plate theory. The boundary integral element method (BIEM) is used to solve for the velocity potential using Laplace equation providing suitable boundary conditions. The fluid model is based on linear wave hypothesis. The effect of wind on wind turbines which are located at the edges and corner of the VLFS is investigated in the model. The Kaimal wind spectrum is used to generate time series of wind speed incident on the blades of the turbine and loads are computed using blade element momentum theory as in wind simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence). The finite element framework is used to develop the model and to find the hydrodynamic loading. Mooring line connections are used to reduce structural instability. In order to reduce the hydroelastic response of VLFS, connection with hinges or semi rigid line connections are observed to be effective. The elastic and dynamic effects of the combined wind-wave loading over the integrated VLFS are being considered. The hydroelastic effects of mooring lines will not be accounted for.
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Shi, Qijia, Daolin Xu et Haicheng Zhang. « Design of a Flexible-Base Hinged Connector for Very Large Floating Structures ». Dans ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-78478.

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Connector of multi-modular VLFS is a key component which determines the connection load and the dynamic behavior of the system. This paper presents a new design of the flexible-base hinged connector (FBHC) for VLFS in order to reduce the connection load. The connector consists of a hinged joint and two flexible bases. A finite element model of the connector is established for the deformation analysis to match up the requirement on the optimal stiffness combination of the connector [1]. Further the strength analysis is also carried out to check the safety of the structure design according to the maximum design loads. By applying the connector model to a three-modular floating platform, the dynamic behavior of the platform is analyzed. The results show that the responses of the modules are within the tolerable range and the connector meets the strength requirements.
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Wang, Chien Ming, Rui Ping Gao, Chan Ghee Koh et Sritawat Kitipornchai. « Novel Hybrid System for Reducing Hydroelastic Response of Very Large Floating Structures ». Dans ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83124.

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This paper presents a novel hybrid system for reducing the hydroelastic response of pontoon-type, very large floating structure (VLFS) under wave action. The hybrid system comprises flexible connectors and “gill cells” which are compartments in VLFS with holes or slits at their bottom surfaces for allowing water to enter or leave freely. The gill cells are modeled by eliminating the buoyancy forces at their locations. In the hydroelastic analysis, the water is assumed to be an ideal fluid and its motion is irrotational so that a velocity potential exists. The VLFS is modeled as an isotropic plate according to the Mindlin plate theory. In order to decouple the fluid-structure interaction problem, the modal expansion method is adopted for the hydroelastic analysis which is carried out in the frequency domain. The boundary element method is used to solve the Laplace equation for the velocity potential, whereas the finite element method is employed for solving the equations of motion of the floating plate. It is found that by appropriately positioning the flexible line connector and a suitable distribution of gill cells in the VLFS, the hydroelastic response and stress resultants of the VLFS can be significantly reduced.
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Papaioannou, Iason, Ruiping Gao, Ernst Rank et Chien Ming Wang. « Hydroelastic Analysis of Pontoon-Type Very Large Floating Structures in Random Seas ». Dans 5th Asian-Pacific Symposium on Structural Reliability and its Applications. Singapore : Research Publishing Services, 2012. http://dx.doi.org/10.3850/978-981-07-2219-7_p319.

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Rapports d'organisations sur le sujet "Very Large Floating Structures"

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Nash, J. G. VLSI (Very Large Scale Integration) Floating Point Chip Design Study. Fort Belvoir, VA : Defense Technical Information Center, novembre 1985. http://dx.doi.org/10.21236/ada164198.

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Parlett, B. N., P. S. Jensen et T. Erickson. Lanczos Algorithm Applied to Modal Analysis of Very Large Structures. Fort Belvoir, VA : Defense Technical Information Center, août 1985. http://dx.doi.org/10.21236/ada160210.

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VIGIL, MANUEL GILBERT. Design of Largest Shaped Charge : Generation of Very Large Diameter, Deep Holes in Rock and Concrete Structures. Office of Scientific and Technical Information (OSTI), avril 2003. http://dx.doi.org/10.2172/810682.

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Gunay, Selim, Fan Hu, Khalid Mosalam, Arpit Nema, Jose Restrepo, Adam Zsarnoczay et Jack Baker. Blind Prediction of Shaking Table Tests of a New Bridge Bent Design. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/svks9397.

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Considering the importance of the transportation network and bridge structures, the associated seismic design philosophy is shifting from the basic collapse prevention objective to maintaining functionality on the community scale in the aftermath of moderate to strong earthquakes (i.e., resiliency). In addition to performance, the associated construction philosophy is also being modernized, with the utilization of accelerated bridge construction (ABC) techniques to reduce impacts of construction work on traffic, society, economy, and on-site safety during construction. Recent years have seen several developments towards the design of low-damage bridges and ABC. According to the results of conducted tests, these systems have significant potential to achieve the intended community resiliency objectives. Taking advantage of such potential in the standard design and analysis processes requires proper modeling that adequately characterizes the behavior and response of these bridge systems. To evaluate the current practices and abilities of the structural engineering community to model this type of resiliency-oriented bridges, the Pacific Earthquake Engineering Research Center (PEER) organized a blind prediction contest of a two-column bridge bent consisting of columns with enhanced response characteristics achieved by a well-balanced contribution of self-centering, rocking, and energy dissipation. The parameters of this blind prediction competition are described in this report, and the predictions submitted by different teams are analyzed. In general, forces are predicted better than displacements. The post-tension bar forces and residual displacements are predicted with the best and least accuracy, respectively. Some of the predicted quantities are observed to have coefficient of variation (COV) values larger than 50%; however, in general, the scatter in the predictions amongst different teams is not significantly large. Applied ground motions (GM) in shaking table tests consisted of a series of naturally recorded earthquake acceleration signals, where GM1 is found to be the largest contributor to the displacement error for most of the teams, and GM7 is the largest contributor to the force (hence, the acceleration) error. The large contribution of GM1 to the displacement error is due to the elastic response in GM1 and the errors stemming from the incorrect estimation of the period and damping ratio. The contribution of GM7 to the force error is due to the errors in the estimation of the base-shear capacity. Several teams were able to predict forces and accelerations with only moderate bias. Displacements, however, were systematically underestimated by almost every team. This suggests that there is a general problem either in the assumptions made or the models used to simulate the response of this type of bridge bent with enhanced response characteristics. Predictions of the best-performing teams were consistently and substantially better than average in all response quantities. The engineering community would benefit from learning details of the approach of the best teams and the factors that caused the models of other teams to fail to produce similarly good results. Blind prediction contests provide: (1) very useful information regarding areas where current numerical models might be improved; and (2) quantitative data regarding the uncertainty of analytical models for use in performance-based earthquake engineering evaluations. Such blind prediction contests should be encouraged for other experimental research activities and are planned to be conducted annually by PEER.
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Linker, Raphael, Murat Kacira, Avraham Arbel, Gene Giacomelli et Chieri Kubota. Enhanced Climate Control of Semi-arid and Arid Greenhouses Equipped with Fogging Systems. United States Department of Agriculture, mars 2012. http://dx.doi.org/10.32747/2012.7593383.bard.

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The main objectives were (1) to develop, implement and validate control procedures that would make it possible to maintain year-round air temperature and humidity at levels suitable for crop cultivation in greenhouses operating in arid and semi-arid regions and (2) to investigate the influence of the operational flexibility of the fogging system on the performance of the system. With respect to the development of climate controllers, we developed a new control approach according to which ventilation is used to maintain the enthalpy of the greenhouse air and fogging is used to adjust the humidity ratio inside the greenhouse. This approach is suitable mostly for greenhouses equipped with mechanized ventilation, and in which the air exchange rate can be controlled with enough confidence. The development and initial validation of the controllers were performed in a small experimental greenhouses located at the Agricultural Research Organization and very good tracking were obtained for both air temperature and relative humidity (maximum mean deviations over a 10-min period with constant setpoints lower than 2.5oC and 5% relative humidity). The robust design approach used to develop the controllers made it possible to transfer successfully these controllers to a much larger semi-commercial greenhouse located in the much drier Arava region. After only minimal adjustments, which did not require lengthy dedicated experiments, satisfactory tracking of the temperature and humidity was achieved, with standard deviation of the tracking error lower than 1oC and 5% for temperature and relative humidity, respectively. These results should help promote the acceptance of modern techniques for designing greenhouse climate controllers, especially since given the large variety of greenhouse structures (shape, size, crop system), developing high performance site-specific controllers for each greenhouse is not feasible. In parallel to this work, a new cooling control strategy, which considers the contribution of humidification and cooling from the crop, was developed for greenhouses equipped with natural ventilation. Prior to the development of the cooling strategy itself, three evapotranspiration models were compared in terms of accuracy and reliability. The cooling strategy that has been developed controls the amount of fog introduced into the greenhouse as well as the percentage of vent openings based on the desired vapor pressure deficit (VPD) and enthalpy, respectively. Numerical simulations were used to compare the performance of the new strategy with a constant fogging rate strategy based on VPD, and on average, the new strategy saved 36% water and consumed 30% less electric energy. In addition, smaller air temperature and relative humidity fluctuations were achieved when using the new strategy. Finally, it was demonstrated that dynamically varying the fog rate and properly selecting the number of nozzles, yields additional water and electricity savings.
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Lazonick, William, Philip Moss et Joshua Weitz. Equality Denied : Tech and African Americans. Institute for New Economic Thinking, février 2022. http://dx.doi.org/10.36687/inetwp177.

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Thus far in reporting the findings of our project “Fifty Years After: Black Employment in the United States Under the Equal Employment Opportunity Commission,” our analysis of what has happened to African American employment over the past half century has documented the importance of manufacturing employment to the upward socioeconomic mobility of Blacks in the 1960s and 1970s and the devastating impact of rationalization—the permanent elimination of blue-collar employment—on their socioeconomic mobility in the 1980s and beyond. The upward mobility of Blacks in the earlier decades was based on the Old Economy business model (OEBM) with its characteristic “career-with-one-company” (CWOC) employment relations. At its launching in 1965, the policy approach of the Equal Employment Opportunity Commission assumed the existence of CWOC, providing corporate employees, Blacks included, with a potential path for upward socioeconomic mobility over the course of their working lives by gaining access to productive opportunities and higher pay through stable employment within companies. It was through these internal employment structures that Blacks could potentially overcome barriers to the long legacy of job and pay discrimination. In the 1960s and 1970s, the generally growing availability of unionized semiskilled jobs gave working people, including Blacks, the large measure of employment stability as well as rising wages and benefits characteristic of the lower levels of the middle class. The next stage in this process of upward socioeconomic mobility should have been—and in a nation as prosperous as the United States could have been—the entry of the offspring of the new Black blue-collar middle class into white-collar occupations requiring higher educations. Despite progress in the attainment of college degrees, however, Blacks have had very limited access to the best employment opportunities as professional, technical, and administrative personnel at U.S. technology companies. Since the 1980s, the barriers to African American upward socioeconomic mobility have occurred within the context of the marketization (the end of CWOC) and globalization (accessibility to transnational labor supplies) of high-tech employment relations in the United States. These new employment relations, which stress interfirm labor mobility instead of intrafirm employment structures in the building of careers, are characteristic of the rise of the New Economy business model (NEBM), as scrutinized in William Lazonick’s 2009 book, Sustainable Prosperity in the New Economy? Business Organization and High-Tech Employment in the United States (Upjohn Institute). In this paper, we analyze the exclusion of Blacks from STEM (science, technology, engineering, math) occupations, using EEO-1 employment data made public, voluntarily and exceptionally, for various years between 2014 and 2020 by major tech companies, including Alphabet (Google), Amazon, Apple, Cisco, Facebook (now Meta), Hewlett Packard Enterprise, HP Inc., Intel, Microsoft, PayPal, Salesforce, and Uber. These data document the vast over-representation of Asian Americans and vast under-representation of African Americans at these tech companies in recent years. The data also shine a light on the racial, ethnic, and gender composition of large masses of lower-paid labor in the United States at leading U.S. tech companies, including tens of thousands of sales workers at Apple and hundreds of thousands of laborers & helpers at Amazon. In the cases of Hewlett-Packard, IBM, and Intel, we have access to EEO-1 data from earlier decades that permit in-depth accounts of the employment transitions that characterized the demise of OEBM and the rise of NEBM. Given our findings from the EEO-1 data analysis, our paper then seeks to explain the enormous presence of Asian Americans and the glaring absence of African Americans in well-paid employment under NEBM. A cogent answer to this question requires an understanding of the institutional conditions that have determined the availability of qualified Asians and Blacks to fill these employment opportunities as well as the access of qualified people by race, ethnicity, and gender to the employment opportunities that are available. Our analysis of the racial/ethnic determinants of STEM employment focuses on a) stark differences among racial and ethnic groups in educational attainment and performance relevant to accessing STEM occupations, b) the decline in the implementation of affirmative-action legislation from the early 1980s, c) changes in U.S. immigration policy that favored the entry of well-educated Asians, especially with the passage of the Immigration Act of 1990, and d) consequent social barriers that qualified Blacks have faced relative to Asians and whites in accessing tech employment as a result of a combination of statistical discrimination against African Americans and their exclusion from effective social networks.
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Russo, Margherita, Fabrizio Alboni, Jorge Carreto Sanginés, Manlio De Domenico, Giuseppe Mangioni, Simone Righi et Annamaria Simonazzi. The Changing Shape of the World Automobile Industry : A Multilayer Network Analysis of International Trade in Components and Parts. Institute for New Economic Thinking Working Paper Series, janvier 2022. http://dx.doi.org/10.36687/inetwp173.

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In 2018, after 25 years of the North America Trade Agreement (NAFTA), the United States requested new rules which, among other requirements, increased the regional con-tent in the production of automotive components and parts traded between the three part-ner countries, United States, Canada and Mexico. Signed by all three countries, the new trade agreement, USMCA, is to go into force in 2022. Nonetheless, after the 2020 Presi-dential election, the new treaty's future is under discussion, and its impact on the automo-tive industry is not entirely defined. Another significant shift in this industry – the acceler-ated rise of electric vehicles – also occurred in 2020: while the COVID-19 pandemic largely halted most plants in the automotive value chain all over the world, at the reopen-ing, the tide is now running against internal combustion engine vehicles, at least in the an-nouncements and in some large investments planned in Europe, Asia and the US. The definition of the pre-pandemic situation is a very helpful starting point for the analysis of the possible repercussions of the technological and geo-political transition, which has been accelerated by the epidemic, on geographical clusters and sectorial special-isations of the main regions and countries. This paper analyses the trade networks emerg-ing in the past 25 years in a new analytical framework. In the economic literature on inter-national trade, the study of the automotive global value chains has been addressed by us-ing network analysis, focusing on the centrality of geographical regions and countries while largely overlooking the contribution of countries' bilateral trading in components and parts as structuring forces of the subnetwork of countries and their specific position in the overall trade network. The paper focuses on such subnetworks as meso-level structures emerging in trade network over the last 25 years. Using the Infomap multilayer clustering algorithm, we are able to identify clusters of countries and their specific trades in the automotive internation-al trade network and to highlight the relative importance of each cluster, the interconnec-tions between them, and the contribution of countries and of components and parts in the clusters. We draw the data from the UN Comtrade database of directed export and import flows of 30 automotive components and parts among 42 countries (accounting for 98% of world trade flows of those items). The paper highlights the changes that occurred over 25 years in the geography of the trade relations, with particular with regard to denser and more hierarchical network gener-ated by Germany’s trade relations within EU countries and by the US preferential trade agreements with Canada and Mexico, and the upsurge of China. With a similar overall va-riety of traded components and parts within the main clusters (dominated respectively by Germany, US and Japan-China), the Infomap multilayer analysis singles out which com-ponents and parts determined the relative positions of countries in the various clusters and the changes over time in the relative positions of countries and their specialisations in mul-tilateral trades. Connections between clusters increase over time, while the relative im-portance of the main clusters and of some individual countries change significantly. The focus on US and Mexico and on Germany and Central Eastern European countries (Czech Republic, Hungary, Poland, Slovakia) will drive the comparative analysis.
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Wu, Yingjie, Selim Gunay et Khalid Mosalam. Hybrid Simulations for the Seismic Evaluation of Resilient Highway Bridge Systems. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/ytgv8834.

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Bridges often serve as key links in local and national transportation networks. Bridge closures can result in severe costs, not only in the form of repair or replacement, but also in the form of economic losses related to medium- and long-term interruption of businesses and disruption to surrounding communities. In addition, continuous functionality of bridges is very important after any seismic event for emergency response and recovery purposes. Considering the importance of these structures, the associated structural design philosophy is shifting from collapse prevention to maintaining functionality in the aftermath of moderate to strong earthquakes, referred to as “resiliency” in earthquake engineering research. Moreover, the associated construction philosophy is being modernized with the utilization of accelerated bridge construction (ABC) techniques, which strive to reduce the impact of construction on traffic, society, economy and on-site safety. This report presents two bridge systems that target the aforementioned issues. A study that combined numerical and experimental research was undertaken to characterize the seismic performance of these bridge systems. The first part of the study focuses on the structural system-level response of highway bridges that incorporate a class of innovative connecting devices called the “V-connector,”, which can be used to connect two components in a structural system, e.g., the column and the bridge deck, or the column and its foundation. This device, designed by ACII, Inc., results in an isolation surface at the connection plane via a connector rod placed in a V-shaped tube that is embedded into the concrete. Energy dissipation is provided by friction between a special washer located around the V-shaped tube and a top plate. Because of the period elongation due to the isolation layer and the limited amount of force transferred by the relatively flexible connector rod, bridge columns are protected from experiencing damage, thus leading to improved seismic behavior. The V-connector system also facilitates the ABC by allowing on-site assembly of prefabricated structural parts including those of the V-connector. A single-column, two-span highway bridge located in Northern California was used for the proof-of-concept of the proposed V-connector protective system. The V-connector was designed to result in an elastic bridge response based on nonlinear dynamic analyses of the bridge model with the V-connector. Accordingly, a one-third scale V-connector was fabricated based on a set of selected design parameters. A quasi-static cyclic test was first conducted to characterize the force-displacement relationship of the V-connector, followed by a hybrid simulation (HS) test in the longitudinal direction of the bridge to verify the intended linear elastic response of the bridge system. In the HS test, all bridge components were analytically modeled except for the V-connector, which was simulated as the experimental substructure in a specially designed and constructed test setup. Linear elastic bridge response was confirmed according to the HS results. The response of the bridge with the V-connector was compared against that of the as-built bridge without the V-connector, which experienced significant column damage. These results justified the effectiveness of this innovative device. The second part of the study presents the HS test conducted on a one-third scale two-column bridge bent with self-centering columns (broadly defined as “resilient columns” in this study) to reduce (or ultimately eliminate) any residual drifts. The comparison of the HS test with a previously conducted shaking table test on an identical bridge bent is one of the highlights of this study. The concept of resiliency was incorporated in the design of the bridge bent columns characterized by a well-balanced combination of self-centering, rocking, and energy-dissipating mechanisms. This combination is expected to lead to minimum damage and low levels of residual drifts. The ABC is achieved by utilizing precast columns and end members (cap beam and foundation) through an innovative socket connection. In order to conduct the HS test, a new hybrid simulation system (HSS) was developed, utilizing commonly available software and hardware components in most structural laboratories including: a computational platform using Matlab/Simulink [MathWorks 2015], an interface hardware/software platform dSPACE [2017], and MTS controllers and data acquisition (DAQ) system for the utilized actuators and sensors. Proper operation of the HSS was verified using a trial run without the test specimen before the actual HS test. In the conducted HS test, the two-column bridge bent was simulated as the experimental substructure while modeling the horizontal and vertical inertia masses and corresponding mass proportional damping in the computer. The same ground motions from the shaking table test, consisting of one horizontal component and the vertical component, were applied as input excitations to the equations of motion in the HS. Good matching was obtained between the shaking table and the HS test results, demonstrating the appropriateness of the defined governing equations of motion and the employed damping model, in addition to the reliability of the developed HSS with minimum simulation errors. The small residual drifts and the minimum level of structural damage at large peak drift levels demonstrated the superior seismic response of the innovative design of the bridge bent with self-centering columns. The reliability of the developed HS approach motivated performing a follow-up HS study focusing on the transverse direction of the bridge, where the entire two-span bridge deck and its abutments represented the computational substructure, while the two-column bridge bent was the physical substructure. This investigation was effective in shedding light on the system-level performance of the entire bridge system that incorporated innovative bridge bent design beyond what can be achieved via shaking table tests, which are usually limited by large-scale bridge system testing capacities.
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