Innovative solutions for minimizing differential deflection and heaving motion in very large floating structures

INNOVATIVE SOLUTIONS FOR MINIMIZING DIFFERENTIAL DEFLECTION AND HEAVING MOTION IN VERY LARGE FLOATING STRUCTURES PHAM DUC CHUYEN NATIONAL UNIVERSITY OF SINGAPORE 2009 INNOVATIVE SOLUTIONS FOR MINIMIZING DIFFERENTIAL DEFLECTION AND HEAVING MOTION IN VERY LARGE FLOATING STRUCTURES PHAM DUC CHUYEN B.Eng. (NUCE), M.Eng. (AIT) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2009 Acknowledgements ACKNOWLEDGMENTS First of all, my greatest thanks go to my supervisor Professor Wang Chien Ming, for his education, ideas, inspiration, advises, prompt and clear comments about our work, answers on many questions, and constant enthusiasm and interest. I consider myself as a very happy person to work with such an outstanding researcher as a supervisor. And I learned a lot about research, scientific philosophy and other things, for instance, how to get joy from the equations and problems. Next, I am grateful to my co-supervisor Professor Ang Kok Keng for his valuable and useful discussions, information and comments through out the research. I am also indeed grateful to Professor Tomoaki Utsunomiya from Kyoto University for his advice and useful discussions on this research study. I would also like to thank the chairman of my thesis advisory committee, Professor Koh Chan Ghee for his valuable advice and suggestions on my research and thesis. I am also thankful for the professors who examined my thesis. Their supportive comments and suggestions were very much useful for the future improvement of the thesis. I’m grateful to the National University of Singapore for providing financial support in the form of the NUS scholarship and facilities to carry out the research. The i Acknowledgements support provided by Mr. Krishna Sanmugam and technicians at Hydraulic Laboratory in the use of equipments and computer facilities to carry out the experiment is also appreciated. In addition, I would like to extend my gratefulness to my colleagues in Civil Engineering Department, especially Mr Tay Zhi Yung, Mr Muhammad Riyansyah, Ms Bangun Emma Patricia, for their friendship, encouragement and valuable discussion during the study. Last but not least, I would like to express the deepest gratitude to my beloved parents, wife and sisters for their eternal support, encouragement and love. I could not finish the whole study without the great love and care from you. ii TABLE OF CONTENTS Acknowledgements Table of Contents Summary i iii viii List of Tables xi List of Figures xii Notations xix Chapter Introduction 1.1 Background information on VLFS 1.1.1 Types of VLFS 1.1.2 Advantages of VLFS 1.1.3 Applications of VLFS 1.1.4 VLFS components 1.2 Literature Survey 12 12 1.2.1 VLFS assumptions, shapes and models 13 1.2.2 VLFS and water interaction modeling 15 1.2.3 Minimizing differential deflection in VLFS 17 1.2.4 Minimizing motion in VLFS 18 1.3 Objectives and scope of study 21 1.4 Layout of thesis 22 iii Table of Contents Chapter Minimizing Differential Deflection in Circular VLFS 25 2.1 Introduction 25 2.2 Problem definition 27 2.3 Basic assumptions and governing equations 29 2.4 Exact bending solutions and boundary conditions 31 2.4.1 VLFS regions without buoyancy force 31 2.4.2 VLFS regions with buoyancy force 32 2.4.3 Boundary and continuity conditions 33 2.5 Results and discussions on effectiveness of gill cells 34 2.5.1 Basic dimensions and properties of VLFS example, loading and freeboard conditions 2.5.2 Verification of results of VLFS with gill cells 34 34 2.5.3 Effectiveness of gill cells in reducing the differential deflection and stress-resultants 2.6 Optimal design/location of gill cells in circular VLFS 36 40 2.6.1 Case – Varying loading magnitudes ql 41 2.6.2 Case – Varying loading radius r0 43 2.6.3 Case – Varying top and bottom plate thicknesses t 45 2.6.4 Case – Varying freeboard hf 47 2.7 Comparing the effectiveness of gill cells with stepped VLFS 48 2.7.1 Case – Varying loading magnitudes ql 49 2.7.2 Case – Varying loading radius r0 50 2.7.3 Case – Varying top and bottom plate thicknesses t 51 2.8 Optimal design/location of gill cells in annular VLFS 52 iv Table of Contents 2.8.1 Dimensions, properties of annual VLFS and proposed gill cells location 52 2.8.2 Optimization formulation 53 2.8.3 Optimization results 54 2.9 Concluding remarks Chapter 56 Minimizing Differential Deflection in Non-circular Shaped VLFS Using Gill Cells 58 3.1 Introduction 58 3.2 Problem definition 59 3.3 Basic assumptions and FEM model for VLFS bending analysis 61 3.4 Results and discussions on effectiveness of gill cells 64 3.4.1 Dimensions and properties of VLFS examples, loading and freeboard conditions 3.4.2 Verification of results 64 64 3.4.3 Effect of gill cells in reducing the differential deflection and von Mises stress 65 3.5 Optimization problem 67 3.6 Optimization results 72 3.6.1 Optimization results for square VLFS 72 3.6.2 Optimization results for rectangular VLFS 78 3.6.3 Optimization results for I-shaped VLFS 84 3.7 Concluding remarks 90 v Table of Contents Chapter Minimizing Heaving Motion of Circular VLFS using Submerged Plate 91 4.1 Introduction 91 4.2 Problem definition 92 4.3 Basic assumptions, equations and boundary conditions for circular VLFS 93 4.4 Model expansion of motion 96 4.5 Solution for radiation potentials 99 4.6 Solution for diffraction potentials 113 4.7 Equation of motion in modal coordinate 114 4.8 Results and discussions 117 4.9 Concluding remarks 128 Chapter Minimizing Heaving Motion of Longish VLFS Using Anti-Heaving Devices 130 5.1 Introduction 130 5.2 Experimental facility and instrumentation 133 5.2.1 Wave tank 133 5.2.2 Wave generating system 135 5.2.3 Data acquisition system 135 5.2.4 Testing condition 138 5.2.5 VLFS model 138 5.2.6 Types of anti-heaving devices 140 5.3 Experimental procedure 142 5.4 Experimental results 143 5.4.1 VLFS with submerged horizontal plate 143 5.4.2 VLFS with vertical plate 147 vi Table of Contents 5.4.3 VLFS with L-shaped plate 151 5.4.4 VLFS with inclined plate 155 5.5 Most effective anti-heaving device 158 5.6 Concluding remarks 165 Chapter Conclusions and Recommendations for Future Work 167 6.1 Conclusions 168 6.2 Recommendations for future work 171 References 174 List of Publications 186 vii SUMMARY In the new millennium, the world is facing new problems such as the lack of land, due to the growing population and fast urban developments. Many island countries and countries with long coastline have applied the traditional land reclamation method to create land from the sea in order to decrease the pressure on the heavily used land space. In recent years, an attractive alternative to land reclamation has emerged – the very large floating structures technology. Very large floating structures (VLFS) can and are already being used for storage facilities, industrial space, bridges, ferry piers, docks, rescue bases, airports, entertainment facilities, military purpose, and even habitation. VLFSs can be speedily constructed, exploited, and easily relocated, expanded, or removed. These structures are reliable, cost effective, and environmentally friendly. VLFS may undergo large differential deflection under heavy nonuniformly distributed loads and large motion under strong wave action. These conditions may affect the smooth operation of equipments, the structural integrity and even the safety of people on VLFS. The main objectives of this study are to develop (1) innovative solutions to minimize the differential deflection of VLFS and (2) innovative solutions to minimize the heaving motion of VLFSs for various shapes and dimensions. Various alternative solutions are treated. For minimizing the differential deflection in unevenly loaded circular VLFS, two solutions were proposed. One solution makes use of the so-called “gill cells” and viii Conclusions and Recommendations for Future Work 3. Some interesting shapes of VLFSs were studied using gill cells to minimize the differential deflection. The current research only considered the loading area to be confined in the central portion of the VLFSs. Since the present numerical model is capable of dealing with arbitrarily shaped VLFS and locations of loaded area, this study can be extended to investigate other shapes and locations of loaded area. 4. Investigation on minimizing differential deflection in VLFS in this study considered VLFS in a benign sea state condition where the influence of wave is neglected. If the VLFS is located in a more severe sea state environment, it is necessary to perform hydroelastic analysis of the VLFS under wave action as well and determine the optimal design of gill cells allowing for this hydroelastic component. Future studies are recommended to investigate the dynamic hydroelastic problem of VLFS with gill cells. 5. In this study, an analytical model was developed to investigate the submerged plate anti-heaving device for minimizing the motion of circular VLFS under wave action was developed for the first time. However, this model is based on 2-D configuration of VLFS and is restricted to only circular VLFS. Future works are needed to investigate the effectiveness of submerged plate used in other shapes of VLFSs. For arbitrarily shaped VLFSs, a 3-D configuration model is required. Therefore, it is necessary to extend the 2-D model to 3-D model to analyze more accurately the behavior and response of the real structure. 6. By performing experimental tests on types of anti-heaving devices including a submerged horizontal plate, a submerged vertical plate, a submerged L-shape plate and a submerged inclined plate attached to the fore-end of a longish flexible floating structure, it has been found that the inclined plate is the best anti-heaving 172 Conclusions and Recommendations for Future Work device. We have only considered the case of an inclined plate of 450. Future studies should investigate the effect of the angle of inclination on the capability of the anti-heaving device. In particular, it would be useful to carry out an optimization study to determine whether there exists an optimal angle of inclination of the inclined plate as an anti-heaving device. 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Marine Structures 20, 71-99. Zilman G. and Miloh T. (2000). Hydroelastic Buoyant Circular Plate in Shallow Water: a Closed Form Solution. Applied Ocean Research 22, 191-8. 185 LIST OF PUBLICATIONS INTERNATIONAL JOURNAL Wang C.M., Pham D.C. and Ang K.K. (2006). Effectiveness and Optimal Design of Gill Cells in Minimizing Differential Deflection in Circular VLFS. Engineering Structures 29(8), 1845-53. D.C. Pham, C.M. Wang and T. Utsunomiya (2008). Hydroelastic Analysis of a Pontoon-Type Circular VLFS with an Attached Submerged Plate. Applied Ocean Research 30(4), 287-96. Pham D.C. and Wang C.M. (2009). Optimal Layout of Gill Cells for Very Large Floating Structures. Journal of Structural Engineering. (In Press) Pham D.C., Wang C.M. and Emma P.B. (2009). Experimental Study on Anti-Heaving Devices for a Longish VLFS. The Journal of the Institution of Engineers, Singapore, 02(4). INTERNATIONAL CONFERENCE Pham D.C., Wang C.M. and Ang K.K. (2005). Minimizing Differential Deflection and Stresses in VLFS Using Gill Cells. Proceedings of the Eighteenth KKCNN Symposium on Civil Engineering, Kaohsiung, Taiwan, 829-34. 186 List of Publications Pham D.C., Wang C.M. and Ang K.K. (2007). Optimal Design of Gill Cells for Very Large Floating Structures. The 7th International Conference on Optimization: Technique and Application (ICOTA7), Kobe, Japan, 255-36. Pham D.C. and Wang C.M. (2007). Effectiveness and Optimal Design of Gill Cells in Minimizing Slope in annular VLFS. Proceedings of the Twentieth KKCNN Symposium on Civil Engineering, Jeju, Korea, 255-8. Pham D.C., Wang C.M. and Emma P.B. (2008). Anti-Heaving Devices for VLFS. Proceedings of the Twenty First KKCNN Symposium on Civil Engineering, Singapore, 286-89. 187 [...]... centers, and theaters 9 Introduction Some floating entertainment facilities have been constructed For example, the world largest floating performer platform was built on the Marina Bay in Singapore in 2007 (Fig 1.9), Aquapolis exhibition center in Okinawa (1975, already removed), the Floating Island near Onomichi which resembles the Parthenon, and floating hotels in British Columbia, Canada, and floating. .. entertainment facilities, recreation parks, mobile offshore structures and even for habitation In certain applications of VLFS such as floating airports, floating container terminals and floating dormitories where high loads are placed in certain parts of the floating structure, the resulting differential deflections can be somewhat large and may render certain equipment non operational Therefore, it... the floating island at Onomichi Hiroshima (Fig 1.6), the floating ferry piers at Ujina Port Hiroshima (Fig 1.7) and the floating restaurant in Yokohoma (Fig 1.8) The world largest floating performance platform (Fig 1.9) was built in Singapore Canada has a floating heliport pad in Vancouver (Fig 1.10) and the Kelowna floating bridge on Lake On in British Columbia (Fig 1.11) Norway has the Bergsøysund floating. .. offshore structures can also be used for floating docks, piers and container terminals Many floating docks, piers, and berths are already in use all over 8 Introduction the world Floating piers have been constructed in Hiroshima, Japan, and Vancouver, Canada In Valdez, Alaska, a floating pier was designed for berthing the 50000-ton container ships The main advantage of a floating pier is its constant position... Yumeshima-Maishima Floating Bridge in Osaka, Japan 6 Fig 1.5 Floating Rescue Emergency Base at Osaka Bay, Japan 6 Fig 1.6 Floating island at Onomichi Hiroshima, Japan 6 Fig 1.7 Floating pier at Ujina Port Hiroshima, Japan 6 Fig 1.8 Floating Restaurant in Yokohoma, Japan 7 Fig 1.9 Floating Performance Stage, Singapore 7 Fig 1.10 Floating helicopter pad in Vancouver, Canada 7 Fig 1.11 Kelowna floating bridge in British... Mega-float in Tokyo Bay, Japan Fig 1.3 Floating Oil Storage Base at Kamigoto, Japan Fig 1.4 Yumeshima-Maishima Floating Bridge in Osaka, Japan Fig 1.5 Floating Rescue Emergency Base at Osaka Bay, Japan Fig 1.6 Floating island at Onomichi Hiroshima, Japan Fig 1.7 Floating pier at Ujina Port Hiroshima, Japan 6 Introduction Fig 1.8 Floating Restaurant in Yokohoma, Japan Fig 1.9 Floating Performance Stage, Singapore... analytical solutions of hydroelastic were derived by making use of the exact circular and annular plate solutions and exact velocity potential solutions for circular domains The effectiveness of this anti -motion device is demonstrated by performing the analysis and comparing the results with and without the submerged annular plate strip Further studies were investigated on minimizing the heaving motion. .. exciting applications of VLFS is the floating airport The first contemporary floating airport is constructed in 1943 by US Navy Civil Engineers Corps by connecting pontoons Recently, with the growth of cities and increase in air traffic as well as the rise in land costs in major cities, city planners are considering the possibility of using the coastal waters for urban developments including having floating. .. restaurants in Japan and Hong Kong In addition, VLFS can also be used as floating power plants Floating power plants for various types of energy are already being used in Brazil, Japan, Bangladesh, Saudi Arabia, Argentina, and Jamaica There are proposals to use VLFS for wind and solar power plants (Takagi 2003 and Takagi and Noguchi 2005) and studies on this are already underway The Floating Structure... Singapore Fig 1.10 Floating helicopter pad in Vancouver, Canada Fig 1.11 Kelowna floating bridge in British Columbia, Canada Fig 1.12 Bergsøysund floating bridge, Norway Fig 1.13 Nordhordland Bridge Floating Bridge, Norway 7 Introduction Fig 1.14 Hood Canal Floating Bridge in Washington States, USA Fig 1.15 Dubai Floating Bridge in Dubai, United Arab Emirates Source: Fig 1.2 ~ 1.8 and 1.10 ~ 1.14 from . INNOVATIVE SOLUTIONS FOR MINIMIZING DIFFERENTIAL DEFLECTION AND HEAVING MOTION IN VERY LARGE FLOATING STRUCTURES PHAM DUC CHUYEN NATIONAL UNIVERSITY OF SINGAPORE. NATIONAL UNIVERSITY OF SINGAPORE 2009 INNOVATIVE SOLUTIONS FOR MINIMIZING DIFFERENTIAL DEFLECTION AND HEAVING MOTION IN VERY LARGE FLOATING STRUCTURES PHAM DUC CHUYEN B.Eng assumptions, shapes and models 13 1.2.2 VLFS and water interaction modeling 15 1.2.3 Minimizing differential deflection in VLFS 17 1.2.4 Minimizing motion in VLFS 18 1.3 Objectives and scope of