해양구조물 원통구조의 충돌강도와 잔류강도 : Collision Resistance and Residual Strength of Offshore Cylindrical Members

다국어 초록 (Multilingual Abstract)

Collisions against offshore based installations have been identified as one of the major hazards considering potential consequences may vary from minor structural damages to major damages where the structural integrity is threatened, production downtime, pollutions and cost associated with repairs. The present thesis deals with the structural behavior of offshore structural components subjected to accidental loads arising from collision. The focus is given on impact response of tubular members and stiffened cylindrical shell columns, as well as residual strength of the latter in damaged condition.
Relevant experimental data of small-scale, steel, welded offshore structural components is compiled. Additional tests are performed on two ring-stiffened cylinder models which can be useful for future benchmarking of numerical and simplified prediction methods for impact response of similar structures. The experiments are described in detail including the test conditions, exact material properties and the method to track impact response. Numerical models are developed and comparative analysis of experiments is conducted. The credibility of numerical assessment of impact response is discussed. Among others, focus is given on the influence of modeling dynamic material properties and experimental impact conditions. Impact response, various energy dissipation modes and deformation behavior are assessed based on the detailed results obtained through numerical analysis. The most important data utilized is force-displacement curve. The mode of response of the offshore structural components in case of a low velocity impact is found similar to the mode corresponding static force-displacement curve. Further analyses covering various cases and conditions are performed and general findings are summarized.
Existing methods of simple in literature procedures providing force-displacement response are re-visited. Impact response of tubulars is classified and improvements are made based on the methods which describe each energy dissipation mode independently. For the case of stiffened cylinders, the effect of stiffening is included in a simplified manner by smearing the stiffeners. Comparison with test and numerical results are encouraging. Using the simple procedures, insights for accidental limit state design are provided allowing either moderate deformation or keeping the struck structure intact.
Finally, post-damage behavior of stiffened cylinders is investigated. A methodology for residual strength assessment of these structures is developed and checked against axial compression test results taken from the literature. Further investigations are made on the design examples. Based on the numerical results simple formulas are derived for quick estimation of residual strength under various loading conditions.

목차 (Table of Contents)

• Abstract i
• Acknowledgements iii
• Contents iv
• List of Figures vii
• List of Tables xiv
• List of Symbols xv
• Chapter 1
• Introduction 1
• 1.1 Background and motivation 1
• 1.2 Aims and scope of work 6
• 1.3 Outline of the thesis 7
• Chapter 2
• Overview of analysis of ship collisions with offshore installations 8
• 2.1 Introduction 8
• 2.2 Design principles and guidelines 8
• 2.3 Mechanics of collisions 12
• Chapter 3
• Impact response of tubular members 18
• 3.1 Introduction 18
• 3.2 Dynamic impact tests on tubulars 20
• 3.2.1 Details of experiments 20
• 3.2.2 Nonlinear finite element modeling 23
• 3.2.3 Results and discussions 26
• 3.3 Force-displacement curves for tubulars in practice 37
• 3.4 Simplified analysis of impact response 40
• 3.5 ALS design of tubulars against collision 46
• 3.6 Strength design of tubular bracings 50
• 3.7 Final remarks 57
• Chapter 4
• Impact response of ring-stiffened cylinders 58
• 4.1 Introduction 58
• 4.2 Quasi-static denting tests on ring-stiffened cylinders 59
• 4.2.1 Details of experiments 59
• 4.2.2 Nonlinear finite element modeling 60
• 4.2.3 Results and discussions 62
• 4.3 Dynamic impact tests on ring-stiffened cylinders 67
• 4.3.1 Details of experiments 67
• 4.3.2 Nonlinear finite element modeling 78
• 4.3.3 Results 81
• 4.3.4 Discussions 90
• 4.4 Parametric studies 101
• 4.5 Simplified analysis of impact response 106
• 4.5.1 Model for unstiffened cylindrical shells 106
• 4.5.2 Treatment of ring-stiffeners 109
• 4.5.3 Comparison with experimental results 110
• 4.6 Strength design of ring-stiffened cylinders 113
• 4.7 Final remarks 115
• Chapter 5
• Impact response of stringer-stiffened cylinders 116
• 5.1 Introduction 116
• 5.2 Quasi-static denting tests on stringer-stiffened cylinders 117
• 5.2.1 Details of experiments 117
• 5.2.2 Numerical model 119
• 5.2.3 Results and discussions 120
• 5.3 Dynamic impact loading on stringer-stiffened cylinders 125
• 5.4 Simplified analysis of impact response 127
• 5.5 Strength design of stringer-stiffened cylinders 129
• 5.6 Final remarks 130
• Chapter 6
• Residual strength assessment of stiffened cylinders 131
• 6.1 Introduction 131
• 6.2 Finite element modeling of damaged stiffened cylinders 132
• 6.3 Validation of numerical modeling strategy 135
• 6.4 Ultimate strength characteristics of damaged ring-stiffened cylinders 138
• 6.4.1 Axial compression 138
• 6.4.2 Radial pressure 142
• 6.4.3 Combined axial compression and radial pressure 144
• 6.5 Ultimate strength characteristics of damaged stringer-stiffened cylinders 144
• 6.5.1 Axial compression 145
• 6.5.2 Radial pressure 147
• 6.5.3 Combined axial compression and radial pressure 148
• 6.6 Final remarks 149
• Chapter 7
• Conclusions and recommendations for further work 151
• 7.1 Conclusions 151
• 7.2 Recommendations for further work 153
• References 155
• List of Publications 164
• Appendix A - Force-displacement curves for tubulars in practice 166
• Appendix B - Measured damage extents in tubular test models 171
• Appendix C ? Tensile tests 172
• Appendix D ? Imperfections measurement results for ring-stiffened cylinder models 183
• Appendix E ? Measured damage profiles 189
• Appendix F - Accelerometer measurements 194