Remerciez-le!

Remerciez @Admin pour avoir partagé cet document gratuitement, de la manière la plus simple, en partageant sur les réseaux sociaux.

Seismic Response of Ground-Supported Circular Concrete Tanks By Ahmed Hafez A D

Seismic Response of Ground-Supported Circular Concrete Tanks By Ahmed Hafez A Dissertation presented to Ryerson University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Program of Civil Engineering Toronto, Ontario, Canada, 2012 © Ahmed Hafez 2012 978-0-494-93368-8 Your file Votre référence Library and Archives Canada Bibliothèque et Archives Canada Published Heritage Branch 395 Wellington Street Ottawa ON K1A 0N4 Canada Direction du Patrimoine de l'édition 395, rue Wellington Ottawa ON K1A 0N4 Canada NOTICE: ISBN: Our file Notre référence 978-0-494-93368-8 ISBN: The author has granted a non- exclusive license allowing Library and Archives Canada to reproduce, publish, archive, preserve, conserve, communicate to the public by telecommunication or on the Internet, loan, distrbute and sell theses worldwide, for commercial or non- commercial purposes, in microform, paper, electronic and/or any other formats. The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. In compliance with the Canadian Privacy Act some supporting forms may have been removed from this thesis. While these forms may be included in the document page count, their removal does not represent any loss of content from the thesis. AVIS: L'auteur a accordé une licence non exclusive permettant à la Bibliothèque et Archives Canada de reproduire, publier, archiver, sauvegarder, conserver, transmettre au public par télécommunication ou par l'Internet, prêter, distribuer et vendre des thèses partout dans le monde, à des fins commerciales ou autres, sur support microforme, papier, électronique et/ou autres formats. L'auteur conserve la propriété du droit d'auteur et des droits moraux qui protege cette thèse. Ni la thèse ni des extraits substantiels de celle-ci ne doivent être imprimés ou autrement reproduits sans son autorisation. Conformément à la loi canadienne sur la protection de la vie privée, quelques formulaires secondaires ont été enlevés de cette thèse. Bien que ces formulaires aient inclus dans la pagination, il n'y aura aucun contenu manquant. ii AUTHOR’S DECLARATION AUTHOR'S DECLARATION FOR ELECTRONIC SUBMISSION OF A DISSERTATION I hereby declare that I am the sole author of this dissertation. This is a true copy of the dissertation, including any required final revisions, as accepted by my examiners. I authorize Ryerson University to lend this dissertation to other institutions or individuals for the purpose of scholarly research I further authorize Ryerson University to reproduce this dissertation by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. I understand that my dissertation may be made electronically available to the public. Ahmed Hafez iii Seismic Response of Ground-Supported Circular Concrete Tanks Ahmed Hafez, Doctor of Philosophy, 2012 Department of Civil Engineering Ryerson University ABSTRACT This study is focused on the nonlinear behavior of ground-supported open top circular concrete tanks under the effect of seismic loads. The tank support conditions are considered in this study where both flexible and nonflexible supports are investigated. A comparison between the behavior of reinforced concrete (RC) and prestressed concrete (PC) tanks is undertaken for flexible base condition. The finite element (FE) method is used to study the nonlinear response of circular tanks under dynamic time-history and push-over analysis. Furthermore, the response modification factors (R) included in current practice are evaluated based on the results of nonlinear dynamic and push-over analysis. Several tank configurations with different aspect ratios, construction method, and base conditions are used in this study to attain reliable results and to validate the R- values. The behavior of circular RC tanks under shrinkage effect is also investigated. Moreover, an innovative approach is presented in this study for flexile base tanks in order to further reduce the seismic response of these structures by using passive energy dissipation systems such as fluid viscose dampers (FVD). The results of this study show iv that higher R-values could be applied to fixed base tanks as compared to hinged base tanks. Also, shallower concrete tanks can be assigned higher R-values as compared to tall tanks. The results of this study show that the type of construction affects the tanks ductility. PC tanks show lower ductility as compared to RC tanks. Furthermore, this study shows that the flexible base tanks with seismic cables do not dissipate the seismic forces, as expected, due to the elastic behavior of the seismic cables. Based on the results of the FE analysis, it is shown that, using FVD reduces the tank response under seismic loads. The use of FVD improves the tank serviceability by reducing the concrete cracking. It is concluded that flexible based tanks equipped with FVD can be used as an economically feasible system in high seismic zones. v ACKNOWLEDGMENTS I would like to express my sincere gratitude to my research supervisor Dr. Reza Kianoush, and co-supervisor Dr. Homayoun Abrishami. I am heartily thankful to my supervisor, Dr. Reza Kianoush, whose encouragement, guidance and support from the initial to the final level of my research has enabled me to develop an understanding of the subject. I offer my regards and blessings to all of those who supported me in any respect during the completion of this study. I am deeply and forever indebted to my mother, Mrs. Amal Taher, and to the soul of my father Mr. Hafez Mohamed for their unconditional love, encouragement and support throughout my entire life. My deepest gratitude goes to my dear wife, Mrs. Mona Elkhadem, and my lovely kids, Mohamed, Maryam, and Sayf for their love, support and understanding. Finally, all praises and thanks are to God, the lord of mankind and all that exists for his help, guidance and support. vi TABLE OF CONTENTS AUTHOR’S DECLARATION II ABSTRACT iii ACKNOWLEDGMENTS v TABLE OF CONTENTS vi LIST OF TABLES xii LIST OF FIGURES xiv LIST OF APPENDICES xxi LIST OF SYMBOLS xxii CHAPTER 1 1 INTRODUCTION 1 1.1 General 1 1.2 Research Significance 2 1.3 Objectives, Assumptions, and Limitations 3 1.4 Outline of Thesis 4 CHAPTER 2 8 LITERATURE REVIEW 8 2.1 General 8 2.2 Ground-supported tank classifications 8 2.3 Seismic damage to LCS 13 2.3.1 Damage to steel tanks 14 2.3.2 Damage to concrete LCS 17 2.4 Previous research studies on seismic response of LCS 17 2.5 Response Modification Factor 24 2.6 Cracking of concrete 31 2.7 Characteristics of concrete model 34 2.8 Passive energy dissipation systems 36 2.9 Applicable codes and standards for LCS 42 CHAPTER 3 46 EFFECT OF TANK PARAMETERS ON SEISMIC RESPONSE 46 vii 3.1 General 46 3.2 Tank behavior under seismic loads 47 3.3 ACI 350.3 design requirements and code background 48 3.4 Effect of tank dimensions on hydrodynamic forces 51 3.5 Finite element implementation 56 3.5.1 Tank configuration and design parameters 57 3.5.2 Computer model and FE analysis 58 3.5.3 Model verification 60 3.5.4 Results of FE analysis 63 3.6 Comparison between the results of FE analysis and closed-form solution 68 3.7 Comparison between results of fixed, hinged, and free base tanks 71 3.8 Summary 73 CHAPTER 4 74 PROPERTIES AND FINITE ELEMENT MODELING OF MATERIALS 74 4.1 General 74 4.2 Finite element program ABAQUS/CAE 74 4.2.1 Selection of finite element analysis technique 74 4.2.2 Conditional stability and time increment in the explicit method 77 4.3 Material properties 79 4.3.1 Concrete Model 79 4.3.2 Smeared cracking 79 4.3.3 Brittle cracking 79 4.3.4 Concrete damaged plasticity (CDP) 80 4.3.4.1 Behavior of concrete in tension 80 4.3.4.2 Behavior of concrete in compression 82 4.3.4.3 Behavior of concrete under cyclic loading 83 viii 4.3.5 Stress–strain relationship in concrete 85 4.3.6 Reinforcement 87 4.3.7 Prestressing Tendons 89 4.3.8 Elastomeric bearing pad 90 CHAPTER 5 92 EFFECT OF SHRINKAGE ON CRACKING 92 5.1 General 92 5.2 Concrete shrinkage 93 5.3 Member restraints 93 5.4 Principal of minimum reinforcement and theory of shrinkage cracking 94 5.5 Degree of restraint 101 5.6 Computer model and finite element analysis 104 5.6.1 Tank configuration and design parameters 105 5.6.2 Finite element model 106 5.6.3 Material properties 108 5.6.5 Loads 109 5.7 Results of analysis 109 5.7.1 Free base condition and model verification 110 5.7.2 Hinged base condition 115 5.7.3 Fixed base condition 116 5.7.4 Sensitivity study 118 5.8 Summary 120 CHAPTER 6 121 NONLINEAR BEHAVIOR OF GROUND-SUPPORTED CIRCULAR TANKS UNDER PUSH-OVER ANALYSIS 121 6.1 General 121 6.2 Tank configuration and design parameters 121 ix 6.3 Finite element analysis 126 6.4 Results of push-over FE analysis 126 6.4.1 Mesh sensitivity study 128 6.4.2 Hinged base condition 129 6.4.3 Fixed base condition 139 6.4.4 Free base condition 148 6.4.5 Discussion of the results 149 6.5 Summary 155 CHAPTER 7 156 NONLINEAR BEHAVIOR UNDER TIME-HISTORY ANALYSIS 156 7.1 General 156 7.2 Tank configuration and design parameters 157 7.2.1 Nonflexible base tanks 160 7.2.2 Anchored flexible base tanks 161 7.3 Computer model and finite element analysis 166 7.3.1 Geometry 166 7.3.2 Material properties 167 7.3.3 Damping 168 7.3.4 Boundary conditions and flexible support 169 7.3.5 Loads 171 7.3.5.1 Prestressing 171 7.3.5.2 Earthquake ground forces 172 7.3.5.3 Gravity load 179 7.3.5.4 Hydrostatic load 179 7.3.5.5 Mass 180 uploads/Litterature/ item.pdf