Table of Contents |
1. | Basic Definitions and Concepts of Structural Mechanics and Theory of Graphs | 1 |
1.1. | Introduction | 1 |
1.1.1. | Definitions | 1 |
1.1.2. | Structural Analysis and Design | 4 |
1.2. | General Concepts of Structural Analysis | 5 |
1.2.1. | Main Steps of Structural Analysis | 5 |
1.2.2. | Member Forces and Displacements | 6 |
1.2.3. | Member Flexibility and Stiffness Matrices | 7 |
1.3. | Important Structural Theorems | 11 |
1.3.1. | Work and Energy | 11 |
1.3.2. | Castigliano's Theorems | 13 |
1.3.3. | Principle of Virtual Work | 13 |
1.3.4. | Contragradient Principle | 16 |
1.3.5. | Reciprocal Work Theorem | 17 |
1.4. | Basic Concepts and Definitions of Graph Theory | 18 |
1.4.1. | Basic Definitions | 19 |
1.4.2. | Definition of a Graph | 19 |
1.4.3. | Adjacency and Incidence | 20 |
1.4.4. | Graph Operations | 20 |
1.4.5. | Walks, Trails and Paths | 21 |
1.4.6. | Cycles and Cutsets | 22 |
1.4.7. | Trees, Spanning Trees and Shortest Route Trees | 23 |
1.4.8. | Different Types of Graphs | 23 |
1.5. | Vector Spaces Associated with a Graph | 25 |
1.5.1. | Cycle Space | 26 |
1.5.2. | Cutset Space | 26 |
1.5.3. | Orthogonality Property | 26 |
1.5.4. | Fundamental Cycle Bases | 27 |
1.5.5. | Fundamental Cutset Bases | 27 |
1.6. | Matrices Associated with a Graph | 28 |
1.6.1. | Matrix Representation of a Graph | 29 |
1.6.2. | Cycle Bases Matrices | 32 |
1.6.3. | Special Patterns for Fundamental Cycle Bases | 33 |
1.6.4. | Cutset Bases Matrices | 34 |
1.6.5. | Special Patterns for Fundamental Cutset Bases | 34 |
1.7. | Directed Graphs and Their Matrices | 35 |
| References | 37 |
2. | Optimal Force Method: Analysis of Skeletal Structures | 39 |
2.1. | Introduction | 39 |
2.2. | Static Indeterminacy of Structures | 40 |
2.2.1. | Mathematical Model of a Skeletal Structure | 41 |
2.2.2. | Expansion Process for Determining the Degree of Static Indeterminacy | 42 |
2.3. | Formulation of the Force Method | 46 |
2.3.1. | Equilibrium Equations | 46 |
2.3.2. | Member Flexibility Matrices | 49 |
2.3.3. | Explicit Method for Imposing Compatibility | 52 |
2.3.4. | Implicit Approach for Imposing Compatibility | 53 |
2.3.5. | Structural Flexibility Matrices | 55 |
2.3.6. | Computational Procedure | 55 |
2.3.7. | Optimal Force Method | 60 |
2.4. | Force Method for the Analysis of Frame Structures | 60 |
2.4.1. | Minimal and Optimal Cycle Bases | 61 |
2.4.2. | Selection of Minimal and Subminimal Cycle Bases | 62 |
2.4.3. | Examples | 67 |
2.4.4. | Optimal and Suboptimal Cycle Bases | 69 |
2.4.5. | Examples | 72 |
2.4.6. | An Improved Turn Back Method for the Formation of Cycle Bases | 75 |
2.4.7. | Examples | 76 |
2.4.8. | Formation of B0 and B1 Matrices | 78 |
2.5. | Generalized Cycle Bases of a Graph | 82 |
2.5.1. | Definitions | 83 |
2.5.2. | Minimal and Optimal Generalized Cycle Bases | 85 |
2.6. | Force Method for the Analysis of Pin-Jointed Planar Trusses | 86 |
2.6.1. | Associate Graphs for Selection of a Suboptimal GCB | 86 |
2.6.2. | Minimal GCB of a Graph | 89 |
2.6.3. | Selection of a Subminimal GCB: Practical Methods | 89 |
2.7. | Algebraic Force Methods of Analysis | 91 |
2.7.1. | Algebraic Methods | 91 |
| References | 98 |
3. | Optimal Displacement Method of Structural Analysis | 101 |
3.1. | Introduction | 101 |
3.2. | Formulation | 101 |
3.2.1. | Coordinate Systems Transformation | 102 |
3.2.2. | Element Stiffness Matrix Using Unit Displacement Method | 105 |
3.2.3. | Element Stiffness Matrix Using Castigliano's Theorem | 109 |
3.2.4. | The Stiffness Matrix of a Structure | 111 |
3.2.5. | Stiffness Matrix of a Structure; an Algorithmic Approach | 116 |
3.3. | Transformation of Stiffness Matrices | 118 |
3.3.1. | Stiffness Matrix of a Bar Element | 118 |
3.3.2. | Stiffness Matrix of a Beam Element | 120 |
3.4. | Displacement Method of Analysis | 122 |
3.4.1. | Boundary Conditions | 124 |
3.4.2. | General Loading | 125 |
3.5. | Stiffness Matrix of a Finite Element | 128 |
3.5.1. | Stiffness Matrix of a Triangular Element | 129 |
3.6. | Computational Aspects of the Matrix Displacement Method | 132 |
| References | 135 |
4. | Ordering for Optimal Patterns of Structural Matrices: Graph Theory Methods | 137 |
4.1. | Introduction | 137 |
4.2. | Bandwidth Optimisation | 138 |
4.3. | Preliminaries | 140 |
4.4. | A Shortest Route Tree and Its Properties | 142 |
4.5. | Nodal Ordering for Bandwidth Reduction | 142 |
4.5.1. | A Good Starting Node | 143 |
4.5.2. | Primary Nodal Decomposition | 145 |
4.5.3. | Transversal P of an SRT | 146 |
4.5.4. | Nodal Ordering | 146 |
4.5.5. | Example | 147 |
4.6. | Finite Element Nodal Ordering for Bandwidth Optimisation | 147 |
4.6.1. | Element Clique Graph Method (ECGM) | 149 |
4.6.2. | Skeleton Graph Method (SkGM) | 149 |
4.6.3. | Element Star Graph Method (EStGM) | 150 |
4.6.4. | Element Wheel Graph Method (EWGM) | 151 |
4.6.5. | Partially Triangulated Graph Method (PTGM) | 152 |
4.6.6. | Triangulated Graph Method (TGM) | 153 |
4.6.7. | Natural Associate Graph Method (NAGM) | 153 |
4.6.8. | Incidence Graph Method (IGM) | 155 |
4.6.9. | Representative Graph Method (RGM) | 156 |
4.6.10. | Computational Results | 157 |
4.6.11. | Discussions | 158 |
4.7. | Finite Element Nodal Ordering for Profile Optimisation | 160 |
4.7.1. | Introduction | 160 |
4.7.2. | Graph Nodal Numbering for Profile Reduction | 162 |
4.7.3. | Nodal Ordering with Element Clique Graph (NOECG) | 164 |
4.7.4. | Nodal Ordering with Skeleton Graph (NOSG) | 165 |
4.7.5. | Nodal Ordering with Element Star Graph (NOESG) | 166 |
4.7.6. | Nodal Ordering with Element Wheel Graph (NOEWG) | 166 |
4.7.7. | Nodal Ordering with Partially Triangulated Graph (NOPTG) | 167 |
4.7.8. | Nodal Ordering with Triangulated Graph (NOTG) | 167 |
4.7.9. | Nodal Ordering with Natural Associate Graph (NONAG) | 168 |
4.7.10. | Nodal Ordering with Incidence Graph (NOIG) | 168 |
4.7.11. | Nodal Ordering with Representative Graph (NORG) | 168 |
4.7.12. | Nodal Ordering with Element Clique Representative Graph (NOECRG) | 170 |
4.7.13. | Computational Results | 170 |
4.7.14. | Discussions | 170 |
4.8. | Element Ordering for Frontwidth Reduction | 171 |
4.9. | Element Ordering for Bandwidth Optimisation of Flexibility Matrices | 174 |
4.9.1. | An Associate Graph | 174 |
4.9.2. | Distance Number of an Element | 175 |
4.9.3. | Element Ordering Algorithms | 175 |
4.10. | Bandwidth Reduction for Rectangular Matrices | 177 |
4.10.1. | Definitions | 177 |
4.10.2. | Algorithms | 178 |
4.10.3. | Examples | 179 |
4.10.4. | Bandwidth Reduction of Finite Element Models | 181 |
4.11. | Graph-Theoretical Interpretation of Gaussian Elimination | 182 |
| References | 185 |
5. | Ordering for Optimal Patterns of Structural Matrices: Algebraic Graph Theory and Meta-heuristic Based Methods | 187 |
5.1. | Introduction | 187 |
5.2. | Adjacency Matrix of a Graph for Nodal Ordering | 187 |
5.2.1. | Basic Concepts and Definitions | 187 |
5.2.2. | A Good Starting Node | 190 |
5.2.3. | Primary Nodal Decomposition | 190 |
5.2.4. | Transversal P of an SRT | 191 |
5.2.5. | Nodal Ordering | 191 |
5.2.6. | Example | 192 |
5.3. | Laplacian Matrix of a Graph for Nodal Ordering | 192 |
5.3.1. | Basic Concepts and Definitions | 192 |
5.3.2. | Nodal Numbering Algorithm | 196 |
5.3.3. | Example | 196 |
5.4. | A Hybrid Method for Ordering | 196 |
5.4.1. | Development of the Method | 197 |
5.4.2. | Numerical Results | 198 |
5.4.3. | Discussions | 199 |
5.5. | Ordering via Charged System Search Algorithm | 203 |
5.5.1. | Charged System Search | 203 |
5.5.2. | The CSS Algorithm for Nodal Ordering | 208 |
5.5.3. | Numerical Examples | 211 |
| References | 213 |
6. | Optimal Force Method for FEMs: Low Order Elements | 215 |
6.1. | Introduction | 215 |
6.2. | Force Method for Finite Element Models: Rectangular and Triangular Plane Stress and Plane Strain Elements | 215 |
6.2.1. | Member Flexibility Matrices | 216 |
6.2.2. | Graphs Associated with FEMs | 220 |
6.2.3. | Pattern Corresponding to the Self Stress Systems | 221 |
6.2.4. | Selection of Optimal γ-Cycles Corresponding to Type II Self Stress Systems | 224 |
6.2.5. | Selection of Optimal Lists | 225 |
6.2.6. | Numerical Examples | 227 |
6.3. | Finite Element Analysis Force Method: Triangular and Rectangular Plate Bending Elements | 230 |
6.3.1. | Graphs Associated with Finite Element Models | 233 |
6.3.2. | Subgraphs Corresponding to Self-Equilibrating Systems | 233 |
6.3.3. | Numerical Examples | 240 |
6.4. | Force Method for Three Dimensional Finite Element Analysis | 244 |
6.4.1. | Graphs Associated with Finite Element Model | 244 |
6.4.2. | The Pattern Corresponding to the Self Stress Systems | 245 |
6.4.3. | Relationship Between γ(S) and b1(A(S)) | 248 |
6.4.4. | Selection of Optimal γ-Cycles Corresponding to Type II Self Stress Systems | 251 |
6.4.5. | Selection of Optimal Lists | 252 |
6.4.6. | Numerical Examples | 254 |
6.5. | Efficient Finite Element Analysis Using Graph-Theoretical Force Method: Brick Element | 257 |
6.5.1. | Definition of the Independent Element Forces | 258 |
6.5.2. | Flexibility Matrix of an Element | 259 |
6.5.3. | Graphs Associated with Finite Element Model | 261 |
6.5.4. | Topological Interpretation of Static Indeterminacy | 263 |
6.5.5. | Models Including Internal Node | 270 |
6.5.6. | Selection of an Optimal List Corresponding to Minimal Self-Equilibrating Stress Systems | 271 |
6.5.7. | Numerical Examples | 272 |
| References | 279 |
7. | Optimal Force Method for FEMS: Higher Order Elements | 281 |
7.1. | Introduction | 281 |
7.2. | Finite Element Analysis of Models Comprised of Higher Order Triangular Elements | 281 |
7.2.1. | Definition of the Element Force System | 282 |
7.2.2. | Flexibility Matrix of the Element | 282 |
7.2.3. | Graphs Associated with Finite Element Model | 282 |
7.2.4. | Topological Interpretation of Static Indeterminacies | 284 |
7.2.5. | Models Including Opening | 287 |
7.2.6. | Selection of an Optimal List Corresponding to Minimal Self-Equilibrating Stress Systems | 290 |
7.2.7. | Numerical Examples | 291 |
7.3. | Finite Element Analysis of Models Comprised of Higher Order Rectangular Elements | 297 |
7.3.1. | Definition of Element Force System | 298 |
7.3.2. | Flexibility Matrix of the Element | 300 |
7.3.3. | Graphs Associated with Finite Element Model | 301 |
7.3.4. | Topological Interpretation of Static Indeterminacies | 303 |
7.3.5. | Selection of Generators for SESs of Type II and Type III | 307 |
7.3.6. | Algorithm | 308 |
7.3.7. | Numerical Examples | 309 |
7.4. | Efficient Finite Element Analysis Using Graph-Theoretical Force Method: Hexa-Hedron Elements | 316 |
7.4.1. | Independent Element Forces and Flexibility Matrix of Hexahedron Elements | 317 |
7.4.2. | Graphs Associated with Finite Element Models | 321 |
7.4.3. | Negative Incidence Number | 325 |
7.4.4. | Pattern Corresponding to Self-Equilibrating Systems | 325 |
7.4.5. | Selection of Generators for SESs of Type II and Type III | 331 |
7.4.6. | Numerical Examples | 334 |
| References | 338 |
8. | Decomposition for Parallel Computing: Graph Theory Methods | 341 |
8.1. | Introduction | 341 |
8.2. | Earlier Works on Partitioning | 342 |
8.2.1. | Nested Dissection | 342 |
8.2.2. | A Modified Level-Tree Separator Algorithm | 342 |
8.3. | Substructuring for Parallel Analysis of Skeletal Structures | 343 |
8.3.1. | Introduction | 343 |
8.3.2. | Substructuring Displacement Method | 344 |
8.3.3. | Methods of Substructuring | 346 |
8.3.4. | Main Algorithm for Substructuring | 348 |
8.3.5. | Examples | 348 |
8.3.6. | Simplified Algorithm for Substructuring | 350 |
8.3.7. | Greedy Type Algorithm | 352 |
8.4. | Domain Decomposition for Finite Element Analysis | 352 |
8.4.1. | Introduction | 353 |
8.4.2. | A Graph Based Method for Subdomaining | 354 |
8.4.3. | Renumbering of Decomposed Finite Element Models | 356 |
8.4.4. | Computational Results of the Graph Based Method | 356 |
8.4.5. | Discussions on the Graph Based Method | 359 |
8.4.6. | Engineering Based Method for Subdomaining | 360 |
8.4.7. | Genre Structure Algorithm | 361 |
8.4.8. | Example | 364 |
8.4.9. | Computational Results of the Engineering Based Method | 367 |
8.4.10. | Discussions | 367 |
8.5. | Substructuring: Force Method | 370 |
8.5.1. | Algorithm for the Force Method Substructuring | 370 |
8.5.2. | Examples | 373 |
| References | 376 |
9. | Analysis of Regular Structures Using Graph Products | 377 |
9.1. | Introduction | 377 |
9.2. | Definitions of Different Graph Products | 377 |
9.2.1. | Boolean Operation on Graphs | 377 |
9.2.2. | Cartesian Product of Two Graphs | 378 |
9.2.3. | Strong Cartesian Product of Two Graphs | 380 |
9.2.4. | Direct Product of Two Graphs | 381 |
9.3. | Analysis of Near-Regular Structures Using Force Method | 383 |
9.3.1. | Formulation of the Flexibility Matrix | 385 |
9.3.2. | A Simple Method for the Formation of the Matrix AT | 388 |
9.4. | Analysis of Regular Structures with Excessive Members | 389 |
9.4.1. | Summary of the Algorithm | 390 |
9.4.2. | Investigation of a Simple Example | 390 |
9.5. | Analysis of Regular Structures with Some Missing Members | 393 |
9.5.1. | Investigation of an Illustrative Simple Example | 393 |
9.6. | Practical Examples | 396 |
| References | 406 |
10. | Simultaneous Analysis, Design and Optimization of Structures Using Force Method and Supervised Charged System Search | 407 |
10.1. | Introduction | 407 |
10.2. | Supervised Charged System Search Algorithm | 408 |
10.3. | Analysis by Force Method and Charged System Search | 409 |
10.4. | Procedure of Structural Design Using Force Method and the CSS | 414 |
10.4.1. | Pre-selected Stress Ratio | 415 |
10.5. | Minimum Weight | 420 |
| References | 432 |