DegreeTutors/Non-linear Finite Element Analysis of 2D Catenary & Cable Structures using Python

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Non-linear Finite Element Analysis of 2D Catenary & Cable Structures using Python

Build an iterative solution toolbox to analyse structures that exhibit geometric non-linearity due to large deflections

Contents

Introduction and Course Overview

In this introductory section, we'll set the stage for what's to come by taking a tour of the course and getting some preliminary housekeeping and setup out of the way.
1. Introduction and course overview
  • 9 mins
  • 507 MB
Preview
2. Course prerequisites
  • 3 mins
  • 151 MB
Preview
Support and Lecture Q&A (Please read!)

    ‘Heavy’ Cables - the Linear Solution

    Cables very often undergo changes in their geometry under loading, either due to cable extension or flex in the cable supports - they are the classic example of a non-linear structure. In this section, we're going to establish a linear (closed-form) cable solution that ignores non-linear effects. This will provide a baseline case to test our non-linear code against later.
    3. Section overview
    • 3 mins
    • 114 MB
    Preview
    4. Deriving a linear heavy cable equation
    • 11 mins
    • 140 MB
    5. Accounting for cable self-weight
    • 10 mins
    • 129 MB
    6. Problem-specific boundary conditions
    • 12 mins
    • 180 MB
    7. Solving for max cable tension
    • 24 mins
    • 205 MB
    7.1 Jupyter Notebook (lecture 7)
    • 60.7 KB

    Getting Comfortable with Non-linearity

    In this section, we'll consider sources of non-linearity in structural behaviour before focusing on geometric non-linearity in particular. The aim of this section is to take any mystery out of the term 'geometric non-linearity'. We'll also explore, at concept level, how we might set about solving for the behaviour of a non-linear structure.
    8. Section overview
    • 2 mins
    • 56.7 MB
    Preview
    9. What is non-linear structural behaviour?
    • 13 mins
    • 174 MB
    10. Large deflections and geometric non-linearity
    • 24 mins
    • 366 MB
    11. An iterative solution strategy
    • 15 mins
    • 207 MB

    The Non-linear Stiffness Matrix

    Non-linear structures exhibit a change in their stiffness as their geometry changes - this change in stiffness is literally what leads to the non-linear behaviour since linear structures have a constant stiffness that links applied loads and deflections. In this section, we'll develop a non-linear stiffness matrix that can account for changes in stiffness due to large deformations.
    12. Section overview
    • 2 mins
    • 79.1 MB
    Preview
    13. Building the transformation matrix
    • 10 mins
    • 145 MB
    14. The linear stiffness matrix
    • 10 mins
    • 146 MB
    15. Additional force due to large deflections
    • 13 mins
    • 187 MB
    16. The local non-linear stiffness matrix
    • 9 mins
    • 122 MB
    17. The global non-linear stiffness matrix
    • 14 mins
    • 203 MB

    Building our 2D Solver Toolbox

    Now that we have a stiffness matrix that can reflect progressive stiffening or softening due to large deformations and we understand, conceptually at least, how to iterate towards a solution, it's time to build out the code that can bring these ideas to life. In this section, we'll do the bulk of our code development.
    18. Section overview
    • 2 mins
    • 90.8 MB
    Preview
    19. Initial setup and data import
    • 30 mins
    • 284 MB
    20. Plotting the initial configuration
    • 18 mins
    • 176 MB
    21. Blocking out the main convergence loop
    • 29 mins
    • 323 MB
    22. Building the transformation matrices
    • 10 mins
    • 106 MB
    23. Adding pre-tension to each member
    • 9 mins
    • 90.8 MB
    24. Building the stiffness matrix
    • 15 mins
    • 186 MB
    25. Solving for displacements
    • 8 mins
    • 83.9 MB
    26. Updating the internal force system
    • 8 mins
    • 98.7 MB
    27. Building a convergence test function
    • 7 mins
    • 98 MB
    28. Calculating axial forces
    • 5 mins
    • 62.7 MB
    29. Allowing for smaller external force increments
    • 25 mins
    • 464 MB
    30. Generating a text summary output
    • 13 mins
    • 177 MB
    31. Adding self-weight calculation
    • 15 mins
    • 160 MB
    31.1 Jupyter Notebook (lectures 19-31)
    • 26.2 KB
    Mid-course check-in

      Visualising the Results

      After the heavy-lifting of the previous section, we'll tackle something a little less intensive in this section. We'll build out the data visualisation that brings our solution to life. What we cover in this section will have a lot in common with previous DegreeTutors courses. This time, in addition to some aesthetic improvements, we'll implement a feature that allows us to 'step- through' the converged stages of our solution. 
      32. Section overview
      • 1 min
      • 53.7 MB
      Preview
      33. Plot setup and data selection
      • 10 mins
      • 97.8 MB
      34. Plotting the undeformed structure
      • 6 mins
      • 105 MB
      35. Building a colour scale
      • 17 mins
      • 208 MB
      36. Plotting the deformed structure
      • 6 mins
      • 80.2 MB
      37. Adding axial force labels
      • 6 mins
      • 64.1 MB
      38. Plotting the applied forces
      • 15 mins
      • 217 MB
      39. Plotting the reactions
      • 5 mins
      • 71 MB
      39.1 Jupyter Notebook (lectures 33-39)
      • 29.4 KB

      ‘Heavy’ Cables - the Non-linear Solution

      By now we've nearly come full circle - we have code that performs an iterative analysis that tries to converge on the final state of the structure. In this section, we'll compare our code's results with the linear cable solution we developed at the start of the course. We'll be able to closely approximate the linear solution but also observe the emergence of non-linear behaviour as the axial stiffness of our cable is progressively reduced.
      40. Section overview
      • 2 mins
      • 67.5 MB
      Preview
      41. Exploring the convergence behaviour
      • 21 mins
      • 316 MB
      41.1 Jupyter Notebook (lecture 41)
      • 38.3 KB
      42. Modelling the cable with large axial stiffness
      • 10 mins
      • 121 MB
      43. Introducing non-linearity by reducing the axial stiffness
      • 6 mins
      • 73.1 MB
      43.1 Jupyter Notebook (lectures 42-43)
      • 27.5 KB
      44. Linear vs. Non-linear comparison for a simple truss
      • 12 mins
      • 209 MB
      44.1 Jupyter Notebook (lecture 44)
      • 28.9 KB

      Modelling Initial Geometry in Blender

      In this section, we'll use Blender to model and export the initial geometry of our structure. This will be a huge time-saver when dealing with larger structures. Again this will be similar to previous DegreeTutors courses however this time we'll also introduce Blender's cloth simulation tools which offer a quick and easy way of generating catenary geometry.
      45. Section overview
      • 2 mins
      • 66.7 MB
      Preview
      46. Simulating initial catenary geometry
      • 15 mins
      • 155 MB
      47. Basic geometry data export
      • 9 mins
      • 89.8 MB
      48. Exporting cable definitions
      • 6 mins
      • 53.4 MB
      49. Exporting restraint data
      • 11 mins
      • 111 MB
      50. Exporting force location data
      • 6 mins
      • 61.7 MB
      50.1 Blender File (lectures 46-50)
      • 142 KB

      Mixing Cables and Bars in the Same Model

      In this section, we'll work on the versatility of our toolbox by implementing the ability to combine cable elements that can only resist tension and bar elements that can resist tension and compression in a single structural model. This marks the completion of our toolbox and leaves you in a good position to expand it further.
      51. Section overview
      • 1 min
      • 52.2 MB
      Preview
      52. Modifying our code for different element types
      • 18 mins
      • 272 MB
      52.1 Jupyter Notebook (lecture 52)
      • 28.4 KB
      53. Analysing a combined cable and bar structure
      • 10 mins
      • 136 MB
      54. Removing slack cable elements
      • 21 mins
      • 349 MB
      54.1 Jupyter Notebook (lecture 54)
      • 48.5 KB
      55. Antenna tower - modelling and analysis
      • 16 mins
      • 206 MB
      Preview
      55.1 Jupyter Notebook (lecture 55)
      • 50.6 KB
      55.2 Blender File (lecture 55)
      • 106 KB
      56. Course wrap up & completion certificate
      • 3 mins
      • 145 MB

      Appendix: Introduction to Blender

      A1. How can Blender help us?
      • 7 mins
      • 146 MB
      A2. Downloading and installing Blender
      • 4 mins
      • 60.1 MB
      A3. Blender overview and interface basics
      • 16 mins
      • 219 MB
      A4. Object versus edit mode
      • 11 mins
      • 140 MB
      A5. Basic modelling - rectilinear structures
      • 11 mins
      • 139 MB
      A6. Basic modelling - organic/curved structures
      • 19 mins
      • 302 MB