Topic outline

  • Assignments

    Personal work reported as a learning diary (50% of the course grade)
    This learning diary replaces the exam in the course where group work -based assignments are used to test the application of theory to practice. The learning diary must be individual and reflect the learning with focus at the low-end to theory and relation to former and future studies, in the middle to main theories and their meaning in context of assignment and at the high-end to the open scientific literature on the subject. For each week describe:

    • Grade 1 (50%): Make brief notes of what you did and why: the video lectures you watched, question hours participated, assignments done and any extra reading that helped your learning. Describe the main idea of the week’s lectures and assignments.
    • Grade 2 (60%) Describe what did you learn, where did you learn it from and what did you needed to learn more that the material did not cover? What things helped you to understand the learning objective and what made it more difficult?
    • Grade 3 (70%): Describe what is the relation between the lectures, the articles and the assignment. Explain the main simplifications done in the assignment and their benefits and weaknesses. Focus on mathematics.
    • Grade 4 (80%): What was the core idea of the assumptions used with respect to the theory applied? Describe the validity of these in your assignment? What was the role of this week in the big picture of thin-walled structures (use written description and mathematics)?
    • Grade 5 (90%): Describe what topics from the lectures and assignments were used in the article? What do you need to learn more to understand these articles better?
    Weeks 1-6 contribute each 1/8 to the personal work grade, while the final summary of all weeks contributes 2/8 to the grade. The summary report should be executive summary of the cumulative learning accumulated over the course. Focus on technical details and their connections between different assignments. Note! Simply putting the reports together by Copy and Paste does not bring any points. In is recommended to have the assignment rounds as appendix and the executive summary as the main document. 
     
    Group work (50% of the course grade)
    The course follows Problem-Based-Leaning concepts and utilises a living document that incrementally form larger entity that covers synthesis of the techniques learned during the course. Each week has specific assignment which supports the overall analysis of thin-walled structures. The assignment is supported by video lectures on the topic, selected articles and weekly question hours where students can ask any questions related to their assignments/project. The video lectures and assignments are given in 6 weeks, followed up by 7th extra week dedicated for the wrapping up of the course assignment. 
     
    The assignments are returned to this folder with short description (max 6 pages of main text + unlimited appendixes, template given in Materials) of the: 
     
    1) Introduction to the weekly assignment with review to relevant literature (books, scientific and technical articles), 
    2) Methods used to solve the assignment including their strengths and limitations, 
    3) Main Results including critical review of the quality of them, 
    4) Discussion and reflection to the overall design task, related sub-questions and courses and next steps as group (written text) and as individuals and 
    5) The roles and time allocation of group members in table format (lectures, assignment, self study of literature, meetings).
     
    The tasks covered are:
     
    Assignment 1. Modelling thin-walled structures by FEM (1/8 of the group assignment grade)
    Given: 15.9.2021
    Due: 22.9.2021 09:00
     
    The idea of the assignment is to introduce you to the modelling of thin-walled structures by FEM and create a reference model that we can use to compare the results of the following weeks. You need to create a structural model in Finite Element software (FEMAP, Abaqus, Ansys etc) of large complex structure; this can be for example a stiffened panel. You need solve it and interpret the results. In case you have your own design, feel free to propose it. In the report:

    • Identify the simplifications made: e.g. beams, shells, solids as elements; shape; materials; Loads
    • Include large modification to the model: mesh size variation, opening. 
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 
    • As extra task you can change the mesh size and comment about the stress criteria convergence that should be used in design. 25% extra. 
    Weekly articles:
    Bazant, Z.P. and Zhou, Y., “Why Did the World Trade Center Collapse?—Simple Analysis”, Journal of Engineering Mechanics, 128(1), 2002, pp. 1-6.  
    Romanoff, J., Remes, H., Varsta, P., Reinaldo Goncalves, B., Lillemäe-Avi, I., Körgesaar, M., Jelovica, J. and Liinalampi, S., "Limit state analyses in design of thin-walled marine structures - some aspects on length scales", Journal of Offshore Mechanics and Arctic Engineering, Vol. 142, June 2020, pp. 030801-1-8.
     
    Assignment 2. Ply and large deflections for beams and plates (1/8 of the group assignment grade)
    Given: 22.9.2021
    Due: 29.9.2021 09:00
     
    The idea of the assignment is to demonstrate how material model of a laminate will affect the response of the plate in terms of displacements, strains and stresses. You need to create a lamina with commercial Finite Element package and expose it to in-plane uniform strain or stress. Analyse the responses in terms of displacements and stresses and vary the direction of load with respect to principal direction in order to see the differences in load-carrying mechanism. In the report:

    • Discuss the factors affecting the accuracy of results
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 
    • As extra task you can model a beam with geometrical non-linearity and study the responses and how does it change when the load level changes. 25% extra. 
    Weekly articles:
    Hill, R., “Elastic Properties of Reinforced Solids: Some Theoretical Principles”, Journal of Mechanics and Physics of Solids, 11, 1963, pp. 357-372.
    Sun, C.T. and Vaidya, R.S., “Prediction of Composite Properties from Representative Volume Element”, Composites Science and Technology, 56(1), 1996, pp. 171-179. 
     
    Assignment 3. Laminates and different structural theories (1/8 of the group assignment grade)
    Given: 29.9.2021
    Due: 6.10.2021 09:00
     
    The idea of the assignment is to demonstrate how laminates behave under bending loads. Make a laminate from several plies and report the stacking sequence. Expose the laminate to bending loads with simply supported and pinned boundary conditions. Discuss the effect of boundary conditions to displacements and stress resultants. Change the structural theory from CLT to FSDT and discuss the differences in solutions. In the report: 

    • Discuss the observations you see from different models and reasons for similarities and differences
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 
    • As extra task you can model a beam with very low shear modulus in the middle layers and study the influence to through thickness strains and stresses and discuss how well the presented theories can model such a case. 25% extra. 
    Weekly articles:
    Reddy, J.N., and Averill, R.C., “Advances in the Modeling of Laminated Plates”, Computing Systems in Engineering, 2(5/&), 1991, pp. 541-555. 
    Carrera, E., “Historical review of Zig-Zag theories for multilayered plates and shells”, Applied Mechanics Reviews, 56(3), 2003, pp. 287-308. 
     
    Assignment 4. Offset beams and periodic plates (1/8 of the group assignment grade)
    Given: 6.10.2021
    Due: 13.10.2021 09:00
     
    In the assignment the stiffened panel from Assignment 1 should be analysed using both offset beams attached to a plate and by modelling the entire assembly as orthotropic plate. You should consider: 

    • Case 1: plate and stiffeners are modelled with shell elements
    • Case 2: plate is modelled with shell elements and stiffeners with offset beams
    • Case 3: the whole assembly is modelled with orthotropic shell elements
    The idea of the assignment is to study the relation between accuracy and computational costs between different models and the sensitivity of the implementation of load and boundary conditions to the responses (displacements and stresses).  In the report you need to:

    • Discuss the observations you see from different models and reasons for similarities and differences.
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 
    • As extra task you can change the offset in the case 3 and see how it affects the responses. Think about the analogy to laminates. 25% extra. 
    Weekly articles:
    Avi, E., Lillemäe, I., Niemelä, A. and Romanoff, J., “Equivalent Shell Element for Ship Structural Design”, Ships and Offshore Structures, Vol. 10, No. 3, 2015, pp. 239–255.
    Paik, J.K., “Some recent advances in the concepts of plate-effectiveness evaluation”, Thin-Walled Structures, 46, 2008, pp. 1035–1046.
     
    Assignment 5. Fatigue and vibration and sub-models (1/8 of the group assignment grade)
    Given: 13.10.2021
    Due: 20.10.2021 09:00
     
    The idea of the assignment is to demonstrate the potential and challenges related to sub-models when for example fatigue strength is concerned. You need to create a sub-structuring problem for selected multi-scale problem (for example opening in stiffened panel) and solve both the macro-scale global and micro-scale local problem. Compare fine mesh results (from round 1 and possibly from round 4 as well) to the equivalent model results and investigate how sensitive the result is to boundary conditions used. Run the models for vibrations. In the report you need to:

    • Discuss the observations you see from different models and reasons for similarities and differences.
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 

    Weekly articles:

    Amini, M.A., Dureissex, D., Cartraud, P. and Buannic, N., “A domain decomposition method for problems with structural heterogeneities on the interface: Application to a passenger ship”, Computer Methods in Applied Mechanics and Engineering, 198, 2009, pp. 3452–3463.

    Remes, H., Romanoff, J., Lillemäe, I., Frank, D., Liinalampi, S., Lehto. P. and Varsta, P., “Factors affecting the fatigue strength of thin-plates in large structures”, International Journal of Fatigue, 101, 2017, pp. 397–407

     

    Assignment 6. Buckling, Ultimate and Accidental Strength (1/8 of the group assignment grade)

    Given: 20.10.2021

    Due: 27.10.2021 09:00

    The idea of the assignment is to show how buckling limit state assessment is affected by the discretization employed in the modelling. You need to run all FE-models from round 4 for buckling analysis (eigenfrequency). Also perform and report an experiment or numerical simulation on the stiffened panel, sheet of paper, beer can or toilet paper roll until ultimate strength has been reached. In the report you need to:

    • Discuss on the modelling of the plates and stiffeners and the influence of the simplifications to the buckling strength.
    • Discuss the lessons learned from the assignment and reflect to the lecture slides and the weekly articles available at the web-site. 

    Weekly articles:

    Bazant, Z., “Structural Stability”, International Journal of Solids and Structures, 37, 2000, pp. 55-67.

    Byklum, E. and Amdahl., J., “A simplified method for elastic large deflection analysis of plates and stiffened panels due to local buckling”, Thin-Walled Structures, 40, 2002, pp. 925–953. 

     

    Assignment 7. (2/8 of the group assignment grade)

    Given: 27.10.2021

    Due: 3.11.2021 09:00

    Compose a summary report of all course assignments (final versions) and create an executive summary of the cumulative learning accumulated over the course. Focus on technical details and their connections between different assignments. Note! Simply putting the reports together by Copy and Paste does not bring any points. It is recommended to have the assignment rounds as appendix and the executive summary as the main document. 


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Week 1. Load and material modeling