1. Risk control in the use of computer models The reflective approach Iain MacLeod

2. Analysis modelling : The use of mathematical methods to predict the behaviour of systems The introduction of structural mechanics and other predictive technologies in the 19 th century reduced the risk of failure in engineering systems dramatically and has underpinned the phenomenal level of technical innovation since then. One of the great achievements of the human intellect. We can predict the future. But it is not 20/20 vision.

3. The reflective approach to modelling requires the engineer to assess continuously the accuracy and appropriateness of the modelling task being carried out. Reflective thinking

4. Analysis Modelling http://www.imacleod.com

6. The modelling process

8. Ask good questions The validation question: Can the model satisfy the requirements? The verification question: Has the model been correctly implemented? Reflective thinking

9. Question 1 How would you go about validating a model The validation question: Can the model satisfy the requirements?

10. Model validation process List all assumptions made for the model and consider whether or not they are acceptable in relation to the objectives of the model. Find or commission test results

11. Question 2 What questions would you ask at the model development stage?

12. Model validation Is the model capable of satisfying the requirements? Model development process What behaviour needs to be predicted? Have adequate resource been allocated in terms of experienced people? Model optimisation. Is the model the most suitable in the context? Estimate values of critical parameters

13. Question 3 What questions would you ask at the solution stage?

14. Is the data correct? Solution process Software validation: Is the software capable of solving the model? Does it have the needed features? Software verification: Has the software been adequately checked for errors?

15. Question 4 What questions would you ask at output assessment stage?

16. Output assessment process Results verification. Has the model been correctly implemented? Qualitative assessment Do the results look right? Results interpretation. What can be learned about the validity of the model from the results? Quantitative assessment Use checking models? Check against estimates made previously What can be learned from a sensitivity analysis? Should the analysis model be changed in the light of information from the output assessment?

17. Does it look right? Looking at results from a model is rich in potential for understanding behaviour of the system Qualitative assessment Results verification

18. Checking models Quantitative assessment

19. Sleipner Platform before collapse - 1991 No deaths but very high financial loss

21. Sleipner - Plan

22. Sleipner - Mesh at Tricell

23. Sleipner - Back of an envelope check Loss > $700m

24. The technical assessment process

25. Large panel construction - room sized concrete floor slabs, storey height wall panels. Code of practice used : CP114 Structural Design of Reinforced Concrete Buildings - did not address important issues in the design of large panel buildings 4 people killed The Ronan Point Collapse 1968

26. The Derbyshire bulk carrier The design rules for the hatches and the coamings for the hatches did not take account of the wave conditions experienced. AS the ship sizes increased the design rules for the coamings were not changed. Sank in the South China Sea in 1980. 44 people drowned

27. The End