Marine Structures: 37 years at DTU. Preben Terndrup Pedersen

Transcription

1 Marine Structures: 37 years at DTU By Preben Terndrup Pedersen

2 How have I spend my professional life? Head of Department of Mechanical Engineering, DTU Leader of Mechanical Engineering, Energy and Production Sector of DTU Professor of Strength of Marine Structures at Department of Naval Architecture and Offshore Engineering, DTU Visiting researcher at Det norske Veritas, Oslo, Norway Research Fellow at Department of Engineering and Applied Physics at Harvard University, Massachusetts, USA Associate Professor in Theory of Vibrations at DTU Assistant Professor at the Department of Solid Mechanics at DTU Engineer at the Danish Defence Research Establishment 2

3 Teaching, Administration, Committees- Teaching: Strength of marine structures to students at DTU. Contributed to four introductory text books Research education: Main supervisor for 32 ph.d. students within Marine Structures Administration Head of Mechanical Engineering at DTU for 15 years Committees and Boards: International Ship and Offshore Structures Congresses (ISSC) Practical design of ships and offshore structures (PRADS) Class Technical committees (Common Structural Rules, Tankers) Patent Appeal Board, Company Boards, Journal editorial boards Academic evaluation boards, ATV, consultancy 3

4 -and Research Selected Research areas: Strength problems of independent LNG/LPG tanks (JJJ) (1974) Offshore cables and pipelines during laying (1976) The program system I-SHIP STRENGTH (JJJ) (1979) Wave induced loads on ships with large bow flare (JJJ) (1979) Warping stresses in open ship hulls (1983) Upheaval Creep of Buried Marine pipelines (JJJ) (1988) Reliability of Jack-up platforms against Overturning (JJJ) (1991) Ship impact analysis for bottom supported offshore structures (1991) Estimation of the probability for parametric roll of ships in a seaway (JJJ) (2007) Wave induced hull girder loads on containerships (JJJ) (2007) Development of analysis procedures for ship collisions and grounding ( ) 4

5 Strength problems of independent LNG/LPG tanks (with JJJ) (RINA 1974) Applied to: Redesign of LNG carriers under construction Basis for class rules for spherical tanks Containment shells in nuclear power plants 5 Other thin walled shells

6 Offshore cables and pipelines during laying (2D in ISP 1976, 3D in PRADS 1987) Applied by: Consultants Classification Societies Offshore operators 6

7 ISH Basic strength (with JJJ) Computer Applications (1979) 7

8 Wave induced loads on ships with large bow flare (JJJ) (RINA 1979 and JSR 1981) Applications Background for IACS rules for longitudinal strength Applied for design of a number of ships with fine lines Statistical part of the theory applied to jack-ups Basis for further research 8

9 Warping stresses in open ship hulls (RINA 1983 and JSR 1985) Applications: Beam theory give insight in the mechanics. Used by most classification societies up to year 2000 (nowadays FEA) Many ship designs were analyzed for hull girder stresses, hatch cover deformations, torsional hull girder frequencies, etc. 9

10 Upheaval of Buried Marine pipelines (with JJJ) (MAST 1988) Applications: For stabilization of inter-field pipelines in the North Sea For new design of buried pipelines 10

11 Reliability of Jack-up platforms against Overturning (JJJ) (1991) Applied by Lauritzen, Mærsk Drilling and Mærsk Oil and Gas for: Joint Industry project Site approval Evaluation of new jack up designs and recently offshore windmills 11

12 Ship impact analysis for bottom supported offshore structures (1991) Applied for development of operational rules for supply ships near small platforms in the North Sea 12

13 Estimation of the probability for parametric roll of ships in a seaway (with JJJ) (IUTAM 2007) 13

14 Wave induced extreme hull girder loads on containerships (with JJJ) (SNAME 2007) Applications: American Bureau of Shipping for design of large containerships Being extended for fatigue damage rates 14

15 Fatigue damage rate results, Low and High frequency damage rates per hour (MAST) 15

16 Analysis procedures for ship collisions and grounding 16

17 Why Collision and Grounding Research (Review paper in MAST 2010) Ship collisions and grounding events constitute 60% of all serious accidents Historical data is not suited for new designs and is too scarce to indicate the risk in sensitive geographical areas Research should contribute to improve IMO and class regulations and to identify risk control options. 17

18 A Schematic Illustration: Collisions (RINA symp. 1996) 18

19 Principle for calculation of collision probabilitity (WEGEMT 1995) The number of possible ship-ship collisions: N a = i j Ω( z z i j ) Q V (1) i (1) i Q V (2) j (2) j f (1) i ( z i ) f (2) j ( z j )V ij D ij da Δt The expected number of ship-ship collision is then determined as N ship -ship = P c N a 19

20 Causation Factor Pc: Illustration of critical situation (with PFH: IMO 1998, Solo watch) 20

21 Probability for collision with offshore structures and for grounding. (JEME 2002) 21

22 Application: Risk Control Options Change in collision probability due to change in route such as: Effect of vessel traffic separation schemes Effect of aids to navigation Effect of vessel traffic systems (VTS) Effect of Electronic Navigational Charts (ENC) Effects of pilots in open waterways Change in causation factor due changes in human behavior such as: Effects of manning Effect of simulator training Effect of psychological screening of navigators Changes in ship design such as: Effects of bridge layout and technical equipment such as radar systems Effect of GPS for position fixing and ECDIS. The effect of redundancy of navigational equipment. Effect of ship speed on causation factor (time to react) Effect of improved maneuverability on causation factor (time to react) Effect of reduced probability of engine blackout or rudder failure 22

23 A Schematic Illustration: Collisions 23

24 External Collision Dynamics (MAST 1998) Estimation of the loss in Kinetic Energy Closed-form Solution Velocities, displacements, collision angle and striking location 24

25 Typical Energy Loss Result (MAST 1998) beta=30 beta=60 beta=90 beta=120 beta= Energy Loss [MJ] Collision Location [m] 25

26 The Schematic Illustration 26

27 Internal mechanics (J. Impact Eng. 1993) Method Simple formulae Simplified Analytical approaches Simplified FEM approaches Non-linear FEM simulation Computation Fewest, hand calculations Few, hand calculations Some, special programs Extensive, expensive software 27

28 Application: Risk Control Options related to crashworthiness Innovative designs to: minimize damage extent in ship side Innovative double hull designs Steel sandwich panels Composite and sandwich panels Pre-designed fracture points Deformable inner barrier in tank to prevent oil outflow reduce the striking vessel s bow stiffness (Buffer bow) 28

29 Structural damage estimates in given grounding scenarios Grounding types Powered grounding Drifting grounding On different bottom profiles On sandy or flat hard slopping bottoms, On shoals, or On different types of sharp rocks. 29

30 Powered grounding on a flat sand or rock bottom (with BC-S: MAST JMST 1996) Main consequence is hull girder collapse 30

31 Powered grounding: Translated probabilities for longitudinal damage (with SZ: OE 2000) ( Ldam / L) M V L F = ( ) ( L / L) M V L F dam xtot xtot 31

32 Consequences of C & G damages Fatalities Oil outflow Economic consequences 32

33 Application: Risk analyses for bridges (JEME 2002). 33

34 Collision probability: Four accident Categories: F total = F cat,i + F cat,ii + F cat,iii + F cat,iv Category I: Ships following the main route Category II: Ships which fail to change course Category III: Ships off-course or drifting Category VI: Drifting ships, ships caught in ice, etc 34

35 External Mechanics: Energy released for structural damage 35

36 Internal mechanics: Bow crushing forces (JIE 1993) 36

37 Internal mechanics: Side way and Deck house collision forces 37

38 Internal Mechanics: Consequences 38

39 Application: Risk Control options IMO Formal Safety Proc edure Prevention Aids to Navigation VTS system Pilots Project information/ Basic Information Hazard Identification Risk Assessment Risk Control Options Decision Making/ Recommendations Cost-benefit Assessment Protection A system to stop traffic on the bridge in emergency situations Scantlings of bridge piers and superstructure Artificial islands for protection against ship collisions 39

40 Ship Impact against Protection Islands (MAST 1994 and with MS in SNAJ 1995) 40

41 Resulting Bridge Risk The results of the risk assessment are given for three risk types; Human safety Property Environment Human safety: The risk related to the above listed risk types can be capitalized and given as the expected cost pr. year 41

42 Conclusions on collisions and grounding research A risk based approach provides a rational methodology for assessing collision and grounding events. Most of the tools exist. Demonstrated for bridges and offshore structures. It seems appropriate that IMO through Goal Based Standards puts more focus on risks associated with C&G. Classification societies have through their Common Structural Rules moved towards limit state design. A logical step would be to consider also C & G as Accidental Limit States (ALS) With such regulation and generally agreed tools it is possible to increase collision and grounding safety through a rational selection and development of different risk control options. 42

43 Research areas: An overall structure? Reliability of Complex Marine Structures Loads: Stochastic Modelling of Environment Effect of Accidental Loads. Structural response: Computational Methods & Prototype simulation Etc. Design Criteria: Mechanics of Structural Materials Progressive Collapse 43

44 Marine support services in universities

45 DTU s Three main goals (pillars) Education Research Innovation - within relevant disciplines, -with professional quality 45

46 On the role of a university for - Industrial exploitation of marine structures 46

47 Historical Note on the Universities Role The beginning Teaching First revolution Research basic research applied research development Second revolution Consulting/entrepreneurship important feed-back to ensure relevance Model for innovation: - Technology Push MarketPull Society Pull (IMO, Class..) 47 IMO, Admins, Class Universities Industry, Research Labs

48 The roles of universities within marine technology Train qualified candidates: - Shipbuilding was previously an art (Architecture), but today substantially an applied science, where naval architects must master a wide range of scientific disciplines. Create a window to the scientific development: - New "tools" comes usually from universities. Ex. are: FEM, CFD, Fracture mechanics, probabilistic methods, etc. Cooperation for development of the science base: - Universities are often strong on developing analytical tools - But weak in design - Universities need good external contacts including the selection of promising research areas. 48

49 Education Relevance Curriculum should balance: - Industry s needs of knowledge, skills and attitudes that can create competitiveness, efficiency and profit - Society s needs for sustainable development and value creation Long term sustainable knowledge Quality Research based teaching Qualified and motivated students and scientific personnel Attractive, robust, dynamic learning and working environment 49

50 Research by Engineering Faculty 1. Produce new knowledge and new understanding of marine technical problems 2. Predict long-range problems, with their impact and possible solutions 3. Transfer knowledge end experience from other fields to the marine field 4. Investigate marine problems in the multidisciplinary environment of a university 5. Evaluate the effectiveness of technological developments, and 6. Provide consultancy services on specific problems 50

51 To promote international cooperation Be an attractive research partner Scientific personnel with international experience International study programmes Exchange of students and scientific personnel (guest professors) (networks) International Research projects: EU.., ISSC, ITTC, conferences, workshops, professional organizations Publish research results in esteemed Journals 51

52 Trends and Strategies University for everybody and budget cuts Stimulates productivity and large classes Marine Technology in DK is small in no. of students. Strategic alliances with industry and administrations Competitive recruiting of students and staff Marine technology should be exciting, and challenging to attract the best students Attractive, robust, dynamic learning and working environment Internationalization Quality and relevance in activity Cooperation with selected institutions 52

53 Conclusion The universities should contribute to the maritime complex by: - Training of professional skilled engineers in cooperation with the maritime industries - Provide long-term scientific research that can provide the basis for innovation in the maritime field. Projects should focus on building the scientific competence rather than individual deliverables. - Being an attractive partner for knowledge building. 53

54 Thank you for your attention