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ANSYS Convergence Regional Conference in Athens
Charis Ntontoros (Dodoros)
 30th of June, 2016
2
 Introductory Information:
 Experienced on Strength Calculations of Ship and Offshore
Structures
 Independent Structu...
30-6-20163
 Current Presentation Demonstrates two Analyses
Performed with Ansys:
 Part A:
Static Analysis on Rock-Dumpin...
4
 A Few Words on the Project:
 Clients based on the maritime sector always need to increase
their operational abilities...
5
 Rock - Dumping Vessel in Figures…
Part A: Static Analysis on Rock-Dumping Fallpipe Tower
Structure
30-6-2016ANSYS Conv...
6
 Rock - Dumping Vessel in Figures…
Part A: Static Analysis on Rock-Dumping Fallpipe Tower
Structure
30-6-2016
Fall Pipe...
7
 A Few Words on the Project :
 The fall pipe tower, located at the deck of the vessel, is
designated to carry the resu...
8
 Pre-Processing: Creating the Structural Model
 Model has been created in SpaceClaim
 Model consists of Surfaces and ...
9
 Pre-Processing: Preparing the Calculation Model
 Importing to Ansys Mechanical
 Preparing Name Selections and Meshin...
10
 Pre-Processing: Preparing the Calculation Model
 Element Types Used:
Shell181, Beam188, Mass21, Conta175, Target170
...
11
 Pre-Processing: Preparing the Calculation Model
Part A: Static Analysis on Rock-Dumping Fallpipe Tower
Structure
30-6...
12
 Pre-Processing: Preparing the Calculation Model
 The beam like structure has been modeled with surfaces for 1
meter ...
13
 Pre-Processing: Preparing the Calculation Model
Part A: Static Analysis on Rock-Dumping Fallpipe Tower
Structure
30-6...
14
 Pre-Processing: Preparing the Calculation Model
 Multiple equipment was installed such as Winches, Pulleys etc.
 Eq...
15
 Pre-Processing: Preparing the Calculation Model
Part A: Static Analysis on Rock-Dumping Fallpipe Tower
Structure
30-6...
16
 Pre-Processing: Preparing the Calculation Model
 Boundary Conditions:
The model has been fixed constrained on the no...
17
 Post-Processing: Calculation & Validation of Analysis
 Extend of the Model - Validation
 Stresses were decreased at...
18
 Post-Processing: Calculation & Results
 Stress Results:
 Equivalent and Shear Stresses as required from the classif...
 Post-Processing: Calculation & Validation of Analysis
30-6-201619
 Stress Results:  Stiffness Results:
Part A: Static ...
20
 Post-Processing: Detailed Analysis, SubModeling &
Reporting
 Detailed stress analysis:
 Focusing on peak stresses
...
21
 A Few Words on the Project:
 Self-elevating, Jack-Up vessels are commonly used for multiple
purposes in offshore pro...
22
 The Jack-Up Vessel in Figures…
Part B: Vibration Analysis on Thruster Foundation Structure
30-6-2016ANSYS Convergence...
23
 A Few Words on the Project:
 The several structural areas of such vessels require detailed
engineering analysis
 On...
24
 The Thruster Foundation & Rudder Propeller:
Part B: Vibration Analysis on Thruster Foundation Structure
30-6-2016ANSY...
25
 A Few Words on the Project:
 Thruster foundations are subjected to vibrational loads originated
by the rudder propel...
26
 A Few Words on the Project :
 First, a modal analysis is performed
 The frequencies under which the Thruster Founda...
27
 Pre-Processing:
 Modeling and Preparation of the Model in Ansys for calculation, is
very similar to the method follo...
28
 Post-Processing: Modal Analysis
 It was known by the Rudder Propeller Manufacturer that the
propeller frequency rang...
29
 Post-Processing: Modal Analysis
Part B: Vibration Analysis on Thruster Foundation Structure
30-6-2016ANSYS Convergenc...
30
 Pre-Processing: Harmonic Analysis (Forced Vibration)
 2 type of loads have been applied (Moments and Forces)
 A poi...
31
 Post-Processing: Harmonic Analysis (Forced Vibration)
 Peak stresses are noted at the frequency area close to the
ei...
32
 Post-Processing: Harmonic Analysis (Forced Vibration)
 Relevant Stress Plots are exported from Ansys Mechanical at t...
33
 Post-Processing: Conclusions
 It is concluded that a fatigue analysis is required for the
assessment of the service ...
34
!THANK YOU FOR YOU ATTENTION!
ANSYS Convergence Regional Conference in Athens
30-6-2016ANSYS Convergence Regional Confe...
18-3-2015Froude Lunchlezing35
Your future, in the Maritime Industry
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Charis Ntontoros (Dodoros) presentation at ANSYS Convergence Conference 2016

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Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure
Part B: Vibration Analysis on Thruster Foundation Structure

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Charis Ntontoros (Dodoros) presentation at ANSYS Convergence Conference 2016

  1. 1. ANSYS Convergence Regional Conference in Athens Charis Ntontoros (Dodoros)  30th of June, 2016
  2. 2. 2  Introductory Information:  Experienced on Strength Calculations of Ship and Offshore Structures  Independent Structural Engineer based in Greece  Partner of C-Job & Partners BV  Naval Architecture and Engineering Office based in the Netherlands  Project References: Passenger, Cargo Ships – Heavy Lift Vessels with Cranes of Operational Capacity up to 150 tons, Yachts…  Dredgers, Rock Dumping Vessels, Jack-Up Vessels, Tugs..  Able to Perform Projects from Concept to Detail Design ANSYS Convergence Regional Conference in Athens 30-6-2016ANSYS Convergence Regional Conference in Athens
  3. 3. 30-6-20163  Current Presentation Demonstrates two Analyses Performed with Ansys:  Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure  Part B: Vibration Analysis on Thruster Foundation Structure ANSYS Convergence Regional Conference in Athens ANSYS Convergence Regional Conference in Athens
  4. 4. 4  A Few Words on the Project:  Clients based on the maritime sector always need to increase their operational abilities by upgrading their offshore structure capabilities  Rock-dumping vessels of 26,000 tons loading capacity are used to install rocks in water depths up to 1,500 meters by means of flexible fallpipe buckets Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  5. 5. 5  Rock - Dumping Vessel in Figures… Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  6. 6. 6  Rock - Dumping Vessel in Figures… Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016 Fall Pipe Tower ANSYS Convergence Regional Conference in Athens
  7. 7. 7  A Few Words on the Project :  The fall pipe tower, located at the deck of the vessel, is designated to carry the resulting loads from installed equipment during operation  The structure has been designed to operate in the most efficient way in respect to the steel strength characteristics, operational effectiveness and weight optimization  34 different equipment items are installed on the fall pipe tower structure, such as Winches and Pulleys  Several Working and Sailing Scenarios can occur during the lifetime of the vessel  Multiple Load Cases (about 40) have been investigated  All Results are assessed in accordance to the rules and regulations provided by the certified classification societies  Using Ansys, a representation of the Stress Occurrences and Deflections is succeeded Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  8. 8. 8  Pre-Processing: Creating the Structural Model  Model has been created in SpaceClaim  Model consists of Surfaces and Lines meshed with Plates and Beam Elements  Some parts were already modeled with solids in other designing software and later imported in .STEP files in SC  Solids have been converted to Midsurfaces through Midsurface Tool in SC  All parts of the model have been checked for their connectivity (Shared Topology)  Shared Node mesh has been achieved.  Thickness property has been assigned in SC  Parts which have been converted from solids to midsurfaces have kept their thickness property in SC Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  9. 9. 9  Pre-Processing: Preparing the Calculation Model  Importing to Ansys Mechanical  Preparing Name Selections and Meshing  Multiple Element Size has been Assigned so as to Minimize Calculation Time Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  10. 10. 10  Pre-Processing: Preparing the Calculation Model  Element Types Used: Shell181, Beam188, Mass21, Conta175, Target170  Tower Structure Consists of Beam Elements  Ship Structure (Hull) Consists of Plate Elements Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  11. 11. 11  Pre-Processing: Preparing the Calculation Model Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens Tower Meshed with Beam Elements Hull Meshed with Plate Elements
  12. 12. 12  Pre-Processing: Preparing the Calculation Model  The beam like structure has been modeled with surfaces for 1 meter height above deck so as to smoothly transit the stresses on the hull structure  Unrealistic Hot Spots were avoided  Tower’s Beam and Ship’s Plate Element Nodes were Connected with Contact Elements  MPC Formulation with Coupled U to ROT  This option is useful when you wish to fully constrain one contact side completely to another. Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  13. 13. 13  Pre-Processing: Preparing the Calculation Model Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  14. 14. 14  Pre-Processing: Preparing the Calculation Model  Multiple equipment was installed such as Winches, Pulleys etc.  Equipment itself was not modeled  Equipment mass was applied at their actual CoG with point masses  In order to simulate the rigidity of the equipment the dummy beams connecting the point mass to the structure were assigned with rigid behavior Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  15. 15. 15  Pre-Processing: Preparing the Calculation Model Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  16. 16. 16  Pre-Processing: Preparing the Calculation Model  Boundary Conditions: The model has been fixed constrained on the nodes of the plate elements at the lower end Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  17. 17. 17  Post-Processing: Calculation & Validation of Analysis  Extend of the Model - Validation  Stresses were decreased at the lower part of the model  Stresses were increased close to the boundaries  Extension of the model was finally sufficient  Reaction Forces retrieved were equal to the sum of the applied loads and self weight of the structure Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  18. 18. 18  Post-Processing: Calculation & Results  Stress Results:  Equivalent and Shear Stresses as required from the classification societies  Top/Bottom – Including out of plane bending (conservative approach)  Stiffness Results:  Total Deflection Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  19. 19.  Post-Processing: Calculation & Validation of Analysis 30-6-201619  Stress Results:  Stiffness Results: Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure ANSYS Convergence Regional Conference in Athens
  20. 20. 20  Post-Processing: Detailed Analysis, SubModeling & Reporting  Detailed stress analysis:  Focusing on peak stresses  Averaging Peak Stress values on the extend defined by Rules  Requesting Membrane Equivalent Stresses with User Defined Result  Sub-Modeling:  Sub-models with refined mesh have been created from the global model in areas of interest  Exporting Stress Plots - Reporting:  Automatically export defined stress plots with “Export Figures” Add-In downloaded from the Ansys Customer Portal Part A: Static Analysis on Rock-Dumping Fallpipe Tower Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  21. 21. 21  A Few Words on the Project:  Self-elevating, Jack-Up vessels are commonly used for multiple purposes in offshore projects, from drilling up to 114 meters depth, to windmill park installations Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  22. 22. 22  The Jack-Up Vessel in Figures… Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  23. 23. 23  A Few Words on the Project:  The several structural areas of such vessels require detailed engineering analysis  One of these areas are the Thruster Foundations on which the Rudder Propellers are bolted at Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  24. 24. 24  The Thruster Foundation & Rudder Propeller: Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  25. 25. 25  A Few Words on the Project:  Thruster foundations are subjected to vibrational loads originated by the rudder propellers  The Rudder Propellers are designed by the manufacturer to operate in a certain frequency range  In accordance to the rudder propeller suppliers, the propeller frequencies are to be “located” in a 25% range away from the thruster foundation eigenfrequencies (natural frequencies), so as to avoid excitation Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens The Thruster Foundation Imported to Ansys
  26. 26. 26  A Few Words on the Project :  First, a modal analysis is performed  The frequencies under which the Thruster Foundation excites are then known  Some of the propeller frequencies given by the manufacturer were belonging in the range of the foundation’s eigenfrequencies, identified in the modal analysis  An Harmonic (Vibrational) Analysis was required  With the Harmonic Analysis it is possible to apply loads on a given frequency range  During the Harmonic Analysis the Force produced by the propeller was induced on the foundation structure on the given frequency by the manufacturer  The Foundation Structure was excited by the propeller induced force  The expected peak stresses were then noted Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  27. 27. 27  Pre-Processing:  Modeling and Preparation of the Model in Ansys for calculation, is very similar to the method followed for the Tower structure project  No further explanation will be provided on this part Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  28. 28. 28  Post-Processing: Modal Analysis  It was known by the Rudder Propeller Manufacturer that the propeller frequency range was between 15Hz and 25Hz  During the Modal Analysis the first 20 Modes of the Thruster Foundation have been requested  From the 20 Modes, the Natural Frequency (Eigenfrequency) for which resonance was noted on the Thruster Foundation was equal to 21.853Hz and 23.267 Hz  2nd and 4th Mode respectively Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  29. 29. 29  Post-Processing: Modal Analysis Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens 2nd Natural Frequency Noted on the Foundation Structure, equal to 21.853Hz 4th Natural Frequency Noted on the Foundation Structure, equal to 23.267Hz
  30. 30. 30  Pre-Processing: Harmonic Analysis (Forced Vibration)  2 type of loads have been applied (Moments and Forces)  A point mass was representing the mass of the Rudder Propeller  Forces, Moments and Point Mass have been Applied on the location where the Rudder Propeller was bolted at, with a Remote Point  Both moment and force loads are applied in the same phase angle in a sinusoidal manner  Moments and Forces have been applied under a frequency range between 15Hz to 25Hz Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  31. 31. 31  Post-Processing: Harmonic Analysis (Forced Vibration)  Peak stresses are noted at the frequency area close to the eigenfrequency of the foundation structure  Relevant Graphs are exported from Ansys Mechanical  Peak Stress at 21.800Hz  Close to 2nd Natural Frequency  Peak Stress at 23.225Hz  Close to 4th Natural Frequency  Max. Peak Stress about 80 Mpa  Can reduce the service life of the vessel Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens @23.225Hz @21.800Hz
  32. 32. 32  Post-Processing: Harmonic Analysis (Forced Vibration)  Relevant Stress Plots are exported from Ansys Mechanical at the frequencies where peaks are noted. @ 23.225Hz Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  33. 33. 33  Post-Processing: Conclusions  It is concluded that a fatigue analysis is required for the assessment of the service life of the structure under the cyclic loads imposed by rudder propeller  Additional reinforcement will further increase the service live of the vessel Part B: Vibration Analysis on Thruster Foundation Structure 30-6-2016ANSYS Convergence Regional Conference in Athens
  34. 34. 34 !THANK YOU FOR YOU ATTENTION! ANSYS Convergence Regional Conference in Athens 30-6-2016ANSYS Convergence Regional Conference in Athens
  35. 35. 18-3-2015Froude Lunchlezing35 Your future, in the Maritime Industry

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