Presentation of Sesam Genie for Topside Analysis, delivered at SUC by Ole Jan Nekstad from DNV.

1. 1
SesamTM
40 years of success
Efficient engineering of topside structures
Ole Jan Nekstad, Product Director Sesam
3 December 2012

2. Efficient engineering of topside structures
Save man-hours and increase quality
by using the latest available
capabilities in concept technologies
for
- Structure modelling
- Deadweight loads
- Environmental loads
- Forces, stresses, deflections
- Beam/plate code checking
- Fatigue from wave or wind
- Refined fatigue
- ULS, FLS, ALS
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3 December 2012
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3. Topside structures (including modules, flare booms, bridges)
On jacket On floater
- Often members only - Often plates and stiffeners and members
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4. Common challenges in design
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5. The importance of the Sesam design loop
40-60% of engineering time
often spent in evaluation
How fast can you do it over again?
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6. How can Sesam GeniE help you
to design a topside structure
Structure
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7. Structure modelling
Easy to facilitate the range from small to large and complex
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8. Structure modelling
Combine detailed models in
a global model
Beam
- FE results, SCF for beam fatigue,
plate fatigue
Plates
FE beam
FE shell
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9. Structure modelling
Make the complete model in Sesam GeniE
- Beams, plates, trusses, double beams, segmented
members, auto creation of tubular joints,
connections
- Automatic model update when inserting, deleting,
moving, copying
- The model topology is always updated, hence major
changes in the model may easily be performed
- You may be become more productive by using
scripting and parametric modelling
- Several engineers can work on parts of the topside
and merge prior to analysis
- Result evaluation may also be performed on same parts
- Same model and loads may be used for several
loading conditions
Re-use data and continue modelling in GeniE
- Older Sesam models
- Sacs, StaadPro, StruCad3D, Ansys
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10. How can Sesam GeniE help you
to design a topside structure
Deadweight loads
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11. Deadweight loads
From structural mass x gravity
From point masses x gravity
Blanket loads (evenly distributed
mass)
Equipments
Specific pressure loads, point or line
loads
Mass of ice x gravity (same as marine
growth for jacket)
Compartment loads
Temperature loads
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12. Deadweight loads
When jack-up is in “fixed structure” modus. Easy to define compartment loads
- Content and filling degree is enough to compute the acting pressures in the walls
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13. How can Sesam GeniE help you
to design a topside structure
Environmental loads
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14. Topsides/modules on jackets or floaters
Topside on jackets Topside on floaters
- All is done inside Sesam GeniE - Opt. 1 - Integrated: Results from Sesam HydroD
- Wind, current, wave (hydrodynamic frequency or time domain
- Morison theory analysis) imported into Sesam GeniE
- Deterministic, stochastic, time domain - Opt. 2 - No load transfer: Accelerations and
deflections are computed in Sesam HydroD and
- Non-linear pile/soil analysis normally included used as basis for load-cases in Sesam GeniE
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15. Option 1: Topsides/modules on floaters
Waves give deformations and stresses in
topsides and modules
- These are converted to deterministic loads
before import to Sesam GeniE
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16. Option 2: Topsides/modules on floaters
Deformations and accelerations used to define load cases in Sesam GeniE
- Accelerations constant or centripetal (from Sesam HydroD)
- Deformations from global structural analysis (used as prescribed displacements in GeniE)
Sp1: 2mm
Sp2: 3mm
Sp3: 5mm Centripetal
Acceleration
Sp4: 2mm
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17. Topsides/modules on jackets
Codes of practice specify different safety factors for structural mass on various parts
of the structure
Sesam GeniE can work with different load factors for structure mass by using a
utility script as found on the Sesam GeniE SnackPack
- I.e. Force = acceleration x mass x load factor
Lower level loads from mass Upper level loads from Rotational acceleration
x acceleration (x & z-dir) mass x acceleration (z-dir) Harmonic induced wave
motion
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18. How can Sesam GeniE help you
to design a topside structure
Results assessment
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19. Efficient engineering – typical steps
First assessment
- Forces, stresses and deflections
Code checking
- Check against prescriptive standards
Member re-design
- Evaluate the effect of modifying section
properties or code check parameters
- Often many attempts – depends on the
engineer’s experience
Design iteration
- A complete re-run of all to document the
re-design
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20. Beam forces and stresses
Forces and stresses in 2D view as well as tabular
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21. Check deflection ratio against AISC levels
Allowable deflection ratio 180, 240, 360 and scanning all load cases
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22. How can Sesam GeniE help you
to design a topside structure
Code checking of members &
stiffened panels
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23. Code checking in GeniE - members
Supporting
- API WSD 2002/AISC ASD 2005
- API WSD 2005/AISC ASD 2005 (API: 2007, 2010 updates)
- API LRFD 2003/AISC LRFD 2005 (withdrawn by API)
- NORSOK 2004/Eurocode 3 1993 (EC: 2008, 2009, 2010 updates)
- ISO 19902 2007/Eurocode 3 1993 (EC: 2008, 2009, 2010 updates)
- DS 412/449
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24. Document code check results
Graphically – complete model
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25. Document code check results
Graphically – parts of structure only
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26. Efficient redesign of members
Redesign (“design iterations”)
- Step1: Preliminary results when
modifying section, material,
stiffener spacing or buckling length
parameters
- Note: The loads and stiffness
are not updated
- Step2: Commit changes to model
- Step3: Re-run analysis and code
check
- Reports may be automatically
re-created
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27. Redesign – single members
Select a capacity member for redesign
Modify parameters
- Preliminary results automatically computed
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28. Redesign – single members
Look at all details (Full Table)
- Shown with colour coding
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29. Redesign – multiple members
Select capacity members for redesign
Modify parameters
- Preliminary results automatically computed
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30. Redesign – segmented beams
Before and after
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31. Redesign – re-run all from one command
The “Run All” command will
- Update structure from members
- Run analysis
- Generate code check loads (positions)
- Execute code check
Recreation of a report
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32. Code checking of stiffened panels
Create panels
- Panels are independent of analysis and finite
element mesh
Three different options to define panels
- Min Box finds the smallest idealised rectangular
panel possible enclosing the possibly non-
rectangular structural region
- Max Area Moment is an alternative algorithm
finding the major axis based on calculation of
area moment of inertia of the surface. This
algorithm will also work for irregular panel Min Box
shapes
- CSR Tank Default is the algorithm usually used
when doing a CSR Tank (PULS) code check
Max Area Moment
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33. Code checking of stiffened panels – ships and offshore
Code checking according to PULS (DNV RP-C201.2)
- Linear and non-linear
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34. Code checking of stiffened panels - offshore
Yield check of plates – based on membrane stress
- Includes a safety factor S
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35. How can Sesam GeniE help you
to design a topside structure
Multiple analysis
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36. Multiple analysis
The “master”
Multiple analysis in same project model
- E.g. Lifting, transport, in-place
- Varying parameters
- Structure
- Boundary conditions
- Load cases
Lifting Condition Transport Condition In_place Condition
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37. Multiple analysis – graphic results
Different results at your finger-tips
- Bending moments shown
Lifting Condition
Transport Condition
In_place Condition
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38. Multiple analysis – code check results
Different results at your finger-tips
- API WSD and default settings used in example below
Lifting Condition Transport Condition In_place Condition
Max Uf = 2.51 Max Uf = 1.85 Max Uf = 4.58
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39. Multiple analysis
Frigg TCP2 MSF removal
Transportation
MSF: Main Support Frame
Lifting Condition
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40. How can Sesam GeniE help you
to design a topside structure
Fatigue
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41. Fatigue of topsides
Sesam supports 3 options
- Deterministic fatigue (regular waves, time domain wave load
analysis)
- More accurate wave loads (any theory and proper drag)
- Simple and straight forward
- Stochastic fatigue (spectral wave load analysis)
- Structural dynamics and better coverage of environmental
conditions
- Prior to fatigue analysis partial damage may be set
- Time domain fatigue (irregular waves, time domain wave load
analysis) – also known as Rainflow Counting Fatigue (RFC)
- Wave loads to instantaneous free surface (also for irregular
sea states)
- Non-linear pile soil effects
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3 December 2012
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42. Fatigue of topsides
Include a refined shell model (finite element model) in the global model for the
purpose of computing stresses, SCF’s for beam fatigue or direct shell fatigue
Use the GeniE SnackPack to auto
convert from beam to shell
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43. Fatigue of topsides
Results can be used to derive SCF for use in traditional beam fatigue
Results can be used to do fatigue of shells – FE size same as thickness and should
be as quadratic as possible
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44. Safeguarding life, property
and the environment
www.dnv.com
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