- 1. 2011 Bentley Systems, IncorporatedAccidental Loading
2. Design Philosophy 2011 Bentley Systems, IncorporatedAccidents
will happen because they are accidents.Design philosophy is to
prevent an accident developinginto a catastrophe. Design to:
Maintain usability of escape ways Maintain integrity of shelter
areas Maintain global load bearing capacity Protection of the
environment2 | WWW.BENTLEY.COM 3. Accidental Loading Design 2011
Bentley Systems, Incorporated Some typical accidental events on
offshore structures are : Ship Impact Dropped Object Blast &
Fire Loading3 | WWW.BENTLEY.COM 4. Accidental Loading Design 2011
Bentley Systems, IncorporatedAccidental events generally involve
large plastic strains. To analyze and design against accidental
events requires software tools capable of predicting: Dynamic
inertial loading * Geometric non- linearity Material non- linearity
* API RP 2FB recommends the use of dynamic analysis for blast
loading4 | WWW.BENTLEY.COM 5. Dynamic Inertial Loading 2011 Bentley
Systems, IncorporatedSACS DYNAMIC RESPONSE MODULEAllows for linear,
quadratic, or cubic interpolation for the time history
input.Variable time step integration procedure.Time history plots
including modal responses, overturning moments, base shear,
etc.Generation of equivalent static loads.Generation of incremental
loads for Elasto/Plastic analysis5 | WWW.BENTLEY.COM 6. Geometric
and Material Nonlinearities 2011 Bentley Systems, Incorporated SACS
COLLAPSE MODULE Gradual development of a plastic hinge through the
member crosssection Development of plastic hinges anywhere along
the length of themember Local Buckling Joint Flexibility Joint
Failure Member Rupture Pile Plasticity User defined strain
hardening6 | WWW.BENTLEY.COM 7. 7Beam Elements 2011 Bentley
Systems, Incorporated Collapse allows for hinge formation at any
point along member length bysub dividing the member into
sub-elements (maximum of 20, default is 8)and monitor the stress
level at each sub-element. Not restricted to hinge formation at
member end an center this predefines the failure mechanism7 |
WWW.BENTLEY.COM Collapse 8. 8Beam Elements 2011 Bentley Systems,
Incorporated Collapse predicts the gradual development of plastic
hingethrough a member cross section by:Dividing the cross-section
into sub-areas and monitoring the stresslevels in each sub-area. By
default tubular cross sections are divided into 12 sub-areas.8 |
WWW.BENTLEY.COM Collapse 9. 9Beam Elements 2011 Bentley Systems,
Incorporated - Member Cross Section Sub-Areas for different cross
sections9 | WWW.BENTLEY.COM Collapse 10. 10Plate Elements 2011
Bentley Systems, Incorporated Collapse allows plasticity to occur
gradually through the plate thickness.Sub-divide the plate
thickness into sub-layers (5).10 | WWW.BENTLEY.COMCollapse 11.
11Yield Criterion 2011 Bentley Systems, Incorporated Collapse uses
Von Mises-Hencky yield Criterion to determine the onsetof
plasticity.11 | WWW.BENTLEY.COM Collapse 12. 12Local Buckling 2011
Bentley Systems, IncorporatedThree methods available to predict
local buckling(1) API LRFD(2) Marshall, Gates et el(3) API Bulletin
2UA moment free hinge is inserted at the locationof a local
buckling point axial capacity retained12 | WWW.BENTLEY.COMCollapse
13. 13Joint Flexibility 2011 Bentley Systems, IncorporatedJoint
Flexibility Distortion of chord cross section dueto forces in the
brace and chord.Particularly important for old structureswhere
joint cans were not used.Collapse has two methods implementedto
predict joint flexibility.These being:(1) Fesslers Approach
(linear)(2) MSL Approach (non-linear)13 | WWW.BENTLEY.COMCollapse
14. Dynamic-Nonlinear Analysis 2011 Bentley Systems,
IncorporatedSACINP(Model File) DYNPAC(Modal Analysis) CLPINPMode
File(partial)Mass File DYRINP DYNAMIC RESPONSE (Force-Time History
Analysis)CLPINA DYROCI (full) COLLAPSE(Non-Linear Analysis)14 |
WWW.BENTLEY.COM 15. Ship Impact 2011 Bentley Systems,
IncorporatedImpact Design Criterion: Low Energy (Operational
Impact)Jacket bracing designed to survive operational impact
(partial yielding at point ofimpact). High Energy (Accidental
Impact)Jacket legs designed to survive accidental impact. Face and
leg Joints to survive accidental impact loading.Jacket bracing
allowed to fail Structure designed to survive loss of
bracemember.allowed).15 | WWW.BENTLEY.COM 16. 2011 Bentley Systems,
Incorporated Ship ImpactTotal Impact (Kinetic) Energy:E = a m V2m =
vessel massa = added mass coefficient (1.4 broadside and 1.1 for
bow/stern )V = vessel velocityGulf of Mexico : m=1000 metric tonsV=
0.5 m/s (operational)16 | WWW.BENTLEY.COM 17. Ship Impact 2011
Bentley Systems, IncorporatedKinetic Energy Absorbed Through:
Localized plastic deformation (denting) Overall elasto plastic
deformation of member Fendering devices (if fitted) Global
deformation of platform Deformation of the ship itself17 |
WWW.BENTLEY.COM 18. Ship Impact 2011 Bentley Systems, Incorporated
Mesh the impacted member to account for local denting.18 |
WWW.BENTLEY.COM 19. Ship Impact 2011 Bentley Systems, Incorporated
Mesh joint to account for local indentation effects19 |
WWW.BENTLEY.COM 20. Ship Impact 2011 Bentley Systems,
IncorporatedTo account for energy absorbed by ship deformation, use
DNV shipindentation curves for 5000 ton vessel impacting a 1.5 m
cylinder.20 | WWW.BENTLEY.COM 21. Ship Impact 2011 Bentley Systems,
IncorporatedDynamic Response Input Added Mass Coefficient. Mass
Velocity Direction Distance Impact Joint21 | WWW.BENTLEY.COM 22.
Ship Impact 2011 Bentley Systems, IncorporatedDynamic Response
Results shipstructure22 | WWW.BENTLEY.COM 23. Ship Impact 2011
Bentley Systems, IncorporatedCollapse Results23 | WWW.BENTLEY.COM
24. Dropped Object 2011 Bentley Systems, Incorporated Dropped
Object AnalysisCertain locations such as crane loading and drilling
areasare subject to dropped objects.The platform should survive the
initial impact from a droppedobject and meet the post-impact
criteria to survive a oneyear environmental load in addition to
normal operatingconditions. Dropped object analysis also required
to determine safe lift heights for platform modification/repair to
avoid production shutdown which can be costly.24 | WWW.BENTLEY.COM
25. Dropped Object 2011 Bentley Systems, IncorporatedTotal Impact
Energy:E = mghm = mass of objectg = gravitational accelerationh =
height from which the object is dropped25 | WWW.BENTLEY.COM 26.
Dropped Object 2011 Bentley Systems, Incorporated Dynamic Response
Input Mass InitialHeight Impactvelocityjoint26 | WWW.BENTLEY.COM
27. Dropped Object 2011 Bentley Systems, Incorporated Dynamic
Response/Collapse Results IMPACT JOINT DISPLACEMENT27 |
WWW.BENTLEY.COM 28. Accidental Loading Design 2011 Bentley Systems,
Incorporated Collapse Results28 | WWW.BENTLEY.COM 29. Blast
Analysis 2011 Bentley Systems, IncorporatedPrimary objectives for
blast resistant design are: Personnel safety Controlled Shutdown
Financial Considerations Environmental considerationsAPI RP 2FB
specifications requires a Ductility LevelBlast (DLB) design for low
probability, highconsequence extreme events.A DLB design requires a
dynamic analysis toaccounts for inertia loading and a
largedeflection analysis to account for geometric andmaterial
non-linear effects.A DLB design is required for temporary
refuge,safe muster areas and escape routes..29 | WWW.BENTLEY.COM
30. Blast Analysis 2011 Bentley Systems, Incorporated Blast
analysis requires definition of Blast Wave:: Two Types of Blast
WavesShock Wave 1. Sudden pressure rise.- Explosions from
materialsin liquid or solid form- Extremely energetic vapor
Idealized profilecloud explosionPressure Wave 2. Gradual pressure
rise Design of Blast Resistant Buildings in Petrochemical
Facilities30 | WWW.BENTLEY.COM 31. Blast Analysis 2011 Bentley
Systems, IncorporatedDynamic Response Input: Time Load SACSFactor
Load case31 | WWW.BENTLEY.COM 32. Blast Analysis 2011 Bentley
Systems, IncorporatedDynamic Response Results:32 | WWW.BENTLEY.COM
33. 2011 Bentley Systems, Incorporated Parvinder Jhita Product
Manager - SACS Bentley Systems Inc 2113 38th Street Kenner LA 70065
Telephone (504) 443 5481 [email protected] |
WWW.BENTLEY.COM
