Sesam for Collapse Analysis

Pål Dahlberg, Sesam Principal Sales Executive

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17 April, 2012

SesamTM 40 years of success

Sesam for collapse analysis

© Det Norske Veritas AS. All rights reserved.

SesamTM

13 December 2011

Benefits from using Sesam for jackets

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Collapse analysis

Requalification

Extreme conditions,

accidents, fire, explosion

New builds covering

entire life cycle

MTO, deflection check,

code check, fatigue

Same model for all stages – can be shared with other units like the floating department

Manage existing

re-analysis models

Understand models over time,

produce and view results

Modification work

- all phases

Design of new parts

Re-design of existing


SesamTM

13 December 2011

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Non-linear analysis - Re-qualification - Accidents - Collapse & large scale deformations - Fire & explosions


SesamTM

13 December 2011

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Packages:

DeepC Coupled global

response

of moored deep water

floating systems

GeniE Design of beam and

plate offshore

structures

HydroD Hydrodynamic

analysis

of ship and floating

offshore structures

The SESAM suite of programs


SesamTM

13 December 2011

Our tools – your solutions – your decisions

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Linear analysis (wave, pile/soil)

Deflections, Stresses,

Code-check, Fatigue, Earthquake

Transportation, lifting


Code-check, Fatigue

xml

Transportation, launching


Code-check, Fatigue

xml

Non-linear analysis,

collapse, accidents,

re-qualifications

fem

../../../../DNV/Workspaces/GeniE_D6100_Rev1/KE_Sacs/Analysis3/Usfos_view.vtf


SesamTM

13 December 2011

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Structural analysis & design

Non-linear analysis - Accidents: Member yields and changes shape

- Impact, Collision, Explosion, Dropped objects

- Geometry changes significantly - Lifting operations, cable structures

- Loads depend on structural response - Wave, current, wind, motions

- Static analysis - Ultimate strength, Energy absorption

- Dynamic simulation (of real events) - Collision, explosion, motions

- Environment (wave, buoyancy, stability, wind)

- Foundation - Pile, soil, spudcan (jack-up)

- Temperature effects - Changed material properties, Fire


SesamTM

13 December 2011

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Non-linear analysis

USFOS is a specialized tool for ultimate resistance

evaluation of typical offshore structures

- Increased efficiency

- Better numerical predictions

- Lower threshold for new users to enter complex physics

The ultimate resistance of a structure is important

for many reasons

- New loading conditions, linear design exceeded, e.g.

- Extreme waves, increased explosion pressure

- Increased platform weight, extra conductors

- Damaged structure (cracks etc) – necessary to repair

immediately?

- Energy absorption performance

- Boat landing, crane operations/dropped objects, vessel

impact etc.


SesamTM

13 December 2011

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Non-linear analysis in Usfos

Why non-linear

- Linear codes cannot describe ductility

(metal)

- Linear codes cannot account for the

change in geometry for increasing

loads

- Usfos includes “all” physical effects and

predicts the “real” behaviour of a

structure


SesamTM

13 December 2011

Importing models into Usfos

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GeniE Sacs

Model Wave loads Soil

Model consistency :

The Sacs input file The GeniE model The Usfos model


SesamTM

13 December 2011

Importing models to Usfos

Migration to Usfos

- Detailed model not needed for Collapse analysis

- This model would benefit from a “clean-up”

- Deck plating Coarse Mesh

- Necessary to get rid of the small gaps

- Beams One element per physical member

- Enough for detection of buckling & Plastic Hinges (end

nodes + middle of beam)

- Gravity + Explicit Deck Loads + Wave load (to be

exported to Usfos)

- More loads can easily be imported to Usfos, but they

should be relevant for collapse analysis

- Remove Dummy beams Not relevant for non-linear

analysis

- Wave loads exported from GeniE as explicit loads

- No need to define wave data and hydrodynamic

coefficients in Usfos

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SesamTM

13 December 2011

Importing models to Usfos

How to do it?

- Start Usfos (Xact) and import the structure and wave load data

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SesamTM

13 December 2011

Collapse analysis

History Plots

- Global Load vs. Displacement of Control Node (normally a node with large displacements)

- Global Stiffness vs. Step Numbers

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SesamTM

13 December 2011

Collapse analysis

Displacements Plastic utilization

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SesamTM

13 December 2011

Collapse analysis

Element forces

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SesamTM

13 December 2011

Boat impact

Boat Impact

- Energy specified by user to be dissipated

- Local Denting of Tube

- Buckling & Plastic Hinges for local Hit Member

- Fracture Criteria based on strains

- In this case when less 0.15

- Global Deformation of the Global Model

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SesamTM

13 December 2011

Boat impact

History Plots (Global Load = 1, means

Max Impact Energy)

- Shown for control node

Plastic utilisation

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SesamTM

13 December 2011

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Safeguarding life, property

and the environment

www.dnv.com

Documents

Sesam for Collapse Analysis