ANSYS Structural Mechanics solutions for the Offshore and ... UK/staticassets/03... · for analyzing a large variety of offshore structures subjected to wave, ... •For Structural

© 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary© 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary

Steve Varnam

ANSYS UK

Seminar

June 14 2011

Engineering Simulation

Software for the Offshore,

Marine and Wave/Tidal

Renewable Energy Industries

Structural Mechanics

© 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary

Agenda

• ANSYS Heritage in Offshore Structural Analysis

– ANSYS ASAS – system level analysis

– ANSYS Mechanical – component level analysis

• Current ANSYS Offshore Structural Analysis

– ANSYS Workbench – System & Component

• Design Modeler

• ANSYS Structural

• Splinter/Fatjack/Beamst

• Links for coupled simulations


ANSYS Offshore Solutions

- proven for Oil & Gas applications

• ANSYS® ASASTM

– Offshore Structural FE Analysis

– Coupled wave/current/wind-structure interaction with

nonlinear structural response

– Fatigue assessment with irregular waves and using

deterministic and spectral methods

• ANSYS® AQWATM

– Fully Integrated Multi-body Hydrodynamic and Motion Analysis

– Mooring, stability, vessel motions in regular and irregular waves

• within time and frequency domain

• with coupled cable dynamics

• with forward speed

• Since 1971, AQWA & ASAS have been developed for analyzing a large

variety of oil & gas offshore structures

– WS Atkins Century Dynamics ANSYS

cargo lowered onto vesselshielding


AQWA & ASAS Overview

- Main Application Areas

• Offshore Structures– Fixed

• Steel Jackets

• Concrete

– Compliant

• Jack-ups

– Floating• FPSOs

• SPARS

• Semi-Submersibles

• Tension Leg Platforms

– Risers

– Offshore Wind Turbines

• Harbours

• Ships– Design

– Offloading

Images courtesy of Arup, Moss Maritime AS, Technip Offshore Finland and REpower Systems AG


ANSYS ASAS

• For more than 30 years, (ANSYS) ASAS has been successfully used

for analyzing a large variety of offshore structures subjected to

wave, current and wind loading

– More than half of all North Sea jacket structures have been designed with the

aid of ASAS

• CAE requirements for Offshore Jacket structures:

– Variety of foundations ranging from concrete gravity-based to steel jackets

– Combined wave, current and wind loading – incl. spectral fatigue

– Variety of local joint flexibility for tubular joints

– Seismic loading

– Soil-pile-structure and soil-pile interaction

– Range from shallow to deep water conditions

– Member and Joint Code Checking (e.g., API RP2a-WSD 21st Ed.)


ANSYS/ASAS

- Typical Applications

• Some example applications

Courtesy of REpower Systems AG

Courtesy of Fraunhofer CWMT

Offshore Wind Turbines

Jacket Structures

Transportation of Spar Truss on Heavy Lift VesselCourtesy of Technip Offshore Finland

Tidal Turbine Structure


ANSYS Mechanical FEA Suite

• Founded in 1970, ANSYS have been

developing generic Mechanical FEA software

for 40 years

• Originally developed for the nuclear industry,

quality was paramount in its design, now

in accordance with ISO quality controls

• ANSYS FEA has the broadest range of

capabilities in the market-place, with

technologies for:

– Linear & Nonlinear (geometric/material)

analyses

– Static, frequency-domain & time-domain

– 0-D to 3-D elements

– Isotropic, anistropic, layered materials

– ....


ANSYS Mechanical Applications

• Offshore Structures

• Pipelines and Risers

• Tubulars, connectors

• BOPs

• Pressure vessels

• Seals

• Hulls

• Etc….

Courtesy of Delta Marine Engineering CompanyCourtesy of ACA Engineering Consultants


Umbillical Analysis

• Geometry built in DesignModeler:

– Core tubing

– 6 helical tubes wrapped around core

– External insulation

• Loads:

– Bent to 36’ radius

– Hydrostatic loads

– End tension

– Gravity


Threaded Connector

• 2D Axisymmetric

model created from

parasolid model

– 9.3e-3” interference

• Loads:

– 10 ksi internal

pressure

– 10,000 lb axial load


Barge Analysis

• Partial deck model

• Maximum load-spreading reaction applied to patches

• Deflections are less than 0.192” in (5 mm) at any point


ANSYS Workbench

• The vehicle for integration of ANSYS Offshore

capabilities is the ANSYS framework called

Workbench

• Workbench acts as a common environment

for all of our mainstream products –

structures, fluids, thermal, electronics ....

• It enables us to interface software modules

directly without going through intermediate

files and manual processes

• For Structural Mechanics users it means

Global & Local analyses in the same system


ANSYS Workbench


Analysis Methods & Solvers

Technology Components

Geometry & Mesh

Materials

Boundaries & Loads

Solution

Post-Processing


ANSYS Structural Mechanics

• Geometry

– Direct CAD Links

• Connect to real CAD models

and create true parametric

analysis

– Create analysis geometry

• Geometry clean-up

• Simplification

• Create Shell & Beam

geometry

– Work with imported files



Elements Technology



Materials Modeling



Composite Materials Modeling

• A full selection of layered element types

• Composite-specific layup builder on a ply-by-ply basis

• Composite-specific post-processing

• Output of manufacturing information

– Flat-patterns

– Ply-Book

Solid-ShellLayered Solid Layered ShellBeam/Pipe/Elbow Discrete/Smeared

Reinforcement



Boundary Conditions, Loadings & Contact

•Full set of Boundary Conditions & Load Types

•Displacements, Forces, Moments, Pressures, Temperatures

•Now with full suite of wave-loading types

•Soil-Pile interaction via SPLINTER

•Automated Contact:

•Node-Node; Node-Surface; Surface-Surface; Line-Line; Line-Surface

•Small and Large Sliding

•Lower and Higher order elements

•Friction Sliding (Small/Large Deformation)

•Shell/Beam Thickness Effects

•Automatic Assembly Contact



Solvers

• Implicit / Explicit solvers

• ANSYS solver technology

evolving to keep pace

with hardware

developments

• Multi-core

• 32 & 64 bit

• Clusters

• GPU



• Postprocessing

• Stress, Strain,

Deformation, Creep,

Contact, Reactions.....

• Images

• Tabular data Excel

• Movie files

• Automated report

generation


Design Assessment

- Introduction

• What is Design Assessment?

– Enables the customer to define additional data that is associated with

their model and then perform custom post processing.

• Custom definition of input data, result definitions & solve + post scripts

– Without any customisation, it enables the combination of existing

solutions

• Static Structural

• Flexible Dynamics (at a specific time)

– Predefined scripts for BEAMST and FATJACK.



• ANSYS Structural analysis


DesignXplorer

• Use parameters in:

• CAD

• DesignModeler

• SpaceClaim

• Engineering data

• Preprocessor

• Postprocessor

• Derived parameters

• DOE

– Select DOE type

– Custom + Sampling (OSF)

• Candidate designs

• Response surface

• Six Sigma analysis

– Manufacturing best/worst case


Offshore System level analysis

Requirement Oil & Gas fixed

Jacket

Wind Turbine

fixed Jacket

Oil & Gas

Floating

Geometry DM/SCDM DM/SCDM DM/SCDM

Wave + Current

(tubular)

ANSYS/Structural ANSYS/Structural ANSYS/Structural

Wave + Current

(shell/solid)

- - Via AQWA

Pile analysis Splinter Splinter -

Aeroelastic

coupling

- ANSYS/Structural

via shared DLL

-

Fatigue (tubular) FATJACK FATJACK FATJACK

Fatigue

(shell/solid)

- - OSAP/nCode

ULS

(tubular/beam)

BEAMST BEAMST BEAMST

ULS (shell/solid) - - OSAP

FSI - - -


Oil and Gas jacket - Geometry


Wind Turbine jacket - Geometry


Oil and gas floating - Geometry




Jacket

Wind Turbine

fixed Jacket

Oil & Gas

Floating


Wave + Current

(tubular)


Wave + Current

(shell/solid)

- - Via AQWA


Aeroelastic

coupling

- ANSYS/Structural

via shared DLL

-


Fatigue

(shell/solid)

- - OSAP/nCode

ULS

(tubular/beam)



FSI - - -


• Coupled hydro-elastic analysis for tubular framed structures

– Fully coupled hydrodynamic loading with non-linear analysis capability

– Automatic computation of hydrodynamic damping

– Regular and irregular waves

– Ability to take RAO results as time history loading

– Tube-in-tube contact

Tubular Coupled Wave-Structures

• Wave loading for application of Morison

forces (coupled for non-linear analyses)

• Calculation of added mass due to

marine growth

• Hydrodynamic mass calculations

• Buoyancy calculations, including

free flooding




Jacket

Wind Turbine

fixed Jacket

Oil & Gas

Floating


Wave + Current

(tubular)


Wave + Current

(shell/solid)

- - Via AQWA


Aeroelastic

coupling

- ANSYS/Structural

via shared DLL

-


Fatigue

(shell/solid)

- - OSAP/nCode

ULS

(tubular/beam)



FSI - - -


• Capabilities– Single pile or pile group analysis

– Soil-pile-structure interaction with single piles or pile groups

– No limit to number of piles or soil layers

– Piles may have non-constant cross sections

– Automatic sub-division of piles taking into account changes in cross section, soil layers, etc.

– Automatic calculation of Mindlin coefficients for group pile analysis

– Automatic generation of lateral forces (P-Y) and skin friction (T-Z) curves

– Efficient nonlinear solution for soil-pile-structure interactions via superelement (sub-structuring) approach

– Non-tubular cross sections

ANSYS Soil-Pile-Structure Interactions

(SPLINTER)


ANSYS Soil-Pile-Structure

Interactions

• It is possible to take account of the non linear

pile stiffness during a transient solution – a

simple test indicates ~ 20% stress reduction.




Jacket

Wind Turbine

fixed Jacket

Oil & Gas

Floating


Wave + Current

(tubular)


Wave + Current

(shell/solid)

- - Via AQWA


Aeroelastic

coupling

- ANSYS/Structural

via shared DLL

-


Fatigue

(shell/solid)

- - OSAP/nCode

ULS

(tubular/beam)



FSI - - -


Wind/Wave/Current & Rotor Blade

Loading

Interface to FLEX5

• FLEX5 is one of a number of highly specialized

wind loading programs

– thoroughly validated for wind turbines

– however, limited to simple substructures

• This limitation can be overcome by combining FLEX 5 with ANSYS.– Simplified substructure (in FLEX 5) can be replaced by a

realistic structural model (in ANSYS) that can accurately model the structural behavior and wave loading

• This capability was initiated, sponsored and verified by REpowerSystems AG



Loading

• Allows complex substructure

modelling for offshore wind turbines

• Fatigue and extreme condition design

• Analysis process:

– ANSYS generates FLEX 5 substructure

input model data.

– FLEX 5 performs WT analysis

– ANSYS reads the FLEX 5 results and

adds wave load to extract member

forces.

– ANSYS performs fatigue analysis via

rain-flow counting.

• It has been successfully applied for

the certification of the Beatrice wind

farm demonstrator project, and others

(e.g., 150MW Ormonde wind farm).Photo courtesy of REpower Systems AG

Interface to FLEX5


Impact of substructure on tower bottom fatigue loads

With Waves

90%

95%

100%

105%

110%

115%

120%

125%

130%

135%

140%

Shear long. Shear lat. Vertical

force

Bending

lat.

Bending

long.

Torsion

OJQ

CCT

FFT

With Wave Loading

Why is this (integrated) Loading Combination Important?


Loading

Global

Natural

Frequencies

OWEC

Jacket

Quattropod

Centre

Colum

Tripod

Flat Face

Tripod

f0 [Hz] 0.33 0.26 0.3

f1 [Hz] 1.64 1.35 0.86

Court

esy o

f R

Epow

er

Syste

ms A

G

Influence of Substructure on Tower Bottom Fatigue Load

Without Wave Loading

Increase of Fatigue Loads up to 35%!




Jacket

Wind Turbine

fixed Jacket

Oil & Gas

Floating


Wave + Current

(tubular)


Wave + Current

(shell/solid)

- - Via AQWA


Aeroelastic

coupling

- ANSYS/Structural

via shared DLL

-


Fatigue

(shell/solid)

- - OSAP/nCode

ULS

(tubular/beam)



FSI - - -


ANSYS - Code Checks (FATJACK/BEAMST)

• Joint Code & Member Code checks including:

– AISC 10th edition working stress and 2nd edition LRFD

– API RP2a-WSD 21st edition working stress

– RP2A-LRFD 1st edition

– BS5950 part 1 1992

– NORSOK 2000

– NORSOK NS3472 1984

– NPD 1992

– DS449 1984 (with 1994 amendments)

– DS412 1984 (with 1994 amendments)

– ISO 19902 implementation started

• Easy-to-use code check facilities including:

– Code checks on time histories

– Code checks on combined load cases

– Visualization of code checks

– Ability to use them in combination with ANSYS calculations


• FATJACK module offers both deterministic and spectral fatigue

capabilities

– for tubular frame structures subjected to waves and current or wind including

wind gusts

– can be used in frequency and time domain

– sea states: JONSWAP, Pierson-Moskovitz, Occhi-Hubble, Scot-Weigel and

Shell New Wave, or user-defined wave spectra

• FATJACK includes explicit SCF definitions

– SCFJ – if crown & saddle SCF is known e.g. from empirical formulae

– SCFA – if SCF is known at specific locations e.g. from FE

– SCFB – if SCF is constant across a section

– SCFP – if SCF values vary with location

• Automatic (empirically derived) SCF definitions based on

– Efthymiou, Wordsworth, Kuang or DS449

ANSYS

- Fatigue Assessments


ANSYS

- Fatigue Assessments: Rainflow counting

• Reduces spectrum of varying stress into simple stress reversals

• Allows the application of Miner’s rule to assess fatigue life of structure

subject to complex loading

• Based on ASTM E1049-85 (2005) Standard Practices for Cycle Counting

in Fatigue Analysis

• It is possible to use results from up to 1000 different transient dynamic

analyses and loading (i.e., multi-directional wave spectra)

• Uses Rainflow counting method to produce stress range histogram

• Results can be combined using a probabilistic approach, output includes:

• fatigue life (based on Miner´s rule)

• usage factors

• damage per wave (history)

• stress histograms


ULS Check in Design Assessment


System to component analysis

• Detailed joint analysis is possible:


Summary

• ANSYS continues to offer and invest in significant

capabilities for offshore applications

– Significant progress in implementing key features of

ASAS in ANSYS Structural Mechanics products

– New Design Assessment tool enabling advanced

customized post-processing, including application of

ANSYS developed code checking tools and user

custom capabilities (not limited to Offshore)

– Separate code checking products

Documents

ANSYS Structural Mechanics solutions for the Offshore and ... UK/staticassets/03... · for analyzing a large variety of offshore structures subjected to wave, ... •For Structural