Seminar – Nov 2010
Steve Varnam Richard Mitchell ANSYS UK
Agenda • ANSYS Heritage in Offshore Structural Analysis ANSYS ASAS – ANSYS • Analysis of Offshore Structures in our mainstream software ANSYS Mechanical – ANSYS • Addressing the next generation of structural analysis requirement ANSYS Workbench – ANSYS • Fatigue • Composites • Optimisation
ANSYS Offshore Solutions - proven for Oil & Gas applications • Since 1971, AQWA AQWA & ASAS have been developed for analyzing a large variety of oil & gas offshore structures – WS Atkins Century Dynamics ANSYS • 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
• ANSYS ® ASASTM shielding – 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 spectral methods
cargo lowered onto vessel
AQWA & ASAS Overview - Ma Main in App Applic licati ation on Are Areas as Images courtesy of Arup, Moss Maritime AS, Technip Offshore Finland and REpower REpower Systems AG
• 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
ASAS - Typ Typica icall Ap Appli plica catio tions ns
• Some example applications
Offshore Wind Turbines
Courtesy Courtesy of Fraunhofer Fraunhofer CWMT
Jacket Structures
Tidal Turbine Structure
Transportation of Spar Truss on Heavy Lift Vessel Courtesy of Technip Offshore Finland Courtesy of REpower Systems AG
ANSYS ASAS - Relevance for Offshore Renewables • 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 Renewables are very similar: – 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 - in a nutshell • • •
Offshore/Marine Structural Finite Element Analysis Coupled wave/current/wind-structure interaction with nonlinear structural response Linear and non-linear analysis – – – –
• • •
Comprehensive modeling capabilities for frame structures Extensive library of Finite Elements Multi-level superelement capability Frequency domain or time history dynamic analysis
Fatigue assessment with irregular waves and using deterministic and s pectral methods Seismic loading using response spectrum technique Comprehensive Code Checking for Framed structures - AISC and API (working stress and LRFD), NORSOK, BS5950 and DS449.
ANSYS ASAS - Coupled Wave-Structures • 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 • 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
ANSYS ASAS - Wind, Wave & Current Loading • Coupled wave/current/wind-structure interaction with nonlinear structural response – Capability to handle compliant structures with regular & irregular waves – Wave theories include: • Conventional waves such as linear wave (Airy), solitary wave (Cnoidal 1 st), Stokes 5th order, Stream function but also Shell New Wave (dispersiv e wave) • Irregular waves such as JONSWAP, Pierson-Moskovitz, user-defined • API Wave recipe
– Current theories include: • API WSD 20th Ed. and LRFD 1st Ed. codes of practice!
ANSYS ASAS - Soil-Pile-Structure Interactions
• 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 ASAS - Code Checks • 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) – IS O 19902 implementation s tarted • 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
ANSYS ASAS - Fatigue Assessments • FATJACK module offers both deterministic and s pectral 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 ASAS - Fatigue Assessments • Rainflow counting fatigue – 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
ANSYS ASAS - Fatigue Assessments
• Rainflow counting fatigue – Within the fatigue (FATJACK) module these results can be combined using a probabilistic based Rainflow Counting approach – Output includes: • • • •
fatigue life (based on Miner´s rule) usage factors damage per wave (history) stress histograms
– Results are stored for further processing (e.g. ASAS Visualizer)
ANSYS ASAS - 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 ASAS – Simplified substructure (in FLEX 5) can be replaced by a
realistic structural model (in ANSYS ASAS) that can accurately model the structural behavior and wave loading
• This capability was initiated, sponsored and verified by REpower
S ys tems A G
ANSYS ASAS - Wind/Wave/Current & Rotor Blade Loading Interface to FLEX5 • Allows complex substructure modelling for offshore wind turbines • Fatigue and extreme condition design • Analysis process: – ASAS(NL) generates FLEX 5 substructure input model data.
– FLEX 5 performs WT analysis – ASAS(NL) reads the FLEX 5 results and adds wave load to extract member forces.
– ASAS 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
ANSYS ASAS - Wind/Wave/Current & Rotor Blade Loading Why is this (integrated) Loading Combination Important? Influence of Substructure on Tower Bottom Fatigue Load Without Wave Loading G A s m e t s y S r e w o p E R f o y s e t r u o C
140% 135% 130% 125%
Impact of substructure on tower bottom fatigue loads With W aves OJQ
With Wave Loading
CCT FFT
Increase of Fatigue Loads up to 35%!
120% 115%
Global Natural Frequencies
OWEC Jacket Quattropod
Centre Colum Tripod
Flat Face Tripod
110%
f 0 [Hz]
0.33
0.26
0.3
100%
f 1 [Hz]
1.64
1.35
0.86
105%
95% 90% Shear long. Shear lat.
Vertical
Bending
Bending
Torsion
ANSYS ASAS - Wind/Wave/Current & Rotor Blade Loading Why is this (integrated) Loading Combination Important? • For local problems it is even more important. G A s m e t s y S r e w o p E R f o y s e t r u o C
– Local eigenfrequency is blade mode (flap
wise direction) – Bracings in one of the lower bays are also part of this local mode shape
• The highest loading on bracings is the out-of-plane bending moment due to waves.
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….
ANSYS Mechanical Solutions
ANSYS Mechanical solutions articulates the best in class CAE products and technology for structural, thermal, acoustics and coupled physics analysis that offers a unique class of integrated simulation solution for the entire product development process …
Product Offering/Target Users • Built upon robust technology offers a range of products with a clear upgrade path from designers to analyst. e c i r P / y t i l a n o i t c n u F
ANSYS Multiphysics ANSYS Mechanical ANSYS Structural ANSYS Professional ANSYS DesignSpace
Front End
Plan
Drafting CAD
Concept Simulation
Mid-Range
Advanced Analysis
High-End
Virtual Prototyping
Evaluate Production
ANSYS ANSYS ANSYS ANSYS DesignSpace Professional Structural Mechanical
Product/Technology Description
Solver Technology ANSYS DesignSpace
ANSYS Professional NLT
Linear Structural Linear Structural Steady State Thermal Steady State Thermal Transient Thermal Linear Dynamics ANSYS Professional NLS Linear Structural Steady State Thermal Nonlinear Structural Linear Dynamics
ANSYS Structural Linear Structural Non-Linear Structural Linear Dynamics Nonlinear Dynamics
ANSYS Mechanical Linear Structural Non-Linear Structural Linear Dynamics Nonlinear Dynamics Steady State Thermal Transient Thermal Acoustics Direct Coupled
Analysis Methods & Solvers Technology Components
• • • •
Elements & Materials Contact Analysis Nonlinear Analysis Solver Technology
Analysis Methods & Solvers Elements Technology Solid Elements
Shell Elements
2D Quad/Tri
Lower/Higher Order
3D – Hexa/Tetra/Wedge/Pyramid
Layered Shells
Layered Solids Solid Shell
Special Elements
Rebars/Reinforcements
Beam Elements
Links/Pipes/Springs
Multi material beam analysis
Cohesive Zone
Beam Cross Section Definition
User Elements Gaskets
Analysis Methods & Solvers Materials Modeling Material Models
Isotropic/Orthotropic Elasticity Hyperelasticity Plasticity Viscoelasticity Viscoplasticity Creep
Hyperelastic Material Other Models
Cast Iron Plasticity Drucker-Prager Shape Memory Alloy USERMAT Gasket Material Concrete
Gasket Material
Gurson Damage
Analysis Methods & Solvers Contact Analysis •
Node-Node; Node-Surface; Surface-Surface; Line-Line; Line-Surface
• Small and Large Sliding • Lower and Higher order elements • Pure Penalty; Augmented Lagrange; Pure Lagrange; MPC contact • Semi-Automatic Contact Stiffness Update • Multiphysics Contact; Rigid Contact • Friction Sliding (Small/Large Deformation) • Shell/Beam Thickness Effects • Contact Manager Wizard • Automatic Assembly Contact
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 loadspreading reaction applied to patches • Deflections are less than 0.192” in (5 mm) at any point
Explicit - Impact
Explicit – Explosion
Explicit - Explosion
Model all aspects of the design • From the topsides.....
Courtesy of Pluere
Courtesy of AKERE Energy, CA
.. ....to the drill bit
ANSYS Workbench • Being part of the ANSYS Workbench infrastructure opens up several enhancements in overall process for the structural mechanics users
– Geometry – Meshing – Post-processing – Reporting – Process scripting & chaining – Automatic Project updates
ANSYS Workbench
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
ANSYS Structural Mechanics • Preprocessing • Materials • Linear-Elastic • Plastic • Hyper-elastic • Creep • Soils, Concrete • Damage models • Meshing • From fully automatic to highly controlled • Loads • Imported data fields • Time dependant • Complex systems • Contact • Model real assemblies • Bonded, Frictionless & Frictional contact
ANSYS Structural Mechanics • Solving • ANSYS solver technology evolving to keep pace with PC developments • Multi-core • 32 & 64 bit • Clusters • GPU
ANSYS Structural Mechanics • Postprocessing • Stress, Strain, Creep, Contact, Reactions • Linearisation • Images • Tabular data
Excel
• Movie files • Automated report generation
ANSYS Structural Mechanics • ANSYS Structural analysis
DesignXplorer • Start with a workbench defined process
– Use parameters in: • CAD • DesignModeler • SpaceClaim • Engineering data • Preprocessor • Postprocessor • Derived parameters
– Define design envelope • Parameter limits • Descrete/continuous
– Define goal • Near target • Min/Max • Trade offs
DesignXplorer • DOE
– Select DOE type – Custom + Sampling (OSF) • Candidate designs • Response surface • Six Sigma analysis
– Manufacturing best/worst case
ANSYS Composite Prep/Post • Composite materials
– Light – Strong – Good corrosion resistance
Composite examples
• Complex manufacturing
– Multiple materials – Multiple directions
Simple geometry's easy to handle
ANSYS Composite Prep/Post • Take loaded FE model from ANSYS Mechanical • Build model as manufactured
– Ply by ply manufacture – Draping – Section cuts • Use proven ANSYS FEA solver • Post process using composite criteria
ANSYS Composite Prep/Post • Composite specific post processing
– Layer by layer – User selected failure mechanisms
– User defined failure criteria
ANSYS nCode DesignLife • Premier fatigue analysis tool • Analyze implications of repeated, fluctuating, and rapidly applied loads, which can result in failure or damage • • • • • • • • • •
Stress-Life (single, multi-curve, Haigh diagrams) Strain-Life (automated multi-axial corrections) Multi-axial safety factor (Dang Van) Seam welds and spot welds High temperature fatigue Vibration fatigue (shaker simulation) Multiple runs in a single analysis Complete duty cycles Multi-processor enabled for fast results Use Python for proprietary or custom methods
Offshore Structures – ANSYS Product Roadmap • Transfer of ASAS unique solver technology to ANSYS Structural Mechanics products
– Single FE product suite – Recognition of ASAS key features • Creation of a Design Assessment system to handle post-processing of analysis results
– Delivered as part of Structural Mechanics products – For offshore related use, this covers load case combinations and code checking • Additional Products
– Separate Code Checking and Fatigue Products
ANSYS Workbench • The vehicle for integration of ASAS capabilities into our mainstream FEA product is the ANSYS framework called Workbench • Workbench acts as a common environment for all of our mainstream products – structures, fluids, thermal, electronics electromagnetics ..... • It enables us to interface software modules directly without going through intermediate files and manual processes
ASAS to Mechanical - Beams and Wave Theories • Beam Post-Processing enhancements
– Shear Force and Bending Moment diagrams • Beam End-Releases • Wave Theories Added (Mechanical already has 4 wave theories implemented) • Irregular waves • Shell New Wave • Constrained Wave
ASAS to Mechanical - Soil-Pile-Structure Interaction • Soil/Pile Interaction Solver (SPLINTER) enhanced to work with Mechanical (via command snippets & Matrix27 elements)
– PILEGEN and PILECALC macros included with the ASAS installation (capability only available via ASAS Offshore license)
Design Assessment - New System in Workbench
• Design Assessment System
– Available with Professional NLS and above – Post-analysis assessments of FEA results – Load Case Combinations • Static Structural • Flexible Dynamics (at a specific time)
Design Assessment - Customization
• Design Assessment System
– Advanced post-processing of FEA results • Targeted at user wanting to do design code assessment based on FEA models and results
– Predefined scripts supplied for ANSYS supplied code checking tools
– Enables the customer to define additional data that is associated with their model and then perform custom post processing • Custom definition of input data • Custom result definitions • Custom Solve & Post scripts (Python based)
Design Assessment - Assessment Types
• ANSYS or User Defined
– ANSYS Supplied Tools • FATJACK – Beam joint fatigue of framed structures
• BEAMCHECK – Member checks on frame structures
• Solution Combination only
– User Defined • User can build/integrate own load case combination and code checking tool
Design Assessment - Additional Code Checking Products
• ANSYS FATJACK
– Beam joint fatigue assessment – New separate product (also remains part of ASAS
FATJACK Fatigue Result
Offshore)
– Python scripts provided • ANSYS BEAMCHECK
– Was available initially at 12.0 – Python scripts provided
Joint Unitary Check for BEAMCHECK
Mechanical - Example Jacket Structural Analysis Project Page showing various “Mechanical” Systems Detailed jacket model in DesignModeler Jacket model in Mechanical Bending moment plot SF/BM plots along member
Mechanical - Example with Design Assessment (1) Project Page showing various “Mechanical” Systems Simple riser in DesignModeler – each of 5 members with different diameter/thickness Mechanical model – APDL macros for wave loading and pile-substructure Stress plot result using Beam Tool
Mechanical - Example with Design Assessment (2) Simple load combination (load factor) with first Design Assessment system Factored deformation Second Design Assessment system applies API code check Code check parameters entered in details panes Unity check result showing Yield utilization
