genie analysis basic

DNV Software Sesam User Course Module 3: Structural Analysis

Det Norske Veritas AS. All rights reserved.

Module 3: Structural Analysis Whats in it for you?

To be able to create and run static and dynamic analyses in GeniE, using Sestra

Learning objectives

Set up your analysis

Edit the Sestra input file for advanced options

Learn the basic capabilities of Sestra

Understand input and output of files in Sestra

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Det Norske Veritas AS. All rights reserved. Slide 3

Setting up and running your analysis Purpose of this section:

Understand how to set up your analysis in GeniE and check the run status

Learn how to set up: - Static and eigenvalue analysis - Tension / Compression analysis


Setting up and running your analysis (1/9)

Analysis activities

GeniE comes with a set of pre-defined analysis activities (workflow processes)

Tools > Analysis > Activity Monitor (Alt+D) - Linear Structural Analysis, Static or

Eigenvalue (Sestra) - Pile Soil Analysis (structure-pile-soil

interaction Wajac, Splice and Sestra) - Wave Load Activity (Wajac and Sestra) - Tension/Compression Analysis (Sestra)

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Setting up and running your analysis (2/9) Run your analysis

Uncheck an activity to skip it

Stop at any time (Start button changes to Abort during execution)

Open Sestra.lis for checking your run

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Sestra.lis file

Info of analysis

Sum of loads and moments

Sum of reaction forces and moments

Get more info when warning/error


Setting up and running your analysis (3/9) Sestra listing (print file) - contains important QA information

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: : PRINTOUT OF DATA GIVEN AS DIRECT INPUT TO SESTRA COMM Default SESTRA commmand file ITOP 1. 0. 0. 0. 0. 0. 0. 0. 0. 0.00E+00 0.00E+00 0.00E+00 INAM 20040510_122532_ RETR 3. 0. 0. 0. 0. 0. 0. 0. 0. 0.00E+00 0.00E+00 0.00E+00 RNAM 20040510_122532_ NORSAM SOLM 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.00E+00 0.00E+00 0.00E+00 CMAS 0. 1. 1. 0. 0. 0. 0. 0. 0. 0.00E+00 0.00E+00 0.00E+00 RSEL 1. 0. 0. 0. 0. 0. 1. 0. 0. 0.00E+00 0.00E+00 0.00E+00 Z : : SUM OF REACTION FORCES AND MOMENTS ********************************** GIVEN IN THE GLOBAL COORDINATE SYSTEM OF THE TOP LEVEL SUPERELEMENT LOADCASE (INDEX) X Y Z RX RY RZ 1 -4.5993E-12 -6.5921E-12 2.9386E+03 -2.7023E+07 -2.7833E+07 -9.2972E-08 : : DIFFERENCES BETWEEN SUMMED LOADS AND REACTION FORCES **************************************************** LARGER THAN 0.00E+00 FOR TRANSLATIONAL COMPONENTS AND LARGER THAN 0.00E+00 FOR ROTATIONAL COMPONENTS LOADCASE (INDEX) X Y Z RX RY RZ 1 -4.5978E-12 -6.5921E-12 9.5497E-12 1.3784E-07 6.7055E-08 -9.2955E-08

Dump of input (created by GeniE)

Sum of reaction forces

Difference between sum of loads and reaction forces


Setting up and running your analysis (4/9) Editing the Sestra input file

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Uncheck

Click to generate file

Edit the sestra input file


Setting up and running your analysis (5/9)

Create an Eigenvalue Analysis

Edit Linear Structural Analysis activity - Choose eigenvalue solver - Decide number of eigenmodes

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No loads in eigenvalue analysis!


Setting up and running your analysis (6/9) Tension / Compression Analysis (1/3)

Makes certain T/C elements structurally inactive if they are under tension or compression.

1. Define the elements in GeniE as truss elements Edit -> Properties -> Beam Type -> Create/edit beam type -> Truss tab

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Tension and Compression element = always active

Tension element = active under tension

Compression element = active under compression



2. Edit the analysis options in the Activity Monitor. Select the loadcases that you want to analyse for tension / compression.

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3. Run the analysis, check the results and the Sestra TensionCompression.lis file

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Simple Tension / Compression example


Setting up and running your analysis (9/9) Feature: Smart loadcombinations

Feature to combine results for loadcases after running the Sestra analysis - Faster than running analysis on actual

loadcombinations - Must be used when combining rotational

acceleration fields - Must be used in analysis with wave loads

and no piles - Irrelevant (setting has no consequence)

for piled structure analysis - Causes combination names not to

appear in Framework

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Det Norske Veritas AS. All rights reserved. Slide 13

Sestra Purpose of this section:

Understand the basic features of Sestra

Get to know the input and output of files

Learn how to do some basic QA of your results


Sestra Features Static and dynamic linear structural analysis Also:

- Stress stiffening (2nd order effect handled in two-step procedure) - Linear buckling - Contact problem - Inertia relief - Tension/Compression analysis

Multilevel superelement analysis for static analysis Supports truss, beam, membrane, shell, solid, spring & damper elements Virtually unlimited problem size

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Overview of general analysis capabilities

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Sestra Static and dynamic linear structural analysis

Static analysis Dynamic analysis

Quasi-Static analysis

Free vibration Forced

response Time / Frequency

domain

Tension / Compression

analysis

Direct analysis Superelement analysis


Sestra Static Analysis Direct analysis

Standard analysis option

Equation of static equilibrium is solved: = =

Multifront solver - By default activated through GeniE - Fast for direct analysis of structure

Supermatrix solver - May be used in certain superelement analyses

Modest CPU consumption

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Static analysis


analysis



Sestra Static Analysis

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Static analysis


analysis


Superelement analysis

Divide model into superelements why?


Sestra Static Analysis Superelement analysis

Divide model into superelements why?

- Faster solution for large structures

- Able to use one superelement in different locations

- Models can be created in parallel by different engineers and then assembled together

Solution process

Establish matrices for each superelement

Reduction eliminates internal d.o.f. for the individual superelements to the interfaces (supernodes)

Retracking determines internal d.o.f.s

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ra , Ka, Ra

ras, ka, Fa

a b

rb , Kb, Rb

rbs, kb, Fb


Sestra Static Analysis Tension / Compression Analysis

Makes certain T/C elements structurally inactive if they are under tension or compression.

Tension only elements can be used to simulate wires

Compression only elements can be used for simulating stubs or supports

Works on an iterative approach to see which elements are in tension/compression.

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Static analysis


analysis



Sestra Dynamic Analysis General

Equation of dynamic equilibrium: + + = () - Mass matrix M times accelerations a=dv/dt - Damping matrix C times velocities v=dr/dt - Stiffness matrix K times displacements r - Time dependent loading R(t) - r(t) is sought time dependent displacements

Solving above equation gives dynamic response to a time varying load (forced response analysis), two alternatives: - Frequency domain - Time domain

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If C = 0 and R 0 Ma + Kr = 0 Free vibration analysis


Dynamic analysis



domain


Sestra Dynamic Analysis

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Dynamic analysis



domain

Forced response

+ + = () Two alternative solution

procedures: - Frequency domain analysis

- Harmonic (sinusoidal) loading R(t) and response r(t)

- Harmonic response r(t) (steady state response)

- Used for stochastic (spectral) fatigue analysis in Framework or Stofat

- Time domain analysis - Arbitrary time dependent loading R(t) - Time dependent response r(t) (transient

response)

Computationally expensive in general


Sestra Dynamic Analysis

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Dynamic analysis



domain

Free vibration

Free vibration = eigenvalue problem

+ = Eigenvalue solvers

- Lanczos Iteration - Default from GeniE.

- Multifront Lanczos - Householder - Subspace iteration

Modest CPU consumtion


Sestra Quasi-Static Analysis

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Quasi-Static analysis

Analysis neglecting dynamic (damping and inertia) effects of structure (no added mass either)

Quasi-static frequency domain analysis often performed when frequency of load much lower than lowest eigenfrequency

Used for stochastic (spectral) fatigue analysis in Framework or Stofat

Equation of static equilibrium: Kr = R(t) - Harmonic loading R(t) - Harmonic response - Equation solved by using complex (real and imaginary) numbers - Solving equation using same procedure as for simple static analysis

- Modest CPU consumption - Two load vectors (real and imaginary) for each harmonic loading


Sestra Input and output

Input to Sestra: - Input Interface Files - T*.FEM - Loads Interface Files - L*.FEM - Sometimes: S-file - S#.FEM - Analysis control data

Output from Sestra: - Results Interface Files

- either: R#.SIN - or: R#.SIF + R*.SIF

- Print file - SESTRA#.LIS - Maintenance file - SESTRA#.MNT

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Post- Processors

Pre- Processors

ENVIRON- MENTAL

ANALYSIS

R10

0.SI

N (R

100.

SIF

+ R

1.SI

F +

R2.

SIF

+

)

L1.FEM + L2.FEM +

T100

.FEM

+ T

1.FE

M +

T2.

FEM

+

SESTRA linear

statics and dynamics

Sesam Manager

Print file (SESTRA100.LIS)

Maintenance file (SESTRA100.MNT)

Analysis control data

(SESTRA100.INP)


Sestra Q/A before and after analysis

Prior to running Sestra: check FE mesh in the modeller

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Verify Sestra results: - Check Print file for warnings and error

messages

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messages

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messages

- Check sum of loads / reaction forces

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messages


- Check difference between summed loads and reaction forces

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messages


- Check difference between summed loads and reaction forces

In Xtract: check stress discontinuities over element borders

- Small discontinuities compared with stress level (

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