Lusas Basics

Introduction to LUSAS

BasicsGeometryMeshAttributesLoadingAnalysisViewing Results

Basics

Opening Lusas:.mdl the model file.mys the results file10806 Linear10805 Nonlinear10804 Time History

Basics

LayersGroupsAttributesLoadcasesUtilitiesReports

BasicsUnits

GeometryCreates the basic shape of the model Points

Lines

Surfaces

Volumes

GeometryPoints defined usingGeometry> Point> Coordinates.Or:To create new entry fields press Tab.When the Z-ordinate is omitted, it is recognised as 0.

GeometryLines are created between points by selecting 2 points and using : Surfaces are created between lines by selecting lines and using:Volumes are created by selecting surfaces and using:

GeometryPoints, lines, surfaces and volumes can all be copied, moved or swept.Moving:Sweeping:Copying:

Geometry

MeshingThe Geometry defines the shape of the model only the mesh is what is actually analysedTo create the mesh:- Chose element type(s)- Assign the elements to the geometry

Meshing - Elements

Beam Elements2 or 3 DimensionalStraight or CurvedThick or Thin (Shear Flexibility)

Other linear elements :Bars or Cables

Meshing - Elements

Beam ElementsGRILL 2D linearBEAM Thick 2D linearBMS3 Thick 3D linearBTS3 Thick nonlinear 3D linearBM3 Thin 2D quadraticBS4 Thin 3D quadraticBMX3 Cross Section Thin 2D quadraticBSX4 Cross Section Thin 3D quadratic

Quadratic = more nodes = curved

Meshing - Elements

Surface ElementsMore analytically expensive than BeamsTriangular or QuadrilateralNumber of nodes / gauss pointThick or Thin ElementsThin no shear flexibility simpler - but only use if all plates are very thinThick include shear flexibility required for most analysis

Meshing - Elements

Surface ElementsPlates For flat modelsShells

ThinThickTrianglesTS3TTS4TSL6TTS6QuadrilateralsQSI4QTS4QSL8QTS8

Meshing - Elements

Joint (spring element)Joint elements are used to connect two or more nodes by springs, with translational and rotational stiffness.

They may have an associated mass and damping.

Mass only joints can be defined

Meshing - ElementsThe number of elements in a regular mesh are controlled by defining line meshes on the boundary lines with no element type.To select the element types:

Use Attributes> Mesh...To assign the mesh to the surface, select the surface to be meshed, then use the treeview and drag the appropriate mesh name from it onto the surface.

Meshing - Elements

Balance between accuracy and effort Ideal value depends on what model is for Use sensitivity tests to get right set up part / all of model identify key result areas vary mesh density and compare results use lowest density that gives consistent resultsConsider varying mesh density through model. Meshing - Layout

Meshing - Layout

Mesh Aspect RatiosHigh aspect ratios can cause numerical problems in the analysisGeneral guideline keep ratio less than 10Meshing - Layout

Attributes

MeshGeometricMaterialSupports

Attributes - GeometricGeometric Attributes not to be confused with Geometry...For line elements need to enter the cross sectional propertiesFor surface elements need to enter the thickness

Attributes - GeometricAttributes> Geometric>New cross section properties can be defined and imported into a model by creating a separate 2d lusas model with the cross section shape. Cross section properties can be obtained from a library or entered directly.

Attributes - MaterialUse Attributes> Material> Material Library/Composite Library and select a material. Or, material properties can be entered directlyTo check where any attribute is assigned, as well as having a coloured beside it, use right-click on the attribute in the treeview, then Select Assignments to see which parts have that particular attribute.

Attributes - SupportsSupports can be assigned to points, lines or surfaces. They can be rigid or springs

When a support is assigned, it will be visualised by a green arrow on the point or line. Use the icon to turn this on/off.If several load cases are created the supports are only applied in the first loadcase, and can only be manipulated when that loadcase is active.

LoadingA load is defined as an attribute, and applied to the geometry.A self weight can be added to the model by selecting Body Force and then entering a linear acceleration of -9.81The arrows can be turned on and off using:

LoadingLoad Types:

Structural Applied to Structure

Prescribed - Moves structure

Discrete defined on local coordinate system and projected onto structure

Loadcases

Any number of loadcases can be created.When a load is assigned to the model it must be assigned to a loadcase. Basic Combinations Smart Combinations EnvelopesWhen loads are assigned to the geometry a load factor can be applied.Supports are defined in first Loadcase

Traffic Loading - AUTOLOADERAttributes > InfluenceDisplace or rotate elements.Bridge > Run Influence Analysis...

Traffic Loading - AUTOLOADERBridge > Vehicle Load OptimisationDoesnt cover Eurocodes yet.

Analysisor File> LUSAS Datafile gives more advanced options

Visualisation of a ModelGeometry Mesh AttributesLabels

ContoursVectorsDeformed MeshDiagramsValuesThe order of the layers on display is shown by the order in the treeview, bottom being most visible

Viewing AssignmentsIn the layers treeview right click on geometry and select properties

Viewing ModelDifferent parts of the model can be made visible and invisible at any stage. The groups function assigns geometry features to different named groups so they can be made visible and invisible easily

Groups:Selection:

Viewing ResultsTo view the results of the analysis, the loadcase used needs to be set active.

Utilities >Print Results Wizard ...Gives tables of results for the visible model

Viewing ResultsUsed to plot deflections, diagrams and contours

Other things Lusas can do: Frequency analysis Buckling analysis Non-linear analysis Automation using Visual Basic Scripts

Help...www.lusas.com Username: lusasPassword: powerfulfeBridge Engineers Working Group Sitehttps://communities.eu.atkinsglobal.com/sites/StructuresWG/default.aspxLusas Technical [email protected]

ChecksCheck the reactions 2. Check the deformed shape 3. Check the value of the deformations.4. Check your LUSAS Solver text output file (*.OUT) for any warning messages. 5. Check mesh refinement6. Check element axishttp://www.lusas.com/protected/instruct/basic_checklist.html

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Lusas Basics

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