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Lusas Basics

lusas basics




Introduction to LUSAS Basics Geometry Mesh  Attributes Loading  Analysis Viewing Results Basics Geometry Mesh  Attributes Loading  Analysis Viewing Results Basics Opening Lusas: 10806 – 10806  – Linear  Linear 10805 – 10805  – Nonlinear  Nonlinear 10804 – 10804  – Time  Time History .mdl – .mdl  – the  the model file  the results file Basics  Attributes Loadcases Groups Utilities Reports Layers Basics Units Basics Geometry Mesh  Attributes Loading  Analysis Viewing Results Geometry Creates the basic shape of the model Points Lines Surfaces Volumes Geometry Points defined using Geometry> Point> Coordinates. Or: To create new entry fields press Tab. When the Z-ordinate is omitted, it is recognised as 0. Geometry Lines 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: Geometry Points, lines, surfaces and volumes can all be copied, moved or swept. Moving: Copying: Sweeping: Geometry Basics Geometry Mesh  Attributes Loading  Analysis Viewing Results Meshing The Geometry defines the shape of the model only – the mesh is what is actually analysed To create the mesh: - Chose element type(s) - Assign the elements to the geometry Meshing - Elements Beam Elements • 2 or 3 Dimensional • Straight or Curved • Thick or Thin (Shear Flexibility) • Other linear elements :  – Bars or Cables Meshing - Elements Beam Elements • GRILL – 2D linear • BEAM – Thick 2D linear • BMS3 – Thick 3D linear Quadratic = more nodes = curved • BTS3 – Thick nonlinear 3D linear • BM3 – Thin 2D quadratic • BS4 – Thin 3D quadratic • BMX3 – Cross Section Thin 2D quadratic Meshing - Elements Surface Elements • More analytically expensive than Beams • Triangular or Quadrilateral • Number of nodes / gauss point • Thick or Thin Elements  – Thin – no shear flexibility – simpler but only use if all plates are very thin  – Thick – include shear flexibility – required for most analysis Meshing - Elements Surface Elements • Plates – For flat models • Shells Triangles Quadrilaterals Thin Thick TS3 TTS4 TSL6 TTS6 QSI4 QTS4 QSL8 QTS8 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 - Elements To select the element types: Use Attributes> Mesh... The number of elements in a regular mesh are controlled by defining line meshes on the boundary lines with no element type. 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 Meshing - Layout • 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 results Consider varying mesh density through model. Meshing - Layout Meshing - Layout Mesh Aspect Ratios • High aspect ratios can cause numerical problems in the analysis • General guideline – keep ratio less than 10 Basics Geometry Mesh Attributes Loading  Analysis Viewing Results Attributes Mesh Geometric Material Supports Attributes - Geometric Geometric Attributes  – not to be confused with Geometry... For line elements need to enter the cross sectional properties For surface elements need to enter the thickness Attributes - Geometric  Attributes> Geometric> Cross section properties can be obtained from a library or entered directly. New cross section properties can be defined and imported into a model by creating a separate 2d lusas model with the cross section shape. Attributes - Material Use Attributes> Material> Material Library/Composite Library and select a material. Or, material properties can be entered directly To check where any attribute is assigned, as well as having a coloured beside it, use rightclick on the attribute in the treeview, then Select Assignments to see which parts have that particular attribute. Attributes - Supports Supports 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. Basics Geometry Mesh  Attributes Loading  Analysis Viewing Results Loading  A 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 -9.81 The arrows can be turned on and off using: Loading Load 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 • Envelopes When loads are assigned to the geometry a load factor can be applied. Supports are defined in first Loadcase Traffic Loading - AUTOLOADER  Attributes > Influence Displace or rotate elements. Bridge > Run Influence Analysis... Traffic Loading - AUTOLOADER Bridge > Vehicle Load Optimisation… Doesn’t cover Eurocodes yet. Basics Geometry Mesh  Attributes Loading Analysis Viewing Results Analysis or File> LUSAS Datafile… gives more advanced options Basics Geometry Mesh  Attributes Loading  Analysis Viewing Results Visualisation of a Model Geometry Mesh  Attributes Labels Contours Vectors Deformed Mesh Diagrams Values The order of the layers on display is shown by the order in the treeview, bottom being most visible Viewing Assignments In the layers treeview right click on geometry and select properties Viewing Model Groups: Different 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 Selection: Viewing Results To 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 Results Used to plot deflections, diagrams and contours Other things Lusas can do: • Frequency analysis • Buckling analysis • Non-linear analysis • Automation using Visual Basic Scripts Help... Username: lusas Password: powerfulfe Bridge Engineers’ Working Group Site Lusas Technical Support [email protected]