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7/27/2019 Strand7_ -Automeshing&LinksCourse

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Strand7 Release 2.4 Features

Presented by Strand7 Pty Limited 1

Table of ContentsGeometry Tools Overview........................................................................................................................3

Multi-Point Link .....................................................................................................................................31

Attachment Link .....................................................................................................................................39

Modelling a Tapered Beam.....................................................................................................................49

Nonlinear Material Beam........................................................................................................................60

Factor vs Position Table..........................................................................................................................77

Creep of Metals at High Temperature ....................................................................................................85

Entering Concrete Creep + Shrinkage Data for ACI 209R-92 .............................................................100

Triaxial Test of Modified Cam-Clay Soil .............................................................................................116

Undertaking a Sloshing Analysis..........................................................................................................129Heat of Hydration .................................................................................................................................133

Load Influence Solver...........................................................................................................................153

Moving Load Overview........................................................................................................................163

Moving Load Tutorials .........................................................................................................................179

Construction Sequence Analysis...........................................................................................................231

Nonlinear Static Solver Sub-Incrementation ........................................................................................264

Quasi-static Solver ................................................................................................................................277

Plate Element Concrete Reinforcement Analysis .................................................................................283

Element Node Force (Free Body Diagrams) ........................................................................................301

User Defined Contours in Plates and Bricks.........................................................................................309


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2 Presented by Strand7 Pty Limited


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Strand7 2.4 Features


Geometry Tools Overview

Introduction

Strand7 2.4 sees the introduction of a number of geometry related features designed to make the transition betweenCAD packages and FEA a smoother process. This document outlines the different geometry tools and options nowavailable in Strand7 2.4. A brief outline is given on each feature as well as detailed tutorials at the end.

Import

As well as IGES and ACIS (SAT) files, Strand7 is now able to import STEP files. For each supported geometry filetype there are a number of import options:

Importing IGES Options:

None: All geometry will be placed in a newImport Group

Subfigures: Geometry is placed in therelevant group from the CAD package. It

can have a heirachy.

Levels: Geometry is placed in the relevantgroup based on defined levels. These arenot heirachical.

Auto: Geometry is placed in groups based

on the subfigure definitions. If nosubfigure definitions exist then the leveldefinitions in the CAD file are used.


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When saving a STEP file from a CAD package the default settings should be sufficient.

Importing STEP Options:

None: All geometry will be placed in a newimport group.

Assemblies: Geometry is placed in therelevant group based on the assemblydefinitions.

Importing SAT Options:

Acis bodies as Groups: a solid body can be defined as a group and imported as such.

Entity Display

The local positive normal direction of aface can now be shown by selecting

Show Normals in theEntity Display.

The direction of the face normal istranslated to the plate afterautomeshing, so to ensure that theplates are oriented in the same way itcan be useful to first check the facenormals.

The face normals can be aligned easily using Tools/Align/Flip Entities.

The other new Entity Display available for geometry in Strand7 2.4 is the ability to see the location of the controlpoints.


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The geometry on the right was originallythe same as the geometry above, however aclean was performed and now the two

faces are duplicates of one another. Thewireframes are no longer distinguishablefrom each other.

Now when the two faces are automeshedthe plate meshes are the same.

Geometry Plates in wireframe display mode

There have also been changes made to the way the geometry clean tolerances work. There are now two options,

Minimum Feature Length and Geometry Accuracy.

Minimum Feature Length is given in the clean geometry dialog and is comparable to the Minimum edge length inprevious versions. This setting controls how small an edge or gap should be before it is cleaned out.

Geometry Accuracy is set in Tools/Options. This settingcontrols how accurate the morphed edges must be in rebuiltgeometry, in other words, how close do vertices or edgesneed to be to one another to be considered a single vertex

or edge.

It is advisable to ensure that the Geometry Accuracy is lessthan or equal to the Minimum Feature Length.

Graft Edges to Faces

When the edge of a face lies on another face in the geometry, the face needs to be made aware of the edge in someway. This will ensure a compatible mesh. One method is to split the face in the CAD package, but in Strand7 2.4the graft tool can be used to graft an edge onto a face. Whether an edge lies on a face is determined by the Distancevalue in the dialog. This setting corresponds to the Minimum Feature Length setting in the clean geometry dialog.If it is changed in one dialog it is changed in the other.


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In the geometry below there are a number of perpendicular faces on the base circular face. Currently they are notconnected to this base in any way. This is shown by the face free edges that run along the edges at each of theintersections between the vertical faces and the base face.

When this geometry is automeshed it can be seen that

there are incompatible edges between the vertical platesand the base plates.

These face free edges can be easily removed by using the graft tool.

Choose Tools/Geometry Tools /Graft Edges to Faces.

Select All the faces in the model and clickApply.

The face free edges between the vertical faces and the base face have now been removed as the edges of the verticalfaces have been grafted to the circular face. Once automeshed you can clearly see that the mesh is now compatible.


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Intersect Edges

When two faces pass through one another we need to ensure they are split to produce a compatible mesh. The first

stage of this is to intersect edges. You can select the two edges and they will be split with a new vertex placed at theintersection. Whether any two edges intersect is determined by the Distance value in the dialog. This settingcorresponds to the Minimum Feature Length setting in the clean geometry dialog. If it is changed in one dialog it

is changed in the other.

Choose Tools/Geometry Tools/Intersect Edges.

Select the edges you wish to intersect.

ClickApply.

Vertices will be placed at the intersections of the edges so that theoriginal single edge is split into two edges.

IfSplit intersected faces is set, and only two intersections werefound on two faces, the faces will also be split along the intersection.

Morph Edges

Gaps between faces can be closed by using the morph edges tool. This tool willpropagate the changes to the geometry definition. This is particularly useful whengaps in the geometry exist due to the way the model was built in the CAD packageor if the geometry has been defeatured in Strand7 for meshing. By morphing theedges together, when exporting the geometry as an IGES or STEP file you can besure that the geometry will be the modified version.


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Choose Tools/Geometry Tools/MorphEdges.

Select the edges you wish to morph.

ClickApply.

The edges will be morphed together.

Note:Note:Note:Note: Morphing automatically occurs in thebackground each time a geometry clean isperformed.

Split Faces by Vertices

Splitting two faces to make them compatible or define a local area can be done by drawing split lines between twovertices. The face is then split according to this line. Multiple lines can be drawn at once to create multiple splitlines. The lines will follow the surface of the face, i.e. a split line on a cylinder will produce a curve around thecircumference.

Toggle Direction: This is analogous to the Norm and Rev options for Select by Region in a cylindrical system.

Unhook: This is used if an incorrect vertex is selected to define the split line, and works in a similar fashion to

Unhookwhen creating elements.

Choose Tools/Geometry Tools/Split Face by Vertices.

Click the two vertices you wish to create a split linebetween.

ClickApply.


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Once split there will be four faces in the model instead ofthe original two. This will lead to a compatible mesh beinggenerated between the two faces after surface automeshing.

Split Face by Plane

Sometimes instead of defining a split line between two vertices it can be easier to define a split line based on a plane.This tool works in a similar fashion to the above split face by vertices only now the face is split according to an entireplane. The plane can be defined based on the global cartesian system or any user defined Cartesian system.

Choose Tools/Geometry Tools/SplitFace by Plane.

Here we wish to split the red faceaccording to the intersecting blue face.The Split Face by Vertices tool would

not be useful in this example as no edgesof the blue face intersect with edges ofthe red face and therefore there are novertices to create a split line between.

Under Plane selectYZ. The blue facelies in the global YZ plane.

Select one of the vertices on the blueface to fill in P1.

ClickApply.

A split line is created across the red face so that it becomes two faces. When this geometry is automeshed it will becompletely compatible.


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The Split Face by Plane tool is not restricted to planar geometry. Othershapes can be split by a Cartesian plane also. This includes cylinders,spheres, cones, and NURBS surfaces.

The cone on the right was split in Strand7 according to an angled UCSplaced approximately half way up the side.

The final option in the Split Face byPlane dialog is Create Cut Faces.

When this is set, planar faces areautomatically generated on the cutplanes.

You can choose whether to create 1 or2 faces. If two separate solids are to bemodelled then 2 faces should begenerated.

Convert Plates to Faces

A tool now exists that allows plate elements to be converted into faces which can then be automeshed.


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A simple example is the plates on the right. Currently these plates are notcompatible and a finer mesh density is also required. This means multiplesubdivide operations would be required. For a small model this is not a

long process however for larger models it may become more timeconsuming.

Choose Tools/Geometry/Face fromPlate.

Select All the plates.

ClickApply.

Clean the geometry to remove freeedges between the faces.

The geometry can then be automeshed and a compatible mesh isproduced with the required finer mesh density.

This tool can be used on any plate type, Tri3, Tri6, Quad4, Quad8 or Quad9.

When plates with a curved edge are to be converted to faces, there are two options available.

Circular Face Edges: When this option is selected, the curved edge of the face is fitted to a circular definition. This is

not necessarily directly mapped to the underlying platesQuadratic Face Edges: When this option is selected, the curved edge of the face is fitted to a quadratic definition (aparabola). This is directly mapped to the underlying plates, however with this setting, nodes on the circumference

may not lie exactly on the same radius.

Convert Beams to Faces

It is possible to convert beam polygons to faces within Strand7 using a new geometry tool. If a closed, 2D planar,beam polygon is present, Tools/Geometry Tools/Face from Beam Polygon will allow this to be converted to asingle planar face.


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Choose Tools/Convert/Face from Beam Polygon.

Select All the beams.

ClickApply.

Note:Note:Note:Note: Beams can be deleted after being converted tofaces by setting Delete Beams.

Four faces will be created based on the four closed beamloops in the model.

Note:Note:Note:Note: Beam polygons must be planar for this tool towork.

There is one other setting in the Face from Beam Polygon dialog that can be changed, Edge Tol (deg). Thissetting controls how the edges are fitted to the beam geometry. If the Edge Tol is set to 0, the edges are an exact fit

to the beam polygon between the nodes. If the Edge Tol is between 0 and 90, the edges will be a polynomial fit tothe beam geometry between the nodes. This is important if the beam geometry is defining a circular or curved area.A line of beams around a curve will be faceted, but by changing the Edge Tol, a polynomial fit through the nodes

can occur to give a smooth curved edge to the face.

Edge Tol (deg) = 0 Edge Tol (deg) = 50

Face from Cavity

If a cavity exists in a model, a face can be created based on this cavity.


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Choose Tools/Geometry Tools/Face from Cavity.

Select the cavity you wish to convert to a face.

ClickApply.

Note:Note:Note:Note: By selecting the tool first you will be able to select thecavity loop instead of the whole face.

A face will be generated based on the cavity.

Rebuild Faces

Sometimes geometry imported from CAD have poorunderlying B-spline surface definitions. While the shape of theface may seem correct, automatic surface meshing of the facemay lead to extremely poor mesh quality due to thetroublesome associated surface definitions. This is undesirablefor finite element analysis.

The geometry on the right has a bad surface definition and assuch the mesh produced is poor quality.

With the new option ofTools/Geometry Tools/Rebuild Faces the user has the option of refitting a new, betterquality surface over the existing surface. This leads to an improved automatic surface mesh.


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Within the Rebuild Faces tool, the user has the option to choose either Auto or Custom settings. IfAuto is used,Strand7 bases the rebuilding of the new face on parameters from the current surface definition. If Custom is chosen,the user has to specify the Degree and the number ofControl Points for the new surface definition in the twosurface parameter directions U Dir andV Dir.

The Degree setting specifies the order of the mathematical expression used to define the new surface. Typicallycustom settings of degree 1 to 3 should suffice, e.g. planar surfaces are degree 1 and curved surfaces are degree 2.

The number ofControl Points required depends on the curvature of the face in the different parameter directions.Usually the default minimum settings wont suffice. By using Entity Display/Geometry/ Show Control Points youcan gain an insight into the number of control points required for the face rebuild.

The geometry on the right has been rebuilt and it can be seenthat a vastly improved mesh has been generated.

It is important to be aware that in many situations, rebuilding the face will cause slight changes to the overallgeometry. Particularly geometry with sharp angles and corners which may not be properly captured during the facerebuild.

Convert to NURBS

When geometry is defined as an analytical surface there can be situations where the geometry definition causes apoor surface mesh. To improve the automesh, the surface can be converted to a NURBS surface.

Choose Tools/Geometry Tools/Convert to NURBS.

Export

Geometry can be exported from Strand7 as either IGES or STEP files so that they can be used in a CAD package.

Different export options are available to ensure the most compatible geometry with your chosen CAD package.


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There are a number of options availablewhen exporting an IGES file from Strand7.This includes the following:

Export Format: It is suggested thatinitially the Default format be used. If thisdoes not generate intended results, thenproduct specific formats, e.g. Rhino,

Solidworks, etc, should be used.

For Default or product specific formats the

Format Options are predefined and cannotbe changed.

IfCustom is selected from the Exportformat dropdown then the FormatOptions box becomes active.

Format Options: In this section of the dialog you can directly specify the IGES file format, e.g. Bounded Surface

(143), Trimmed Parametric Surface (144), etc, the Curve definition, i.e. Model or Parameter, and howPeriodicFaces are handled. You can also specify if the surface should remain analytic or be converted to NURBS.

As part of the housekeeping that may have been done in Strand7 you can choose to export the geometry so that itkeeps the specified colour. The colour used can be based on Face Colour, Group Colour or Property Colour. Thegroups the different faces are assigned to can also be exported. The Strand7 groups can be exported as levels using

Groups as Levels and the Full Group Path can be included instead of just the local group tree name. There is noheirachy in IGES files and so the actual Strand7 group heirachy will not be maintained on export.

There are a number of options availablewhen exporting a STEP file from Strand7.This includes the following:

Export Format: It is suggested thatinitially the Default format is used. If this

does not generate intended results, thenproduct specific formats, e.g. Rhino,

Solidworks, etc, should be used.

For Default or product specific formats the

Format Options are predefined and cannot

be changed.IfCustom is selected from the Exportformat dropdown then the FormatOptions box becomes active.

Format Options: In this section of the dialog you can directly specify the STEP file format, e.g. Config ControlDesign (AP 203) orAutomotive Design (AP 214), the Curve definition, i.e. Model or Parameter, and how

Periodic Faces are handled. You can also specify if the surface should remain analytic or be converted to NURBS.

As per the IGES export format you can choose to export the geometry according to its colour definition. The

colour used can be based on Face Colour, Group Colour or Property Colour.

Unlike the IGES file format hierarchical groups are supported by the STEP format. As such, groups areautomatically exported as they appear in Strand7. IfFull Group Path is set then the group name is the full grouppath concatenated with a back slash.


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The following tutorials should aid in the understanding of the new geometry tools available in Strand7 2.4.

Tutorial 1

The first model to be imported is the STEP file of an auger, to be automeshed using plateelements. This model will be used to demonstrate the use ofGraft Edges to Faces inStrand7.

Choose File/New.

Set the units to Nmm.

Choose File/Import and importAuger.stp.

CAD file units do not need to be reset.

Choose Tools/Clean/Geometry and perform a default clean of the model.

If the imported geometry is cleaned andmeshed as is, it can be seen that the spiral ofthe auger (yellow) is not connected to theshaft (green). This can be further illustratedby observing the face free edges and noting

that there is a free edge at the expectedconnection.

The graft tool can be used to correct this.


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Choose Tools/Geometry Tools/Graft Edgesto Faces.

Select All the faces in the model.

ClickApply.

A dialog will appear listing the changes that were

made to the geometry.

You will notice that after this step there is nolonger any face free edge along the connectionbetween the shaft and the spiral. This is confirmedupon automeshing where it is seen that the spiralmesh is fully connected to the mesh of the shaft.


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Tutorial 2

The second model to be imported is the IGES file of a fan, again

to be automeshed using plate elements. This model willdemonstrate the use ofGraft Edges to Faces as well as Split Faceby Plane.

Choose File/New and set the units to Nmm.

Import the file Fan.igs.

Accept the default CAD file units.

Choose Tools/Clean/Geometry and perform a default clean of the model.

Choose Global/Groups and investigate the different groups that have been imported as part of the CAD file.

Predefining groups can make it easier to work with a model in the later stages of the analysis.

Choose Tools/Automeshing/SurfaceMesh.

Enter a Maximum edge length of

2.5%.

Select the Target tab.

Under Plate type select Quad8.

ClickMesh.

You will see that there are a number of areasthat are not compatible, e.g. at the bladeintersections and the collar and shaftconnection.


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Two examples of the incompatible meshesare shown on the right. You can see that themesh of the blades (purple) is not connected

to the top (green) and bottom (blue) partsof the fan.

Also you can see that the collar (orange) isnot compatible with the shaft (red).

Many of these incompatibilities can be taken care of by using the graft tool.


Choose Tools/Geometry Tools/Graft Edges toFaces.

ClickApply.

An automesh of the geometry as it now stands showsthat the mesh around the blades and collar is nowcompatible.

There is still a section of the model however that was not corrected using the graft tool and requires furtherinvestigation.


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If we look at the connection between the shaft and the base of the fan we cansee that the mesh is still incompatible in this region. This is because it is actuallythe intersection of two faces. There is currently no actual edge that lies on the

face of the shaft.

Delete all the plates in the model.

Choose Global/Groups and turn off all the groups except the Shaft and Bottom Plate.

Choose Tools/Geometry

Tools/Split Face by Plane.

The shaft needs to be split in the XYplane, so that it is split in two.

Select the section of the shaft thatpasses through the bottom plate.

Under Plane selectXY.

Under P1 select a vertex that lies onthe plane of the bottom plate.

ClickApply.

The shaft has now been split and an edge lies on the plane of the bottom plate. The inner section of the bottomplate needs to be split so that the mesh will be compatible. This can be done using the graft tool again.

Select the inner Bottom Plate face and one halfof the recently split shaft.

Choose Tools/Geometry Tools/Graft Edgesto Faces.

ClickApply.

The inner face of the Bottom Plate will be splitinto two sections and now when meshed will havea compatible mesh line with the shaft.

Remesh the model using the 2.5% Maximum edge length specified earlier.

This mesh is now completely compatible and could be used in an analysis.


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Tutorial 3

The third model to be imported is an IGES file of a silo consisting of

both horizontal and vertical stiffeners. This example will use GraftEdges to Faces, as well as Intersect Edges and Split Face by Verticesto prepare the model for automeshing.

Choose File/New and set the units to Nmm.

Import the file silo.igs.

Accept the default CAD file units.

Perform a default clean of the geometry (Tools/Clean/Geometry).

Investigate the face free edges in the model.

You will see that the vertical and horizontal stiffeners have face freeedges on all edges indicating they are not attached to the silo walls.This can be seen if the structure is surface automeshed as it currentlystands.


Choose Tools/Geometry Tools/Graft Edges toFaces.

ClickApply.

When looking at the face free edges in the modelnow you should find that there are no free edgesbetween the stiffeners and the silo walls. The meshhere will be compatible.


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Remeshing the model at this stage we can see that while the mesh is compatiblebetween the silo walls and the stiffeners, the mesh is incompatible between thevertical and horizontal stiffeners.

Correcting this is a two step process. First we need to use Intersect Edges to place a vertex at each of theintersections between the stiffeners and then we can use Split Face by Vertices to split the stiffeners and make themcompatible.

Select All the faces in the model. Choose Tools/Geometry Tools/Intersect

Edges.

ClickApply.

This will find the intersections between edges in the

model and place vertices at these intersections. Youshould find that there are now vertices at each of theintersection points between the vertical and horizontalstiffeners (an example of this is circled in red).

The vertical stiffeners now need to be split according to these vertices.

Choose Tools/Geometry Tools/Split Face by Vertices.

Zoom in on one of the intersections between the vertical andhorizontal stiffeners.

Click one of the vertices at this intersection. (A rubberband line

will be drawn similar to when an element is created. This linedefines the line along which the face will be split).

Click the other vertex at the intersection to define the split line, itwill be drawn in yellow.

Repeat this at each of the remaining intersection locations aroundthe silo.

Note:Note:Note:Note: Multiple lines can be drawn in the one step.

ClickApply.

Any face the lines lie on will be split according to the drawn line.


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When this geometry is meshed all the mesh will be compatible.


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Tutorial 4

This tutorial demonstrates the use of the Face from Beam Polygon tool and Graft Edges to Faces tool.

Open the model, Face fromBeam Polygon.st7.

Choose Tools/GeometryTools/Face from Beam

Polygon.

Select all the beams.

We have a sufficient number of

beams defining the curved sectionsso we can map the face directly tothe beams.

Under Edge Tol (deg) enter 0. Set Delete Beams.

The beams will be converted to three faces.

Each closed polygon of beams has created a face, however thegeometry is not yet ready to be automeshed. If you look at thegeometry you can see that the larger green face is not split

according to the smaller octagonal faces.

Choose Tools/GeometryTools/Graft Edges to Faces.

Select all the faces.

ClickApply.

The large face will be split accordingto the octagonal faces.

The larger face will be split according to the octagonal faces.

However the octagonal faces will also still be present. This meansthere are coincident octagonal faces.


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ChooseTools/Clean/Geometry.

Under Duplicate faces

select Leave one face. ClickApply.

The duplicate faces will becleaned, leaving only three,compatible faces in the model.


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Tutorial 5

This tutorial demonstrates the use of the Rebuild Faces tool.

Create a new file and set the units to Nmm.

Import the file Rebuild.igs.

Perform a default clean of the model.

Use the Entity Display to show the wireframes.

The wireframes in this model appear to be skewed towardsthe centre of the geometry.

Surface Automesh the geometry using the defaultsettings.

You can see from the figure on the right that the mesh is ofpoor quality. There are a number of distorted triangularelements.

The reason for this can be seen if we look at the control points for the geometry.

ChooseView/Entity Display and click on the Facestab.

Set Show Control Points.

There is a cluster of control points around the centre of thegeometry and the U and V lines are skewed due to this.


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Choose Tools/GeometryTools/Rebuild Faces.

SelectAuto.

ClickApply.

After the rebuild you will see

that the wireframes are moreuniform so we anticipate animproved mesh quality.

Remeshing the geometry shows the mesh is now more regular with better quality elements.

TheAuto setting in Rebuild Faces allows Strand7 to choose the Degree and number ofControl Points based onthe current values.

Use the Entity Inspector to determine the Degree and number ofControl Points for the geometry.

Note:Note:Note:Note: When Control Points are displayed on the geometry the red lines correspond to the U parameter direction

and the blue lines correspond to the V parameter direction.


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Custom settings can also beused in Rebuild Faces.

Choose Tools/GeometryTools/Rebuild Faces.

Select Custom.

Set Degree to be 3.

Set Control Points to be 4.

Note:Note:Note:Note: Use the currentgeometryDegree and ControlPoint settings as a guide whendeciding the Custom numbers.

Note:Note:Note:Note: The number ofControlPoints must always be at least

one more than the Degree.When the geometry is meshedyou will find that againcompared to the initial modelthe mesh quality is very good.


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Strand7 R2.4 Features


Multi-Point Link

Introduction

The multi-point link is a new link type that allows the definition of a multi-point constraint equation between anynumber of node/degree of freedom combinations.

There are several uses for this link including:

Distributing load to a number of nodes without affecting the stiffness.

Connecting incompatible meshes.

Connecting dissimilar meshes, e.g. Quad8 to Quad4, brick to plate.

Overview Choose Create/Link.

Select Multi-Point from the dropdown.

The multi-point link allows any number of nodes to be connected to a single

Slave node. There can also be a constant in the equation.

Any number of points can be included in the multi-point link.

Nodes can be selected by either entering the node number manually or selectingthe node with the hotpointer, which automatically fills out the node number.

There are two options when considering how factors for the nodes should be

applied, Equal and User specified.EqualEqualEqualEqual

When equal is selected, an equal weighting factor of 1 is applied to all the nodesattached to the slave and the value for the slave is the sum of the attached nodes,plus any constant. For example, for the figure on the right we have

N73=N134+N170+N109+N158+N200+N150+N69+N37+N41+N101

There are three options for equally linking the degrees of freedom, bothtranslations and rotations can be linked, only translations or only rotations.


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User specifiedUser specifiedUser specifiedUser specified

User specified allows you to specify any arbitrary relationship between each of thenodes and the degrees of freedom. For example, for the figure on the right wehave

N5(DX) = -2.5N4(DY) + 1.3N3(DZ) + 1.0N2(DX) + 0.6N1(DX)

When selecting a multi-point link, the array of links will be selected as a group as it is the array that defines the entirelink. For example, in the figure above by selecting just one of the links, the whole array will be selected.

The multi-point link is compatible with NASTRAN and ANSYS MPCs when importing and/or exporting.


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Tutorial 1

Open the model Multi-Point Link Tutorial 1.st7.

This model shows a frame system with three free nodes.These free nodes represent different components thatshould be attached to the frame but which are notmodelled. Instead the loads from these components areto be applied via enforced displacements. These threenodes then need to be connected to the frame so thatthe loads from all of them are applied. The multi-pointlink is ideal for this.

The enforced displacements applied to the free nodesare:

NodeNodeNodeNode DXDXDXDX DYDYDYDY DZDZDZDZ RXRXRXRX RYRYRYRY RZRZRZRZ345 260 170 0 2.5 0 0

343 0 350 -90 0 0 0

344 150 -300 140 0 0 6

Choose Create/Link.

Select Multi-Point fromthe dropdown.

Under Factors selectEqual.

Under DoF select Both.

Under Points enter 3.

Select the Slave node asthe node at the top of theframe.

Select the three free

nodes as the three pointsfor the multi-point link.

You will see rubberband linesappear to allow you tovisualise the multi-point link.

ClickApply.

This will create the link.


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Choose Solver/Linear Static and clickSolve.

Open the Linear Staticresult file.

Use the peek tool to

investigate the displacement atthe top of the frame. You willsee that these displacementsare the addition of thedisplacements at the threenodes attached to the multi-

point link.

For example for DXdisplacements

260mm + 150mm = 410mm.


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Tutorial 2

The figure in the right shows two components. The base of the blue plates are

fixed, while there are enforced displacements applied to the nodes at the top ofthe red plates generating a lifting load. These components should be attached attheir interface, however currently the two meshes are incompatible.

The multi-point link can be used to ensure these two components act as a fullyconnected section.

Open the model Multi-Point Link Tutorial 2.st7.

Show the plates in Property Wireframe to make creating the links easier.

The figure below shows a zoomed view of the incompatible mesh.

Links will be created according to the following:

Link NoLink NoLink NoLink No EquationEquationEquationEquation

1 DX (Node 111) = 0.5DX(Node 107) + 0.5DX (Node 108)

2 DY (Node 111) = 0.5DX(Node 107) + 0.5DX (Node 108)






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To enter these specific equations the User specified multi-point link is required.

Choose Create/Link.

Select Multi-Point from the dropdown.

Under Factors select User specified.

Under Points enter 2.

Select the appropriate Slave node.

Select the two points.

Assign DXas the DoF for all points.

Enter a Factor of1 for the Slave and 0.5 for the twopoints.

ClickApply.

Repeat this to create the remaining five links connecting the appropriate nodes.


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Open the Linear Static result file.

Investigate the displacements and stresses in the model.

In tutorial 2, the slave nodes are those attached to the red plates. But what happens to the model if the slave nodesare attached to the blue plates.

Open the model Multi-Point Link Tutorial 2 (Alternate Connection).st7.

Choose Edit/Online Editor and select the Link tab.

Investigate the link definition for the for the four multi-point links in the model.


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Investigate the displaced shape of the structure.

You can clearly see that the connection at the ends is not maintained.


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Attachment Link

Introduction

One of two new links developed for Strand7 Release 2.4 is the attachment link. This document discusses the linkand how it works as well as providing some worked examples.

Overview

The attachment link can be used to connect incompatible meshes in Strand7. The link forms a connection betweena node and anywhere on the face or edge of an element.

The link can be created manually in the same manner as other links.

Choose Create/Link.

SelectAttachment from thedropdown.

The option is given to link the

Translations and Rotations separately or

Both together.

A node attached to a beam, plate or brick

is selected and then attached tosomewhere along another beam, on theedge or face of a plate or brick.

Position on Face refers to where on thebeam, plate or brick the attachment linkshould be placed.

When selecting a position along a beam, only the u value is usedand should be a number between 0 and 1. For example, if abeam is 10m long and you want the attachment to be at 3mfrom the end, you should enter u = 0.3.

For a plate u and v refer to the natural coordinates on the face

of the plate. Therefore 0,0 is the centre of the plate for a Quad4element. The figure on the right shows an attachment linkcreated from the end of the beam to u = v = 0. u and v should

range from 1 to +1 for a Quad4 element.

The same u and v for plates is applied to brick elements,however it now refers to each individual face of the bricks.


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The figure on the right shows an attachment link positionedaway from the centre of the plate using non zero u and v values.

Perhaps of more use is the ability to automatically create the attachment between the different elements. This is atwo step process that involves assigning an attachment attribute to the elements and then automatically creating theattachment link.

There are three types of attachment available, Rigid, Flexible and Direct.

The model on the right consists of three vertical beams and onehorizontal beam, however the horizontal beam is not connectedto the vertical beams at the node.

Choose Attributes/Beam/Attachment.

Under Type, select Rigid.

Select the end of the vertical beam you wish to attach.

ClickApply.

This assigns the attachment attribute to the end of the beam.

Choose Tools/Attach Parts.

ClickApply.

An attachment link is created

between the horizontal and verticalbeams.

When loaded and solved, thedeform as if they are connected atthe nodes.

The attachment attribute assigned becomes more important if there is a gap between the parts.


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A 100mm gap now exists between the horizontal and verticalbeams.

Under Type select Rigid.

Under Max Gap (mm) enter 100.

ClickApply.


ClickApply.

A rigid link is created between the end of the horizontal beamsand the vertical beams. The attachment link is then placed atthe end of this link.

Under Type select Flexible.

When this is select a beam element is created between theend of the horizontal beam and the vertical beam, withthe attachment link on the end of this beam.

This is useful for modelling contact scenarios as the beamelements created can be assigned as point contacts.

Under Type select Direct.

When Direct is set, the attachment is made directlybetween the end of the horizontal beam and the verticalbeams, regardless of the gap.


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Plate elements can have the attachment attribute assigned to the edge or to the face. When assigning it to the faceyou can select whether the gap direction is in +z, -z or Both.

Attachment attributes are also available for brick faces, geometry edges and geometry faces.


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Tutorial 1

In this first example we will use the plate

edge attachment to create a model of a lugon a base plate.

Open the model Attachment Link Tutorial 1.st7.

The base plate is fully fixed around the

edges and an edge pressure has beenapplied to the top of the bolt hole in thelug.

In this model the base plate mesh was hand built, but at a laterstage the lug was added via automeshing. This has led to anincompatible mesh that is currently singular.

This can be seen in the figure on the right.

ChooseAttributes/Plate/

Attachment/Edge.

Select the bottom edge of theplates of the lug, along the lineof where you wish the plates tobe attached.

Under Type select Rigid.

Enter a Max Gap (mm) of0.

ClickApply.

The attachment attribute will be shown on the plates.


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ClickApply.

This will create the attachment links between the lug and the base plate.

When this model is solved, the mesh now acts as fully welded as required.


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Tutorial 2

Open the model Attachment Link

Tutorial 2.st7.This second example shows a circular tanksitting on soil.

The soil consists of a square brick mesh,while the tank is a circular plate mesh.These two meshes are currently notcompatible.

Two load cases are applied, gravity and ahydrostatic load.

The tank is to be modeled only sitting on the soil, therefore the plates should be free to move away from the bricks.The base of the tank is modeled half the thickness above the bricks and point contact elements will be placedbetween the bricks and plates to correctly capture this contact scenario. The figure on the left below, shows the gapbetween the plates and bricks. When the plates are shown in solid it can be seen that the outer surface of the tank isflush with the soil, below right.


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Hide the brick elements.

ChooseAttributes/Plate/Attachment/Face.

Under Type select Flexible.

Under Direction select +z. Under Beam Type select 1.

Enter a Max Gap (mm) of25.

The thickness of the tank is 50mm, therefore the

distance between the midplane of the plates and thebrick elements should be half this.

ClickApply.

The attachment attribute is assigned to the plates and drawn appropriately.


ClickApply.

This will create the beam elementsbetween the plates and the bricks.Attachment links will connect the ends ofthe beam elements to the brick faces.


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The attachment links and beam elements are shown in the figure below.

Change the beam property to a Normal Point Contact with the following properties.

Initial Stiffness = 1 10-9

N/mm.

Friction C1 = Friction C2 = 0.3.

Set Dynamic Stiffness and Use in first iteration.

Run the Nonlinear Static Solver.

Displacement results forthe model show the tankbeing loaded such that it

compresses the soil it issitting on. The results areas you would expect if themesh between the tankand the soil werecompletely compatible.


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Modelling a Tapered Beam

Introduction

This feature allows the user to taper a beam element along its length, with respect to the local x and y axes of thecross-section. This function may be applied to the beam sections provided in the Strand7 library, as well as anyUser-Defined sections (BXS). The capabilities and accuracy settings of the function are discussed; tutorials to createa simple tapered beam structure are also included.

Overview

ChooseAttributes/Beam/Taper.

The dialog box contains several factors that control the characteristicsof the tapered beam.

N1/N2

A positive non-dimensional value used to specify a scaling factor for

the cross section at the ends on the beams original cross-section (asdefined in the property section). The numbers entered for N1 and N2can either be constants or equations that define the ratio as functionsof the position of the beam end.

Swap

Swaps the values of N1 and N2. Since the beam end is not often

apparent (it can be determined via the Entity Inspector hover overthe element with the Shift key pressed), one can simply apply thechosen values of N1 and N2 onto the beam. If the beam tapers in thewrong direction then this button can be used to SwapSwapSwapSwap the valuesbefore re-applying.

Axis

The direction of the taper will be determined by the local x-axis or y-axis of the beam section (as defined in the property section). Note

that you may taper in both x and y directions by successiveapplications.

Taper Characteristics

Taper directions can be biased to one side or another by using theseoptions; the behaviour is summarised in figure below.


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PrecautionsPrecautionsPrecautionsPrecautions

The values N1 and N2 only scale the D value (y-direction)

and B value (x-direction) for tapering, while values of L,T1, T2 and T3 remained unchanged.

If the whole section has to be tapered accordingly, a User-Defined beam section can be employed, by using the BXSfiles.

The beam plane 12 will be rotated if the taper Top or

Bot option is selected. This is due to the fact that beamnode position will remain unchanged and be located at thecentroid of either tapered or non-tapered section. This isillustrated in the figure below.

x

y

Beam section plane tilted due toselection y-top taper option.


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Accuracy of Tapered Beam

The Elastic Strain Energy in a beam can be expressed as follows:

dxEI

MU

L

i = 02

2

wherei

U is the Elastic Strain Energy;

M is the internal bending moment varying along the beam;

E is the Youngs Modulus varying along the beam;

I is the moment of inertia about neutral axis;

L is the total beam length;

x is the variable length from one beam end.

If a loading is gradually applied onto a beam such that kinetic energy can be neglected, and it eventually causes thebeam to displace in the same direction of loading; then this physical load is said to be transformed into elastic strainenergy stored internally in the beam. And therefore, the conservation of energy states that the work done byexternal load is equal to the internal energy stored at the state of equilibrium as following:

ie UU =

thus, dxEI

MP

L

= 02

22

1

where P is the applied load;

is the vertical deflection in the same direction of applied load.

For example:

A solid rectangular cross sectional beam has a second moment of area and internal bending moment varying alongthe length of the beam:

33

212

=

L

xthI

( )xLPM =

Substituting into the conservation of energy equation and assuming Eis constant along the beam:

h

xL

P

2h

t


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( )

( )

( )

3

3

0 3

2

3

3

0 33

22

817766.0

2

12

2

12

22

1

Eth

PL

dxxL

xL

Eth

PL

dx

L

xthE

xLPP

L

L

=

=

=

So if we let P= -1000 N, L= 0.1 m, E= 1x109Pa, t= 0.002 m, h= 0.025 m; then = -0.0261685 m.

In the following section a Strand7 model of this problem is built and the results compared.

Strand7 output : - 0.0261726 m [based on 5 integration points]

The Strand7 default number of integration points for a beam is 5.To improve the accuracy of the Strand7 tapered beam, you canincrease the number of integration points within the beam length.This can be done by:

Choose Property/Beam to open the beam property dialogbox.

Under Section tab, enter a value of 6 for Integration Points. Resolve the model and note the change in DY value.

Repeat for 7, 8, 9, and 10 Integration Points along the beamlength.

Theory

Exact -0.0261685

4 points -0.0262389

5 points -0.0261726

6 points -0.0261687

7 points -0.0261685

8 points -0.0261685

9 points -0.0261685

Strand7

10 points -0.0261685


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Examples

Three examples are included to demonstrate the functionality of the beam taper attribute tool.

Example 1Example 1Example 1Example 1

Random Hollow Rectangular Beam

This example shows the method ofsetting up a tapered beam in both localx- and y- axes by using constant valuesas well as using simple equations toderive the appropriate values. Themodel consists of a standard rectangularhollow section which tapers without

changing its thicknesses.


Tapered Bridge Section

This example illustrates the ability of thebeam taper attribute tool to taper the

cross section of the beam accordinglywith the inclusion of thicknesses andother features (BXS section).


Defining Taper Using Equations

This example provides a simpledemonstration to taper any beam

configuration with the use of equations.


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Example 1: Random Hollow Rectangular BeamExample 1: Random Hollow Rectangular BeamExample 1: Random Hollow Rectangular BeamExample 1: Random Hollow Rectangular Beam

Choose File/New.

Choose Global/Unitsand setNmm. Choose Create/Node:

Node 1: (0,0,0) Node 2: (20,0,0) Node 3: (50,0,0) Node 4: (60,0,0) Node 5: (90,0,0) Node 6: (120,0,0)

Choose Create/Element and create 5 Beam2 elements connecting the 6 nodes with individual property:

Beam 1: prop1, node 1-2 Beam 2: prop2, node 2-3 Beam 3: prop3, node 3-4 Beam 4: prop4, node 4-5 Beam 5: prop5, node 5-6

ChooseView/Entity Display and select Solid as display mode and checkDraw Axes under Beam tab.

Choose Property/Beam, and under the Geometrytab, select Edit, select HollowRectangle and keyin following values:

B: 10 [mm] D: 10 [mm] T1: 1 [mm] T2: 1 [mm]

Click the Copy To button and copy the currentproperties to all other beam properties 2 ~ 5.


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The model should now look like this:


Highlight Beam 1, and apply the following options to it:

N1: L/10 N2: L/10-0.5

Axis: both x and y Select Sym

Beam 1 is now tapered in a converging manner, in both localx- and y- axes symmetrically. Note that the thickness of thebeam at both sides remains constant, as the taper functiondoes not apply to thickness of the section defined by

Library or Edit under geometry tab in Property/Beam.If thickness tapering is required, BXS files may be used toenable the tapering of whole section. Also note that thevariable L used in the N1/N2 boxes refers to element length.

Select Beam 2, and assign the following parameters:

N1: 1.5 N2: 1.0 Axis: both x and y Select Top for both operations

Beam 2 is now tapered but in a practical sense, it shall beadjusted to fit geometrical edges.

Select nodes 3 ~ 6. Choose Tools/Move/by Increment Move by an appropriate value as well as direction, in

this case, y = 2.5 [mm] and z = -2.5 [mm].

Note: values are approximated by 0.5*(N1 N2)*X, where X

represents D (local y-axis) or B (local x-axis), depending onthe taper direction.


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Highlight Beam 3, and apply the following parameters:

N1: 1.0 N2: 0.5 Axis: x Select Top

Select nodes 4 ~ 6.

Choose Tools/Move/by Increment Move by z = -2.5 [mm].

Apply these options to Beam 4:

N1: 0.5; N2: 1.0 [x-Axis, Sym] N1: 1.0; N2: 0.5 [y-Axis, Bot] Move nodes 5 and 6 by y = -2.5 [mm].

Lastly, Beam 5 is tapered divergently in the local y-axisdirection:

N1: 0.5; N2: 2.5 [y-Axis, Bot] Move node 6 by y = 10.0 [mm].

You can clearly see that the thicknesses in Beam 5 remain unchanged regardless of how the element is tapered.


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Example 2: Tapered Bridge SectionExample 2: Tapered Bridge SectionExample 2: Tapered Bridge SectionExample 2: Tapered Bridge Section

Choose File/New.

Choose Global/Units and set Nmm.

Choose Create/Node:

Node 1: (0,0,0) Node 2: (3e4,0,0) Node 3: (0,0,1e4) Node 4: (3e4,0,1e4)

Choose Create/Element and create 2 Beam2 elements connecting the 2 of 4 nodes together with individualproperty:

Beam 1: prop1, node 1-2 Beam 2: prop2, node 3-4

ChooseView/Entity Display and select Solid as display mode as well as checkDraw Axes under Beam tab.

Choose Property/Beam, and under the Geometrytab, select Edit, select BXS and open up the filebridge section.bxs:

Click the Copy To button and copy the currentproperties to beam property 2.

Depending on how you connect the nodes in forming the beam element, the beam local axes may be aligned

differently.

Choose Tools/Align/Beam Axesand in this case, select 1 Axis,Y, and + underAlign, With, and Dircategories respectively, then highlight Beam 1 and Beam 2 and clickApply.


Select Beam 1, and apply these parameters to it:

N1: 2.5 N2: 0.5 Axis: y Select Bot

Select Beam 2, and taper it in the local x-direction:


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N1: 1.5 N2: 0.5 Axis: x Select Sym

Take note that the whole cross section in the specific direction is now scaled by the taper function, including beamthicknesses and features.

Example 3: Defining Taper Using EquationsExample 3: Defining Taper Using EquationsExample 3: Defining Taper Using EquationsExample 3: Defining Taper Using Equations

Three beams of different crosssections shown on the right areready to be tapered according to

user-defined functions.

Open the modelFunctioned Beams.st7.


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First taper the I-beam (Beam Property Type 1) as a function of X-position of the nodes into a diverging quadratic I-beam. So select all

Beam Property 1 elements and:


Assign equations to both N1 and N2:

x^2/5000^2+1 Taper iny-Axis, and Sym manner.

What is happening behind the scenes is that the node coordinate valuein global X axis has been extracted and treated as the x value in theequation assigned to both N1 and N2.

Now, try to taper the other two beams using sinusoidal functions in both 1-axis and 2-axis respectively:

Assign equations to both N1 and N2 of the solid circular section beam (Beam Property Type 2):

2*sin(x/46)+1Taper iny-Axis(2-axis), and Sym manner.

Assign equations to both N1 and N2 of the Z beam (Beam Property Type 3):

2.5*abs(cos(x/50))+1Taper inx-Axis(1-axis), and Sym manner.

Refer to Entering Numerical Data in the Strand7 Online Help for all available mathematical functions andparameters. Now the beams look like this:

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