GP E Getting Started Auto Meshing

7/25/2019 GP E Getting Started Auto Meshing

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RM BridgeProfessiona

GETTING START

R

l Engineering Software for Bridges of all Ty

D - AUTO MESHING

Bridge V8i

uly 2013

es


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RM Bridge

Getting Started - Auto Meshing I

Bentley Systems Austria

Content

1 General .............................................................................................................. 1-1

1.1

The Example (Tutorial) .............................................................................. 1-4

2 Composite cross section ..................................................................................... 2-1

2.1 Create steel boundary of Part 1 .................................................. ................. 2-1

2.2 Create concrete boundary of Part 2 ............................................................. 2-4

2.3 Place boundary subdivision points to composite boundaries (Parts 1+2) ..... 2-5

2.4 Placing stiffeners........................................................................................ 2-6

2.5 Generate auto-elements .............................................................................. 2-9

2.6 Fine-tuning of the auto-mesh .............................. ...................................... 2-10

3

Cross section with three voids ........................................................... ............... 3-19

3.1 Create outer boundary of Part 1 ................................................................ 3-19

3.2 Create holes ............................................................................................. 3-21

3.3 Create initial mesh ................................................................................... 3-22

3.4 Fine-tuning of the auto-mesh .............................. ...................................... 3-22

3.5 Shear lags ................................................................................................ 3-25

4 Cross section defined by point-wise boundaries ............................................... 4-29

4.1 Create outer boundary of Part 1 ................................................................ 4-29

5

Useful informations ........................................................................................ 5-38

5.1 Meshing of cross section boundary where border contains curved lines .... 5-38

5.2 Referencing of auto-elements ................................................................... 5-41

5.3 Some of advantages against one-by-one element creation......................... 5-42

5.4 Element nodes along bridge axis .............................................................. 5-44

5.5 Unique intersections ................................................................................. 5-44

5.6 Zero degree rule ....................................................................................... 5-45


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RM Bridge General

Getting Started - Auto M e s h i n g 1-1


1 General

The following example will show creation of cross section elements using boundaries and

auto-meshing for a small bridge structure. All input steps are described in detail and weinvite you to follow the procedure as follows to get a feeling for the program use.

Definition:

1. Two new types of construction lines

Circle and circular arc.

2. Boundaries

Geometrical definition of the boundary, boundary line segments and subdivision

points.

3. Use of line-wise or point-wise defined boundaries

4. Auto-Mesh

Geometrical definition of auto-elements and their relation to boundaries.

5.

Stiffeners and shear lags at the boundaryTheir relation to boundary and elements.

Needed knowledge (basic knowledge is enough):

Project creation

How to create axis (and stations)

Part definition

Variable definition

Cross section definition

How to create construction lines

How to place stiffener at element

Element definition

Any border around elements of cross section is calledBoundary.

The border around elements that define single part of the cross section is called Outer

boundary. All elements within outer boundary are called auto-elementsand procedure for

their construction is called auto-meshing.

Border inside of outer boundary that does not contain any element is calledBoundary hole.

Border of element edges inside of outer boundary that are not defining boundary hole is

calledBoundary constraint.

Boundary constraint can be closed or opened (and is called Closed constraint inside of

outer boundaryor Opened constraint inside of outer boundaryrespectively).

Boundary is defined by set of connected boundary line segments.


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RM Bridge General



Every boundary line segment contains begin point, end point and optionally additional

boundary line segment subdivision points. We will name begin and end point as subdivision

points too, the only difference is that they are read-only for the user.

There exist two different approaches how to define boundary:

Line-wisedefinition

o Boundary line segment is defined by construction line. Begin and end point

of line segment are defined by intersection of underlying construction line

and other two construction lines.

o Boundary line segment can be part of straight line, complete circle or part of

it, complete arc or part of it.

o Boundary line segment can be split into more line segments. Split point is

defined with intersection with given construction line.

Point-wisedefinition

o Boundary line segment and its begin and end point are defined by two con-

struction lines intersections.o Boundary line segment can be rounded with given radius.

o Boundary point can be rounded or cut-off with given radius.

Line-wise and point-wise boundaries can be used at same cross section.

Orientation of the boundary is not important for meshing (boundary hole does not need to

have opposite orientation than its outer boundary and closed constraint can have opposite

orientation than its outer boundary).

There are two new types of construction lines available for easier creation of cross section

with curved borders (they are useful only for line-wise defined boundaries since point-wise

boundaries accept radius as a parameter):

1. Circle with given radius where centre is defined by intersection of two construction

lines.

2. Arc with given radius where two bow points are defined by intersections between

two construction lines. Bow is generated from first to second point in clockwise di-

rection if radius is positive. Bow contains two legs (extended bow lines to infinity)

that can be turned off.


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RM Bridge

Getting Started - Auto M e s h i n g

Bentley Systems

Icons for circle and a

creation icons.Note: If you are familiar w

change element edge to ap

auto-meshing generated ele

Instead use circle and arc co

c creation can be found next to other c

ith one-by-one element creation, you probabl

ear as curved edge. There is no way to chan

ents, because their edges depend on border of

struction lines for boundary creation (and auto-

General

1-3

Austria

nstruction line

know how to

ge curvature of

the boundaries.

meshing).


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RM Bridge General



1.1 The Example (Tutorial)

A composite cross section and its elements will be created:

We will also place one stiffener to steel part of the cross section.

Also cross section with three voids and its elements will be created:


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RM Bridge General



We will also place two shear lags to the boundary.

Last example will be creation of cross section using point-wise boundary definition:

There are boundaries and auto-meshing icons available on top of preview window:

First row contains general line-wise boundary actions, second row general point-wise

boundary actions, third row deals with boundary subdivision points and fourth row contains

actions for element creation.


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RM Bridge Composite cross section



2 Composite cross section

First example shows how to create composite cross section (1+2=3) and their elements us-

ing line-wise boundaries and auto-meshing. Only few mouse clicks and parameters areenough to get good mesh, but we will use more steps in this example just to show all possi-

bilities that auto-meshing provides.

2.1 Create steel boundary of Part 1

Lesson 01 Some of the data is

already prepared, for

example needed con-

struction lines.

Select Compositecross section. Construc-

tion lines are ready for

boundary creation.

Pick Outer boundary

icon.

Activate Part 1


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Before you start with whole process for automatic generation of elements using bounda-

ries, you should remember one difference to well-known approach where you created

elements one-by-one:

For elements made one-by-one: you had to select sequence of intersection points

between construction lines.

For line-wise boundary construction: select sequence of construction lines.

Click at construction

line CL_5 to start creat-

ing the outer boundary

for part 1.

Note to start by clicking the construction line inside the range of the boundaryto be

drawn to get the proper direction of the circumference of the boundary lines describing

the cross-section. For the following boundary lines the program will show the direction

of the boundary line being drawn when moving the cursor over a construction line.

Move with the mouse

over construction line

CL_14 (in downwards

direction) and click the

mouse to add new

boundary line segment.

In this way the construction lines describing the circumference of the cross-section can

be selected one after another in consecutive order.

In this case we continue in clock-wise order as follows:

CL_10, CL_72, CL_8, CL_9, CL_12, CL_6, CL_11, CL_9, CL_7, CL_73, CL_10,

CL_13.

(Of course counter-clockwise circumference would also be possible).

Important: When you finish with the sequence, do not click at first construction line

CL_5 again. That would generate wrong boundary with duplicated CL_5 (boundary

would not be closed or would be closed wrong). Closing is done automatically by Mod-

eler when you press ENTER (it connects boundary line segment at CL_13 with line seg-

ment at CL_5).

You can always UNDO the selection with pressing BACKSPACE key. Pressing ESCkey will cancel operation and delete the boundary.

If you see dotted boundary lines it means that boundary could be closed this way if you

would press ENTER key.


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Press ENTER key to

complete boundary

creation. Dialog with

general boundary prop-

erties appears. You canset different parameters

(part, boundary type,

boundary parent, shear

lag properties, color

etc.). After clicking at

Ok button boundary

is closed. Modeler

closes the boundary at

the point of intersection

between last and first

selected construction

line - you should seeclosing lines as dotted

lines before you

pressed ENTER.

Boundary for part 1 is

created.


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2.2 Create concrete boundary of Part 2

Lesson 02 Activate Part 2. We are

still in action to create

outer boundary...




for part 2.

Now continue with selection of construction lines in following order:

CL_4, CL_32, CL_64, CL_5, CL_65, CL_21, CL_3.

Press ENTER key to complete boundary creation and press Ok button in next dialog.

Boundary for part 2 is

created.

You can see that boundary line segment at construction line CL_5 was split to three

boundary line segments. This is necessary because element edges of composite parts 1

and 2 will have to match.

Also boundary line segment at construction line CL_1 was split to three boundary line

segments. This may be useful if points at opposite sides of boundary should move paral-

lel. In this way points of middle boundary line segment at CL_1 will move parallel topoints of middle boundary line segment at CL_5.

Split of entire boundary or boundary line segment can also be done by user. Just use

icons for splitting. To undo the split ie. to merge two consecutive boundary

line segments that use common construction line, icon can be used.


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2.3 Place boundary subdivision points to composite boundaries(Parts 1+2)

If we would generate mesh at this moment, some thin triangles would be generated that are

not expected as elements. Therefore we need additional points at the boundary. You canplace points individually, globally over entire boundary with maximal given distance be-

tween them or with special approach that looks for opposite edges. For composite cross

sections, third method is very useful.

Lesson 03

Select icon for bound-

ary subdivision. Then

select upper boundary

that defines Part 2.

Dialog for placement of

subdivision points ap-

pears. Keep current

selection and press

Ok.

The above method sends rays from every boundary line seg-

ment begin point in horizontal and vertical direction. Ray hassome range and width. If entire ray hits single boundary line

segment where no subdivision points already exist, it creates

subdivision point at intersection coordinates.


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We are still in action

for placing boundary

subdivision points. Just

click at lower steel

boundary of Part 1 andpress Ok in dialog. In

this case subdivision

points at coordinates (-

0.0275, -0.3) and

(0.0275, 0.3) were for

example created. Simi-

lar happened at lower

side of the boundary

(noted with green brush

in the picture here).

This special approach does not stop here. If new point is also

added to neighbouring boundary, the process is repeated there

too. In this particular example two additional points were cre-

ated at boundary of Part 2 at coordinates (-0.0275, 0.0) and

(0.0275, 0.0).

2.4 Placing stiffeners

Stiffeners can be placed at the boundary. If elements are not generated yet, stiffener refer-

ences the boundary. After auto-elements within boundary are created, stiffeners change the

reference to touched elements. If user deletes mesh elements, stiffener reference changes

back to the boundary.

Lesson 04

Select stiffener at

boundary line segment

icon from top list of

action icons. The icon

can be found under

normal stiffener icongroup.


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Proceed similar as

when placing normal

stiffener at normal

element. The only dif-

ference is that insteadof selecting element

edge, boundary line

segment has to be se-

lected. Click at long

right vertical boundary

line segment of steel

part that is sitting at

construction line CL_8.


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line CL_67 that inter-

sects the boundary.

Chose the side (for ex-

ample click somewherebelow CL_67). Dialog

with stiffener parame-

ters opens. Just confirm

and stiffener will be

placed.


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2.5 Generate auto-elements

We are now ready to mesh both boundaries.

Lesson 05

Select Create boundary

elements from top ac-

tion icons.

Select boundary of part

1.

Dialog with question

appears (only if first

time meshing of par-

ticular boundary is exe-

cuted). We would like

to connect all points

directly without gener-

ating elements thathave nodes in interior

of the boundary. There-

fore we say No. Ele-

ments should be visible

now.

Repeat the same proce-

dure for part 2 too. We

are still in action to

mesh, therefore just

click at the boundary

and above dialog ap-pears again. Mesh for

Part 2 boundary should

be visible after pressing

No.


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2.6 Fine-tuning of the auto-mesh

User may not completely agree with the mesh that was generated. There may be too largeelements, or he wants smaller elements at particular area because of detailed FEM calcula-

tion. There are many ways how to improve the quality of the mesh.

Lesson 06

Let us concentrate at

very small area on top

of the steel boundary of

Part 1. As you can see,

reference point wasalready prepared at

intersection between

construction lines CL_2

and CL_10.

If we select that refer-

ence point and click at

Edit icon on left side,

we get information in

separate dialog that

touched elements

around that pointshould be refined. Re-

finement is shown with

dotted lines within the

element.

Another way for refinement is to place set of subdivision points at particular boundary line

segment.


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both long vertical line

segments in middle of

steel boundary. We

would like to generate4 points at line on left

and right sides. To do

this, click first at Sub-

division points at line

segment icon.

Select long vertical line

segment of boundary of

Part 1.


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Dialog appears where

we can set range of the

points at line segment

and distance between

them. We declare 6points. Ignore first and

last pivot point should

be checked on, because

every line segment al-

ready has a read-only

point at relative posi-

tion 0.0 and 1.0, and we

do not want to generate

duplicates. Such input

will generate 4 new

points within line seg-

ment. Press Applybutton and points

should be placed and

boundary automatically

remeshed.

We can see that some thin triangles have been generated, be-

cause subdivision points at left long vertical line segment are

missing. There are two ways how to place them.

We can use same ap-

proach as above or do it

different way: Click aticon Mirror subdivi-

sion points in bound-

ary icon group. We will

mirror the points be-

cause orientation of

both line segments is

opposite (one is show-

ing down and another

showing up). This is

the only situation

where user really cares

about orientation of theboundaries.


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Select source line

segment where points

already exist and then

target line segment

where we want to over-ride subdivision with

source points. After this

operation we get 6 ele-

ments with reasonable

size.

Easy tuning of the mesh can be done by individually (interactive) placing of subdivision

points. Subdivision points can be defined in three ways:

1. By relative distance from begin of the line segment (begin of line segment has value

0.0 and end has 1.0). To place point at middle of line segment, relative value 0.5 has

to be used. If we place multiple points at once (as explained in examples above),

such type of subdivision points is used. Relative value can be set by variable too asit will be shown later.

2. By absolute distance from begin of line segment. Absolute value can be set by vari-

able too as it will be shown later.

3. By construction line. Point is placed at intersection between boundary line segment

and given construction line.


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Lesson 07


upper boundary (Part2). We would like to

have more elements in

middle in the way that

their width somehow

matches with width of

the steel.

Select Subdivision

point defined by con-

struction line.

Click sequentially at

four intersections be-

tween boundary of part

2 and construction lines

CL_7 and CL_8. After

every click boundary

and its neighbouring

boundaries are

remeshed.


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Hint: To delete the

subdivision point (of

any type) during inter-

active placement of the

points, just hold leftSHIFT and click at

existing subdivision

point. Remesh will be

executed immediately.

Another way to delete

the points interactively

is to chose Remove

subdivision point icon

and click at points.

Another way for modifying subdivision is doing it from boundary line segment edit dialog.

Lesson 08


top of lower boundary

(Part 1). We would like

to have more elements

in rounded area. There-

fore select left curved


that sits at arc construc-tion line CL_73.


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Click at Edit icon on

left side and Edit

boundary dialog will

open. It has three tab

pages. Line segmentpage is selected be-

cause we selected line

segment only (not

complete boundary).

We can see that

rounded element is notwell approximated to

the boundary arc,

which is additional

reason to subdivide this

line segment with addi-

tional points. We can

easily add new point.

Just select any row in

the table of points and

press Copy icon. It

creates a copy of se-

lected point at samecoordinates. The status

of newly created point

in last column of the

table is Overlap, be-

cause it overlaps with

another point. (Hint: we

could easy delete over-

lapped points using

Purge icon).


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Select newly created

point in the list. Point is

also highlighted in pre-

view window. Now

correct Relative pa-rameter of the point to

0.4 in the dialog and

press ENTER key. You

will see that point in

preview window is

placed near middle of

the arc. Do not worry if

mesh was not recreated

with new point, be-

cause preview window

shows only temporary

data.

We would like to add

point to opposite arc

line segment too; there-

fore two icons are

available for switching

to next or previous line

segment. Just click next

until you move to op-

posite arc line segment.

You may be asked to

save your changes be-fore moving.

Insert new point as ex-

plained before, but set

its relative value to 0.6.

(Hint: it is possible to

bind relative or abso-

lute value with cross

section Variable).


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The dialog contains

Ignore when meshing

checkbox for every


Unfortunately all over-lapped line segments

are already purged

when creating the

mesh, but there may be

the reason where user

wants to say if particu-

lar line should not be

considered during mesh

generation. Example

may be if particular line

segment of boundary

that defines shear lag isintersecting or outside

of outer boundary.

Press Ok to save the

changes and to close

the dialog. If old mesh

was just deleted and not

remeshed, look for

mesh icon and remesh

the boundary again.

Composite cross section and its elements are now ready to use.


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RM Bridge Cross section with three voids



3 Cross section with three voids

Another line-wise boundary example will show how to:

create holes,

define shear lags,

set global subdivision points over entire boundary with given distance

create elements that have nodes in interior of the boundary,

3.1 Create outer boundary of Part 1

Lesson 09

Select Slab3Voids

cross section. Construc-

tion lines are ready for

boundary creation.


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Pick Outer boundary

icon.

Activate Part 1




for part 1.

Move with the mouse

over construction line

CL_4 and click the

mouse to add new


Now continue with selection of construction lines in following order:

CL_60, CL_65, CL_43, CL_9, CL_42, CL_63, CL_59, CL_3.

You can always UNDO the selection with pressing BACKSPACE key. Pressing ESC

key will cancel operation and delete the boundary.

If you see dotted boundary lines it means that boundary could be closed this way if you

would press ENTER key.


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Press ENTER key to

complete boundary

creation. General

boundary properties

dialog appears. Acti-vate Generate global

subdivision points and

correct maximal edge

length to 0.5m. After

clicking at Ok button

boundary is closed and

created. Many subdivi-

sion points were placed

at boundary line seg-

ments in the way that

distance between two

of them at same linesegment is not larger

than given length.

3.2 Create holes

Now select Boundary

as a hole icon on top.

Select outer boundary

to tell who will be the

parent of the hole.


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Click at the first circle

from left and press

ENTER key. Again

boundary creation dia-

log appears that sug-gests global points with

such maximal distance

that circle will contain

8 points. Confirm with

Ok.

We need two more

holes. We are still in

holes insertion action,

therefore just select

outer boundary to tell

who the parent of next

hole is and click at

middle circle. Press

ENTER key and Ok

in dialog. Repeat the

same way with circle

on right side. Our

boundary with three

holes is now ready to

be meshed.

3.3 Create initial mesh

Search for mesh icon

on top icons in bound-

ary icon group and

generate the mesh.

When question for al-

lowing element nodes

inside of boundary ap-pears, say Yes.

3.4 Fine-tuning of the auto-mesh

User may be satisfied with generated mesh or not. It may happen that mesh is not symmet-

ric if boundary is symmetric or he does not like to have triangular elements etc. He also

may expect lower number of elements in particular area of the boundary.


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If we look at our example, it is obvious that we do not need small elements at left and right

side of the cross section.

Lesson 10

Pick Delete subdivi-sion point icon and

delete marked points.

We can see that it

would be nice to have

additional point at bot-

tom middle of cross

section. Pick icon Add

subdivision point de-

fined by constructionline and place new

point in middle bottom

of cross section. Alter-

native how to add such

point: select line seg-

ment and open edit

dialog. Add new point

to the list with exact

relative value 0.5.

There are also some

triangles on bottom leftand right side of the

boundary. Pick Add

subdivision point de-

fined by relative dis-

tance and add two

points as shown here.

There are also some

triangles on top middle

of the boundary that we

do not want to have.

Pick Add subdivisionpoint defined by rela-

tive distance and add

two points as shown

here.

We may want fewer elements. Therefore advanced options are available to optimize the

mesh.


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Lesson 11

Select entire boundary

(do not select just sin-gle line segment).

Click Edit icon on

left side. Boundary edit

dialog appears. It is

same dialog as for

modifying boundaryline segment, just an-

other tab page is se-

lected.

We can change here parameter for maximal distance between globally defined points or

turn them on or off. Remark: if you already deleted global point interactively, it will berecreated if you press Subdivide button. All other points user inserts in advance interac-

tively or in line segment tab page are not global and will not be deleted if user turns global

points off by unselecting above checkbox.

Right side of the dialog (next to preview plot window) contains some icons. You can for

example hide construction lines or show elements as filled polygons (may be useful if you

mesh boundary with holes).

Status at bottom of the dialog shows if meshing succeeded or if data is capable for meshing.

Left bottom side of dialog is there for advanced users that want to play with mesh optimiza-

tion parameters. The only items the usual user will use are drop-down button for Meshing

presets and Minimize number of inside points. Minimizing inside points is used if we do

not want that element nodes will be created inside of boundary. There are presets prepared

for particular shape of the boundary (Long edges, Only quadrangles,... ). User can easily

switch between them and immediately see in preview if he gets expected mesh.


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Select Long edges

preset and press

Remesh button. This

preset tries to generate

longest possible edgesinside of boundary, but

still keeps good quality

of the elements. Press

Ok button to save the

changes.

We have to delete just

few subdivision pointsto get very good mesh.

Pick Remove subdivi-

sion point icon and

remove points showed

here.

Such mesh is just one

of many different

meshes we can pro-

duce.

3.5 Shear lags

Shear lag properties are easy to add using boundaries. They just have to be defined as

closed constraint.


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Lesson 12

Select Boundary as

closed constraint iconon top.


to tell who will be the

parent of the constraint.


line CL_67 on right

side of the cross sec-

tion. You may be

prompted that current

boundary mesh will bedeleted if it exists. Con-

firm.


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Continue with clicking

at construction lines to

generate boundary as

shown here and press

ENTER key.

Boundary creation dia-

log with general prop-

erties appears. Set shear

lag property and con-

firm with Ok.

We need shear lag at

left side of the bound-

ary too. Select again

outer boundary to tell

who is parent of the

constraint and generate

boundary as shown

here.

For this training example a variable shear_lag is already prepared and ready to use. Con-

struction lines CL_66 and CL_67 should change shear lag area with above variable. Change

now shear_lag value to 1.0 to make shear lag area wider.


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Boundaries are now

ready to mesh. Pick

mesh icon and select

outer boundary to gen-

erate mesh auto-elements.

Lesson 13 You can now play with

shear_lag value and see

how element nodes

could move through

stations.


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RM Bridge Cross section defined by point-wise boundaries



4 Cross section defined by point-wise boundaries

Next boundary example will show how to:

create boundaries point-wise,

move/add/delete boundary points

round/cut off corners and round edges,

add point-wise void hole with given radius,

add and round opened constraint.

4.1 Create outer boundary of Part 1

Lesson 14 Some things are al-

ready predefined, for

example necessary con-

struction lines.

Select PointWise

cross section. Construc-

tion lines are prepared

and ready for boundary

creation.


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Pick Outer boundary

icon from Point-wise

boundary row.

Activate Part 1

Click at intersection of

construction lines

(CL_1, CL_3) to startcreating the outer

boundary for part 1.

Select intersection (CL_1, CL_4) and continue with selection sequence in clock-wise

order as follows (of course counter-clockwise circumference would also be possible):

(CL_4, CL_13), (CL_6, CL_14), (CL_8, CL_9), (CL_7, CL_9), (CL_5, CL_14), (CL_3,CL_13).

You can always UNDO the selection with pressing BACKSPACE key. Pressing ESC

key will cancel operation and delete the boundary.

If you see dotted boundary lines it means that boundary can be closed this way if you

press ENTER key or click on beginning intersection point.

To finish with bound-

ary creation just click

again on beginning

intersection point

(CL_1, CL_3) or press

ENTER.

Dialog with general

boundary properties

opens. After clicking

OK boundary is

closed and defined.


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Some of the corners

can be rounded now.

Pick Set radius for


or boundary pointfrom Point-wise

boundary row.

Set radius value to 1.0.

Select boundary corner

where (CL_5, CL_14)

intersect. Do the same

for (CL_6, CL_14).Corners should be

rounded now.

Set radius value to 10.0

now and select bottom

edge of the cross sec-

tion. Edge should berounded now. Radius

can be negative too,

depends if we want

rounding on the left or

right side of line (direc-

tion of boundary out-

line defines what is left

or right).


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Corners can be rounded

or cut-off. To cut off

the top left corner of

the cross section, set

radius to -0.1 and clickat boundary corner.

Now set radius value to

0 and click at the cor-

ner point or corner line

and corner will have

the same look again.

Rounding can be re-

moved also in different

way: segment of

rounded line has to be

selected and deleted.

Now select Boundary

as a hole icon.

Set value of radius inthe variable r1, select

outer boundary to spec-

ify parent of the hole

and click twice at inter-

section of lines

(CL_11, CL_10). Dia-

log for placing a

boundary hole will ap-

pear. Just click OK

and void hole with ra-

dius r1 should be visi-

ble.


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Click again at outer

boundary to specify

parent of next hole and

click twice at intersec-

tion (CL_2, CL_10)and press OK in crea-

tion dialog. Repeat the

same procedure for

intersection (CL_12,

CL_10).

There may be a need to

force meshing engine

to generate element

edges at particular,

wished areas. For thisreason constraints can

be created inside of

boundary. Select

Boundary as opened

constraint.


to specify parent of the

constraint and click at

intersections (CL_11,

CL_13) and (CL_12,

CL_13). To finish with

creation of the con-

straint press ENTER

or click at end point

(CL_12, CL_13) of

constraint again. In

creation dialog just

press OK.


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We can also set radius

for the constraint. Pick

the Radius icon, set

radius value to -15.0

and select the con-straint. It should be

rounded now.

There may be a need to

add additional points to

the boundary. Select

icon Insert boundary

point.

Now select boundary

line segment on the top

and click at intersection

(CL_2, CL_13). New

point is added. We are

still in the action to addnew points, therefore

we can simply continue

with sequence of se-

lecting boundary line

segments and intersec-

tions.

To move the point to

another position Move

boundary point icon is

used. Just select newly

created point and moveit to the intersection

(CL_1, CL_2).

Note: Subdivision

points cannot be moved

or deleted this way.


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To delete the newly

added point, use icon

Delete boundary

point. Select the points

you want to delete. Fornow delete lately

moved point at inter-

section (CL_1, CL_2).

Last step is to add addi-

tional subdivision

points to the bounda-

ries. For this we will

use icon Subdivide

entire boundary.

First we select outer

boundary and set sub-

division maximal edge

length to 0.5.

Then select opened

constraint and set sub-

division maximal edge

length to 0.6.


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Cross section bounda-

ries are subdivided now

and ready for meshing.

Pick Create boundary

elements icon and

select outer boundary.

Question for allowing

element nodes inside of

boundary appears.

Click Yes. You

should see the elements

now.

Lesson 15 Final situation.

There exists one feature regarding point-wise boundaries that may be practical to use.

For creation of point-wise boundary there is no need to create construction lines in ad-vance (except of main axis). RM Bridge has special construction line of type Point by

relative coordinate which can be used for point-wise boundary construction.


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If you click during

boundary creation

somewhere where no

construction lines inter-

section exist, a dialogfor placing construction

line intersection ap-

pears. Here you can

correct the offset to

base lines (main axis)

or even set variables for

offset. After pressing

Ok new construction

line cross is created and


added.

Combination of mouse

clicking with one hand

and pressing ENTER to

close the dialog with

another hand and cross

section can be very

easy created.


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RM Bridge Useful informations



5 Useful informations

There might appear situations where some things are not working as expected or they are

not clear. We will try to explain such situations here.

5.1 Meshing of cross section boundary where border contains curvedlines

Imagine following boundary (not a real example, but well suitable for explanation of the

problem):


46/53




This boundary is defined by 3 straight lines and one arc. If we try to mesh this boundary,

we get following message:

The reason for error is that boundary you see is not same as raw polygon going to be

meshed. Raw data used for meshing is a sequence of connected points (polygon with

straight lines):


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To avoid the error, at least one additional boundary subdivision point should be added to

the arc in the way that following raw polygon will be used for meshing:

Such boundary has no self-intersections and mesh can be generated. Finally auto-elements

are approximated to border of the boundary and we see following mesh:


48/53




5.2 Referencing of auto-elements

All elements of single outer boundary should be treated as a group, because all of them are

created together during remesh process. Even for simple operations (like adding single sub-

division point) all old elements are deleted and new elements created. If you would place

additional information (reference points etc.) to any of the elements, the mesh could not bedeleted and new mesh generated. Therefore try to avoid referencing auto-elements from

any other objectsin Modeler. Instead those objects should reference construction lines.

Of course referencing of auto-elements is possible, but you should do it only if you are

100% sure that you will not have to change (remesh) the elements.


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RM Bridge


Bentley Systems

5.3 Some of advantages

There might be just few ad

when elements are created o

construction lines. But whe

ments are expected, auto-m

significantly. Example is foll

64 construction lines were u

just to set their dependencie

ment edge. Imagine what eff

All steps with this approach

construction lines (sets depeadds additional construction

When using auto-meshing a

That is easier, because user

generate a boundary. Placin

construction lines may be ne

Above example was made u

Usef

against one-by-one element creati

antages using auto-meshing instead of well-k

ne-by-one if we expect only few elements and

part of cross section border is curved or m

shing approach reduces number of needed co

owing cross section made with one-by-one app

sed and you can imagine how time consuming

, create each element and then set radius for e

ort it costs if user decides for doubled density o

are usually not done in sequence. Normally use

ndencies), generates element and sets elementlines, generates some of elements, and so on.

proach, almost all construction lines are genera

as to care just about cross section border points

of subdivision points is next step, where onl

ded. Last step is meshing and fine-tuning.

ing auto-meshing approach in much shorter tim

l informations

5-42

Austria

on

nown approach

se just straight

re than 10 ele-

nstruction lines

oach:

approach it was

ery curved ele-

the elements.

r generates few

urvatures, then

ted in first step.

. Next step is to

few additional

e:


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RM Bridge


Bentley Systems

Another way (same example

Number of needed constructi

Usef

how to get auto-elements:

on lines was reduced from 64 to 28!

l informations

5-43

Austria


51/53

RM Bridge


Bentley Systems

5.4 Element nodes alon

Cross section is recalculated

change too in the way that

segment, following rule mus

This may occur if for examp

tive distance. Point with rel

defined by construction line:

5.5 Unique intersections

There is no restriction about

ing a line-wise boundary. O

cular construction line appe

ing the mouse closer to the i

Usef

bridge axis

at every station along axis. Location of eleme

esh is always valid. If we concentrate at singl

t be kept subdivision points should never s

le one point is defined by construction line and

tive distance may change its position faster t

number of intersections between construction li

e example is when jump from straight constru

rs. User can decide which intersection will be

tersection:

l informations

5-44

Austria

t nodes should

boundary line

itch positions.

another by rela-

an another one

nes when creat-

tion line to cir-

sed with mov-


52/53

RM Bridge


Bentley Systems

5.6 Zero degree rule

There exists one limitation u

is limited to rounded parts o

If new subdivision point at

line and two intersections w

regarding angle in counter-c

Modeler always decides for

near second intersection wh

boundary circle from above

Usef

sers have to be aware, but it will appear very r

boundaries:

uch boundary line segment has to be defined

ith boundary line segment exist, then intersecti

lockwise direction from zero degree point of

first counted intersection, even if user clicks

en choosing construction line (bellow picture

icture):

l informations

5-45

Austria

are in praxis. It

by construction

ns are counted

omplete circle.

ith the mouse

concentrates at


53/53

RM Bridge


If we move violet constructi

counted intersection is chos

bellow zero angle point a

subdivision point completel

lowing pictures):

We suggest for such cases to

instead.

Usef

n line down, intersections are calculated again

n. In following case right side of construction

nd therefore second intersection became first i

changed its location (concentrate on red mark

use subdivision points defined by relative or a

l informations

5-46

and always first

line was moved

ntersection and

ed point in fol-

solute distance

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