GTSTRUDL
Modeling Base Plate
Attachments with Partial Welds
Rob Abernathy
CASE Center
GTSUG
June, 2012 Seattle, WA
GTSTRUDL
What is a “Partially Welded Attachment”?
Attachments are assumed to be welded to the base
plate along all attachment lines. However, in some
situations, only part of the attachment is welded to the
base plate. In versions 31 and earlier of the Base
Plate Wizard, this situation could only be modeled by
creating a custom attachment which included the
welded parts of the attachment and omitted the
unwelded parts. Version 32 adds new tools to allow
modeling the unwelded parts of attachments.
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GTSTRUDL
Custom Attachment Omitting Unwelded Lines
A wide flange welded on the flanges but not the web could
be modeled as 2 lines, leaving out the line representing
the web. You would need to create the two line version
since the standard profiles are assumed to be welded all
around.
Standard
W8x10
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Custom
W8x10 Flanges
only
3
GTSTRUDL
Custom Attachment .gtbp Files
From Appendix A1 The GTBP File Format
100 ID type Profile_ID OffsetX OffsetY RotX RotY RotZ Extension
110 Profile_ID Shape Mirrowed Name Table values[6]
int Profile_ID: Matches with Profile_ID in Attachment (100)
int Shape:
1: I, 2: tube, 3: channel, 4: T, 5: 2L, 6: L, 100: Arbitrary
120 Profile_ID type X1 Y1 X2 Y2 CX CY THICK
$ ---- Attachments: Standard W8X10 --------------100 1 0 1 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
110 1 1 0 W8X10 WSHAPES9 7.8900 3.9400 0.1700 0.2050 0.0000 0.0000
$ ---- Attachments: Custom W8X10 --------------100 1 0 1 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
110 1 100 0 W8x10-Flanges Custom 7.8900 3.9400 0.0000 0.0000 0.0000 0.0000
120 1 0 -1.9700 3.8425 1.9700 3.8425 0.0000 0.0000 0.2050
120 1 0 -1.9700 -3.8425 1.9700 -3.8425 0.0000 0.0000 0.2050
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GTSTRUDL
Issues with Omitted Lines
Omitting attachment lines that are not welded introduces two
concerns. They may or may not affect your results – engineering
judgment must be exercised.
Issue 1: If an unwelded and therefore un-modeled part of the
attachment were to translate in the –Z direction (into the base
plate) or the base plate were to deflect in +Z direction in an
area where an omitted line was would cause an
inconsistency between the physical structure and the
mathematical model.
Issue 2: An “extension” model could not be created for the unmodeled part of the attachment, effectively precluding using
this method for unwelded portions of the attachment.
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GTSTRUDL
How to Model Unwelded Attachment Sections?
The edge of a plate butted against but not welded to a
base plate should transfer compressive force to the
base plate, but not tension or shear (ignoring friction)
forces and no moments. This condition will be
referred to as “Contact Only”.
Two components in GTSTRUDL can model this type
of action: Nonlinear Spring (NLS) elements and TYPE
SPACE TRUSS members declared as
COMPRESSION ONLY with the NONLINEAR
EFFECTS command.
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GTSTRUDL
Modeling Contact Only with NLS
Nonlinear springs are already used to model the
compression-only bearing surface, in much the same
way as is needed for Contact Only, exerting only +Z force
without shear. However, NLS elements add more
complexity, requiring curve data and element stiffness
assignments like the bearing surface NLS:
NONLINEAR SPRING PROPERTIES
CURVE 'BearSurf' FORCE
0.0 0.0 -3907664.702093 -10.0
END OF NONLINEAR SPRING PROPERTIES
NONLINEAR SPRING ELEMENTS
INCIDENCES
'S1‘ ATTACHED TO JOINT 1
STIFFNESS
'S1' Z CURVE 'BearSurf' FACTOR 0.06250
END OF SPRING DATA
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GTSTRUDL
Modeling Contact Only with Compression Only
TYPE SPACE TRUSS members designated as
COMPRESSION ONLY with the NONLINEAR EFFECTS
command will also transfer only +Z resistance without
shear or moments. For several reasons, compression
only members was decided as the modeling method:
1. Simple, easy to understand commands
2. Able to be viewed in GTMenu
3. Less complicated internal nonlinear processing
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GTSTRUDL
Stiffness Connection between Contact Only
Attachment and Base Plate
Both the compression-only and NLS methods need a
spring constant to represent the resistance to
compression between the Contact Only attachment
and the base plate. This resistance can be viewed as
the transverse compression of the base plate due to
the –Z force applied by the Contact Only attachment. A
spring constant equal to a short, stubby steel member
was chosen to model the transverse stiffness of the
base plate.
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GTSTRUDL
Implementing Contact Only in the
Base Plate Wizard
A Contact Only designation has been added to
attachment lines, along with a line’s start and end location
and its thickness. Because any part of an attachment may
be Contact Only, any attachment with Contact Only will
make that attachment ‘Arbitrary’, instead of wide flange,
channel, etc. More on Arbitrary vs. standard profiles later.
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GTSTRUDL
Contact Only Modeling Rules #1 and #2
#1 - If a joint is part of both welded and unwelded lines, it is
considered to be welded. Note: this should only occur at line
ends.
#2 - Base plate joints along a Contact Only line have new joints
created ½ plate thickness above (+Z) them, corresponding to the
top of the plate.
$ ---- Base Plate Wizard user defined data ---------------------$ Plate: 4.000 in X 6.000 in x 0.5000 in  Thickness = 0.5
$ ---- CONTACT ONLY joints and connecting members ---JOINT COORDINATES
36 1.723 1.637 0.250; 37 1.723 3.000 0.250; 38 3.319 1.637 0.250
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GTSTRUDL
Contact Only Modeling Rules #3 and #4
#3 - Compression-only members (TYPE SPACE TRUSS)
are added between the plate joints and the new Contact
Only joints.
#4 - AX equal to MeshSize*MeshSize is assigned to the
new members.
TYPE SPACE TRUSS
MEMBER INCIDENCES
25
36
13;
26
37
MEMBER PROPERTIES AX 1.000000
25 TO 27
NONLINEAR EFFECTS
COMPRESSION ONLY MEMBERS 25 TO 27
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27
38
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GTSTRUDL
Contact Only Modeling Rules #5 and #6
#5 - If the attachment is modeled as a Rigid Footprint,
then the RIGID SOLID includes the new Contact Only
joints, but not the plate joints.
#6 - If the attachment is modeled as 2D finite elements
(extension), then the first row of the extension elements
are incident to the new Contact Only joints, not the
plate joints.
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GTSTRUDL
Simple Example
Create an 8” x 10” plate with a
W8X10 centered, with a 1” mesh.
Generate a .gtbp file and an input
file and run it.
View in GTMenu, noting the
RIGID BODY display.
Edit the attachment and set the
web as Contact Only (unwelded).
Generate a .gtbp file and an input
file and run it.
View in GTMenu, noting the
RIGID BODY display.
Compare the two .gtbp files.
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GTSTRUDL
Simple Example: Generate files
Save the fully welded standard
profile into Simple.gtbp and
then create an input file
Simple.gti. Check the
“Process Input File” box to be
able to view the model in
GTMenu.
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GTSTRUDL
Simple Example: View in GTMenu
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GTSTRUDL
Simple Example: Set
Web as Contact Only
On the Attachment page, edit the
attachment by double-clicking
the column, then click the ‘Edit
Weld Status’ button.
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GTSTRUDL
Simple Example: Select Web and Change Status
Note that the web is marked as line
1. Click the “1” in the Line #
column. Line 1 becomes dashed,
indicating it’s selected.
In the Tools menu, select “Set selected
lines as Contact Only. Line 1 returns
to a solid line, but is now rose colored,
indicating that the web is now
considered Contact Only.
Click the OK button to accept the
new weld status.
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GTSTRUDL
Simple Example: Accept Contact Only Change
When you return to the Edit
Attachment dialog, the web
line will still be blue. Click
the OK button at the bottom
of the dialog to commit the
new weld status.
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GTSTRUDL
Simple Example: Generate Contact Only Files
When a standard profile has Contact Only
lines, it must be stored as an Arbitrary
profile. This dialog informs you of that and
also offers two renaming options. Click the
NO button (reject the suggested new name)
to bring up the New Attachment Name
dialog.
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You can select from the existing
tables or type in a new name.
Type in a new profile name. 39
character limit for both names.
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GTSTRUDL
Simple Example: View Contact Only in GTMenu
Note the web is now modeled as a row of joints above the mid-plate joints.
These new joints are ½ plate thickness in the +Z direction and the RIGID
SOLID includes the new joints and not the plate joints.
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GTSTRUDL
Simple Example: Geometry Close-up
Only Z force (which is FX
for the members) is carried
by the truss members (81
and 82 in this picture) and
only a compressive force.
If joints 100 and 23 move
away from each other, the
member 81 transmits no
force.
$ ---- CONTACT ONLY joints and connecting members ---JOINT COORDINATES
100
4.000
2.000 0.250;
101
4.000
TYPE SPACE TRUSS
MEMBER INCIDENCES
81
100
23;
82
101
32;
MEMBER PROPERTIES AX 1.000000
81 TO 87
NONLINEAR EFFECTS
COMPRESSION ONLY MEMBERS 81 TO 87
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3.000
0.250;
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GTSTRUDL
Simple Example: Compare .gtbp Files
Simple.gtbp
$ ---- Attachments: 1 attachments specified --------------100 1 0 1 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
110 1 1 0 W8X10 WSHAPES9 7.8900 3.9400 0.1700 0.2050 0.0000 0.0000
SimpleContactOnly.gtbp
$ ---- Attachments: 1 attachments specified --------------100 1 0 1 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
110 1 100 0 W8x10-Flanges PartiallyWelded 7.8900 3.9400 0.0 0.0 0.0 0.0
120 1 4 0.0000 -3.8425 0.0000 3.8425 0.0000 0.0000 0.1700
120 1 0 -1.9700 3.8425 0.0000 3.8425 0.0000 0.0000 0.2050
120 1 0 0.0000 3.8425 1.9700 3.8425 0.0000 0.0000 0.2050
120 1 0 -1.9700 -3.8425 0.0000 -3.8425 0.0000 0.0000 0.2050
120 1 0 0.0000 -3.8425 1.9700 -3.8425 0.0000 0.0000 0.2050
Attachment type ( 1 = W shape, 100 = Arbitrary)
Profile
Table name
Line type (0 = welded, 4 = Contact Only)
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GTSTRUDL
Example 2: Partially Welded Channel
Compare results from a fully
welded channel (C8x11.5) with
results from two partially welded
channels welded with the
patterns shown.
Pattern 1
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Pattern 2
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GTSTRUDL
Example 2: Plate with Anchors and Loads
Loads are applied at the
end of 10” 2D
extension, creating MX
(loads Down and UP)
and MY (loads Left and
Right).
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GTSTRUDL
Example 2: Create Custom Attachment
Since the weld patterns do not match the standard profile
lines (flanges and web), a custom attachment is required
with the line definition matching the weld pattern. The
custom attachment below (MyChannels::C8x11.5Parts2x4) breaks the flanges into 2 parts and the web into
4 parts.
110 1 100 0 C8x11.5-Parts2x4 MyChannels 8.0000 2.2600 0.0 0.0 0.0 0.0
120 1 0 -0.4610 -3.8050 -0.4610 -1.9025 0.0000 0.0000 0.2200
120 1 0 -0.4610 -1.9025 -0.4610 0.0000 0.0000 0.0000 0.2200
120 1 0 -0.4610 0.0000 -0.4610 1.9025 0.0000 0.0000 0.2200
120 1 0 -0.4610 1.9025 -0.4610 3.8050 0.0000 0.0000 0.2200
120 1 0 -0.4610 3.8050 0.6690 3.8050 0.0000 0.0000 0.3900
120 1 0 0.6690 3.8050 1.7990 3.8050 0.0000 0.0000 0.3900
120 1 0 -0.4610 -3.8050 0.6690 -3.8050 0.0000 0.0000 0.3900
120 1 0 0.6690 -3.8050 1.7990 -3.8050 0.0000 0.0000 0.3900
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GTSTRUDL
Example 2: View Custom Attachment
This is the view you would see
in Edit Weld Status. Create
separate .gtbp files for each
pattern.
Then write and run the .gti
files and compare the
ResultsSummary files.
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GTSTRUDL
Example 2: Results Comparison
Von Mises
S1
S2
B1
B2
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All Welded
15675
17580
-18089
612
701
Pattern 1
18658
19951
-20309
607
703
Pattern 2
31578
35413
-34347
614
646
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GTSTRUDL
Attachments in .gtbp and the Attachment File
The .gtbp and Attachment File formats are described in
Appendices A1 and A2 of the Base Plate Wizard User
Guide. In addition, examples of custom attachments are
shown in the file ‘SampleUserDefinedAttachments.txt’ in
the <install>\GTStrudl\xx\BasePlate folder (“<install>” =
C:\Program Files (x86) or your alternative location, and
“xx” = the version number).
Custom attachments built on a standard profile are simple,
as we have seen. The next slide shows the standard
profile lines – if they match your welds it is simple to create
a partially welded attachment file.
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GTSTRUDL
Standard Profile Lines
This the line layout with line numbers for the standard profiles
from the GTSTRUDL AISC 9th Edition tables. The Edit Weld
Status dialog easily lets you change the status of any
individual line to Contact Only. If only part of a line is Contact
Only, then you will need to create a custom Attachment File.
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GTSTRUDL
Custom Attachments in the Attachment File
$ In the .gtbp file
110 1 100 0 C8x11.5-Pattern2 MyChannels 8.0000 2.2600 0.0 0.0 0.0 0.0
120 1 0 -0.4610 -3.8050 -0.4610 -1.9025 0.0000 0.0000 0.2200
120 1 4 -0.4610 -1.9025 -0.4610 0.0000 0.0000 0.0000 0.2200
120 1 4 -0.4610 0.0000 -0.4610 1.9025 0.0000 0.0000 0.2200
120 1 0 -0.4610 1.9025 -0.4610 3.8050 0.0000 0.0000 0.2200
$ In the AttachmentFile
TABLE 'MyChannels'
$
Name
NumberOfLines
100 C8x11.5-Pattern2 8
$
X1
Y1
X2
Y2 THICK
$ ------------- ------- ------- ---------0.4610 -3.8050 -0.4610 -1.9025 0.2200
-0.4610 -1.9025 -0.4610 0.0000 0.2200
-0.4610 0.0000 -0.4610 1.9025 0.2200
-0.4610 1.9025 -0.4610 3.8050 0.2200
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Type
---4
4
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GTSTRUDL
Export Anchor Results for Capacity Anchor Check
The new ANCHOR commands
in GTSTRUDL 32 need the
anchor geometry and results
to check anchor capacity by
Appendix D of the ACI code.
The ability to extract this data
has been added to the Anchor
Results dialog. Click the Write
ANCHOR LOADS button to
create a file with the geometry
(optional) and results in the
format required by the
ANCHOR CONFIGURATION
command.
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GTSTRUDL
Generated ANCHOR CONFIGURATION Commands
ANCHOR 1 X
1.000
ANCHOR 2 X
9.000
ANCHOR 3 X
1.000
ANCHOR 4 X
9.000
LOAD 'Down'
1 VX
113.9 VY
2 VX
-99.7 VY
3 VX -119.1 VY
4 VX
104.9 VY
END LOAD DATA
LOAD 'Up'
1 VX -119.1 VY
2 VX
104.9 VY
3 VX
113.9 VY
4 VX
-99.7 VY
END LOAD DATA
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Y
Y
Y
Y
1.000 TYPE 'Anchor1'
1.000
9.000
9.000
257.7
243.8
256.5
241.9
TENSION
TENSION
TENSION
TENSION
34.7
22.2
506.0
631.2
-256.5
-241.9
-257.7
-243.8
TENSION
TENSION
TENSION
TENSION
506.0
631.2
34.7
22.2
33