GT STRUDL Tips and Techniques

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GT STRUDL Tips and Techniques

• GTSUG 2002, San Diego, CA
• June 19-22, 2002
• Leroy Z. Emkin
• CASE Center

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Initial Instability andMultiple Structures
PERFORM NUMERICAL INSTABILTY ANALYSIS PERFORM
NUMERICAL INSTABILTY ANALYSIS WITHOUT REDUCE
BAND STIFFNESS ANALYSIS WITHOUT REDUCE BAND
Example command file with single joint
instabilities C\Temp\Tmp\BM2_01.gti
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Internal Member Section Force Calculations
Example command file sequence C\Temp\Tmp\Sectio
nForcesLoadComb.txt
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Real Reaction Components
------------------------------------------------
------------------------ EXAMPLE OF REACTION
COMPUTATIONS IN A RELEASED DIRECTION AT A
SUPPORT JOINT, THE OUTPUT REACTION COMPONENT IS
EQUAL TO THE APPLIED JOINT FORCE COMPONENT IN THE
RELEASED DIRECTION. SEE ITEM NO. "C" ON PAGE
13-17 IN THE GTSTRUDL USER GUIDE ANALYSIS,
SECOND EDITION. FOR EXAMPLE JOINT
RELEASES 2 FORCE Y IN ORDER TO CREATE AN
"ACTUAL" REACTION COMPONENT IN THE GLOBAL
Y-DIRECTION, RATHER THAN A REACTION COMPONENT
WHICH IS EQUAL TO THE APPLIED JOINT FORCE IN
THE RELEASED DIRECTION, THE FOLLOWING JOINT
RELEASE SPECIFICATION IS NECESSARY DELETE
JOINT 2 REL ADD JOINT REL 2 KFY 0.0
EQUIVALENT TO A FORCE Y RELEASE
--------------------------------------------------
---------------------- Example command
file C\Temp\Tmp\Reaction-Real-New.gti
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Dynamic Analysis Support Reactions
There has been some confusion regarding the
interpretation of support reactions computed by
GTSTRUDL during a dynamic response analysis.
Since the procedure used by GTSTRUDL to compute
such support reactions is not explained in the
user documentation, the following explanation is
provided. Interpretation of reactions at support
joints in a dynamic analysis
1. The
reactions at support joints are computed by
GTSTRUDL as the external joint forces
required to equilibrate the sum of the internal
member end forces acting on the support joint
(see the LIST REACTIONS command discussion
in the GTSTRUDL User Guide Analysis, and the
GTSTRUDL Reference Manual). 2. In a dynamic
analysis, the member end forces include the
influence of the inertial (i.e., mass)
forces acting at the joints to which the member
is connected (i.e., "mass x acceleration"
forces).
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Dynamic Analysis Support Reactions (Cont.)
3. However a. The member end forces
include the inertial force effects, and b.
The reactions are computed based on the member
end forces only, and do not account for
the inertial force effects, then, the computed
reactions are not in equilibrium with both
the member end forces and the inertial
joint forces. Therefore, the reactions
represent the external joint forces that are
required to be in equilibrium only with the
member end forces. In other words, the
influence of the inertial joint forces are not
subtracted out from the member end forces
when reactions are computed.
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Dynamic Analysis Support Reactions (Cont.)
4. An example of the above is a horizontal
(X-direction) cantilever beam fixed at the
left joint and on a roller support (FORCE X,
MOMENT Z joint release) at the right joint.
One-half of the beam mass is lumped at each
joint. From a dynamic analysis, the horizontal
(X-direction) reaction at the roller support
will not be equal to zero since it is computed
by GTSTRUDL as the horizontal reaction
required to equilibrate the member's axial
force at the right end of the beam. Since the
axial force in the member is in equilibrium
with the inertial force at the right joint,
and since the X-direction reaction is in
equilibrium with the axial force in the
member at the right end of the beam, the computed
X-direction reaction equals the horizontal
inertial force ("mass x horizontal
acceleration" force of the lumped mass at the
right support joint), rather than being
equal to zero.
5. Since the difference between the exact
reaction value and the one computed by
GTSTRUDL is the inertial joint force (i.e., the
force due to the "joint lumped mass x
acceleration"), and if this joint mass is small
(such as one-half of the mass of the members
incident on the support joint) when compared
to the total mass of the structure model, this
difference is often negligibly small.
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Dynamic Analysis Support Reactions (Cont.)
6. To avoid the above problem with the
computation of support reactions in dynamic
analysis problems, the following can be done
a. Define a new joint close to the actual
support joint (say 1 inch or 2 cm
from the support joint). b. All
members incident on the support joint should
instead be incident on the new
joint, and any nonstructural mass applied to
the support joint should instead be
specified as acting at the new
joint. c. The sum of one-half of the
mass of all members incident on the
new joint will now be lumped at the new joint
rather than at the support joint,
and any specified nonstructural mass will also
be acting at the new joint.
d. Define a fictitious member with very
large properties (i.e., a rigid
member), BUT with ZERO mass, to go from the new
joint to the support joint. The
ZERO mass condition can be defined by giving
the weight density of the fictitious
member as a very small value
(e.g., CONSTANTS DENSITY 0.00001 for the
fictitious member).
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Dynamic Analysis Support Reactions (Cont.)
e. ALTERNATIVELY, rather than defining
a new joint near the support
joint, and rather than defining a fictitious zero
mass rigid member, the following
can be done IF both (i) the mass
of all members incident on a support joint, AND
(ii) any specified nonstructural
mass at the support joint, are negligible in
comparison to the mass of the entire
structure model, THEN specify
CONSTANTS DENSITY 0.00001 for such members, AND
do not specify the nonstructural
mass to act at the support joint. f.
Using the above procedures to avoid the problem
with the computation of support
reactions in dynamic analysis problems,
and in the cantilever beam example described
in Number 4 above, the horizontal
(X-direction) reaction corresponding to the FORCE
X joint release will be computed
as 0.00 as expected.
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Response Spectrum AnalysisBase Shear Calculations
Explanation C\Temp\Tmp\ComputeBaseShear-2.pdf
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ShearWallDesign forResponse Spectrum Analysis
Results
Explanation C\Temp\Tmp\ShearWallDesign-Example.
pdf
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Cable Compression Forces?
Explanation C\Temp\Tmp\GTSTRUDL.Cable-Tips.pdf
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Steel Design by AISC LRFD2
Explanation C\Temp\Tmp\01-LRFD2-1stCycle-new.tx
t C\Temp\Tmp\02-LRFD2-ITERATE-new.txt
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GTMenu View Tolerence
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Split at Intersection
Explanation C\Temp\Tmp\Industrial-Bm2.fix.gti
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Multiple User Data Sets by Command

• Open user data set containing user steel
  section tables
• path full path to a.ds data set file, OR
• a.ds in the current Working
  Directory
• OPEN USERDATA FILE path' READ EXISTING
• ------------------------------------------------
  ------------------

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Multiple User Data Sets fromMacros

• 
  
• Open user data set containing user steel
  section tables and dynamic load data
• 
  
• OPEN USERDATA FILE 'Input user data set file
  name (a.ds) in Working Directory or full path'
  -
• READ EXISTING
• ---------------------------------------

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Increasing Productivity and Reliabilityof the
Menu User Interface

• The Startup Macro
• The Common or Personal Macro

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Increasing Productivity and Reliabilityof the
Menu User Interface (Cont.)

• The Startup Macro

------------------------------------------------
--------- This is the Common Startup Macro put
your company-wide startup commands here. You
can edit this file from Tools -- Macros. Click
"Startup" and then "Edit". ---------------------
------------------------------------ UNITS
METERS KILONEWTONS DEGREED CENTIGRADE OUTPUT
ORDERED OUTPUT DECIMAL 3 PARAMETERS 'CODE'
'LRFD2' ALL 'STEELGRD' 'A36' MEMBERS
EXISTING 'BM-1' TO 'BM-1000' 'STEELGRD'
'A572-G50' MEMBERS EXISTING 'COL-1' TO
'COL-1000' -------------------------------------
----------------------
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Increasing Productivity and Reliabilityof the
Menu User Interface (Cont.)
Example command file sequence C\Temp\Tmp\Select
FAILCKSmooth.txt
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Increasing Productivity and Reliabilityof the
Menu User Interface (Cont.)
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Batch Processing
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Ask the Experts Answer Questions that you
have submitted.