A. To specify a steady-state analysis
To specify analysis of structure subject to steady, harmonically varying loads, use the following procedure.
Note: This requires a STAAD.Pro Advanced Analysis license.
You must have a load case which contains a modal calculation command. This load case number defines the weights and weight moment of inertias for the eigensolutions for steady state or harmonic analysis.
Note: Steady state analysis cannot be specified in the graphical user interface. The commands must be entered directly into the STAAD input file using the I. STAAD.Pro Editor.
-
Enter the command to initiate the steady state analysis:
PERFORM STEADY STATE ANALYSIS
See TR.37.6.1 Purpose for details.
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On the next line, enter the specification for the forcing type:
Frequency and force type Command Case 1: A single forcing frequency as joint force loads. BEGIN STEADY FORCE
Case 2: A single forcing frequency as ground motion. BEGIN STEADY GROUND
Case 3: Several forcing frequencies as joint force loads. BEGIN HARMONIC FORCE
Case 4: Several forcing frequencies as ground motion. BEGIN HARMONIC GROUND
- Optional:
For either case in which several forcing frequencies (i.e.,
harmonic
), define the harmonic output frequencies:FREQUENCY FLO f1 FHI f2 NPTS f3
- Optional:
Case 1: For the case of a single forcing frequency as joint loads, do the
following:
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Specify the frequency and damping option:
STEADY FORCE FREQ f1 { DAMP f2 | CDAMP | MDAMP }
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Specify the joint loads which occur at a given phase angle:
JOINT LOAD PHASE { X | Y | Z } f7
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Enter the joint numbers along with the forces and moments occurring at
those joints:
joint-list FX f1 FY f2 FZ f3 MX f4 MY f5 MZ f6
-
You may use the following command to utilize the equivalent joint loads
from a previous load case.
COPY LOAD i1, f1, i2, f2 … in, fn
See TR.37.6.5 Steady Force Loading for details.
-
Specify the frequency and damping option:
- Optional:
Case 2: For the case of a single forcing frequency as ground motion, do the
following:
-
Specify the frequency, damping, and output basis:
STEADY GROUND FREQUENCY f1 { DAMP f2 | CDAMP | MDAMP } { ABSOLUTE | RELATIVE }
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Specify the ground motion direction, magnitude, and optional
phase:
GROUND MOTION { X | Y | Z } { ACCELERATION | DISPLACEMENT } f3 PHASE f4
-
Specify the frequency, damping, and output basis:
- Optional:
Case 3: For the case of multiple forcing frequencies as joint loads, do the
following:
-
Specify the frequency and damping option:
HARMONIC FORCE { DAMP f2 | CDAMP | MDAMP }
-
Specify the joint loads which occur at a given phase angle:
JOINT LOAD PHASE { X | Y | Z } f7
-
Enter the joint numbers along with the forces and moments occurring at
those joints:
joint-list FX f1 FY f2 FZ f3 MX f4 MY f5 MZ f6
-
You may use the following command to utilize the equivalent joint loads
from a previous load case.
COPY LOAD i1, f1, i2, f2 … in, fn
-
Use one of the following methods to specify the amplitude of the
forcing function:
Method Command Specifying coefficients for the formula a×ω2 + b×ω + c AMPLITUDE A a B b C c
Using frequency - amplitude data pairs AMPLITUDE f1 a1 f2 a2 … fn an
See TR.37.6.7 Harmonic Force Loading for details.
-
Specify the frequency and damping option:
- Optional:
Case 4: For the case of multiple forcing frequencies as ground motion, do the
following:
-
Specify the frequency, damping, and output basis:
HARMONIC GROUND { DAMP f2 | CDAMP | MDAMP } { ABSOLUTE | RELATIVE }
-
Specify the ground motion direction, magnitude, and optional
phase:
GROUND MOTION { X | Y | Z } { ACCELERATION | DISPLACEMENT } f3 PHASE f4
-
Use one of the following methods to specify the amplitude of the
forcing function:
Method Command Specifying coefficients for the formula a×ω2 + b×ω + c AMPLITUDE A a B b C c
Using frequency - amplitude data pairs AMPLITUDE f1 a1 f2 a2 … fn an
See TR.37.6.6 Harmonic Ground Motion Loading for details.
-
Specify the frequency, damping, and output basis:
- Optional:
To include steady state or harmonic results in the output, include the following:
PRINT HARMONIC DISPLACEMENTS { ALL | joint-list }
-
Enter the command to close the steady state command block.
END STEADY
See TR.37.6.9 Last Line of this Steady State/Harmonic Analysis for details.