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 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 STAAD.Pro Editor.

Enter the command to initiate the steady state analysis:
```
PERFORM STEADY STATE ANALYSIS
```
See TR.37.6.1 Purpose for details.

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:
1. Specify the frequency and damping option:
```
STEADY FORCE FREQ f1 { DAMP f2 | CDAMP | MDAMP }
```
2. Specify the joint loads which occur at a given phase angle:
```
JOINT LOAD PHASE { X | Y | Z } f7
```
3. 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
```
4. (Optional) 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.
(Optional) Case 2: For the case of a single forcing frequency as ground motion, do the following:
1. Specify the frequency, damping, and output basis:
```
STEADY GROUND FREQUENCY f1 { DAMP f2 | CDAMP | MDAMP } { ABSOLUTE | RELATIVE }
```
2. Specify the ground motion direction, magnitude, and optional phase:
```
GROUND MOTION { X | Y | Z } { ACCELERATION | DISPLACEMENT } f3 PHASE f4
```

(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
```
(Optional) 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
```

(Optional) 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.

(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
```

(Optional) 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.

(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.