TR.37.6.5 Steady Force Loading
This set of commands may be used to specify JOINT loads on the structure, the forcing frequency, the modal damping, and the phase relationship of loads in each of the global directions.
General Format
This command specifies the forcing frequency and damping for a case of steady forces.
STEADY FORCE FREQ f1 { DAMP f2 | CDAMP | MDAMP }
Where:
Parameter | Description |
---|---|
FREQ f1 | the steady state frequency in cycles/sec at which the joint loads below will oscillate. |
DAMP f2 | Damping ratio for all modes when DAMP is selected. Default value is 0.05 (5% damping if 0 or blank entered). |
- DAMP indicates to use the f2 value for all modes
- MDAMP indicates to use the damping entered or computed with the DEFINE DAMP command if entered, otherwise default value of 0.05 will be used
- CDAMP indicates to use the composite damping of the structure calculated for each mode. You must specify damping for different materials under the CONSTANT specification
Joint Loads
Refer to TR.32.1 Joint Load Specification for additional information on Joint Loads
JOINT LOAD ( [ PHASE *{ X | Y | Z } f7] )
Where:
Parameter | Description |
---|---|
PHASE f7 | Phase angle in degrees. One phase angle per global direction. |
Bracketed data may be entered for each global direction on the same line. All moments specified below will be applied with a phase angle of 0.0. All forces specified below will be applied with the phase angle specified above, if any. Default is 0.0.
Next are the joint forces, if any. Repeat as many lines of joint force data as needed.
joint-list *{ FX f1 | FY f2 | FZ f3 | MX f4 | MY f5 | MZ f6 }
Where:
Parameter | Description |
---|---|
FX f1, FY f3, FZ f3 | specify a force in the corresponding global direction. |
MX f4, MY f4, MZ f6 | specify a moment in the corresponding global direction. |
Copy Loads
The next command, Copy Load, may optionally be placed here to use the equivalent joint loads from prior cases. This feature enables using the more complex loading commands like selfweight, floor load, wind load, etc. that are not directly available here.
COPY LOAD
i_{1}, f_{1}, i_{2}, f_{2} ... i_{n}, f_{n}
Where:
Parameter | Description |
---|---|
i_{1}, i_{2} ... i_{n} | prior primary load case numbers that are in this analysis set. |
f_{1}, f_{2} ... f_{n} | corresponding factors |
This command can be continued to additional lines by ending all but last with a hyphen. These cases must have been between the Perform Steady State Analysis command and the prior Analysis command (if any).