TR.37.10 Floor Spectrum Command
This command is used to specify the calculation of floor spectra from time history acceleration results. The Floor Response Spectrum command must immediately follow an analysis command associated with the time history load case. The acceleration used may be either the absolute acceleration or the relative to ground acceleration.
General Format
First line of this Floor Spectrum Data.
GENERATE FLOOR SPECTRUM
Specify Floor Groups
Each new floor definition starts with the next command:
BEGIN FLOOR DIRECTION { GX | GY | GZ }* { TITLE }
GX, GY, and GZ specify up to 3 global directions for which acceleration vs frequency spectra will be generated for this floor. Optionally enter a Title/Description (up to 50 characters) for this floor that will be displayed on the graphs in post processing.
The next one or more lines will identify the floors which will have spectrum curves generated either by referencing a NODE GROUP (see TR.16.1 Listing of Entities by Specifying Groups) or explicitly listing the joints that constitute the floor. For multiple groups, enter each on a separate line.
{ _jointgroup | jointlist }
Enter as many lines as necessary to specify all of the groups needed to define this floor.
If more floors are to be defined, then repeat the BEGIN FLOOR DIRECTION command followed by the _jointgroup_ name data. Enter as many floors as desired.
After the last floor definition, enter the following parameters that will be used in all of the Floor Spectrum calculations.
OPTIONS ( { FLOW f1 | FHIGH f2 | FDELTA f3 | DAMP f4 (… fn)| RELATIVE } ) print-options
This command may be continued to the next line by ending the line with a hyphen.
Where:
| Parameter | Description |
|---|---|
| FLOW f1 | Lowest frequency to be in the calculated spectrum. The value for FLOW should be at least 0.01 Hz. |
| FHIGH f2 | Highest frequency to be in the calculated spectrum. |
| FDELTA f3 | The spectrum will be calculated at f3 intervals from the FLOW value (f1) to FHIGH (f2). |
| DAMP f4 … fn | Up to 10 damping values may be entered. One spectrum will be generated for each damping value for each global direction requested for each floor defined. The spectrum will be based on these modal damping ratios. |
| RELATIVE | If there is ground motion defined and you want the spectra to be based on the relative acceleration of the floor to the ground acceleration, then enter the relative parameter. Default is absolute. |
The print-options are:
| Parameter | Description |
|---|---|
| THPRINT i1 | Option to print the time history acceleration being used in each spectrum calculation.
|
| SPRINT | Include this parameter to print the calculated spectrum. |
Last line of the floor spectrum data:
END FLOOR SPECTRUM
Example 1 - Using a Forcing Function
This partial input utilizes direct input data from a forcing function.
DEFINE TIME HISTORY TYPE 1 FORCE 0 -20 0.5 100 1 200 1.5 500 2 800 2.5 500 3 70 16 0 ARRIVAL TIME 0 DAMPING 0.075 * LOAD 1 LOADTYPE SEISMIC TITLE Time History case * Mass model required SELFWEIGHT X 1 SELFWEIGHT Y 1 SELFWEIGHT Z 1 JOINT LOAD 1 TO 6 FX 62.223 FY 62.223 FZ 62.223 * Time loads TIME LOAD 2 FX 1 1 PERFORM ANALYSIS GENERATE FLOOR SPECTRUM BEGIN FLOOR DIRECTION GX GZ Ground Motion _FL1 _FL17 BEGIN FLOOR DIRECTION GX GZ Floor 18 A/C Unit 36 _FL18 OPTIONS FLO 0.5 FHI 35.0 FDEL 0.1 – DAMP 0.03 0.05 0.07 END FLOOR SPECTRUM
Example 2 - Using External Data File
This complete input example uses an external seismic data file.
STAAD SPACE Floor Spectrum Example
START JOB INFORMATION
ENGINEER DATE 27-Oct-08
END JOB INFORMATION
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 0 3 0; 3 5 3 0; 4 5 0 0;
MEMBER INCIDENCES
1 1 2; 2 2 3; 3 3 4;
MEMBER PROPERTY AMERICAN
1 3 TABLE ST W12X26
2 TABLE ST W14X34
UNIT FEET KIP
DEFINE MATERIAL START
ISOTROPIC STEEL
E 4.176e+006
POISSON 0.3
DENSITY 0.489024
ALPHA 6.5e-006
DAMP 0.03
END DEFINE MATERIAL
UNIT METER KN
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 FIXED
4 PINNED
CUT OFF MODE SHAPE 30
DEFINE TIME HISTORY
TYPE 1 ACCELERATION
READ EQDATA.TXT
ARRIVAL TIME
0.0
DAMPING 0.05
START GROUP DEFINITION
JOINT
_FLOORNODES 2
_BASENODES 1
END GROUP DEFINITION
LOAD 1 DEAD + LIVE
SELFWEIGHT X 1
SELFWEIGHT Y 1
SELFWEIGHT Z 1
MEMBER LOAD
2 UNI GX 1
2 UNI GY 1
2 UNI GZ 1
GROUND MOTION X 1 1 9.806000
PERFORM ANALYSIS
GENERATE FLOOR SPECTRUM
BEGIN FLOOR DIRCTION GX Nodes 2
_FLOORNODES
BEGIN FLOOR DIRCTION GX Nodes 1
_BASENODES
OPTIONS FLO 0.5 FHI 60.0 FDEL 0.1 DAMP 0.05 REL
END FLOOR SPECTRUM
FINISH