8.8.2.2. Batch
The RESP command in time-history is used to generat e the response spectrum, use either of the follow-
ing:
Command(s):RESP
GUI: Main Menu> TimeHist Postpro> Generate Spectrm
RESP requires two previously defined variables: one containing frequency values for the response
spectrum (field LFTAB) and the other containing the displacement time-history (field LDTAB). The fre-
quency values in LFTAB represent not only the abscissa of the response spectrum curve, but also the
frequencies of the one-degree-of-freedom oscillators used to generat e the response spectrum. You can
create the LFTAB variable using either the FILLDATA command or the DATA command.
The displacement time-history values in LDTAB usually result from a transient dynamic analysis of a
single-DOF system. You can create the LDTAB variable using the DATA command (if the displacement
time-history is on a file) or the NSOL command (Main Menu> TimeHist Postpro> Define Variables).
A numerical time-integration scheme is used to calculate the response spectrum.
8.8.3. Data Smoothing
If you are working with noisy results data such as from an explicit dynamic analysis, you may want to
"smooth" the response. This may allow for better understanding / visualization of the response by
smoothing out local fluctuations while preserving the global characteristics of the response. The time-
history "smooth" operation allows fitting a 'n'th order polynomial to the actual response.
This operation can be used only on static or transient results i.e., complex data cannot be fitted.
8.8.3.1. Interactive
This capability is available in the variable viewer's calculator through a function smooth (x1,x2,n) where
x2 is the dependent time history variable (such as TIME), and x1 is the independent time history variable
(such as response at a point), and 'n' is the order of fit.This function is available only by typing in the
expression portion of the calculator.
For example to evaluate a second order fit for the UY response at the midpoint of a structure: (smooth
variable x1 with respect to variable x2 of order “n”):
Smoothed_response = SMOOTH ({UY_AT_MIDPOINT},{TIME},2)8.8.3.2. Batch
If you're working with noisy results data, you may want to "smooth" that data to a smoother represent-
ative curve.
Four arrays are required for smoothing data. The first two contain the noisy data from the independent
and the dependent variables, respectively; the second two will contain the smoothed data (after
smoothing takes place) from the independent and dependent variables, respectively. You must always
create the first two vectors (DIM) and fill these vectors with the noisy data (VGET) before smoothing
the data. If you are working in interactive mode, ANSYS automatically creates the third and fourth
vector, but if you are working in batch mode, you must also create these vectors (DIM) before
smoothing the data (ANSYS will fill these with the smoothed data).
Once these arrays have been created, you can smooth the data using the SMOOTH command (Main
Menu> TimeHist Postpro> Smooth Data). You can choose to smooth all or some of the data points
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationThe Time-History Postprocessor (POST26)