Hi,
I have a quick question.
I’m begining using the modul DYNA for earthquake analysis.
For my spectral analysis i wanted to sign my mode using CDC method.
Here is my teddy program:
+PROG DYNA
HEAD
CTRL OPT MCON VAL 3
CTRL OPT STYP V2 CQC V3 +9
EIGE NEIG 50 TYPE REST LC 1001
LC NO 901
EXTR TYPE A MAX 911 STYP CQC
END
Thank you for your answers and help.
Best regards,
Gérard
Hello Gérard
I am not quite sure what your questions is 
.
As far as I understand, you want to calculate a structure according to the response spectrum analysis method. As a consequence you have to superpose the modal results (e.g. bending moment) an the directional components. For both results you have to choose the superposition method. These methods are defined within different DYNA commands.
CTRL STYP CQC:
Superposition of the horizontal seismic action.
According to EC1998-1 3.2.2.1(3) the response spectrum has two orthogonal components. Both of these components have to be taken into account. Therefore you have to superpose the directional components or the results in x- or y-direction.
EXTR … STYP CQC:
Superposition of the individual modal contributions (results).
Further information can be found in our online tutorial.
www.sofistik.com > Infocenter - Overview > Documentation - Tutorials > Dynamic analysis > Earthquake Analysis with RSA
Or you look at our corresponding TEDDY example.
TEDDY > File > Examples > dyna > english > dyna_superposition_response.dat
Best regards
Frederik Höller
Your SOFiSTiK Support Team
Hello,
Thank you for your answer.
My question was that in order to get the maximum acceleration (modal results) you can change the sign of one mode. I used this code :
+PROG DYNA
HEAD
CTRL OPT MCON VAL 3
CTRL OPT STYP V2 CQC V3 -9 $ here to change the sign of mode number nine which is one of the principal mode.
EIGE NEIG 50 TYPE REST LC 1001
LC NO 901
EXTR TYPE A MAX 911 STYP CQC
END
I wanted to know if there was a method of superposition that can provide a total response with maximum values than others. As for example, if to change sign of one mode in CQC method can be way to consider.
Thank you again for your help.
Best,
Gérard
Just to be clear, the sign of the maximal modal results is lost, because the results of the spectral solution do not correlate in time or space. Therefore the maximal results could be positive or negative.
Nevertheless the consequence of the sign of a modal results can be considered by calculating different DYNA calculations (with different signs) and superimpose the results.
Your code evaluates the max node acceleration. The Value 3 -9 has the effect, that the sign of the results is orientated by the eigenform of the mode 9.
In order to consider the effect of the sign you could try to superimpose the results in a following maxima run (e.g. SUPP COMB 500 EXTR MAMI ETYP NODE TYPE AX). But I am not completely sure if this is working as intended. Just give it a try.
Just as an additional background information a short publication about the correct treatment of the directional superposition of the response spectra.
Anidis_2013.pdf (280.7 KB)
