Hi,
Would it be possible to consider adding dynamic response analysis types? I’m thinking of Dynamic Frequency, Random, Time and Shock. The pre-requisite would be a linear constrained modal analysis. The input load for each analysis would be:
Frequency - Frequency Spectra
Random - Power Spectral Density
Time - Signal vs. Time
Shock - Shock Spectra
Base excitation should also be supported (acceleration input of constraint points.)
Thanks and regards,
Rod Giles
Check the 1.4.0 dev version. It supports all dynamic analyses that are available in CalculiX: CalculiX: Overview of the finite element capabilities of CalculiX Version 2.20
Hi,
Thanks Jakub, that’s really great to hear. I’ll download version 1.4 and take a look.
Best regards,
Rod
PrePoMax is only a pre and post-processor for the solver CalculiX. Any new functionality, like random response analysis, must be first supported by CalculiX to be later available in PrePoMax.
Hi Matej,As per Jakub’s post, version 2.20 of Calculix supports the following analysis types:
frequency (linear)
dynamic
linear
transient modal dynamics
steady state dynamics
harmonic periodic loading
non-harmonic periodic loading
Would you happen to know if the ‘non-perioding loading’ uses a PSD as an input?
Best regards,
Rod
This is described in the CalculiX User’s Manual:
For nonharmonic loading […] the loading across one period is not harmonic and has to be specified in the time domain. […] Internally, the nonharmonic loading is expanded into a Fourier series.
So it’s not the same as random response analysis.
Code_Aster seems to be capable of performing random vibration analyses (DYNA_ALEA_MODAL operator).
Really interesting me, so a dynamic time history analysis e.g earthquake loading can be visualise the graph nicely. However some precalculation is needed inside PrePoMax since displacement history only allowed in CalculiX, not acceleration.
This kind of boundary condition is called base motion in CalculiX (and in Abaqus). Both displacement and acceleration type is supported in CalculiX. Abaqus also supports the velocity type.
Right, but not modal dynamic analysis of earthquake loading. Only displacement history allowed in CalculiX, or i miss to check the latest versions?
That’s right:
Acceleration boundary conditions can only be used for harmonic steady state dynamics calculations, displacements can be used for any modal dynamic or steady state dynamic calculation.
Btw. structures subjected to earthquake loading are often analyzed using the response spectrum procedure. Unfortunately, this one is also not supported in CalculiX. However, Code_Aster supports it (COMB_SISM_MODAL operator)
Response Spectrum Analysis approaches are common use in designing based on peak, however it has many limitation e.g input curves consistency (elastic or inelastic) and problem also in sign convention of absolute value results, conservative, short building periods, etc. This has long discussion by many, also the author of these methods (Wilson & Clough) also notifying about the limitations…
Time History Analysis is advantages and eliminate the problem since the structures are being use dynamic analysis as is as base motion subjected to earthquake.
I recall M.Martin, ccx user, explaining about a software able to translate Eurocode seismic accelerograms into displacements to enter into ccx by means of amplitude card.
At that time I recall testing it, but computational cost is huge and there was a bug which is still open.
I can’t find the original software suggested by MMartin but here there is another freeware source for this purpose.If anybody knows any other option please comment.
Building code mainly use response Spectrum curves, a ration of spectral acceleration in fraction of gravity for some ranges of structure natural periods. This analysis type is not available in CalculiX, not too wonder since the goals are in nonlinear capabilities. A dedicated software for earthquake, OpenSees also not have the feature. Someone can extend or implementation response Spectrum analysis by doing extraction of dynamic analysis output and following the procedures, including modal combination.
Time history analysis is not much discussed by many building codes, it separated by some specifics guidance about nonlinear dynamic time history analysis, earthquake acceleration recorded can takes from strong ground motion database. Of course computational effort is required due to fully analysis at every step of time in seismic durations. An inclusion of nonlinear material and geometry.c an contributes also.
It seems not a bugs regarding to beam element (B31), more appropriate to categories as currently limitation. Is really to modeling a beam by single element trough thickness of C3D8R which only one integration point? composed beam and plate/shell element not completely available yet in CalculiX.
There’s many software for further processing of earthquake ground acceleration, provide ones are from NIST…