dynamic shock and random analyses??

[ksarita20]

hey all,


can any one tell me the exact differance between dynamic shock analysis and dynamic random analysis. i searched pro/e help but couldnt exactly understand. i think if some one can give me some examples for both these anayses, i will be really happy.


thanks in advance


Sari
Edited by: ksarita20

 

[GeorgeTsonev]

you can read for both of it in technical support -knowledge base in ptc site.If you want follow this link


http://ptc.com/appserver/cs/search/kdb.jsp


george
Edited by: GeorgeTsonev

 

[mch]

Sari,


A dynamic shock analysis is in the time domain and a dynamic random analysis is in the frequency domain. Which you use is normally dependent upon the loading input data you have been given. Don't forgat that a dynamic shock spectrum combines both the input loading and the damping present in your structure.


If you have a non-random excitation, then you should use dynamic time (for time domain) or dyanmic frequency (for frequency domain).


Regards,


Rod

 

[Luis Aguirre]

Rod and Sari,


A dynamic shock analysis also known as a seismic analysis is in reality a frequency domain technique. This type of analysis is based on a single degree of freedom model excited with the time domain forcing function to generate what is call response (shock) spectrum. As Rod mention the spectrumwill include the damping when is generated.


The difference between shock and random analysis has to do with the statistical characteristics of the forcing function that will excite the system. If the forcing function is ergodic (statistical parameter don't change between samples and time) then the model should bedone asrandom analysis. In the other hand if theexciting load is not ergodic thena solution can be approximated by using a dynamic shock analysis.


The easiest Way to find out what type of analysis to run some times depends only in the information given. For example, if the model is to be excited with as Power Spectrum Density Function (PSD) then random analysis will be used. If the model is to be excited with a response spectrum then the analysis should be done using a shock analysis.


I hope this information helps


Luis

 

[ksarita20]

Thanks you both for ur explination. I think i understood what your are saying. Butcan any of provide me withsome dynamic shock analysis example. I didnt findany in PCT helpor knowledge base.The reason why i need that is i dont have an input spectrumfor the problem.So if i know howand what is required to define the analysis. i can try to generate it with thedata that i have.


Problem: todoseismic analysis on a steel structure anchored to the ground.Depending on the locationwhere it is installed, ihave to use the IBCcode and calculate the shear force (V)at the base and the response spectrum.( I am still working on that.)


So if i use theresponse spectrumcalculated here as the input formy shock analysis, thenwhatdoes the shear force at thebase mean.


Can it beuse it in static analysiswhich represents asimplified analysis of the earthquake motion.





i really apreciate if any one can guide me.


thanks inadvance.



Edited by: ksarita20