hello to everybody

- I'm a beginner in CAESAR II and I need simulate a model to seismic loads but I do not understand this:


Inputs:
frequency cutoff = 33 Hz.
damping coeff. = 0
Nº of frequencies = 100

I do not see frequencies greater than 1,0 Hz (or 1,1 Hz). Why?

- The other question is: I need to put a force in pipes due to the discharge of pressure relief valves. So what I do is, taking in consideration that the maximum design pressure is 1,95MPa and pipe has a NPS=12in, therefore the applied force in the pipe would be the result of this two conditions which is app. 25 MPa.
It seems to be exaggerated.
What am I doing wrong ?

If anyone can help me just let me know.
Thank in advance.
Drama

A dynamic seismic analysis is not something that should be performed without guidance. Is there someone there that can help you, and review your work (and assumptions)?

The "Frequency Cut-off" is the frequency at which you're telling the solver to stop extracting eigen-values (natural frequencies) and eigen-vectors (mode shapes). For a seismic analysis this cut-off is usually 33hz (because all the energy in an earthquake is below this value). CAESAR II will solve for one frequency above your cut-off (it has to detect that it passed the cut-off).

The "Damping Ratio" should be left alone. You can read the "help text" on this item (press [F1]) for more information. I wouldn't change this unless you have a really really really good reason.

The "Max No of Eignevalues Calculated" (which I believe you refer to as the "Nº of frequencies" is just that - the maximum number of eigen-values extracted. This is an entry you should leave as zero - unless you're dealing with an academic problem. In a realy system you don't know how many frequencies to extract, so it is better to deal with the cut-off value.

The CAESAR II eigen-solver stops at whatever comes first, either the frequency cut-off or the maximum number of frequencies. If you solved for 100 frequencies, and your maximum was only 1.1 hz, you have a very flexible system - probably way too flexible. I recommend you recheck your input (both the model and the dynamic input) to make sure everything makes sense.

For the "relief" issue, check out the RELIEF example problem. You can find this in \caesar\examples.

Hello

Yes Richards, actually I work with a collegue that has a good knowledge of Caesar, but unfortunately is working outside during one month. Most of his time he is out of contact. Sporadically I have spoken with him.

So I'm here once again to ask for some help, if it is possible.

I have been studing what you said to me, about seismic loads.
I put some guide supports where I saw some exaggerated motion. And I reset my dynamic inputs too, setting the frequency array spaces (that I called by "Nº of frequencies in the last post) of 100 to 300. I am now visualizing an increment of the frequencies values which in the last post I said that were app. 1,1 Hz and now they are about 12 Hz (still far away of 33 Hz).

Let me tell you that my piping system has 3 colectors (headers pipes) and about 15 connections pipes.

Is it too complex to Caesar? Maybe, I should split it in two piping systems.

Best Regards,
Drama.

Hello

Yes Richards, actually I work with a collegue that has a good knowledge of Caesar, but unfortunately is working outside during one month. Most of his time he is out of contact. Sporadically I have spoken with him.

So I'm here once again to ask for some help, if it is possible.

I have been studing what you said to me, about seismic loads.
I put some guide supports where I saw some exaggerated motion. And I reset my dynamic inputs too, setting the frequency array spaces (that I called by "Nº of frequencies in the last post) of 100 to 300. I am now visualizing an increment of the frequencies values which in the last post I said that were app. 1,1 Hz and now they are about 12 Hz (still far away of 33 Hz).

Let me tell you that my piping system has 3 colectors (headers pipes) and about 15 connections pipes.

Is it too complex to Caesar? Maybe, I should split it in two piping systems.

Best Regards,
Drama.