Dear all,
I got the project on dynamic analysis.For that client asking me to calculate natural frequencies.Is it possible in CAESAR, if so how?I tried to do so by using example given in CAESAR help,but i got error saying that static/dynamic combination case 1 is empty.Please help me in this regard.

Hi Yesu,
Are you clear about what you want to do? natural frequency can be calculated manually if you have minimum required data with you like span,end connection, wts,
what i will advise look for manual method rather going into Caesar as it give you grasp on the topic.
regards

If you set the "Dynamic Analysis Type" to "Modal", all you have to do is set the "cut off frequency" on the Control Parameters Dialog. Set this value to 40 or 50.

If you have errantly defined a "static/dynamic" combination, just delete it.

Remember complete your static anlaysis before getting into Modal to calculate frequencies...

I would like to extend my querry furthur as follows,
The natural frequencies obtained ranges from 300 to 400 Hz. Does Caesar software give any warning or failure messege if the frequency crosses safe limit, if yes where in output i can see it.
pls guide

Regards
Suhas.

Piping systems have an infinite number of natural frequencies. "Safe" is a relative idea. There is no way for CAESAR II to judge this "idea".

Dear Yesu & Suhas,

If you are really concerned about 'Safety' and respect for the motherland we belong to, first get yourselves trained in the basics of structural dynamics and CAESAR II software's related calculation methods, if you have not been trained in your engineering school about the same earlier!

regards,

sam

Natural frequencies are normally checked against acoustic natural frequencies of the piping system, RPM range of recip. or rotary equipments connected to piping systems.

Wow!!!!!!! What a nice way to encourage new learners.How does the question of respect for motherland arise in this forum ? I thought this is a purely technical forum .

Siv

"What a nice way to encourage new learners"

If somebody asks questions on a forum that is an open affair as this is and one asks a simplistic question there is a price to be paid the teacher for the lesson.

this question "I would like to extend my querry furthur as follows,
The natural frequencies obtained ranges from 300 to 400 Hz. Does Caesar software give any warning or failure messege if the frequency crosses safe limit, if yes where in output i can see it.
pls guide" is incredibly vague (naive?) and as Rich pointed out CAESAR II does not think we do... and WE are the judge of the work.

So when somebody asks how do I reduce a bending moment? or some other simple question there will always be a price for the lesson....

Siv,

My understanding is that whoever has asked the question on 300-400 Hz natural frequencies, first need to get his ideas cleared on fundamentals of Dynamics. This , is what the person has supposedly done in a college , but does not seem so from the standard of his question.

Youngstars who don't know about piping and piping codes ( as that is typicaly not taught in colleges )are certainly encouraged in this forum.But youngstars who don't know anything about mechanics don't deserve any word of encougarement as first they have to do what they should have done in college i.e. getting their ideas cleared on engineering sciences before they proceed with a professional career.Othewise there are many careeers ( where they don't need to know mechanics) that they should opt for.

Such quality of questions , put the capability of all stress engineers from our part of the world in bad light and that is why Sam has mentioned (if you can read between the lines ).

Pl. be honest enough to take his point in a constructive manner as tomorrow if people like you take the proper path of self development, not only you will gain, but the whole piping community also will gain from your expertise.

Regards

With due respect to Mr Anindya I just want to put one request here If it is possible to create another discussion forum for junior member. Because in so many organization there is not good enough stress expert to guide junior stress engineer. Myself a regular visitor of this forum & getting so many things from this forum. My special thanks to Mr Anindya for his guidance & help and replying immediately whenever I send any query to his personal mail Id.
I think if another junior forum is created then junior people can feel free to ask there question & can get the answer by sharing knowledge among each other. Whenever it will not be possible for junior member to solve a problem then the same can be refer to present forum.

"What a nice way to encourage new learners."

1. If your employer is too cheap to send new CAESAR II users to appropriate training, and has no experienced users around to provide it, then shame on them. (How's that for a plug, Richard or Dave?)

2. If new CAESAR II users expect to ask very naive questions on this forum and GET FOR FREE THE TRAINING THEIR EMPLOYER IS TOO CHEAP TO PAY FOR then the price, as my friend Mr. Luf suggests, is going to be paid in other ways.

3. Anybody that thinks that computer software is a substitute for thinking has a whole lot to learn about the real world.

4. Anybody that thinks the rest of the world is standing in line eagerly awaiting the opportunity to kiss their a** has a whole lot to learn about the real world.

5. This is, at times, a very difficult engineering specialty. Even some of the easier problems are pretty tough to try to solve by remote control. And new users tend to not pose problems in a very complete form. This can sometimes require the person attempting to provide an answer to expend a lot of extra (unpaid) effort. And we also understand that providing guidance for new users expands the pool of qualified CAESAR II users and may serve to reduce our wages and/or limit our own employability.

So you new users think you have the right to have poorly defined questions answered (including all of the contingencies you originally neglected to mention), by competent users, and courteously? GET REAL!!!

Uhm, that would strike me as solving the SYMPTOM not the PROBLEM. If someone is not able to do the assigned work, professional responsibility means that they need to ask for the resources to do the work properly. If you want a forum JUST for jr members, well then you have the blind leading the blind... at least in this forum someone can say "you have no idea what you're doing, get help".

Anyone who thinks that complete strangers on the internet can solve their problems or train them really needs to be working somewhere where mistakes are unlikly to matter much. (grin).

So, if the problem is that people are not being trained, sending them off to the internet where Sturgeon's law applies is NOT the solution. Discussions such as on this board are ONLY useful if people can take information back to their desk and decide if it is correct and it applies to their particular situation.

When I am mentoring, I will often send people off to figure stuff out on their own, but I expect them to come back to me saying "this is what I think, this is why" and then we can discuss whether they are moving in the right direction.

I have gone to my boss in the past and said "I am not comletely comfortable with this work, can we bring someone in with more experience to review the work". I have also asked questions in this or other forums, and if the viewpoints of those whom I respect though having judged what they say match what my OTHER research has brought to light, that will add some comfort.

However, at the end of the day, the organziation doing the anaylsis has the responsiblity to do it correctly, and if they don't have the senior people to train and supervise they have no business doing the work.

Shannon
PS, sturgeons law, note this is from a non-accredited source so should be verified before using...
http://en.wikipedia.org/wiki/Sturgeons_law

Amen very wise thoughts indeed!

" And we also understand that providing guidance for new users expands the pool of qualified CAESAR II users and may serve to reduce our wages and/or limit our own employability. "

Thanks for revealing the real reason.

Hope this was said in a lighter mood.

Siv

Dear Siv,

You too have revealed that we are not only cheap by cost, but by behaviour!

I heard people in high pressure vessel field rejecting items made of steel from a particular country because of low quality.

What about Indian engineers buying degrees through money, caste or region? How long the World buy our products, if we are not qualified enough, just cheap!

regards,

sam

OK so you've thrown all your toys out of the pram.

Is this a good time to close out this topic ?

Sam,
Too harsh, this is global problem. I have reviewed lot of works from the different part of world.

Same issues exist, reason which I see is lack of experienced supervisor and managemnet guys thinking engineering is not that important. I refer to PetroBas platform which sunk due to managment same school of thought.

Folks, we should understand in the first place why we are doing it? Do I have sufficient skills to do it? what will be the impact?
If this is answered, analyst/designer will not go wrong.

regards,