Happy new year 2007
regarding caesar application guide page 3-28,
can i put Y instead of +Y?
also can i put ANC instead of Y?
what are the differences?
regards
ozm

No not really.

Assuming the default coordinate system where the "global Y axis" is up:

- a "Y" support prevents motion along the global Y axis, both up and down.

- a "+Y" support allows motion in the positive global Y direction, so the node is free to move up, but it can't move down.

- an "anchor" fixes all six degrees of freedom, so the node can't move at all.

These are three different types of restraints, and they each have their uses. Perhaps, maybe, sometimes, for analytical reasons you may be able to switch between "Y" and "+Y", but you really should be modeling reality (what is in the field).

This is a really scary question to see posted here. If you are still struggling with the concept of Anchor vs. +Y vs. Y restraints, shouldn't you have someone working with you personally to sort it all out?

This is really basic stuff. It's like getting into a car, pulling onto a superhighway in rush hour, and then turning to your passenger and asking him which pedal is the brake.

Learning to do pipe stress analysis is far more difficult than simply learning to use the software. In fact, sometimes I think the COADE guys (and their competitors) have made the software too easy to use. I suppose that's more a function of the incredible amount of computer horsepower available in this day and age.

But it's necessary that a CAESAR II user be able to relate the input he creates to describe his piping system with what is shown on the drawings and/or isos and also what exists or will exist in the real world. It's apparent from this question that you have not yet come to grips with this most basic tool of the trade.

Suprised why?? One can easily click on a members name and read their posts.

Managers think that anyone with a copy of CAESAR II is "qualified".

Most Owners (their cost people) just want the cheapest price without regard to competency.

I imagine this goes back to prehistoric times... Ugh was selling a round wheel but was being outsold by UGGGHHH who had a cheaper square wheel. It took a long time for the round wheel to win out!

thanks ray
angry men!
pls first read my question then answer!
regarding 3-28 application guide!!!restraint settlement
Actually my question was about 1500 ton tower and its settelment and elements.
when you give displacement and put 0 for dx,dz,rx,ry,rz i think its not important you choose +y,Y or Anc,isnt it?
regards

Actually, if you specify displacements you don't have to (also) define restraints. It is sufficient to define the boundary condition only once.

Thanks a lot ray
so in that example it is not necessary we define +y cnode?
we can consider 95 to 1095 as a rigid and give displacement to 1095.
you understood my question!
best regards
ozm

Not in this instance. The reason the +Y is there is so that the pipe can "lift-off" the support. If this had been a U-bolt, then the displacements alone would be sufficent.

Thanks a million

Boundary conditions are always important. There will be a difference between the analytical effect of the following restraint models:

95 +Y CNODE 1095
1095 DX a DY b DZ c

and

95 Y CNODE 1095
1095 DX a DY b DZ c

for some combinations of a, b, and c; but perhaps not for the ones you choose for your problem. Again, I suggest you are using this forum as a crutch to avoid the effort of actually thinking about your piping system, and the real-world means for building and using the mathematical constructs that CAESAR II allows you to enter as boundary conditions. And I again further suggest that time you spend actually thinking for yourself will be far better for you in the long run than advice on the question that you posed from any or all of us.

This is not an exam at university. We, as professionals, have progressed far beyond that. We have the obligation to investigate that which we do not understand about our job assignments. We have the obligation to use our analytical tools properly, and to make sure that the piping systems that are built and operated according to our analysis correspond to the input to our analytical model, or that our analysis of existing systems corresponds to the actual hardware.

We have a responsibility to our profession, and to our employers, and to our clients, and to the workers who will operate the plants that we design, to THINK about what we are doing. Asking very specific questions about one particular diagram in the CAESAR II documentation is a good way to learn how to use the software. But it DOES NOT advance you toward the ultimate goal of being able to understand how a particular piece of real-world hardware can, and cannot, be modeled. Only THINKING for yourself can do that. You neeed to visualize the hardware that is represented by the drawings that you have, or you need to visit the site and stare at the actual hardware until you KNOW how it works, and how it does not work. We can't help you with that.

I once had a very bright young man with several university degrees working for me, trying to learn this business. But he absolutely refused to believe that it was necessary for him to go to the field and learn to work there. So he is doing something else for a living. I am sure he is doing well at it; he was very bright and very well educated. But neither sheer intelligence nor vast amounts of education are sufficient to become a good pipe stress analyst.

Several of the respected users of this forum do not have university degrees. One of those, that I know of, has taught post-graduate courses on the subject at a respected university. They are successful as pipe stress analysts because they can think, and have thought extensively in their pasts, about how real-world hardware acts and how to translate that behavior into a mathematical model.

Please understand. Of all the users on this forum, the user most likely to visit the plant you are working on is you. When piping systems fail, people are at risk. The risk of you actually being there when a failure occurs is vanishingly small, but it exists. It's better to do the analysis right and add another couple of zeros between the decimal point and the probability of failure.

There has been a series of piping failures in power plants in China over the last couple of years that have claimed several lives. We in the U.S. are not immune to that problem either; the Mojave power plant failure in the early 1980's took 9 or 10 lives. We have had major refinery incidents too.

This is a serious business. University was just a game played between the professors and the students, under rules established by the textbook writers. The textbook writers gave you all the facts, openly in the example problems but taking greater and greater pains to disguise them on the homework problems.

Now, in the real world, as a professional, you have all three roles. You, as the textbook writer, are the only one who can investigate and discover the facts necessary to solve the problem. You, as the professor, are the one responsible for making sure that the analytical model you use is the correct one for each problem. And you, as the student, receive the reward for being correct or bear the disgrace of being wrong. You will prepare a report and submit it to be checked by someone who will, to a large extent, acccept many of your judgments because of the time constraints placed upon his role. This is not a responsibility to be taken lightly.

This forum is an investigatory tool, and we as other users can only serve in the role of textbook writer, providing you with more facts that can be applied to one particular phase of your problem. We cannot, without seeing all of your drawings and specifications, act as either the professor or the student or the checker. Your responsibility is to take the new facts that we presnt to you, and THINK about them.

It takes a lot of hard work to use your intelligence and education to acquire sufficient understanding of this subject to become a competent professional. Those of us who have put in the effort can occasionally be grumpy about the apparent lack of effort of the younger generation. So it has been, throughout history, in all cultures, in all trades and professions, and in all generations.

But we have progressed from living in caves to our current situation because enough of each succeeding generation has accepted, and learned from, well-meaning advice however poorly it was presented to them.

If you choose to tune us out as angry [old] men, I can safely predict you will not be in this business 10 years from now. Good luck in your next career, whatever it may be.

I salute you craig!

I salute you craig too!
your article is very nice but i dont understand its relation with my question.
regards

I am hardly angry... your questions are typical for someone who lacks knowledge (egad whats the difference between a +Y, Y or an anchor come on!) and experience but somehow you are left alone with no help at hand to look over your shoulder, but your boss has bought a copy of Caesar II figuring that thats all thats needed.

Am I mad nope! Whatever you do both good or bad will not impact me or any human I know. Obviously your boss has missed one important part of the design process.... checking. The checker should be experienced and competent and if he or she existed in fact would have been the perfect person for you to talk to.

Not mad maybe a little bit sad or disappointed but I'll get over it!


On a positive note at least your lokking at the manuals, they will be of significant help over time!

i know the differences between +Y, Y or an anchor, every body knows.
unfortunatly you havent understood my question.
pls read it again.
my question was about some problems in software not about concepts.
when you put 0 for dx,dz,rx,ry and rz(specially for huge equipments) you dont need to define +y or y or other restraints. if you define +y or y or anc in these cases they are same and without effect.
please go to 3-28 application guide and read it and then read the second post of Ay.
my first question was not in a right english but i corrected it at second step now my important thing is my english.i must improve it against such a misunderstanding!
bye hardly angry people
my god!!!!

Now now don't be angry as for god he has other matters more important to tend to.....

Perhaps the problem here lies in the subtleties of English.

The question should not focus on THE right way to model a certain situatin but, instead, A right way to model that certain situation.

Here, where we have an extremely large weight associated with this node, the +Y, Y and ANC would probably always produce the same results in the Y direction - that node will always show a displacement of 0.000. (Unless we pull in another thread which considers the stiffness that we actually use for "rigid", or, if a situation arises where that load is not present.) If the results are the same, one model is no better way than the other. But this variability in modeling cannot be assumed for other situations.

Other systems will be very sensitive to the dictinction between +Y,Y, and ANC.

Many of the posts here are from users who wish to avoid the ambiguity in this sort of modeling approach. Yes, if you always review the results to check you modeling assumptions, many variations in input can be validated. Unfortunately, there are users who build models with their own set of (unverified) assumptions and use the information in this forum (or program documentation) without checking the impact on the results.

Focus on the results more than the input.

I use the output to confirm that the input is correct. I think there are too many users who do it the other way around - that confidence in the input implies that the output has to be correct. That confidence may not be justified.

Alls well that ends well(shakespeare).
regards
ozm