hiz
Happy new year to all of you.
I am in learning phase of stress analysis. To my bad luck i dont have any senior to guide me and i am learning it by myself. when i model a piping system in caeser and check it for stress analysis, it give code stress check pass or fail in case of suspension and expansion loading but when i check stress report against operation loading (W+T+P) is says that
no code stress check processed.... and in allowable stress it give zero.
can any body tell me that what is cretaria of fidning allowable stress in case of operation loading (w+t+p) and what mistake i am making that ceaser is not processing code stress check. I tried to find it from asme b31.3 but i could only found equations for allowable stresses in case of suspension expansion & occosional loading in flexible analysis chapter.
I hope you will guide me in this regard....

First of all, I think you really need a senior engineer who can support you. Learning pipe stress analysis by doing can be dangerous.
Luckily you have read the B31.3. That code indeed doesn't give equations to check the stress in operational condition. The reason for this is that the code is not intented to check it. Primary and secundary stresses are checked seperately, and therefor the SUS and EXP have a stress check in CII. This is the basic for pipe stress engineering and you should really understand this rule, and the implementation of this rule in a good piping design.

Also check this topic for more info about allowable stress: http://www.coade.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=9084&page=1#Post9084

In addition you can find in which "load cases" we need to check "code stress compliance" for "each codes" covered by Caesar II. The summary is given in C2quick.pdf file in "code stress". Please search the pdf file in Caesar directory.

THANKS Sir;
From your reply i am understanding that we dont need to to check stress code compliance in case of operation laoding (OPE = w+p+t)as i see that some time i get very high stress value on few nodes.
i am not doing practicaly stress analysis. I am just learning it and i know that with out supervision of senior stress engineer i cannot implement it and i hope one day i ill get a good stress analysis senior engineer to help me more....
But i am very keen to make my name in field of stress analysis

Thanks sir i ill surely check quick reference guide.

The post referenced by Corne above is one of the "Sticky Topics". You'll find these at the very top of the list in the CAESAR II Forum. You should read all of these, they are very informative. In addition, you can find a wealth of information if you use the [Search] facility, to the right, just above the calendar.

Dear all,
Before coming with the final word, I advise you to refer the
Appendix P,ASME B31.3(post 2004).
You can find that the code is recommending to perform "Code stress Checking for the OPE Load case".

Thanks sir now i am clear about conceopt of stress in operation cases.
Thanks richard i have read all post in mentioned topic.

Dear markme026, Sami

Please refer to the link:
http://www.coade.com/ubbthreads/ubbthrea...=true#Post22421

I believe to check for OPE case (per appendix P of B31.3) it is available in CAESAR. Just check button in the Config Setup an it will be activated.

Though, I haven't done this officially since none of the Clients that I worked with had requested this to be done. Plus, code itself only RECOMMENDS it. Thus, it is not compulsory....yet. (Though sooner or later they will.)
But sometimes I just do it just to be on the safe side.
Better safe than sorry eh...

Not to quibble too much with your terms...
B31.3 does not "recommend" the operating stress check. B31.3 provides an "alternative" to the expansion stress check in the base Code. This alternative is defined in Appendix P and, in fact, has more required calculations than what's found in the base Code. But, like you say, CAESAR II takes care of this.
Please refer to other Forum discussions on this topic.

I agree. "Alternative" is the correct term to be used.
Thanks dave.

As a humble suggestion to you all, i insist you people to go thru the
training manual of Caeser II(c2TR - tarting from 6-18 to 6-20); this will clarify all of your concern(related to Hot Sustained, sustained etc; giving consideration to almost every school of thoughts).

Satisfying the Code recommended check for the Sustained Stress & also for the Stress at Operating condition(as per Appendix P, is as good as the previous recommendations of the Code(i.e, the Sustained & Exp. stress range).

Only thing is that, here, the term SL is expected to have added to the Liberal case of Exp. stress Range(Eq.1(b)of Para 302.3.5(d)), and instead the whole of the Computed Stress developed for the Operating case is equated with this.

The benefit is that you need bother about switching between the Liberal & non-Liberal case.

Can anyone of you help me in explaining the basis of deciding the
"Friction Stiffness Factor", which is used to linearise the the effect of friction in case of the Non-Linear restraints.

Following is the part of the notes appeared in c2TR(training manual,
page no 5-50)in regard with this.

I have pasted it here, to just make you aware of What i am really seeking for.


From page No.5-50 of c2TR:
"Stiffness Factor for Friction (0.0 - Not Used)
(Active for: Harmonic, Spectrum, Modal, Range, and Time History)
As noted above, all of CAESAR II’s dynamic analyses are currently linear, so non-linear effects must be linearized.
Modeling of friction in dynamic models presents a special case, since friction actually impacts the dynamic response in
two ways—static friction (prior to breakaway) affects the stiffness of the system, by providing additional restraint, while
kinetic friction (subsequent to breakaway) actually affects the damping component of dynamic response; due to
mathematical constraints, damping is ignored for all analyses except time history and harmonics (for which it is only
considered on a system-wide basis).
CAESAR II allows friction to be taken into account through the use of this Friction Stiffness Factor. CAESAR II
approximates the restraining effect of friction on the pipe by including stiffnesses transverse to the direction of the
restraint at which friction was specified. The stiffness of these “frictional” restraints is computed as:
Kfriction = (F) (S) (Fact)
Where:
Kfriction = stiffness of frictional restraint inserted by CAESAR II
F = the force at the restraint taken from the static solution
S = mu, friction coefficient at restraint, as defined in the static model
Fact = Friction Factor from the control spreadsheet
This factor should be adjusted as necessary in order to make the dynamic model simulate the system’s actual dynamic
response (note that use of this factor does not correspond to any actual dynamic parameter, but is actually a “tweak”
factor to modify system stiffness). Entering a friction factor greater than zero causes these friction stiffnesses to be
inserted into the dynamics job. Increasing this factor correspondingly increases the effect of the friction. Entering a
friction factor equal to zero ignores any frictional effect in the dynamics job."