Hi all,
I have a problem with the introduction of several spectrums in the program Caesar 2. I must analyse a pipeline with several spectrums because this one go through several buildings. I have set a interval of nodes for each spectrum. When I run the analysis the stresses are enormous.

Thank you, regards and congratulations for the program !

Open a Support Request on eCustomer and send in your job file for review.

Did you specify "Anchor Movement" in your Spectrum Load Cases (the last column)? If you have more than one shock spectra in your load case and no value in that column, CAESAR II will calculate displacements based on your entered spectra. These numbers are often very large. And you will see big displcements at your boundary conditions.
Try zeros in that last column to check this.
Then replace those zeros with expected support displacements.

so, if the column is all zero, are all spectra used in all the system at the same time?

No, the displacements associated with each row in your load case definition will be evaluated independently and then summed with the inertial components. See page 5-24 of the Technical Reference Manual.

Hi,
I have read the issue in the technical reference manual. My problem was that I did not know what happens when I don´t indicate the displacements of each affected anchor to each spectrum. In manual says that in the default situation, the program entry the corresponding to the lowest frecuency. But, the lowest frecuency of each spectrum?, the lowest frecuency in each spectrum is zero, and the acceleration is not the higest, my system don´t enter in resonance with a so low frecuency and this is not the most unfavorable situation. I don´t know if I have understood it.

Thank you

The old problem.
If the user set at anchor movement zero, then Caesar do not anchor movement zero in this cases.
Better woud be Caesar take only anchor movement from spectrum, if anchor movement entry is empty so have the user the coice.
Anchor movement entry is 0 ==> then no spectrum movements
Anchor movement entry "blank" ==> then with spectrum movements
Anchor movement entry 5 mm ==> then with 5 mm movement

very clear your explanation thank you. But if the movements are taken from the spectra, what is that of taking the lowest frecuency?. In the graphics of each spectra?.

With the acceleration at your lowest frecuency in your spectrum input Caesar2 estimated a displacement.

all the pectra have a range of frecuencies from 0 to 34 Hz. So, Caesar II takes all the displacements from the frecuency 0 (the lowest)? but is it not the most unfavorable, the acceleration is higher in other frecuencies.

Danke schön aus Spanien für deine Hilfe

First...
I think in the spectrum input a lowest frequency zero (0) will made a syntax error.
I allways take 0.01 Hertz.
Second ...
The spectrum anchor movement effect come only from the lowest frequency
(Its a displacement from very slowly movement between buildings or restraints).
See also more details NUREC.

Bitte schön aus Deutschland.

It's a response spectrum, your looking at a system's response to the event. A rigid mode will track ground acceleration (ZPA in fact) and a very, very flexible mode will reveal the ground displacement. (I the first sentence I reference system response and in the second I emphasize ground input.)
If not entered in multi-spectra input, CAESAR II sets this anchor displacement on the lowest entered frequency. Some users ignore the low frequency end of their spectrum thinking there is no system mode that low to be excited. If you don't go low enough in frequency, you may end up with large values for this derived displacement and then big stress. Look for the "P" in the label for the largest "modal component" of the total stress.
In many installed piping systems the strain component does more damage than the inertia component.

I done a little testruns with Caesar II Vers 5.3
At anchor node 40 (higher floor) and node 10 (lower floor)
One spectrum at node 40 and one at node 10.
This will be Multiresponse Analysis.
Both spectrum the same, but only the first cell in spectrums are different (node 40: 0.1 Hz ; 500 mm/s2) and (node 10: 0.1 Hz ; 0 mm/s2).
In optional input -include pseudo anchor movement YES-
very big stress and displacement results.
Then in optional input -include pseudo anchor movement NO-
realistic stress and displacement results.
Thats ok, because switch with pseudo anchor movement YES/NO do it right.
Before in Caesar Vers. 5.2 was this not the case i think so.
Here allways was a anchor movement from first spectrum acceleration include automatic also with pseudo anchor movement NO in optional input.

However, Mr.Diehl can you give for me the sources ( Nureg ??) for this
rule (anchor movement from first acceleration in spectrum)?
Must the stress engineer this do or can be do ?

Because, many pipe engineers take for pipes (go over more floors; every floor have a different spectrum) one wrapping spectrum for all nodes ==> single response, so this then without anchor movement.
If the spectrum at higher floor different (first acceleration) to the lower floor then this way maybe not conservativ.

Thank you for your interest and your efforts Ohliger .

About the last thing you have written, about taking only a spectrum for all, despite of the fact of being the higest. I think that with two spectra opperating at the same time, the acceleration of one spectrum can go in the opposite direction to the other, and the piping suffers more because of contractions or expansions. So, is more conservative more than one spectrum.

I dont think so.
With this way you become at lower floor higher accelerations ( from the higher floor). Thats right.
But you miss with this method the Pseudo anchor movement.
See what Mr. Diehl had write :
"In many installed piping systems the strain component does more damage than the inertia component."
My Opinion:
Spectrum Analysis ( Response calculation)can have 3 componets
1. Modal components
2. Missing Mass components
3. Pseudo anchor movement components

Point 1 und 2 must be combined and satisfied limit stress.
Point 3 can allone calculated ( without Point 1 und 2)and have a limit stress ( 3 Sm ; ASME or 6 Sm).
Caesar II do it not so.

I don´t know why you miss Pseudo anchor movement. If you use the last column on the right, you have the SAM.

I believe there has been no change to the implementation of seismic anchor motion between CAESAR II V5.20 & V5.30; the program would not calculate a strain for a single spectrum (everything strains together) and will calculate strain, if none entered, where two or more spectra are entered in a single direction.
CAESAR II does not apply a different allowable limit for these strains.
Yes, if you envelop all floors into a single shock spectrum, you will not automatically consider the strain portion of the load. This is also true if you model the building steel in CAESAR II, those strains cannot be isolated.

what are you referring to with the strain portion?. Strain due to relative movements?

Yes, strain due to relative seismic movement.

SAM is missing if you have independent spectrums and made
one spectrum over all floors.