Greetings!
Does anyone know if Caesar can perform dynamic analysis on a buried pipeline per B3.4?
I'm working on a relatively long pipeline (about 2000' long, API 5L X65). Most portion of the pipe is buried and has several 3R bends. I'm particularly asked to use B31.4 and not to use B31.3. (DOT permitting requirements, etc). One of the issues that I'm facing in this case is that the buried pipe crossing various areas that have different seismically induced settlements ranging from 2" to 12"(absolute). It seems that is very tedious work to assign this displacements to each individual supports (about 200 supports that been produced through soil modeler) and perform static analysis. My idea was to perform dynamic analysis and determine ISM's to each group of supports. The issue I’m running in to is that the software is giving me the following message and does not calculate any code stresses.
"Dynamic code stress summation cannot be performed for offshore or PD 8010 at this time"
I’m using version 2017 of the software.
Thanks in advance for your inputs.

Hi there,

I don't see any possibility to carry out with Caesar II any kind of dynamic analysis on buried piping, regardless what Code is used for analysis.

You need to go back and review Caesar II approach for buried piping analysis. Pipe material density, fluid density, insulation/lining/... density - ALL are set to ZERO and the weight affects are ignored since piping is continuously supported.
The consequence is that inertial properties of the buried piping are meaningless to be used in dynamic analysis.

Do a search on this Forum for Earthquake analysis of buried piping. I remember that long time ago, there were some inquiries and very interesting responses regarding this subject. Briefly, since dynamic analysis cannot be employed, earthquake effects might be simulated by introducing distributed strains in the buried pipe spools. American Lifelines Alliance (ALA) standard for Steel Buried Piping Analysis may be consulted in this regard - there are some indications how to assess those equivalent distributed strains.

Regards,

You may consider the provisions of guidelines as for example IITK-GSDMA Guidelines for Seismic Design of Buried Pipelines [ www.iitk.ac.in/nicee/IITK-GSDMA/EQ28.pdf ], as well you may find out a lot of good technical literature- for example the file attached.

Thank you all for the valuable inputs. I have studied all the references suggested. I'm going to use the distributed strain method suggested by ALA. I will also take a closer look at the B31E allowable limits. I may need to run FEA analysis since the code that I'm using allows pipe to yield. The criteria is to ensure that the pipe does not break and spill.
My question regarding the dynamic analysis based on B31.4 is still remained unanswered. Even for an above ground system, Caesar software doesn't perform calculations for code stress per B31.4. Any thoughts?
Regards,

CAESAR II will perform stress calculation and evaluation in accordance with B31.4. CAESAR II does not have the ability to combine B31.4 stresses calculated in the statics module with B31.4 stresses calculated in the dynamics module. With your seismic event estimated by a static load, you will have regained your ability to calculate and evaluate your B31.4 stresses.

HI Dave,
I have a query regarding the buried piping
I have a pipe which is buried and enters in to a valve pit which is non buried and again the pipe is buried after that.The valve and the pipe inside the valve chamber is non buried.I analysed the pipe run and found that the displacement at the valve node is 6 mm.
to reduce this is it advisable to put an anchor at the start and end node of pipe where which the pipe enters and leaves the pit.
what do u suggest to reduce the displacement.

Please advise

Jojo

If you are using an anchor, why not just one?

Good morning Dave,

According to what you comment, I would like to clarify a bit what I understood from your comment, if I perform a dynamic analysis under B31.4 I will not be able to obtain the admissible for efforts within the dynamic response?

Should I then carry out static load cases for earthquakes to be able to evaluate these admissible ones?

Are the loads obtained in the dynamic analysis the ones that I should use to design my supports? Or should I take the charges from the static? the query is that I have values ​​twice the load in static compared to dynamic.

Another query would be that in the majority of cases that have been reviewed, the combinations for the dynamic earthquake modulus are the following

First case

Case = EARTHQUAKE H
Factor = 1
Direction X
Case = SISIMO V
Factor = 2
Direction Y

Second case

Case = EARTHQUAKE H
Factor = 1
Direction X
Case = SISIMO V
Factor = 2
Direction Y

Should I make more combinations?

The Civil area carried out an analysis in SAP as follows:


Own weight D
Fluid (water in pipe) F
Preestres P
Earthquake Spectrum in X Ex
Earthquake Spectrum in Y Ey
Earthquake Spectrum in Z Ez



D + F + P + 0.7Exyz
D + F + P + 0.7Eyxz
D + F + P + 0.7E (-x) yz
D + F + P + 0.7Ex (-y) z
D + F + P + 0.7E (-y) xz
D + F + P + 0.7Ey (-x) z
D + F + P + 0.7E (-x) (- y) z
D + F + P + 0.7E (-y) (- x) z
D + F + P + 0.7Exy (-z)
D + F + P + 0.7Eyx (-z)
D + F + P + 0.7E (-x) and (-z)
D + F + P + 0.7Ex (-y) (- z)
D + F + P + 0.7E (-y) x (-z)
D + F + P + 0.7Ey (-x) (- z)
D + F + P + 0.7E (-x) (- y) (- z)
D + F + P + 0.7E (-y) (- x) (- z)


My pipe is supported on a cable-stayed bridge with cables, the supports were modeled with the stiffness of each cable

I think seismic analysis of buried piping should have a completely different approach. Something like this https://rb.gy/5hmf0u