buried piping analysis_al kaye ppdfb07.pdf

BURIED PIPING ANALYSISBURIED PIPING ANALYSIS

Al ( l) KAlwyn (al) KayeAltech Engineering Inc.,Altech Engineering Inc.,

9309- 96 Str Edmonton, AB, Canada T6C-3Y6 ph/fx: 001-780-4659762 eml: [email protected]/fx: 00 780 65976 g@

Disclaimer -The information provided herein is provided for training purposes only and without warranty of any kind and may or may not be suitable in any particular case or application. In no event shall the author or COADE or its suppliers be liable in any way for indirect special or consequential damages of any nature including without limitation lost businessliable in any way for indirect, special, or consequential damages of any nature, including without limitation, lost business profits, or liability or injury to third persons, whether foreseeable or not, regardless of whether COADE or its suppliers have been advised of the possibility of such damages.

Objective of this session

In this session we will: Discuss current practices of pipeline modeling &

analysis Examine the data inputs for sound buried piping and

pipeline stress analysis Make suggestions for sound input data especially Make suggestions for sound input data, especially

where information is not known or available Learn the inputs, generate some results &

conclusions Briefly discuss some key equations.

Specialty or particular analysis cases are not included : The Specialty or particular analysis cases are not included : The methodology is general and an overview for training purposes only.

Buried Piping

buried piping is a composite design of elements which must be integrated successful installation depends on all componentsintegrated successful installation depends on all components working together

the designers assumptions about native soil and bedding conditions & final soil /trench conditions will undermine or validate the analysis& final soil /trench conditions will undermine or validate the analysis

hence the data should be carefully selected and executed obtain field installation information monitor the trenching and

installation process if possible (To enable the validity of theinstallation process if possible. (To enable the validity of the analysis.)

when installation is outside the designers control or scope a proper prescriptive package developed from the engineers design basisprescriptive package developed from the engineers design basis and analysis is imperative.

pipeline companies, operators, engineers and many other organizations have standard practices to enhance quality reduceorganizations have standard practices to enhance quality reduce cost and simplify and accelerate installation. These will affect the calculation inputs.

Terminology

Anchor blocks or paddle flanges are employed to restrain the pipeline f fand may be rigid or flexible and may have a diversity factor when

combined or used with combined lines. See next page. Virtual anchor (VAL). The length of pipe which supplies sufficient restraint

f i l f i ti t b l i l th b d ti i t d i l l d dfrom axial friction to balance axial growth based on anticipated axial load due to temperature and pressure is a virtual anchor length. This is a computed length along the pipeline created when sufficient soil restraint is generated by soil friction or soil holding the pipe which equals or exceeds the displacementsoil friction or soil holding the pipe which equals or exceeds the displacement growth of the pipeline which is trying to overcome the frictional resistance. In free body force terms the total frictional resistance force is greater than the combined thermal expansion growth force plus any longitudinal force present. A VAL may be inherently developed in the ground depending on the length of pipeline soil conditions, depth of burial, compaction, pipeline coating, contact friction etc. ). Note; If sufficient (VAL) length of pipe is available, the pipe upstream of the VAL cannot affect the pipeline downstream of the VAL and vice versaVAL cannot affect the pipeline downstream of the VAL, and vice versa.

Stiffness. All elements and restraints including the soil have a stiffness which must be determined to perform a satisfactory analysis.

Terminology Contd ;Anchor blocks & Anchor or Paddle Flanges are often required for substantial thrust restraint and for load transfer between the piping and the soil.

Anchor Flanges

Soil Models support is key to any analysis Caesar II models soils as springs of stiffness equivalent to the soil data

Bili iBilinear springs

All the world is a spring - especially true for buried piping

Modeling limits

boundary conditions are ground entry/exit anchor blocks if applied virtual anchor; inherently developed and hence its location virtual anchor; inherently developed and hence its location

may vary for different loading conditions and load cases long pipelines achieve static equilibrium which avoids the

need to model or analyze whole pipelines similitude can often be used to simplify the analysis. Employ

standard or repeatable design elements to simplify the p g p yanalysis and all aspects of the work execution also.

too many elements doesnt make a better solution. Examine for and focus on areas of interestfor and focus on areas of interest

General Modeling Techniques

Build the piping model first {error check it} and then select the buried modeler to create the buried (soil) model.

Use explorer to locate the folder and example file. Use the existing piping model UGA5 C2 to avoidthe existing piping model UGA5.C2 to avoid complications . In the lab we will convert it to a buried model and run the analysis.

Make yourself a copy of the file UGA5 for the lab example 1 in case you make an entry mistake and need to recover the fileto recover the file.

Attendees can copy the original files using the theConference Procedure (or the MASTER FILES folder /directory shown next page)

Separate sheets of the step by step inputs is attached for easy data input reference.

General Modeling Techniques Contd.

Use existing piping model UGA5.C2 to avoid complications

OpentheexistingexamplefileUGA5p g p

Ifdesignerwasstartingfromscratchthepipeinputfileisselected

General Modeling Techniques Contd.Preliminary (Parent) Piping modelPreliminary (Parent) Piping model

Note: the simple supports which will ultimately become buried will be overwritten by CAESAR II as soil supports

GroundExit

buried will be overwritten by CAESAR II as soil supports with stiffness's computed from the input soils data.

GroundEntry

Preliminary (Parent) Piping model showing initial supports

General Modeling Techniques Contd.CrossingsCrossings

Pipelines buried under concrete or asphalt roadways or culverts that are designed to support vehicular or other loads require less soil cover.

There are many sources for rules and guidance such as There are many sources for rules and guidance such as API RP 1102 ; STEEL PIPELINES CROSSING RAILROADS AND HIGHWAYS

The calculations described herein do not cover situations such as railway, highway, water crossings or other special cases.

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Modeling; select the applicable Pipeline Code.

Pipelines can be built to a variety of International Codes; even with changes from one code to another by altering the selected code in the window below at the appropriate node number where the code or specification changenode number where the code or specification change occurs.

Eg. switching from B31.4 - 2006 Pipeline Transportation B31 3 2008 PSystems for Liquid Hydrocarbons to B31.3 - 2008 Process

Piping at the plant boundary or fenceline. [note BS 8010 P2 S2.8 is under PD8010]

Note; We will employ Z662 the Canadian Pipeline Code for all the node numbers.

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Modeling; Insert the Pipe Properties from the Pipespec dataPipespec data.

Pipeline materials are normally specialized materials eg have much higher UTS values than pipe in other industries and operate closer to yield with narrower margins p p p y gbetween Yield and UTS.

Pipeline materials are normally supplied by custom Mill Run Orders however standard and other piping code materials are frequently used for many pipelines or parts of pipelines Attention to the proper selection and application of the correct code andpipelines. Attention to the proper selection and application of the correct code and code limits (break points and spec changes) is essential.

Analysis is Elastic, but because the analysis in Caesar is beam element and Pipeline Analysis by other normal simplified methods encompasses general pressure, primary loading and bending stress methods.

General Pipeline analysis is not a linearized through the section Local Analysis unless a specific local analysis is undertaken by separate analysis (other than C2).

Pipeline design codes do not allow materials to operate in the Plastic Range although Pipeline design codes do not allow materials to operate in the Plastic Range although frequently local stresses may result in local deformations or discontinuities or locally high stress levels. Care and engineering judgment is essential to assess the location and potential for specific areas which will require additional or more detailed analysis. Pipelines may operate under plane stress or plane strain and analysis of both is frequently requiredmay operate under plane stress or plane strain and analysis of both is frequently required.

Plastic/FRP has specific and limiting properties and characteristics which require special attention (see end of notes)

Modeling; select the applicable Pipeline Code.Choices for selecting the applicable piping codes are in the drop down in the materialChoices for selecting the applicable piping codes are in the drop down in the material button, which is selected at the first element for which the code applies. Automatic CAESAR column duplication keeps and applies these values to all the subsequent spreadsheets (piping elements) until the value is changed in the appropriate spreadsheet field.

SelectthePipelineCode

SelectthePipelineMaterial

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Modeling; select the applicable Pipeline Code.

Note; for pipeline codes eg. B31.4, B31.8 or Z662 the Allowable Hot and Cold stresses are not automatically filled in as for normal Caesar materials input under ASME and other piping codes because to date there are no hot and cold allowable tables provided in those codes. [Only Sy is used as filled in when the Allowable Stress box is checked.] Notealsothematerial

li ti tl llistingcurrentlyonlygoestoX80andU100materialalthoughX90andother(higherandi t di t t th)intermediatestrength)materialsareavailableandmaybeused.Inthatcaseentertheactuallvalues.

Selectingthecodeinsertsmaterial

. allowables providedthisboxischecked

Modeling; Define Design Conditions in the Preliminary (Parent) Piping/Pipeline Model.Preliminary (Parent) Piping/Pipeline Model.

Operating and Design pressure and temperature.N t U 300 i O ti d 350 i D iNote; Use 300psig Operating pressure and 350psig Design

pressure for example 1 Installation temperature is a critical factor in the modeling Installation temperature is a critical factor in the modeling

analysis and outcome. The expansion formulation Ldt means that the starting temperature has a large effect because of the large lengths involved in pipeliningbecause of the large lengths involved in pipelining.

Note; Use 60F install temp & 80F Operating for example1. Cold climates have special features needing attention and Cold climates have special features needing attention and

specific deign and analysis measures eg. moisture increases stiffness very significantly right up to total rigid anchoring especially at crossings pools of water or groundanchoring especially at crossings, pools of water or ground entry exit

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Modeling; select the Pressure & Temp.Completing and checking the Preliminary (Parent) Piping/Pipeline ModelCompleting and checking the Preliminary (Parent) Piping/Pipeline Model.Dont BURY a BAD Model

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Complete the Parent (prelim.) model first then ERROR Modeling; Contd

p (p )CHECK it before trying to make buried model

ERRORCHECK button RUN button(aftererrorsfixed)

NotesFYI WONTRUN (untilerrorsfixed)WarningsRead ,dontnecessarilyneedfixing

The Buried Soil Modeller

Th i t fi ld t d i th t bl b l Th The input fields are presented in the table below. The user can enter known values here or perform what if scenarios. Fortunately since about 1988 the load and stiffness data are computed by CAESAR II (unless of course we want to use our own or other values in these fields).

The regions which have a soil model (and hence soil The regions which have a soil model (and hence soil restraint) against the pipe are marked in the boxes from mesh as buried to the end mesh. Eg. the start & end nodes for soil modelling o ld be at gro nd entr andnodes for soil modelling would be at ground entry and ground exit nodes in the CAESAR PIPELINE MODEL.

The Buried Soil Modeller; .

The input fields are presented in the table below.

.[there is additional discussion of the formulas for these load & stiffness calculations at the end of the presentation]

The Buried Soil Modeller;

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Next step is to Create the Soil Model Data.

Soil Models

The soils data needed for input would normally come from

We have to pause input on the above spreadsheet to briefly discuss where the numbers to enter come from while examining the input spreadsheets

p ythe soils report. It is standard for these required values to be provided. On many occasions that may not be available. For analysis prior to soils testing or to test what if studiesFor analysis prior to soils testing, or to test what if studies the values can be estimated or previously collected (or assumed) values can be employed.

For these reasons the Caesar Technical Manual and User Guide provide sample values and explanations and more are provided herein. There are many sources of literatureare provided herein. There are many sources of literature for Pipe Burial depth deflection calculations.

Depth Pipe burial depth calculations are based on S l ' d fl ti d V Mi ' b kli tiSpangler's deflection and Von Mise's buckling equations.

Note; Once the soil model(s) are entered CAESAR II will perform these long and tedious calculations as long as we understand the proper input data.

Soil Models Soils Types

Type of soil . The specific locations ability to support pipe depends on the type of soil degree of compaction and conditiondepends on the type of soil, degree of compaction and condition of the soil, i.e. density and moisture content. A stable soil is capable of providing sufficient long-term bearing resistance to

t b i d i U t bl il h t i ilsupport a buried pipe. Unstable soils such as peat, organic soil, and highly expansible clays exhibit a significant change in volume with a change in moisture content.

For cohesive soils (clays) or granular-cohesive soils, if the unconfined compressive strength per ASTM D2166 exceeds 1500 Ib/ft2, the soil will generally be stable.

For cohesive soils, if the shear strength of the soil per ASTM D2573 is in excess of 750 Ib/ft2, the soil will generally be stable.

For sand if the standard penetration "Blow" value N is above For sand, if the standard penetration Blow value, N, is above 10, the soil will generally be stable

Soil Models Stiffness

Soil stiffness is either native (the condition of undisturbed il) hi h tiff b hi d b tisoil) or higher stiffnesss can be achieved by compaction,

either natural compaction or mechanically induced compaction.

The measure of stiffness is given as the Proctor Density Soils types are grouped into "stiffness categories" (SO).

Th d i t d SC1 th h SC5 SC1 i di tThey are designated SC1 through SC5. SC1 indicates a soil that provides the highest soil stiffness at any given Proctor density and higher numbered soil classifications y g(SC2-SC4). SC5 soils are unstable and should not be used as backfill or bedding.

See table next pg.

Soil Modeling ; Compaction

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Soil Models contd.

Modulus Considerations - The soil modulus is very i t t t i i b i l l i dl f th ilimportant to piping burial analysis regardless of the soil type. Extensive research and engineering analysis has shown that a soil modulus of 1,000 psi provides very good support to all classes of pipe.

There are two Soils Modeling Techniques available in CAESAR IICAESAR II CAESAR II Basic Model ; discussed American Lifelines Alliance ; example to do in lab

Soil Models contd.

Soils/Geotechnical Reports Recommended reading

Follow these helpful references.[1] Bowles Foundation Analysis[2]http://epg.modot.org/index.php?title=320.1_Preliminary_Geotechnical_Report#320.1.4.2_Summary_for_Preliminary Geotechnical Report Form M 41Preliminary_Geotechnical_Report_-_Form_M-41[3] Contractor's guide to geotechnical engineering: how to decipher a soils reportConcrete Construction, May, 2002 by Thomas A. Chapelhttp://findarticles.com/p/articles/mi_m0NSX/is_5_47/ai_91139460/[4] http://www.geotechnicaldirectory.com/page/Software/Laboratory_testing_(soil).html[5] GUIDANCE NOTES ON GEOTECHNICAL INVESTIGATIONS FOR PIPELINES http://sig.sut.org.uk/pdf/PipelineGeotechInvestigGuidNotes%20Rev0300.pdf[6] Geotechnical Reports in Underground Construction (ref. B.M.Bohlke Geotech Design Reports get a Litmus Test ASCE Civil Engineering; Dec.1996, pp. 47-49) http://www.th.gov.bc.ca/Publications/eng publications/geotech/TB GM9801 Guide Geotech Rpts.pdfhttp://www.th.gov.bc.ca/Publications/eng_publications/geotech/TB_GM9801_Guide_Geotech_Rpts.pdf[7] Geotechnical Testing, Observation, and Documentation By Tim Davis

Soil Models contd.Soils/Geotechnical Reports

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Soil Models contd.Soils/Geotechnical Reports Contd It is necessary to be knowledgeable about the techniques and parameters and be specific in

acquiring the data. This chart shows what works and what doesnt, but you will rarely obtain even a few of these

parameters.

Soil Models contd.Soils/Geotechnical Reports Contd .

The best reference for pipeline test methods & report outcomes is fromhttp://sig.sut.org.uk/pdf/PipelineGeotechInvestigGuidNotes%20Rev0300.pdf

Soil Models Inputs

Other (alternate) valid soil model numbers start with 2. Soil model #1 is reserved for user-defined soil stiffnesss. Soil model #1 is reserved for user defined soil stiffness s. Up to 15 different soil models may be entered for a single job

the inputs are

ThesedefaultvaluesinsertedbyCAESAR;alterasappropriate

Thermalexpcoeffisbroughtforwardfromthepipematerialintheparent(preliminarymodel)spreadsheet

Soil Models Inputs

In example1 (this lab; file UGA5) we are using Soil model #2 New soil model numbers are required for changing soil. New soil model numbers are required for changing soil

conditions AND changes in soil cover.

user would add other soil models here; assumemodels here; assume there is only one soil model . ie. #2

Soil Models these are the CLASSIC Inputs(based on PENG paper et al.)

The CAESAR II Users Guide Section 18 has good help fields [ and the online help (F1) ].

Either the friction coefficient [Note if Su the undrained shear strength (for clay) is entered below this field may be left blank.]

f = friction coefficient, typical values are:

0.4 for silt0.5 for sand0.6 for gravel

= soil density (Required value) pipeline stress engineer should discuss with the soils engineers. Almost always comes from Soils Report.

H = buried depth- Known or assumed

= interface friction angle for cohesionless soils ; also used in the American Lifelines Alliance Sand/Gravel Soil Model typical values are:

sand 27 to 45 deg.silt 26 to 35 deg.clay 0 deg.

This is also frequently calledq = angle of internal friction.Note the internal friction angle is the angle at which a pile of the soil is no longer stable and slides

Soil Models InputsThe CAESAR II Users Guide Section 18 has good help fields [ and the online help (F1) ].

Su = undrained shear strength, typical values are:

Typically for clays the friction coefficient would be left blank and would be automaticallyTypically for clays the friction coefficient would be left blank and would be automatically estimated by CAESAR II as Su/600 psf.If Su is given (i.e. have a clay-like soil), then Ftr should be multiplied by Su/250 psf. If the overburden compaction multiplier is given then Ftr is multiplied by this value also.

Fig. Adhesion- Undrained Shear Strength


m = overburden compaction multiplier ; typical values are based on the Compaction or Proctor Number:

i T bl b R d d B ddi d B kfill M t i lsee previous Table above : Recommended Bedding and Backfill Materials

1-1.5 for no compaction or dumped (loose fill) 2-4 for 75-95% compaction 5 for >95% compaction p>5 for very rigid or constrained pipesHigher values can be used if warranted eg slurry concrete mix (such as used at corners) or frozen ground.This value is used in the soil restraint equations to generate the restraint ultimate loads and stiffness's.

dQu dQd = yield displacement factors, typical values are:

The yield displacement from EDA (Eng. Design Associates) is given as a range of D/25 to D/60 but that source does not differentiate between axial and lateral versus uplift (above the pipe) and down (bedding below the pipe). These are typically all different values unless the soil is extremely homogenous and equally p p ) yp y y g q ycompacted for the region of influence all around the pipe . Normally the undisturbed or compacted bedding under the pipe has higher stiffness and lower yield displacement factor (down). Also the lateral pipe trench walls will have different values from the backfill material placed adjacent to the pipe depending on the compaction level and the width of the trench.


= thermal expansion coefficient, use the standard values for the pipeline material - eg from the material tables Section VIII Part IID or standard material reference. [units in L/L/deg. xE-6 ].The thermal exp coefficient is brought forward from the pipe material in the parent (preliminary model) spreadsheetp g p p p (p y ) p

T = temperature change, enter the temperature differential of the pipeline : (install operating) This is used to determine the growth and propensity of the pipeline to overcome soil friction.

f = friction coefficient soil to soil coefficient from above:f = friction coefficient, soil to soil coefficient from above: = friction coefficient, soil to pipe coefficient below:F = coating factor used in the American Lifelines Alliance Sand/Gravel Soil Model

Do NOT confuse soil to soil friction coefficient with the friction factors of soil against various coatings (or as F used in American Lifelines Alliance Sand/Gravel Soil Model) . This only occurs at the pipe adjacent to the soil and does not govern the soil behavior and the soil spring model. This does govern however in computing the axial load and travel of the pipeline necessary to overcome the soil friction holding the pipe. This is also inherent in the length required to develop full restraint of the pipeline (virtual anchor length).

These values are more conservative than often used (eg. for steel or plastic) and will yield higher friction loads. Often it is wise to bound the solution using half the above to generate higher displacements and hence higher bending stresses (but lower frictional loads).

Soil Modeling Inputs ; American Lifelines AllianceThese are the ALA Inputs in the order presented in the program for cohesive (clay like) soil..

.Thermalexpcoeff.isbroughtforwardfromthepipematerialintheparent(preliminarymodel)spreadsheet.

Soil Modeling Inputs ; American Lifelines Alliance = dry soil density ; typical values are y y ; yp

= effective soil density (Required value) pipeline stress engineer should discuss with the soils engineers. The specific and real numbers at a location almost always come from the Soils Report. But note they can vary from position to position so an average value is used unless specific location data is required for a local problem area.

Soil Modeling Inputs ; American Lifelines Alliance .

H = buried depth- Known or assumed

c = soil cohesion of backfill ; convert values to psic = soil cohesion of backfill ; convert values to psi0 psf (0psi) . for loose dry sand 580-720 psf (4-5psi) for soft clay. 1500 psf (10.4psi) for hard clay.

= adhesion factor ; typical values0 -1.5 varies as the shape factor and stickiness of the soil See Fig. Adhesion-Undrained Shear Strength above

H

.Fig. Surface Load and Resulting Pressure


dT = yield displacement factor, axial ; soil displacement at which Ultimate Axial Load is developed - typical values are;

Dense sand 0.4 in (2.5mm) Loose sand 0.2 in (5mm)Stiff clay 0.3 in (7.5mm)Soft clay 0.4 in (10mm)

dP = yield displacement factor, lateral ; soil displacement at which Ultimate Lateral Load is developed

values are calculated from: dP = 0.04( H + D/2) but the resulting value must be limited to a Max.Multiplier x OD ( this multiplier between 0.1 to 0.15 is entered in this field )

Note: Where specific values could alter the outcome test result data should be requested from the soils engineerNote: Where specific values could alter the outcome test result data should be requested from the soils engineer and/or soils analysis report.

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Qu and Qd = yield displacement factors ; vertical uplift and vert download(modelling on the soil springs) ; - from Lifelines Alliance Eqns (3-3)

qu(H) = Multiplier x H

(D) M lti li OD

Where H = depth of Burial; D = pipe OD

qu(D) = Multiplier x OD

sand 0.1 in (2.5mm)clay 0.2 in (5 mm)

qd = Multiplier x OD

. (or sand)(clays)

Soil Modeling Inputs ; American Lifelines Alliance . EXAMPLE 1

Note; Use for example 1 American Lifelines Alliance Model inputs soil type: = soft clayD = pipe Diameter = 12 in = 305 mmD pipe Diameter 12 in 305 mmH = depth burial ,distance to top of pipe: = 59 inch = 1.4986 m. =149.86 cm. = internal friction angle of the soil: = 19 deg.c = soil cohesion representative of the backfill: = 4.5 psi. = 3.1 N./sq.cm. = soil density: = .043 lb/in3 = 75 lb./cu.ft= 1.2 tonne/m3= 0.0012kg/cm3

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Soil Modeling Inputs ; American Lifelines AllianceThese are the ALA Inputs in the order presented in the program forThese are the ALA Inputs in the order presented in the program for granular (gravel like) soil. Only two new terms are introduced. Gravel NOT used in this exercise.

= dry soil density ; typical values are

Ko = coeff of pressure at rest ; typical value =1

If omitted value defaults to Ko=1-sin (internal Friction angle of Soil)

B l f ALA I t f l ( l lik )Balance of ALA Inputs for granular (gravel like) soil terms are the same as presented before. Gravel NOT used in this exercise.

Soil Modeling Inputs Recall ; Soil model #1 is reserved for user-defined soil stiffness's. This Soil Model file is saved as Filename.SOI We want to have soil modeling from nodes 50 to 150, plus increased mesh (more

soils springs) at the bends

Ground Exit

New soil model numbers are required for changing soil conditions AND changes in soil cover.

GroundExit

Wewantmore(increasedmesh)buriedsoilspringsatthecornersNodes60&140

GroundEntry

WewantburiedsoilspringmodelsfromNode50to150

Soil Modeling Inputs .

C2 automatically puts the increased mesh at the bends. In this lab we did it manually User does not have to increase mesh at bendslab we did it manually. User does not have to increase mesh at bends. User does have to decide where else to increase mesh for model refinement.

Note; none of the other Load and Stiffness data fields have to be completed

Soil Modeling Inputs The From To mesh Checked boxes were to demonstrate where and The From To mesh Checked boxes were to demonstrate where and

how increased mesh refinement is added. CAESAR will automatically provide closer meshing at bends.(called Zone1)

Other locations for mesh refinement include where better modeling, accuracy or detail is needed when a branch ties into a long buried header (tees) a local discontinuity .user-defined node within or near Zone 1 ground entry/exit

Fig . Zone

Buried pipe deforms laterally in areas immediately adjacent to changes in directions (i.e. bends andtees). The length over which the pipe deflects l t ll i t d th l t l b i l th Definitions

CAESAR USER GUIDE pg 4-11

laterally is termed the lateral bearing lengthLb = 0.75 [4EI/Ktr] 0.25

CAESAR II places three elements in the vicinity of this bearing span to properly model the local load distribution.Either many, closely spaced, low stiffness supports are added or a few, distant and high stiffness supports are added.Where the deformation is lateral, smaller elements are needed to properly distribute the forces from the pipe to the soil.

Soil Modeling Inputs C2 automatically puts the increased mesh at the bends. In this lab we did it manually User does not have to increase mesh at bends if you have true underground restraints, these must be added AFTERburial as C2 removes all entered restraints on pipe that is eventually buried. (see warning below)

lab we did it manually. User does not have to increase mesh at bends.

GroundExit

CAESAR will automatically provide closer meshing at bends.(called Zone1)

A very long run of pipe will display all three mesh zones.

G dGroundEntry

Thispipelineisnotlongenoughto developavirtualanchor.

We already have an anchor at the left endpoint in the modelWealreadyhaveananchor attheleftendpointinthemodel

Soil Models ; inserted into Piping Model

Note none of the other Load and Stiffness data fields have to be completed. When converted to Buried Input the filename is the former filename with suffix B Select file SaveAs to change the jobname if required.Note ; Caesar will add /insert new nodes (as needed). existg numbering will not be alteredNote ; Caesar converts to zero density all pipe that is ; y p p

converted to buried. It must, because soil support is assumed universal and uniform and there is no unsupported length or bending moment arising from unsupported mass.

Hence (mass) dynamic analysis of such buried pipe is invalid

ConvertinputfrompreliminarymodeltoBuriedModelwithsoil.

Hence (mass) dynamic analysis of such buried pipe is invalid.

p p y

Note ;use (keep ) filename UGA5B [B is for the buried model]

Run the Buried Piping Model

When the model is now run you When the model is now run you see the calculations in the screen listing which at the end can be captured and printed.

The stiffnesss are created as stiffness per unit length Thesestiffness per unit length. These are multiplied by pipe length to provide the node point stiffnesss

Soil Models ; inserted into Piping Model Note; Should have a filename UGA5B ..if not open the ***B file to work ; p

with the buried model. In this case UGA5B.c2Note ; there is now Soil Stiffness and Load Data

as required from Nodes 50 thru 150

Soil Models ; inserted into Piping Model Note ; the Soil Stiffness and Load Data is computedNote ; the Lateral Bearing Length is computed

Note the physically placed anchor (before ground entry.) This could be any designer selected physical anchor anywhere in the pipeline.

Buried Piping Analysis

axialgrowthcausingbendingisconcentratedatbearingpoints(e.g.tees&bends); analysiswillprovideimprovedgrowthin&outofsoil;notegrowthshapebelow

Significant Results ;

loadscanbeusedtosizethrustblockset.al. morereliablestiffnesssmeansmorereliableanalysis

Modeling Inputs ; Caesar Basic Model Inputs

CAESAR Basic Model inputs (for those who wish to try the Basic (traditional) Caesar model or manual load and stiffness entries

Su = Undrained Shear Strength = 4.5

The computed values for the Basic CAESAR II input if manually calculated (for example to put in the soil spreadsheet manually rather than CAESAR II computed values ) are shown in p p y p )the Table below.

Table . Soil Resistance properties ; example problem

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Installation and field validity of Modeling

Application of these methods is based on the assumption that the design values used for bedding, backfill and compaction levels will be achieved with good field practice and appropriate equipment If these assumptions are not met the deflections can be higherappropriate equipment. If these assumptions are not met, the deflections can be higher or lower than predicted by calculation.

Linear Versus Non-Linear the soil spring model is Bi linear (or higher ) and the soil has non-linear behaviour. (Recall Slides 4&6)

H N Li i li h d fl id i i l t d i However Non Linear pipeline hardware or fluid response is a special case not covered in an introductory course such as this. Also dynamics, upsets or transients and the soil or pipeline response to unsteady state conditions are not covered and require additional engineering analysis. Corollary is that lumped mass dynamic analysis of such buried pipe hardware in Caesar II is therefore invalid because of the buried conversion to no mass and zero density .y

Modeling and Analysis of Plastic & FRP Buried pipe The response of fiberglass/plastic pipe to burial loads is dependent on the flexibility of the

pipe wall. This pipe flexibility can be found using the "pipe stiffness" value as defined and determined by ASTM D2412 testsdetermined by ASTM D2412 tests.

Pipe with pipe stiffness values greater than 72 psi typically resist native backfill loads with minimal pipe deformation. The pipe stiffness of small diameter fiberglass pipe, 1 to 8 inch diameters, typically meets or exceeds 72 psi. Two to three feet of native backfill cover with a soil modulus greater than or equal to 1 000 psi is generally sufficient to protect this category ofsoil modulus greater than or equal to 1,000 psi is generally sufficient to protect this category of pipe from small vehicular and dead weight soil loads. Code defined Crossings are documented in the pipeline codes . Vehicle crossings (other than infrequent small vehicles) require more detailed loading analysis.

Technical Discussion Modeling Philosophy

Note ; Many references will discuss and employ the modulus of subgrade reaction and/or the modulus of soil reaction. This value is not used directly in most pipeline software calculation inputs. The American Lifelines Alliance has this excellent discussion;

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Technical Discussion Modeling PhilosophyFig. Bending Moment at Buried Pipe Bends

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Plant Engineering, Design, Planning, Execution Project Management of Quality, Cost Effective Plants. Efficient use of capital, shorter development times and faster implementation to reach better outcomesand faster implementation, to reach better outcomes .

Chemical Plants Breweries/DistilleriesPharmaceutical/BiotechPlantsincl.Digesters,Fermenters.

Pharmaceutical

Oilsands and Mining plants for including materials handling. Petrochemical ,Energy.and Pipelines Pilot plants and advanced technology equipment Forestry incl digesters chip and palletizer facilities

Treatment

g ,Forestry incl.digesters, chip and palletizer facilities.

Innovation for Fabrication & Construction Cos.Technology developers and entrepreneurs in Pharmaceuticals,Power Plant, Heavy Machinery,

Fabrication, Construction, Exploration, Offshore, Oilsands and Petrochemical Industries.

Pipelines Instrumentation, Mechanical, Civil, Structural, Process. Qualified Failure & Construction Inspection plus Load Studies. Construction design, detailing & support, EPC, Fixed-Bid, PPP.

Tanks

PetroChemical Boilers, Pressure Equipment, Water Treatment & related Facilities

Specifications, full project services, scheduling and planning Project Management PEER system to forecast, budget, track.

Bio-Fuels

, q p ,

Chemicals

buried piping analysis_al kaye ppdfb07.pdf

Documents