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AutoPIPE Wiki 08. AutoPIPE vs Caesar Benchmark
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              • 02-03.a1: Example 1 - After import, how to fix piping that are not all connected?
              • 02-03.a2: Example 2 - After import, how to fix piping that are not all connected?
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              • -02-03.n: Import / Export caesar (cii) or Areva PDMS (cii) with AutoPIPE
                • +01. Import / Export CAESAR (cii) file - AutoPIPE
                • 02. AutoPIPE vs CAESAR load combinations
                • 03. C-Node or Connecting Nodes in Caesar
                • 04. Compare AutoPIPE Input Grids with Caesar Spreadsheets
                • 07. Where are similar caesar settings in AutoPIPE?
                • 08. AutoPIPE vs Caesar Benchmark
                • 09. Piping codes availability between AutoPIPE and caesar
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              • 04-001: While importing or copy paste into AutoPIPE model, the node numbers are renaming automatically. How to import / copy geometry without changing the node numbers?
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    08. AutoPIPE vs Caesar Benchmark

    Applies To
    Product(s): AutoPIPE
    Version(s): ALL;
    Area: Results
    Date Logged
    & Current Version
    Oct. 2017
    11.01.00.23

    Model Definition

    AutoPIPE:

    The model taken is a pump system where Pump A(Point 1) or Pump B(Point 90) or both Pump A and B are in operation. The point 170 is connected to a vessel oriented in Z axis and at this point we enter a flexible anchors(by CAESAR under the WRC297 and by AUTOPIPE under user flexibility)

    Pipe OD at Pump A or B 168.3 mm
    Wall Thickness at Pump A or B 7.1 mm
    Pipe OD after the reducer 219.1 mm
    Wall Thickness after the reducer 8.2 mm
    Temperature for the pump in Operation 450 degC
    Temperature for spare Pump 80 degC
    Material A106B
    Piping Code B31.3:2006
    Allowable Stress at 80 degC 137.89 N/mm2
    Allowable Stress at 405 degC 86.29 N/mm2
    Pressure 10 bar
    Earthquake Loading

    AutoPIPE
    Number of load cases : 4
    Load case 1 - E1
    X-Multiplier= 0.100
    Y-Multiplier= -0.050
    Z-Multiplier= 0.000

    Load case 2 - E2
    X-Multiplier= 0.000
    Y-Multiplier= -0.050
    Z-Multiplier= 0.100

    Load case 3 - E3
    X-Multiplier= -0.100
    Y-Multiplier= -0.050
    Z-Multiplier= 0.000

    Load case 4 - E4
    X-Multiplier= 0.000
    Y-Multiplier= -0.050
    Z-Multiplier= -0.100

    caesar
    UNIFORM LOAD Changes
    U1
    X1 Dir = .10 g`s
    Y1 Dir = .00 g`s
    Z1 Dir = .00 g`s

    U2
    X2 Dir = .00 g`s
    Y2 Dir = -.05 g`s
    Z2 Dir = .00 g`s

    U3
    X3 Dir = .00 g`s
    Y3 Dir = .00 g`s
    Z3 Dir = .10 g`s

    E1= U1+U2 (CAESAR)
    E2=U2+U3(CAESAR)
    E3=-U1+U2(CAESAR)
    E4=U2-U3(CAESAR)

    Wind Loading

    Number of load cases : 4

    Ground elevation for wind : 0.00 mm
    Wind shape factor multiplier : 0.700
    Exposed Segments - A B
    Wind application method : Normal

    Load case 1 - W1
    X= 1.000
    Y= 0.000
    Z= 0.000

    Load case 2 - W2
    X= -1.000
    Y= 0.000
    Z= 0.000

    Load case 3 - W3
    X= 0.000
    Y= 0.000
    Z= 1.000

    Load case 4 - W4
    X= 0.000
    Y= 0.000
    Z= -1.000

    User defined wind profile
    Height (mm)   Press (N/m2 )
    -----------   --------------
    From : Ground
    to : 7000.00   480.00
    to : 10000.00  540.00
    to : 15000.00  630.00
    to : 20000.00  700.00
    to : 25000.00  760.00
    to : 50000.00  990.00

    Valves between 10-15,15-20,70-75,75-80 Nodes
    Weight
    5000 N each
    Reducer between 1-5,85-90 Nodes
    OD1/WT1
    OD2/WT2

    .
    168.3 mm/7.1mm
    219.1 mm/8.2mm

    Welding Tee  Node point:
    45

    Elbow

    Radius 1.5 OD=304.8 mm

    Node points:
    25,40,50,60,65,105,115,120,130,140,150,155
    Spring Hanger

    Node Point 20: Stiffness Rate:133N/mm ,Cold load:14083 N
    Node Point 35: Stiffness Rate: 67N/mm ,Cold load:5928 N
    Node Point 55: Stiffness Rate: 67N/mm ,Cold load:4943 N
    Node Point 70: Stiffness Rate:133N/mm ,Cold load:14547 N

    V-Stop(+Y support)

    Node points:
    110,125,135,145

    Support Friction=0.3

    Line Stop (Stop in X direction) simulated by an incline support

    Node point:
    110

    Support Friction=0.3

    Flexible Nozzle

    AutoPIPE used User Flexibilities
    CAESAR II used WRC297

    Node point:
    170

    Vessel Axis = Global Z
    Axial Translation Stiffness=32422 N/mm
    Longitudinal Bending Stiffness=39422 Nm/deg.
    Circumferential Bending Stiffness=8916Nm/deg.

    Thermal Anchor Movements:

    Node point:
    1, 90

    Case T1: DY = 2.35mm, Case T3: DY = 2.35mm
    Case T2: DY = 2.35mm, Case T3: DY = 2.35mm

    RIGID Support and Anchor Stiffness

    AutoPIPE caesar

    Support Rigid Stiffness
         Translation: 1.7512 E+9 N/mm
         Rotation: 1.3558E+12 Nm/degree

    Anchors Rigid Stiffness
         Translation: 1.7512 E+9 N/mm
         Rotation: 1.3558E+12 Nm/degree

    Default Friction Stiffness: 1.7512e+10 N/mm

    AUTOPIPE does not allow you to change the friction stiffness but the friction tolerance is used to check analysis convergence.

    Support or Anchors Stiffness
         Translation: 1.75E+11 N/mm
         Rotation: 1.1298E+11 Nm/degree

    Friction Stiffness: 4.38e+006 N/mm

    The friction stiffness, the friction angle variation, the friction slide multiplier and the coefficient of friction are able to be set in the configuration file.

    Simulated Valves

    AutoPIPE caesar

    AutoPIPE assumes that a valve is 100 times stiffer than the connecting pipe material at the start of the valve.

    The Surface Area Factor is the factor used to multiply the insulation weight of the pipe per units length to get the insulation weight of the valve per units length.

    To simulate the rigid element like CAESAR II , the valves are going to be modeled like an element with 10 times the wall thickness of the pipe and we will have to correct the weight entered(5000 N) because in this case the weight per meter is much bigger.

    PIPE3 is the pipe with 82 mm wall thickness.

    The weight of the pipe total =3170 N/m
    The element 533 mm= 1689.6 N
    The element 419 mm=1328.2 N

    The weight of the check valve(533 mm) to be entered should be :
    5368.9-1689.6= 3679.3 N

    The weight of the check valve(419 mm) to be entered should be :
    5289.8 N-1328.2 N=3961.6 N

    The insulation density has been changed from .2 Kg/dm3 auf 1.75 x .2=.35 Kg/dm3

    CAESAR II forms rigid elements by multiplying the wall thickness of the element by 10. The inside diameter, and the weight of the element, remain unchanged.

    The weight of insulation added is equal to the same weight that would be computed for an equivalent straight pipe times 1.75 and cannot be changed.

    According to CAESAR II Miscellaneous Data

    The element 533 has a total weight of
    9381+439+253=10073 N/m

    That means a weight of 5368.9 N

    The element 419 has a total weight of
    11933+439+253= 12625 N/m

    That means a weight of 5289.8 N

    Post Processing Load Case (Non-linear)

    Sustain Stress

    AutoPIPE caesar

    GR(1)=GR+MaxP(1)

    GR=Weight
    MaxP(1)=The max pressure into the system (Between P1,P2,P3)
    (1)=Analysis Set 1

    L13=W+P1+H
    L14=W+P2+H
    L15=W+P3+H

    -W=Weight
    -P1=Presure 1
    -P2=Pressure 2
    -P3=Pressure 3
    -H=Hanger

    No stress

    Operating loading cases are only to check the displacements & forces and moments

    AutoPIPE caesar

    GT1(1)=GR(1)+T1(1)
    GT2(1)=GR(1)+T2(1)
    GT3(1)=GR(1)+T3(1)

    T1(1)=Temperature 1 for analysis set 1
    T2(1)=Temperature 1 for analysis set 1
    T3(1)=Temperature 1 for analysis set 1

    L2=W+D1+T1+P1+H
    L3=W+D2+T2+P2+H
    L4=W+D3+T3+P3+H

    T1=Temperature 1
    T2=Temperature 2
    T3=Temperature 3
    D1 =Displacement by T1
    D2=Displacement by T2
    D3=Displacement by T3

    Expansion Stress

    Operating loading cases are only to check the displacements & forces and moments

    AutoPIPE caesar

    Amb to T1(1)
    Amb to T2(1)
    Amb to T3(1)
    Max Range
    GR(1)--> P1(1) P1(1)>T1(1)

    Thermal expansion from Ambient temperature to T1(1),T2(1),T3(1)
    Through the load sequencing, we start to apply 1st the weight(GR) ,2nd the max Pressure ,3rd the temperature.
    Max Range=the maximum difference between the temperatures(T1,T2,T3)

    Exp1=L2-L13
    Exp2=L3-L14
    Exp3=L4-L15

    Occasional Case - Static Earthquake

    The combination is done by summation of the absolute value of each term at the stress level

    AutoPIPE caesar

    E1 =  in x and -1/2 x in y dir
    E2 = in -x and -1/2 x in y dir
    E3 = in z and -1/2 z in y dir
    E4 = in -z and -1/2 z in y dir

    Dir = direction

    To be checked:

    SUS+E1
    SUS+E2
    SUS+E3
    SUS+E4

    SUS = GR(1) +MaxP

    U1=in x dir
    U2=-1/2 x in y dir
    U3=in z dir
    To be build:
    L5=OP1+U1+U2
    L6=OP1-U1+U2
    L7=OP1+U2-U3
    L8=OP1+U2-U3
    L19=L5-L2=U1+U2
    L20=L6-L2=-U1+U2
    L21=L7-L2=U2+U3
    L22=L8-L2=U2-U3
    To be Checked:
    L13+L19
    L13+L20
    L13+L21
    L13+L22

    U is for uniform load in g
    U1+U2=E1
    -U1+U2=E2
    U2+U3=E3
    U2-U3=E4
    OP1=Operating 1
    The check has been done only for OP1.It should be repeated for OP2 and OP3
    To be able to check the non linear effect of static earthquake ,a loading case OP1+static Earthquake has to be build and after this loading case minus the OP1, give us the non linear effect of the static earthquake which has to be added to the sustain in Absolute value.

    Occasional Case - Wind

    The combination is done by summation of the absolute value of each term at the stress level

    AutoPIPE caesar

    W1 = Wind in X dir
    W2 = Wind in -X dir
    W3 = Wind in Z dir
    W4 = Wind in -Z dir

    To be checked:

    SUS+W1
    SUS+W2
    SUS+W3
    SUS+W4

    A User Profile is going to be given (a Pressure per elevation)

    WIN1=Wind in X dir
    WIN2=Wind in -X dir
    WIN3=Wind in Z dir
    WIN4=Wind in -Z dir

    A User Profile is going to be given (a Pressure per elevation)
    The same system has to be used as the static earthquake.

    The Units File
    AutoPIPE caesar

    By Autopipe you can create your own units file but you have to define your own conversion coefficients. The basic is the English units(English.unt) 

    and we have created a metric units file called CAESAR.unt)

    The Units file to be used is set under:

    General Model Options dialog

    A different units file for the input and output can be set. If you need to change the units, you can always go back to General Model Options dialog and change it.

    AUTOPIPE.unt are set per default in English units. If you change the name for instance SI.unt into AUTOPIPE.unt. The default unit is going to be SI.

    By CAESAR II you can as well create your own units but the conversion factors are already calculated for you and you only need to choose the units you want. The basic calculation is as well done in English units. The units file is called for instance FUCHS.fil and have to be stored into the system directory from CAESAR II to be able to be used on all calculations.

    Once you set by the CAESAR.CFG the default units file, the input you create is set to these units.

    To get other units by the output, you only need to change the units in the configuration file after that. It is always possible to change the input units

    By using CAESAR Tools/convert Input to new units

    The Configuration File
    AutoPIPE caesar

    Edit Model options Dialog. 

    The configuration file from CAESAR II is located in the working directory and not attached to the input file. That means that it is a common file from a certain directory. The main disadvantage is that if you change anything in this config because of a certain input and you rerun another input under this directory, the results are going to be changed..

    Analysis Loading Definition
    AutoPIPE caesar

    AUTOPIPE static analyses by load increments.

    It is important to note that in an AUTOPIPE analysis, each load case is an increment of load, not a total load as in Caesar.

    For a linear analysis, the results for each load case are obtained all at once and the “Gaps/Friction/Soil" option has to be disabled.

    For a nonlinear analysis the results are obtained sequentially.

    Non-Linear load increments, the steps are:

       1-Analyze for Gravity; then
       2-Analyze for thermal, specifying gravity as the initial state i.e. GR->P1->T1

    The “Static analysis set” is set under Loads/Static Analysis Set

    Note: Ignore Friction E and Ignore Friction GR options have to be unchecked since CAESAR II the friction is always acting

    The code and non-code combinations are created automatically and we can define as many analysis sets up to 999 and combine the results as we want.

    User non-code combinations can be created and typically used to create operating cases to examine maximum forces and moments on equipment nozzles and supports or anchors.

    Note: The hydrotest is a linear analysis and typically defined in a 2nd analysis set to define this case.

       GT1=GR+T1 ->  Operating 1 by CII
       GE1=GR+E1 -> SUS+U1+U2 by CII
       GW1=GR+W1 -> SUS+WIND1 by CII

    We have as well to define operating 1 + Wind1 by the non-code combination to define the maximum forces and moments on supports.

    Load Combinations can be selected for printing

    CAESAR II is performing analyses for total loads.

    That means that CAESAR II is throwing every item (Weight, displacements, Temperature and so on) in a basket and adds everything together regardless when it happens.

    If analyses are performed for total loads, the steps are:

       1-Analyze for gravity(Weight)
       2-Analyze for gravity(Weight) +Thermal(T1) =OP1 (Operating case) ,then
       3-subtract step 2 from step 1 to obtain thermal

    The loading cases will look like:

       L1=W+P1(SUS)
       L2=W+P1+T1+D1(OPE)
       L3=L2-L1(EXP)

    SUS= sustained
    OPE=Operating case
    EXP= Expansion case=Stress range

    To sum up ,you can find following annotations

    AutoPIPE caesar

    Gr
    T1
    GT1
    W1 (Wind)
    E1

    W+P1
    T1+D1
    W+D+T1+P1
    Win1 (wind)
    U1 (earthquake)


    To obtain non linear analysis in Caesar II, create a loading case operating, then operating + wind or +earthquake, then subtract the operating + wind or + earthquake from operating alone. Then this occasional load will be added to the sustained stresses and compare to 1.33 Sh for instance by ASME B31.3

    By the load case editor, you can define the type of loading. To notice that the basic allowable stresses taken are set by the stress type:

    SUS -> sustained stress against Sh
    EXP -> Expansion stress against SA=f (1.25 Sc+0.25 Sh) when the liberal stress is not activated Otherwise SA=f (1.25Sc+0.25Sh) + (Sh-SL) when the liberal stress is activated.

    This is activated by the CAESAR II Config. OPE -> there is no stresses check, it is only valid to check the forces and moments. It is important to notice that first the basic loading cases are defined, then their combinations

    It is always possible to save the loading cases to be able to reuse it on other input.

    In the load case options , you can define the output statut: which allows you to specify whether or not you will be able to check the loading case.

    Output type:

    To define on which level your combination is going to be (at diplacement/force/stress or at Dipl/force or Disp/stress or force/stress or disp or force or stress).

    Combination method: Algebraic ,Scalar ,SRSS ,Abs ,Max ,Min ,SignMax ,SingMin

    Snubbers: active or not active

    Hanger stiffness: Rigid, Ignor ,as design

    Elastic Modulus: Ec or Eh

    Friction multiplier: to turn on(1) or off (0)the friction

    With our example having 4 loading cases in Static earthquake and 4 wind directions,we end up having already 36 loading cases defined with the friction on.As the friction is not always acting,we should do the same loading cases without friction.

    CAESAR II loading became quite complicated

    For the wind load, we define the wind pressure per elevation or use other codes.

    Input Check
    AutoPIPE caesar

    Big advantage using AutoPIPE, check the input using 1 of 2 methods :

    1. Input grid
    2. Model input listing

    Setup File Parameters

     

     

     

    Setup File Parameters

    Pipe Properties

    Note: This is the simulation of the rigid element with 10 times the wall thickness but the weight is kept the same and the insulation are multiplied by 1.75

    Pipe Properties

    Reducers

    Reducers

    Elbows

    There are very small differences between SIFI ,SIFO .Autopipe has only one flexibility factor, CAESAR II has 2(inplane / outplane) but same value

    Elbows

    Tees

    Tees

    Material Data

    Material Data.

    Temperature and Pressure

    Temperature and Pressure

    Anchor Movements

    Anchor Movements

    Restraint System

    Restraint System

    Spring Hangers

    Spring Hangers

    Flexible Nozzle at 170

    Flexible Nozzle at 170

    Earthquake Load-cases

    Earthquake Load-cases

    E1= U1+U2
    E2=U2+U3
    E3=-U1+U2
    E4=U2-U3

    Wind Load-cases

    Wind Load-cases

    Results Comparison
    AutoPIPE caesar

    Max GR(1) Stress

    The difference(37.52-36.91) is 1.6%

     

     

     

    Max Displacement DY

    The difference(9.36-9.35) is 0%

     

     

     

    .

    Max Displacement DX

    the difference(2.8-2.79) is 0%

     

     

     

    Max Displacement DZ

    The difference(5.7-5.67) is 0%

     

     

     

    Stress comparison in Temperature T1,T2,T3

    T1(1)Max Stress =67.89 N/mm2 :difference = 5.1%

    T2(1)Max Stress =67.13 N/mm2 :difference = 0.4%

    T3(1)Max Stress =68.07 N/mm2 :difference = 3.7%

    Stress comparison in Temperature T1,T2,T3

    EXP(T1) Max Stress = 64.4 N/mm2

    Highest Stresses: (N./sq.mm. )
    LOADCASE 16 EXPANSION CASE CONDITION 1
    CodeStress Ratio (%): 33.2 @Node 130
    Code Stress: 64.4 Allowable: 193.9

    EXP(T2) Max Stress non linear= 67.4 N/mm2

    Highest Stresses: (N./sq.mm. ) LOADCASE 17 EXPANSION CASE CONDITION 2
    CodeStress Ratio (%): 34.7 @Node 98
    Code Stress: 67.4 Allowable: 193.9

    EXP(T3) Max Stress non linear= 65.5 N/mm2

    Highest Stresses: (N./sq.mm. ) LOADCASE 18 EXPANSION CASE CONDITION 3
    CodeStress Ratio (%): 33.8 @Node 130
    Code Stress: 65.5 Allowable: 193.9

    Comparison of Sustained and Thermal Forces and Moments

      Non-Linear Analysis  

    Notes:

    1. With +ve % difference results are CAESAR II bigger than AUTOPIPE. On 28 results, 23 cases CAESAR II gives higher Forces and Moments.

    When the difference is above 6.6 % ,it is always the case that CAESAR II is calculating higher forces and moments. The maximum difference is 24.2%.

    2. AutoPIPE has a more advanced non-linear analysis engine with load sequencing and we can expect a more accurate non-linear results than CAESAR

    Node Point 1

    Node Point 90

      Linear Analysis  

    Notes:

    To get CAESAR II to make analysis linear, set the restraints as Y instead of +Y supports at node points: 110 ,125,135, and 140. If enter as +Y, the supports are non linear. The friction by the loading cases are set to zero.

    That means that you cannot do a linear analysis on the same input. We have to create a separate input to set up the conditions for non-linear analysis.
    AUTOPIPE is able on the same input to have non-linear and linear analysis because it can create a new analysis set with the linear conditions.

    Node Point 1

    Node Point 90

    Comparison of  Occasional Loads in T1 temperature case

      Non-Linear Analysis 

    Notes:

    1. With +ve % difference results are CAESAR II bigger than AUTOPIPE. On 32 results, 23 cases CAESAR II gives higher Forces and Moments.

    One result, AUTOPIPE is bigger than CAESAR II ,we have a difference of 17%. Otherwise in most cases CAESAR II is calculating  higher forces and moments with a maximum of 19.3%

    2. AutoPIPE has a more advanced non-linear analysis engine with load sequencing and we can expect a more accurate non-linear results than CAESAR

    Node Point 1

    Node Point 90

      Linear Analysis  

    Notes:

    1. The Linear Results are consistently under 5% difference, with only one result at 6.1 %

    Node Point 1

    Node Point 90

    CONCLUSION

    To provide specific answer to even a slightly complex system differences like the system at hand would require all the assumptions and methods adopted in both the applications completely, which is not practical.

    Comparing results between two applications is always tricky and are bound to be different apart from very simple cases. Although the basic theory and assumptions behind the two applications may be the same, but as the products evolve the different components may start to diverge slightly based on selected options. These divergences may compound when the models depart from being very simplistic models.

    For example, if you run very simple cantilever models in both the applications with a tip force applied, you will get exactly the same results:

    Length of pipe (ft)

    Free end force (lbf)

    AP Displacement (in)

    CII displacements (in)

    0.5

    10,000

    0.0008

    0.0008

    1.0

    10,000

    0.0021

    0.0021

    2.0

    10,000

    0.0085

    0.0085

    5.0

    10,000

    0.0946

    0.0946

    10.0

    10,000

    0.7135

    0.7135

    This could tell us that both the applications are using the same beam theory with shear deformation included. When we depart from simplistic models then some assumptions / implementations like below may come in to play: 

    1. Rigid support stiffness values
    2. Rigid elements stiffness values defined for the two applications
    3. Bend elements formulation
    4. Flexible joints formulation
    5. Pressure thrust load vector formulation
    6. Post processing assumptions and options
    7. Many other

    On individual level, there may be slight differences in these formulations. However, when the whole system is analyzed, the differences may get compounded due to interaction of these individual differences. One can trust any application if one understands the assumptions involved in the solution and understands that the results are a fair approximation of the actual system. Some applications may have a better representation of a particular component / analysis, while the other may be good in another area.

    A good way to gain more confidence in to any application results is to start with simple models, perform a few tests on the component / analysis, and confirm that the results simulate the actual system reasonably well. AutoPIPE QA program backs up the results generated by the program with a rigorous set of hand calculations and published results.

    To sum it up, AUTOPIPE has a more advanced non-linear analysis engine with load sequencing and we can expect a more accurate non-linear results than CAESAR II. Caesar non-linear results are consistently higher than AutoPIPE. By the comparison, the maximum differences for Stresses and Displacements was 5.1 %. 

    See WIKI here for typical reasons why results may be different.  

    See Also

    Import / Export CAESAR (cii)

    Bentley AutoPIPE

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    • Mike Dattilio Created by Bentley Colleague Mike Dattilio
    • When: Tue, Oct 10 2017 6:44 PM
    • Mike Dattilio Last revision by Bentley Colleague Mike Dattilio
    • When: Thu, Sep 16 2021 4:17 PM
    • Revisions: 55
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