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)
AutoPIPENumber of load cases : 4Load case 1 - E1X-Multiplier= 0.100 Y-Multiplier= -0.050 Z-Multiplier= 0.000
Load case 2 - E2X-Multiplier= 0.000 Y-Multiplier= -0.050 Z-Multiplier= 0.100
Load case 3 - E3X-Multiplier= -0.100 Y-Multiplier= -0.050 Z-Multiplier= 0.000
Load case 4 - E4X-Multiplier= 0.000 Y-Multiplier= -0.050 Z-Multiplier= -0.100
caesarUNIFORM LOAD ChangesU1 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)
Number of load cases : 4
Ground elevation for wind : 0.00 mmWind shape factor multiplier : 0.700Exposed Segments - A BWind application method : Normal
Load case 1 - W1X= 1.000 Y= 0.000 Z= 0.000
Load case 2 - W2X= -1.000 Y= 0.000 Z= 0.000
Load case 3 - W3X= 0.000 Y= 0.000 Z= 1.000
Load case 4 - W4X= 0.000 Y= 0.000 Z= -1.000
User defined wind profileHeight (mm) Press (N/m2 )----------- --------------From : Groundto : 7000.00 480.00to : 10000.00 540.00to : 15000.00 630.00to : 20000.00 700.00to : 25000.00 760.00to : 50000.00 990.00
.168.3 mm/7.1mm219.1 mm/8.2mm
Radius 1.5 OD=304.8 mm
Node Point 20: Stiffness Rate:133N/mm ,Cold load:14083 NNode Point 35: Stiffness Rate: 67N/mm ,Cold load:5928 NNode Point 55: Stiffness Rate: 67N/mm ,Cold load:4943 NNode Point 70: Stiffness Rate:133N/mm ,Cold load:14547 N
Line Stop (Stop in X direction) simulated by an incline support
AutoPIPE used User FlexibilitiesCAESAR II used WRC297
Vessel Axis = Global ZAxial Translation Stiffness=32422 N/mmLongitudinal 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 = 2.35mmCase T2: DY = 2.35mm, Case T3: DY = 2.35mm
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.
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/mThe element 533 mm= 1689.6 NThe 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 of9381+439+253=10073 N/m
That means a weight of 5368.9 N
The element 419 has a total weight of11933+439+253= 12625 N/m
That means a weight of 5289.8 N
GR=WeightMaxP(1)=The max pressure into the system (Between P1,P2,P3)(1)=Analysis Set 1
-W=Weight-P1=Presure 1-P2=Pressure 2-P3=Pressure 3-H=Hanger
Operating loading cases are only to check the displacements & forces and moments
T1(1)=Temperature 1 for analysis set 1T2(1)=Temperature 1 for analysis set 1T3(1)=Temperature 1 for analysis set 1
T1=Temperature 1T2=Temperature 2T3=Temperature 3D1 =Displacement by T1D2=Displacement by T2D3=Displacement by T3
Amb to T1(1)Amb to T2(1)Amb to T3(1)Max RangeGR(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)
The combination is done by summation of the absolute value of each term at the stress level
E1 = in x and -1/2 x in y dirE2 = in -x and -1/2 x in y dirE3 = in z and -1/2 z in y dirE4 = in -z and -1/2 z in y dir
Dir = direction
To be checked:
SUS = GR(1) +MaxP
U1=in x dirU2=-1/2 x in y dirU3=in z dirTo be build:L5=OP1+U1+U2L6=OP1-U1+U2L7=OP1+U2-U3L8=OP1+U2-U3L19=L5-L2=U1+U2L20=L6-L2=-U1+U2L21=L7-L2=U2+U3L22=L8-L2=U2-U3To be Checked:L13+L19L13+L20L13+L21L13+L22
U is for uniform load in gU1+U2=E1-U1+U2=E2U2+U3=E3U2-U3=E4OP1=Operating 1The check has been done only for OP1.It should be repeated for OP2 and OP3To 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.
W1 = Wind in X dirW2 = Wind in -X dirW3 = Wind in Z dirW4 = Wind in -Z dir
A User Profile is going to be given (a Pressure per elevation)
WIN1=Wind in X dirWIN2=Wind in -X dirWIN3=Wind in Z dirWIN4=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.
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
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..
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= sustainedOPE=Operating caseEXP= Expansion case=Stress range
To sum up ,you can find following annotations
W+P1T1+D1W+D+T1+P1Win1 (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 ShEXP -> 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.
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.
Big advantage using AutoPIPE, check the input using 1 of 2 methods :
1. Input grid2. Model input listing
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
There are very small differences between SIFI ,SIFO .Autopipe has only one flexibility factor, CAESAR II has 2(inplane / outplane) but same value
The difference(37.52-36.91) is 1.6%
The difference(9.36-9.35) is 0%
the difference(2.8-2.79) is 0%
The difference(5.7-5.67) is 0%
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%
EXP(T1) Max Stress = 64.4 N/mm2
Highest Stresses: (N./sq.mm. )LOADCASE 16 EXPANSION CASE CONDITION 1CodeStress Ratio (%): 33.2 @Node 130Code 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 2CodeStress Ratio (%): 34.7 @Node 98Code 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 3CodeStress Ratio (%): 33.8 @Node 130Code Stress: 65.5 Allowable: 193.9
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
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.
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%
1. The Linear Results are consistently under 5% difference, with only one result at 6.1 %
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)
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:
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.
Import / Export CAESAR (cii)