Bab 04 P Error Checking...

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Chapter IV Error Checking, Static Load Cases, and Analysis

Training on Caesar II1

BAB IV

ERROR CHECKING,LOAD CASE, and

STATIC ANALYSIS


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4.1. Error Checking

Static analysis cannot be performed until the error checkinghas been successfully completed.

Only after error checking is completed are the requiredanalysis data files created.

CAESAR II does not allow an analysis to take place if theinput has been changed and not successfully error checked.

Error Checking can only be done from theinput spreadsheet, and is initiated by

executing the Start Run or Batch Runcommands from the toolbar, menu or theQuit options menu (the Quit options menuappears upon closing the spreadsheet).


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4.2. Quit Options Menu

The Start Run command exits the inputprocessor, starts the error checkingprocedure and returns the user to theMain Menu for further action.

The Batch Run command causes theprogram to check the input data, analyzethe system, and present the resultswithout any user interaction.

Batch processing focuses the users attention on the creation of

input and the review of output by expediting the steps in between.

Once invoked, the error checker reviews the CAESAR II modeland alerts the user to any possible errors, inconsistencies, etc.These items are presented to the user as Errors, Warnings, or

Notes.


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Errors are flagged when there is a problem with the model dueto which analysis cannot continue. An example is if no length

of element is defined for a piping element. This error must becorrected before continuing.

Example ofFatal ErrorDialog


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Note Dialog, this third category of alert is the informational note. These

messages simply inform the user of some noteworthy fact related to the

model. An example of a note may be a message informing the user of

the number of hangers to be designed by the CAESAR II program. For

notes, there is nothing for the user to correct.

Example ofNote Dialog


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.

4.3. Available Commands for Error Checking

OK

Indicates that the message has been reviewed by theuser, and the error checking should continue.

Cancel Cancels error checking and returns to the MainMenu.

File

Print

Prints the most recent message.

File - Print All Prints all messages.

Option Restart Restarts the error checking process.

Option - Fatal Only

Causes the program to display onlyfatalerror messages, ignoring notes and warnings.

Option Off Turns off, or ignores subsequentoccurrences of, the most recently displayed message.

Option - Return

Returns to the piping input processor.This is generally selected when a fatal error must be fixed.


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Once error checking has been completed, the program then performs a few

miscellaneous calculations such as those for nozzle flexibilities and thecenter of gravity report (these calculations may be printed out with theMiscellaneous Data reports in the Static Output Processor).

Once the model has been successfully error-checked, the user mustgenerate the required files in order to continue the analysis. This is done bypressing OK with the Generate Files option selected on the closing dialog.

4.4. Error Checking Closing Dialog


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4.5. Building Static Load Cases

The first step in the analysis of an error-checked piping modelis the specification of the static load cases. This is done by

selection of the Analysis-Static options from the CAESAR II

Main Menu (model should be error free).

Upon entering the static load case editor, a screen appearswhich lists all of the available loads that are defined in the

input, the available stress types, and the current load cases

offered for analysis. If the job is entering static analysis for the

first time, CAESAR II presents a list of recommended load

cases. If the job has been run previously, the loads shown are

those saved during the last session.

A typical load case editor screen is shown below:


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The user can define up to ninety-nine load cases.

Load cases may be edited by clicking on a line in theLoad List area.

Only the load components listed in the upper left-hand

portion of the screen may be specified in the load cases.

The entries must be identical to what is shown on the

screen.

Available stress types are specified at the end of the load

case entry in parentheses. Stress type determines thestress calculation method and the allowable stress to use

(if any).


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Edit-Insert This command inserts a blank load casepreceding the currently selected line in the load list. If no

line is selected, the load case is added at the end of the list.Load cases are selected by clicking on the number to theleft of the load case.

Edit-Delete This command deletes the currently selectedload case.

File Analysis This command accepts the load cases and

runs the job.

Recommend This command allows the user to replacethe cur-rent load cases with the CAESAR II recommendedload cases.

Load Cycles

This button alternatively hides or displaysthe Load Cycles field in the Load Case list. Entries in thesefields are only valid / required for load cases defined withthe fatigue stress types.


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4.6. Providing Wind Data

Up to four different wind load cases may be specified for anyone job.

The only wind load information that is specified in the pipinginput is the shape factor. It is this shape factor input thatcauses load cases WIN1, WIN2, WIN3, and WIN4 to be listed

as an available load to be analyzed. More wind data is required, however, before an analysis can

be made. When wind loads are used in the model, CAESAR IImakes available the screen to define the extra wind load data.Once defined, this input is stored and may be changed on

subsequent entries into the static analysis processor. To specify the wind data needed for the analysis select the tab

entitled Wind Load for the appropriate wind load case. Thescreen shown below appears:


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4.7. Specifying Hydrodynamic Parameters

Up to four different hydrodynamic load cases may bespecified for any one job.

Several hydrodynamic coefficients are defined on theelement spreadsheet. The inclusion of hydrodynamic

coefficients causes the loads WAV1, WAV2, WAV3,and WAV4 to be available in the load case editor.

A CAESAR II hydrodynamic loading dialog is shownin the following figure.


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4.8. Execution of Static Analysis

The static analysis performed by CAESAR II follows theregular finite element solution routine. Element stiffnessare combined to form a global system stiffness matrix.

Each basic load case defines a set of loads for the endsof all the elements. These elemental load sets are

combined into system load vectors.

Using the relationship of force equals stiffness timesdisplacement (F=KX), the unknown system deflectionsand rotations can be calculated.

The known parameters, however, may change duringthe analysis as hanger sizing, non-linear supports, andfriction all affect both the stiffness matrix and loadvectors.


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The root solution from this equation, the system-widedeflections and rotations, is used with the element stiffnessto determine the global (X,Y,Z) forces and moments at theend of each element. These forces and moments aretranslated into a local coordinate system for the elementfrom which the code-defined stresses are calculated.

Forces and moments on anchors, restraints, and fixed

displacement points are summed to balance all globalforces and moments entering the node.

Algebraic combinations of the basic load cases pick up thisprocess where appropriate - at the displacement, force &

moment, or stress level. Once the setup for the solution is complete the calculation of

the displacements and rotations is repeated for each of thebasic load cases. During this step, the Incore Solutionstatus screen appears.


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Incore Solution Module

This screen serves as a monitor of the

static analysis. The screen is brokendown into several areas.

The area on the upper left reflects thesize of the job by listing the number ofequations to be solved and the

bandwidth of the matrix which holdsthese equations. Multiplying thenumber of equations by the bandwidthgives a relative indication of the jobsize.

This area also lists the current load

case being analyzed and the totalnumber of basic load cases to besolved. The iteration count, as well asthe current case number, shows howmuch work has already been

completed


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The right side of the solution screenprovide information to the userregarding status of non linear restraintsand hangers in the job. Nonlinearrestraints status may be steppedthrough on an individual basis by usingthe [F2]/[F4] function keys.

In the lower left screen of the big boxare two bar graphs which indicatewhere the program is in an individualsolution. These bar graphs illustratethe speed of the solution.By checking the data in this first box,

an experienced user will have a goodidea of how much longer to wait for theresults.


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Static Output Screen

Following the analysis of the system deflections and rotations, theseresults are post-processed in order to calculate the local forces,moments, and stresses for the basic load cases and all results for thealgebraic combinations (e.g. DS1-DS2). Theses total system resultsare stored in a file with the suffix _P (e.g. TUTOR_P)*.

During this post processing, the Status screen lists the current elementfor which the forces and stresses are being calculated. Once the lastelements stresses are computed, the output processor screen is

presented. It is through this menu the graphic and tabular results of theanalysis can be interactively reviewed by the user.

Notes :

* The _A or input file or the _P or output file are all that is required to archivethe static analysis.The remaining scratch files may be eliminated from the system without anyimpact on the work completed.


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4.9. Notes on CAESAR II Load Cases

Definition of a Load Case

In CAESAR II terms, a load case is a group of piping system loads that areanalyzed together, i.e., that are assumed to be occurring at the same time. Anexample of a load case is an operating analysis composed of the thermal,deadweight, and pressure loads together. Another is an as-installed analysis ofdeadweight loads alone.

A load case may also be composed of the combinations of the results of otherload cases; for example, the difference in displacements between the operatingand installed cases. No matter what the contents of the load case, it alwaysproduces a set of reports in the output which list restraint loads, displacementsand rotations, internal forces, moments, and stresses.

Because of piping code definitions of calculation methods and/or allowable

stresses, the load cases are also tagged with a stress category. For example,the combination mentioned above might be tagged as an EXPansion stresscase.

The piping system loads which compose the basic (non-combination) load setsrelate to various input items found on the piping input screen. The table belowlists the individual load set designations, their names and the input items which

make them available for analysis.


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Designation Name Input items which activate this load case

W DeadweightPipe Density, Insulation Density (with insulationthickness), Fluid Density, or Rigid Weight

WNC WeightPipe Density, Insulation Density (with insulationthickness), Rigid Weight

T1

T2

T3.

.

.

T9

Thermal Set 1

Thermal Set 2

Thermal Set 3.

.

.

Thermal Set 9

Temperature #1Temperature #2

Temperature #3.

.

.

Temperature #9

P1

P2P3

.

.

.

P9

Pressure Set 1

Pressure Set 2Pressure Set 3

.

.

.

Pressure Set 9

Pressure #1

Pressure #2Pressure #3

.

.

.

Pressure #9



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D1

D2

D3

.

.

.

D9

Displacement Set 1

Displacement Set 2

Displacement Set 3

.

.

.

Displacement Set 9

Displacements (1st vector)

Displacements (2nd vector).

Displacements (3rd vector).

.

.

.

Displacements (9th vector)

F1

F2

F3

.

.

.

F9

Force Set 1

Force Set 2

Force Set 3

.

.

.

Force Set 9

Forces/Moments (1st vector), cold spring (Material # 18 or19), and spring initial loads

Forces/Moments (2nd vector)

Forces/Moments (3rd vector)

.

.

.

Forces/Moments (9th vector)

Designation Name Input items which activate this load case(continued)


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Designation Name Input items which activate this load caseWIN1

WIN2

WIN3

WIN4

Wind Load 1

Wind Load 2

Wind Load 3

Wind Load 4

Wind Shape Factor

Wind Shape Factor

Wind Shape Factor

Wind Shape Factor

WAV1

WAV2

WAV3

WAV4

Wave Load 1

Wave Load 2

Wave Load 3

Wave Load 4

Wave Load On

Wave Load On

Wave Load On

Wave Load On

U1

U2

U3

Uniform Loads

Uniform Loads

Uniform Loads

Uniform Loads (1st vector)

Uniform Loads (2nd vector)

Uniform Loads (3rd vector)

Designation Name Input items which activate this load case(continued)

Note :Available piping system loads are displayed on the left hand side of theStatic Load Case screen.


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Basic load cases may consist of a single load such as WNC for an as-installedweight analysis, or they may include several loads added together such asW+T1+P1+D1+F1 for an operating analysis. The stress categories: SUStained,EXPansion, OCCasional, OPErating, and FATigue are specified at the end of the

load case definition. The complete definition of the two examples are: WNC(SUS) and W+T1+P1+D1+F1 (OPE). Each basic load case is entered in thismanner in a list for analysis.

Note : Available stress types are displayed in the lower left hand side of the StaticLoad Case screen.

Results of the basic load cases may be combined using algebraic combinationcases. These algebraic combinations are always entered following the last of thebasic load cases. Combinations of basic load cases are designated using theprefix DS, FR or ST to indicate whether the combination is done at thedisplacement, force, or stress level respectively followed by a number indicatingthe order of the basic load case in the load list. The two former combinations (DSand FR) are done algebraically (signs are considered), while the last (ST) iscombined absolutely. Combination load cases should also have stress typesassigned.

Note : Summing load cases at the DS level is important when signs must beconsidered, such as for a EXPansion case,. Summing load case results at theST level is important when stresses must be combined absolutely, as for anOCCasional case.


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Load Case Designation Comments

1 W+T1+P1+D1+F1 (OPE) The operating Load Case

2 W+P1+F1 (SUS) The installed Load Case (for sustained stresscalculations)

3 U1(OCC) A uniform Load Case modeling a seismic load

4. DS1-DS2(EXP) The difference between the displacements ofLoad Case #1 (operating) minus the displacementsof Load Case #2 (installed); the displacement rangeof the piping; used to calculate expansion stress rangegoing from cold to hot.

5 ST2+ST3(OCC) The stresses from Load Case #2 (sustained) plusthe stresses from Load Case #3 (occasional);used to compare the occasional stresses with theirallowable.

A Valid example of algebraic combinations of load cases


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Case # 1 W+D1+T1+P1+F1 (OPE) ....OPERATING

Case # 2 W+P1+F1 (SUS)....SUSTAINED LOAD CASE

Case # 3 DS1-DS2 (EXP)....EXPANSION LOAD CASE

Recommended Load Cases

Most users will specify only one temperature and one pressure.Such input would simplify the recommended cases to:


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