190644870 caesar static load case editor

8/12/2019 190644870 Caesar Static Load Case Editor

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CAESAR II STATIC LOAD CASE

EDITOR

Loren Brown

Senior Engineer/Developer

CADWorx & Analysis Solutions

Intergraph Process, Power, & Marine


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CONTACT US

Feedback: [email protected]

Suggestions: [email protected]

Technical Support:

[email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]


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TYPES OF LOADS

Primary LoadsForce driven, cause

catastrophic failure.

Weight, Pressure, Point Loads, Uniform Loads,

Hanger Loads, Wind and Wave loads.

Secondary LoadsStrain based, cause fatigue

failure.

Temperature, Displacements.


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AVAILABLE LOAD TYPES IN CAESAR II

W (Weight), WNC (Weight No Contents)

WW (Water-filled Weight)

P (Pressure), HP (Hydrotest Pressure)

T (Temperature), D (Displacement)

H (Hanger Pre-loads), F (Concentrated Loads)

U (Uniform Loads)

Win (Wind), Wav (Wave and Current)

CS (Cut Short or Cut Long)


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Available Stress Types in CAESAR II

OPEOperating

SUSSustained

EXPExpansion OCCOccasional

HYDHydrotest

HGRHanger Design FAT - Fatigue


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Load Case Definition

Operating case contains all loads in the

system.

L1 = W+P1+T1+H (OPE) this is called a basic load case

Sustained Case contains only primary loads.

L2 = W+P1+H (SUS) another basic load case

Expansion Case is the difference between the

operating and sustained cases.

L3 = L1-L2 (EXP) this is called a combination load case


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Combination Load Cases

Used to add or subtract results from

previously defined primitive load cases.

Necessary for proper EXP and OCC code stress

definition.

Not used for restraint or equipment load

definition, nor for displacement reporting.


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Why subtract SUS from OPE?

Why not simply use L3 = T1 (EXP)?

Because the restraint configuration may result in

an incorrect solution.

Nonlinear restraints drive the restraint

configuration.

Other loads in the system combine to change the

restraint configuration.


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Nonlinear Restraints

Stiffness of Restraint changes depending on

position of pipe or forces on restraint.

Examples:

Uni-directional Restraints (+Y)

Gaps in restraints

Friction

Large-rotation rods

Bi-linear Restraints


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Force vs. Distance in Nonlinear

Restraints


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Example 1: T1 (EXP)

This is how the line is modeled in

Caesar II. The gaps are equal on

both sides of the pipe. No loads are

yet applied.

The thermal forces have closed

the gap on the right side.

L3 = T1 (EXP)

Total Displacement for T1 (EXP) = 1 x Gap


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Example 2: L1L2 (EXP)

L2 = W+P1 (SUS) L1 = W+P1+T1 (OPE)

Weight has caused the pipe to close

the gap to the left. This can happen

when the pipe pivots about a

different restraint.

Operating conditions have caused

the pipe to close the gap to the

right, even against the weight force

trying to hold it on the left.


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Example 2 (cont)

If we subtract the displacements of the SUS

case from OPE we get:

Total Displacement for L1-L2 = 2 x Gap

In a linear system T1 (EXP) = L1L2 (EXP)

In a nonlinear system this is not guaranteed.

This represents the effect of temperature in the

presence of other loads.

This is a displacement stress range, not starting

from the neutral position.


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Occasional Load Cases

For most piping codes (not the offshore

codes):

Set up an OPE case that includes the occasional

load

Subtract the standard OPE case from the OPE that

includes the occasional load. We call this the

segregated occasional load case. Add the above load case results to the SUS load

case results for the code stress check


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Example 3: Occasional Load Cases

Assume we have a uniform load representing aseismic load, U1.

L1 = W+P1+T1 (OPE) standard operating

L2 = W+P1 (SUS) L3 = W+P1+T1+U1 (OPE) operating with occasional load

L4 = L1-L2 (EXP)

L5 = L3-L1 (OCC) segregated occasional

L6 = L2+L5 (OCC) * occasional code stress case

* use scalar combination method.


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Combination Methods

Algebraic: Used for subtracting two load cases.

Takes the displacements from the referenced casesand subtracts them.

Then computes forces, moments, and resultant stressfrom these displacements.

Scalar: Used for adding two load cases.

Adds the stresses from the two referenced load cases. Unlike algebraic the stresses are not recomputed from

displacements.


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Notes on combination methods

Dont use algebraic for adding two load cases.

You cant take credit for occasional loads acting

opposite to operating loads.

Dont use scalar for subtracting two cases.

This results in a lower code stress than actual.


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Output Types

Displacement

Usually reported only for basic load cases

Force

Usually reported only for basic load cases

Stress

Reported based on code requirements.


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Example 4Restraint Loads

The algebraic difference between these two conditions will result in a positive

force on the restraint. This is an impossible condition. But the EXP code stress is

correctly computed for this condition.


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What to report

Suppress the HGR cases and the segregatedoccasional load cases.

Report displacement, force for all primitive

load cases. Dont report stress for the operating load

cases.

This is not true for offshore codes, nor FRP codes,nor buried pipe codes.

Report only stress for combination load cases.


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Using the Hot Modulus of Elasticity

It is required to use the cold modulus of

elasticity for stress computation.

You can reduce restraint loads by use of the

hot modulus of elasticity.

Create identical OPE cases, one with hot

modulus for restraint loads, and one with cold

modulus for use in the combination with SUS

for determining EXP stress.


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Using the Friction Multiplier

Friction Multiplier acts on the Mu value

entered on each restraint in the model.

Input 0.0 for no friction and 1.0 for full

friction.

Create identical load cases, but change the

value of Friction Multiplier on one of them.

Compare the results in the Restraint Summary

and report the worst-case results.

190644870 caesar static load case editor

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