c2 cau express load cases

7/27/2019 C2 CAU Express Load Cases

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CAU Express 2012 1

Load Cases

Dave Diehl

CAESAR II

Using the full potential of

load case combinations

Background

CAESAR II recommends a set of basic load

cases for analysis.

A user can edit and add to these load cases.

Load cases are built or modified to collect

specific stress calculations and, more general

structural response (e.g. equipment & support

loads and pipe displacements). This presentation is not an introduction to basic

load case concepts but a review of the potential

found in the static load case processor.


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CAU Express 2012 2

Load Cases

Dave Diehl

Load Combinations

Load combinations and their control are

accessed through the Main Menu:

or from the Piping Input:

Load Combinations

Two tabs are reviewed in this presentation

Load Case Editor

Load Case Options


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CAU Express 2012 3

Load Cases

Dave Diehl

Load Combinations

Load Case Editor

Highlights of recommended load cases

Addressing nonlinear response (restraints)

Building standard load case lists

Specifying load cycles (fatigue evaluation)

Load Combinations

Load Case Options

General overview

Combination methods

Manipulating friction effects

Using hot modulus for equipment loads


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CAU Express 2012 4

Load Cases

Dave Diehl

The Load Case Editor

Are Recommended Load

Cases Adequate?

CAESAR II Recommended Cases satisfy

Sustained & Expansion Stress calculations

Other non-B31.3-style codes have their own criteria

Special situations have additional impact

Hanger sizing

Hydro leak test

Does not create stress ranges betweenoperating cases

Does not create occasional states


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CAU Express 2012 5

Load Cases

Dave Diehl

Special Situations

Hanger Sizing

Load Cases may be

affected by the Hanger

Design Control Data

Special Situations

Hanger Sizing

Additional load cases are required


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CAU Express 2012 6

Load Cases

Dave Diehl

Special Situations

Hanger Sizing

Special Situations

Hanger Sizing

L1L2 L3


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CAU Express 2012 7

Load Cases

Dave Diehl

Special Situations

Hydrostatic Leak Test

A hydrostatic leak test may impose a unique set

of structural loads on a piping system, especially

a vapor system.

CAESAR II addresses this loading with an

additional load case whenever a hydrostatic test

pressure (HP) is defined

Special Situations



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Load Cases

Dave Diehl

Special Situations


Special Situations


You can also control the application of insulation

weight in the hydrostatic test case:


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Load Cases

Dave Diehl

Stress Ranges between

Operating States

CAESAR II will create expansion range

calculations between ambient (e.g. W+P1) and

each operating state

But that may not identify the greatest stress

range

Running temperatures above AND below ambient

Valve states could alter stress range

T1 T2

Hot

AmbientA meter station,

one leg hot, one

leg ambient;

may fail the tee:

Stress Ranges between

Operating States

Recommended cases:

L1: W+P1+T1 (OPE)

L2: W+P1+T2 (OPE)

L3: W+P1 (SUS)

L4: L1-L3 (EXP)

L5: L2-L3 (EXP)

Adjusted cases:

L1: W+P1+T1 (OPE)

L2: W+P1+T2 (OPE)

L3: W+P1 (SUS)

L4: L1-L3 (EXP)

L5: L2-L3 (EXP)

L6: L1-L2 (EXP)

T1 T2

Hot

AmbientA meter station,

one leg hot, one

leg ambient;

may fail the tee:


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CAU Express 2012 10

Load Cases

Dave Diehl

Addressing Nonlinear

Response (Restraints)

Sustained stress

Operating - strain = force-based load

Occasional stress

Operating with occasional - Operating = Occasional

Layout Position

Here is the modeled starting point of the

system. Equal gap

Occasional stresses can be isolated in linear

systems or in systems that remain linear

X

Z

Nonlinear Example


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CAU Express 2012 11

Load Cases

Dave Diehl

Independent, +X Wind

X

Z

L1: W+T1+P1 (OPE)

L2: W+P1 (SUS)

L3: WIND1 (OCC)

L4: L1-L2 (EXP)

L5: L2+L3 (OCC)

L3

Nonlinear Example

Independent, -X Wind

X

Z

L1: W+T1+P1 (OPE)

L2: W+P1 (SUS)

L3: -WIND1 (OCC)

L4: L1-L2 (EXP)

L5: L2+L3 (OCC)

L3

Nonlinear Example

But this position, based on a wind only load

case, ignores the true starting position the

operating position.


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CAU Express 2012 12

Load Cases

Dave Diehl

Operating Position

X

Z

L1: W+T1+P1 (OPE)

L2: W+P1 (SUS)

L3: W+T1+P1+WIND1 (OPE)

L4: W+T1+P1-WIND1 (OPE)

L5: L3-L1 (OCC)

L6: L4-L1 (OCC)

L7: L1-L2 (EXP)

L8: L2+L5 (OCC)

L9: L2+L6 (OCC)

L1

Nonlinear Example

Operating Loads & +X Wind

X

Z Here we see that, based on the operating

position, the same +X wind will now engage the

guide

Response to Wind Load

alone

L1: W+T1+P1 (OPE)

L2: W+P1 (SUS)



L5: L3-L1 (OCC)

L6: L4-L1 (OCC)

L7: L1-L2 (EXP)

L8: L2+L5 (OCC)

L9: L2+L6 (OCC)

L1L3

L5

Nonlinear Example


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CAU Express 2012 13

Load Cases

Dave Diehl

Operating Loads & -X Wind

X

Z

While the X wind will remain free

Response to Wind Load

alone

L1: W+T1+P1 (OPE)

L2: W+P1 (SUS)



L5: L3-L1 (OCC)

L6: L4-L1 (OCC)

L7: L1-L2 (EXP)

L8: L2+L5 (OCC)

L9: L2+L6 (OCC)

L1L4

L6

Nonlinear Example

Building standard load case lists

Many firms have standardized their load sets

In more and more instances, these are very

comprehensive

Seismic, wind, blast

FPSO

Fatigue

and therefor, tedious and prone to error You can copy existing load cases from one job

to another


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Load Cases

Dave Diehl

Sharing Load Cases

Sharing Load Cases Fatigue


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CAU Express 2012 15

Load Cases

Dave Diehl

Sharing Load Cases Fatigue

Sharing Load Cases Seismic


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CAU Express 2012 16

Load Cases

Dave Diehl

Sharing Load Cases

Heres a very complex list ofloads that one

would not want to enter each time.

Specifying Load Cycles

(Fatigue Evaluation)

You can associate a number of cycles (N) or a

cyclic factor (f) with each thermal state of the

piping system.


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Load Cases

Dave Diehl



But a proper application of N would be with the

individual range(s) analyzed.



But a proper application of N would be with the

individual range(s) analyzed.


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CAU Express 2012 18

Load Cases

Dave Diehl

Load Case Options

General Overview

A few highlights will be reviewed here


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Load Cases

Dave Diehl

Combination Methods

How are these terms

used?

Combination Methods

Expansion stress range is an algebraic

combination of two load cases


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Load Cases

Dave Diehl

Combination Methods

Sustained and occasional stresses are

combined in a scalar fashion

Combination Methods

LoadCase

Content Stress Type Combination Method Description

1 W+T1+P1 (OPE) Operating state

2 W+P1 (SUS) Installed state

3 U1 (OCC) X inertial

4 U2 (OCC) Y inertial

5 U3 (OCC) Z inertial

6 D1 (OCC) X support displacement

7 D3 (OCC) Z support displacement

8 L3+L4+L5 (OCC) SRSS combination Composite inertial

9 L6+L7 (OCC) SRSS combination Composite displacement

10 L2+L8 (OCC) Scalar combination Occasional stress code check

11 L1-L2 (EXP) Algebraic combination Non-seismic expansion case

12 L9+L11 (EXP) Scalar combination Approx. expansion code check

Seismic loads (both inertia and support

displacement) may combine spatial components

by square root sum of the squares (SRSS).


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CAU Express 2012 21

Load Cases

Dave Diehl

Combination Methods

You may want to extract the maximum response

from a variety of operating cases

Here, a single operating case

appears with a group of 8

seismic combinations

It would be convenient to

show the maximum

displacement of each node

and maximum restraint load from all these cases

Combination Methods

Note how SignMin & SignMax are used here;

also, there is no stress output for SignMin.


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CAU Express 2012 22

Load Cases

Dave Diehl

Combination Methods Review

CombinationMethod ofstructuralresponse ofstress TypicalUseStructu re StressAlgebraic xi f(xi) Traditional

responsesummation

ExpansionrangeScalar xi i Sustained+

occasionalSRSS SRSS(xi) SRSS(i) Spatialseismic

summationAbsolute |xi| iMaximum MAXof(|xi|),retainsign MAXof(i) Collectmaximum

cyclicloadCollectmaximumstress

Minimum MINof(|xi|),retainsign MINof(i)SignedMaximum MAXof(xi) MAXof(i) Used

togethertocollectrangeofrestraintload&pipemovement

SignedMinimum MINof(xi) MINof(i)

Manipulating Friction Effects

What is the coefficient of friction steel-on-steel?


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CAU Express 2012 23

Load Cases

Dave Diehl

Manipulating Friction Effects

You can easily bracket the effect of friction in a

single run 10

60

30

Using hot modulus for

equipment loads

While most stress evaluation specifies using the

reference (ambient) modulus of elasticity for

pipe stress, the modulus at temperature may be

used for equipment load calculation.

This may significantly reduce the magnitude of

strain-based loads


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CAU Express 2012 24

Load Cases

Dave Diehl

Using hot modulus for

equipment loads

Carbon steel stiffness

drops 9% @ 300C Cr-Mo steels drop 23%

@ 600C

In Conclusion

There is more to CAESAR II load case

combinations than Use Recommended


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Load Cases

Dave Diehl

Thank You for Your Attention

Any Questions?

c2 cau express load cases

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