bab 07 restraints

Training on Caesar II1

Chapter VII Restraints

RESTRAINTSBAB VII



7.1 Anchors

Connecting node

(rigidly fix)

Stiff : 6 DOF



7.2 Anchors with Displacement

Displacement for

the node

Dis : 6 DOF



7.3 Flexible Anchors

Use six flexible restraints

Put :

4 restraints on first element

2 restraints on next element



7.4 Flexible Anchors with Predefined Displacement

Use six flexible restraints

Put :

* 4 restraints on first element

* 2 restraints on next element

* Define connecting node

(Cnode)

* Spec : displacement



Flexible Anchors with Predefined Displacement

Continued...



7.5 Flexible Nozzle (WRC Bulletin 297)

Adhere to these requirements when modeling flexible nozzles:• Frame only one pipe element into the nozzle node.• Do not place restraints at the nozzle node.• Do not place anchors at the nozzle node.• Do not specify displacements for the nozzle node.

CAESAR II automatically performs the following functions:• calculates nozzle flexibilities for the nozzle/vessel data entered by the user• calculates and inserts restraints to simulate the nozzle flexibilities• calculates flexibilities for the axial translations, circumferential, and longitudinalbending



Example :



7.5.1 Flexible Nozzle with Predefined Displacements

Define a unique vessel node on the Nozzle Spreadsheet

Applly the predefined displacement to the vessel node



7.5.2 Flexible Nozzle with Complete Vessel Model

Define a unique vessel node on the Nozzle Spreadsheet

Model the actual vessel length using pipe element

Use an anchor to model the vessel anchorage point

Run a rigid element between the vessel node defined on the Nozzle Spreadsheet and the centerline of the vessel



Example : Full WRC 297 and Vessel

Model



7.6 Double Acting Restraints

Rotational

Translational



7.7 Single-Directional Restraints

+Y : move freely pos Y

: restraints neg Y

CNode : Connecting Node



7.8 Guide

• Double-acting restraints with or without a specified gap.

• Connecting Nodes (CNode) can be used with guides.

• May be using the global coordinate or restraints type GUI

• A “guide” pipe in horizontal : acting in the horizontal plane, orthogonal to the axis of pipe

• A “guide” vertical pipe : X and Z direction supports

• Direction cosines : compute by CAESAR II



Example :



7.9 Limit Stops

• Single or double-acting restraint whose line of action is along the axis the pipe

• The sign on the single-directional restraints : unlimited free movement

• The gab is the distance of permitted free movement along the restraints line of action

• Always positive, restraints type : LIM

• Connecting Nodes (Cnode) may be used with any Limit Stop Model



Example :



7.10 Windows• Equal leg windows are modeled using two double-acting

restraints with gaps orthogonal to the pipe axis.• Unequal leg windows are modeled using four single-acting

restraints with gaps orthogonal to the pipe axis.• The gap is always positive. If there is no sign, then the

restraint is double-acting and the gap exists on both sides of the line of action of the restraint. If there is a sign on the restraint then the gap exists on the “restrained” line of action of the restraint, i.e. a +Y restraint is restrained against movement in the -Y direction, and any gap associated with a +Y restraint is the free movement in the -Y direction before the restraint begins acting.



7.11 Rotational Directional Restraints with Gaps



7.12 Single Directional Restraints with Predefined Displacement



7.13 Single-DirectionalRestraint and Guide



7.14 Restraint Settlement

Single directional restraints

Predefined displacement



7.15 Skewed Double-Acting Restraint



7.16 Skewed Single-Directional Restraint

May be non linear

vector

Direction cosines

A long positive line of action

Connecting Nodes (Cnode) can be used



7.17 Restraint Between Two Pipes

(Use of CNodes)



7.18 Restraint Between Vessel and Pipe Models

CNode connecting pipe to rigid element (vessel shell)

Linear or nonlinear



7.19 Restraints on a Bend at 45o

Rigid rod

Single direction restraints

Move freely +Y direction



7.19.1 Restraints on a Bend at 30o

and 60o

3 nodes angle

0o “near” point

To node

“far” point



7.20 Vertical Dummy Leg on Bends

7.20.1 Near/Far Point Method• Easy input• Dummy leg acts along centerline of vertical run• Dummy leg does not act at the proper place on the bend

curvature

7.20.2 On Curvature Method• Easy input• Dummy leg acts at the proper place on the bend curvature• Dummy leg does not act along the centerline of the vertical run

7.20.3 Offset Element Method• Difficult input• Dummy leg acts at the proper place on the bend curvature• Dummy leg acts along centerline of vertical run



7.21 Vertical Leg AttachmentAngle



7.22 Horizontal Dummy Leg on Bends

Dummy leg is defined as a zero-eightrigid supported on oneend by a spring can.



7.23 Large Rotation Rods (Basic Model)

XROD

YROD

ZROD

Gap Len

Mu Fi

Tolerance : 1o

swing : 5o

+Y or Y

concave



7.24 Large Rotation Rods (Chain Supports)

Large rotation swing : chain support (Y-Z plane)

two pipes : move freely relative to each other in the axial direction (Y-X) plane



7.25 Large Rotation Rods

• Stif, Len, Fi : must be filled

• with or without CNode

Spring Hangers

Constant Effort Hangers

Very small



7.26 Large Rotation Rods (Struts)

Rod pull up Large rotation effect.

Bilinear : 2 direction Type

Stif K1 (Initial Stiffness)

Gap K2 (Yield Stiffness)

Mu Fy ( Yield Load)



Continued…



Plastic Hinges

bending

Plastic deformation

Plastic hinge

overheated

Translational

torsional

Bi-linear restraints



7.27 Sway Brace Assemblies

Example: Sway Brace Installed in the Cold Position

Spring rate: 150 lb/in.Initial loading: 150 lbAllowed movement: 3 in.

• Eliminate vibration

• Cold position

• single compression spring

• preventing additional movement



Example: Sway Brace Installed in the Operating Condition

Spring rate: 150 lb/in.Initial loading: 150 lbAllowed movement: 3.0 in.Calculated displacement: .5 in.

First :

Analyze without the sway brace displacement

CAESAR II 0.5 (D2, Vector 2)

Load on sway brace =

Pre-Load + Hot deflection*Spring Rate



END OF RESTRAINTS

bab 07 restraints

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