STRUCTURAL ANALYSIS OF MECHANICAL
MODULES FOR MODULAR DESIGNED
NUCLEAR PLANTS
JUNE, 2011
By: Steven K. Sherfey, P.E.
Presented By: Ankit (Andy) J. Patel
AGENDA
Modular Construction
 Mechanical Modules
 Design & Analysis of Mechanical Modules
 Design Requirements
 Special Modeling Techniques
 Benefits to Using Special Modeling Techniques
 Questions

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Parallel Tasks on Modular Plants
Shorten Construction Schedule
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MODULAR CONSTRUCTION OF NUCLEAR
PLANTS

Structural Modules
Sub assemblies of the main building walls, floors, and
ceilings.
 Assembled on-site and lifted into place


Mechanical Modules

Structural Steel Frames


Contains Piping, Valves, Instruments, Conduit, Cable
Trays, Ductwork, and equipment such as tanks, pumps,
etc…
Fabricated off-site and transported to and installed
on-site.
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MECHANICAL MODULES
A large structural rectangular frame
 Module size is controlled by Transportation
Limitations.

12ft x 12ft x 80ft (3.7m x 3.7m x 24.4m)
 80 tons (73 metric tons)


Supports many mechanical components
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PIPE / VALVE MODULE
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74147A
Startup Feedwater Pump Module
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Sketch of module supporting cable tray,
HVAC duct work, and piping
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GTStrudl Model of module supporting cable
tray, HVAC duct work, and piping
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DESIGN & ANALYSIS OF MECHANICAL
MODULES
Set of Drawings
 Structural analysis software, GTStrudl.
 Module design must be qualified for at least
three conditions

Transportation
 Lifting
 Operation

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DESIGN REQUIREMENTS
All applicable codes and standards must be
followed.
 Codes and standards must address all design
requirements
 Criteria may differ for different safety
classifications of the module.

Safety related – Most stringent criteria
 Quality related
 Non-Safety related – Least stringent criteria

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SPECIAL MODELING TECHNIQUES

Technique #1

Create tables of Mechanical properties of equipment
on module.
Cross sectional properties
 Material properties
 Maximum spans of piping, cable tray, conduit, and
ductwork


Properties for transportation and lifting will be
different from operation condition.
Water and insulation weight not included in Trans. & Lift.
 Piping Modulus of Elasticity, E, should be reduced from the
actual value for operation.

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TECHNIQUE #1 -- TABLES OF PROPERTIES
Piping Properties
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TECHNIQUE #1 -- TABLES OF PROPERTIES
(CONT.)
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SPECIAL MODELING TECHNIQUES (CONT.)

Technique #2

Model continuation of commodities to one or two
spans off module.
Simulates accurate dead weight and seismic loads onto the
module .
 Realistic forces and moments induced on members.
 Reduce hand calculations.

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SPECIAL MODELING TECHNIQUES (CONT.)

Technique #3

Accounting for off module thermal influences
In conjunction with technique #2 ensures accurate thermal
expansion loads onto the module.
 Results from external pipe stress analysis need not be
considered if technique #3 is used conservatively.

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SPECIAL MODELING TECHNIQUES (CONT.)

Technique #4

Accounting for piping operational loads
Use combined support design loads from the piping
analyses instead of individual load case loads.
 Will be a combination of all load cases
 Accounts for dead weight, seismic, thermal, and any
other loads on the on module piping.
 Apply the maximum pipe support loads from seismic
condition to the normal operation condition.
 Consider the loads plus and minus to be conservative.

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SPECIAL MODELING TECHNIQUES (CONT.)

Technique #5

Add conservatism to prepare for future modifications
Increase the component loads by 10-20%
 Dead and live loads from piping, tanks, pumps, valves,
etc…
 Limit the stresses to 90% of allowable.
 Member stresses, local stresses, and weld stresses.


Added conservatism should only be considered in the
initial design phase and can be taken out during
future analysis.
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DESIGNING FOR TRANSPORTATION

Module must be designed with inherent rigidity since
transportation poses a risk of damaging the module


Design the module to withstand certain designated
accelerations in the direction of travel, lateral to travel, and
vertical.
Using GTStrudl, create a model
Using Technique #1, add to the model all components
attached to the module, such as piping, conduit, ductwork,
cable tray, valves, pumps, etc…
 Valves and Pumps should be modeled as rigid members
 Piping, conduit, cable tray, etc. should be modeled as
flexible according to their physical properties.



By including the components into the model, proper
transportation effects can be simulated onto the structure.
The analysis must address structural member stresses,
weld stresses, and local stresses for transportation load
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DESIGNING FOR LIFTING
Module will be lifted and installed into place
using lifting lugs
 Lifting Lugs should be designed using standard
safety factors (SF = 2.0) applied to the maximum
lifting lug load.
 The model used for transportation can be used
with lifting boundary conditions to calculate the
maximum load acting on the lugs.
 The analysis must address structural member
stresses, weld stresses, and local stresses for
lifting loads cases.

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DESIGNING FOR OPERATION

The off module piping, conduit, ductwork, and cable trays
will apply loads to the module and should be modeled using
the following techniques:
Use Technique #2 to model in the off-module spans of each
item.
 Use Technique #3 to apply conservative thermal expansion
loads to the piping.
 If loads from a pipe stress analysis are available, use
Technique #4 to apply these loads as applied forces onto the
module.
 Techniques #5 should be used in all three conditions to add
room for future modifications to the module.


The analysis must address structural member stresses,
weld stresses, and local stresses for operation load cases.
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BENEFITS OF USING THE SPECIAL
MODELING TECHNIQUES
Provides accurate and conservative results.
 Helps prevent major structural design
modifications due to changes made during design
finalization, procurement, or construction phases.
 Provides significant savings in time and cost of
construction.

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
Questions???
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