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Seismic Analysis for a Turbine Building with
Spring Supported Turbine / Generator Deck

• Feifei Lu, PE
• Shaw Power Group, Charlotte, NC
• June 23, 2011

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Topic Outline

• Overall Introduction
• Turbine building
• Spring and damper device
• Method Discussion
• Results Comparison
• Conclusion
• MathCad Application

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Background Introduction

• steel framing structure
• EBF SCBF
• eccentrically braced frame (EBF) below the
  Turbine operating deck and special concentric
  braced frame (SCBF) above the operating deck

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Background Introduction

• Turbine Building structural steel frame
• First-Bay concrete structure
• Foundation 6 feet deep reinforced concrete
  foundation mat

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Spring Damper Device
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Spring Pedestal Design Basis

• Benefits of spring pedestal
• Seismic Isolation of TG
• Vibration isolation of TG
• Generic site design

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Spring Devices

• Stiffness matrix is used to model each spring
  device. (Ref. GT STRUDL Vol.1 Section 2.1.9.2.4)
• Horizontal spring matrix and Vertical spring
  matrix
• GT STRUDL Input

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Damper Devices

• Viscous Damper Element is used to model the
  damper devices. (Ref. GT STRUDL Vol.3 Section
  2.4.3.7)
• GT STRUDL Input

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Method discussion

• Method 1 Weighted Average Composite Modal
  Damping
• Method 2 Viscous Damper Element with Rayleigh
  Proportional damping
• (Ref. GTStrudl Damping Models for Dynamic
  Analysis by Dr. Swanger)

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Method discussion (Method 1)

• Method 1 Weighted Average Composite Modal
  Damping (Ref. NRC REGULATORY GUIDE 1.61 DAMPING
  VALUES FOR SEISMIC DESIGN OF NUCLEAR POWER
  PLANTS)

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Method discussion (Method 1)

• Based on viscously damped free vibration (Ref.
  Dynamics of Structures Theory and applications to
  Earthquake Engineering, Second Edition, By Anil
  K. Chopra)
• Therefore,
• 
  ?

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Method discussion (Method 1)

• Sample calculation

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Method discussion (Method 1)

• GT STRUDL Input
• CONSTANT
• MODAL DAMPING PROPORTIONAL TO STIFFNESS 0.04
  MEMBERS ( All Steel member)
• MODAL DAMPING PROPORTIONAL TO STIFFNESS 0.07
  MEMBERS ( All Concrete member)
• SPRING DAMPER
• MODAL DAMPING PROPORTIONAL TO STIFFNESS 0.488
  MEMBERS (Horizontal springs)
• MODAL DAMPING PROPORTIONAL TO STIFFNESS 0.226
  MEMBERS (Vertical springs)
• COMPUTE MODAL DAMPING RATIOS AVERAGE BY ELEMENT

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Method discussion (Method 2)

• Rayleigh damping value for the rest of the
  structure is calculated based on the classic
  Rayleigh damping method. (Ref. GTStrudl Damping
  Models for Dynamic Analysis by Dr. Swanger)

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Method discussion (Method 2)

• GT STRUDL Input
• CONSTANT
• DAMPING PROPORTIONAL TO STIFFNESS 3.36E-3 MASS
  0.421
• .......
• COMPUTE MODAL DAMPING RATIOS PROPORTIONAL BY
  ELEMENT

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Response Spectrum
Ref. "Fundamentals of Earthquake Engineering",
Elnashai, Amr, and Di Sarno, Luigi-Wiley 2008,
pp. 242.
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Response Spectrum
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Results (Mode Shape)
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Results (Mode Shape)
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Results (Mode Shape)
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Results (Model Damping)
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Results (Displacement)

• Method 1
  Method 2
• SUMMARY OF MAXIMUM GLOBAL DISPLACEMENTS
• INDEPENDENT IN EACH COORDINATE
• RESULT MAXIMUM LOAD JOINT
• X-DISP 0.702437E00 801 JCON685
• Y-DISP 0.122054E01 802 J2180072
• Z-DISP 0.103463E00 802 J2180128
• SUMMARY OF MAXIMUM GLOBAL DISPLACEMENTS
• SRSS VECTOR LENGTHS
• RESULT MAXIMUM LOAD JOINT
• XYZ-DISP 0.122351E01 802 J2180072

SUMMARY OF MAXIMUM GLOBAL
DISPLACEMENTS INDEPENDENT IN EACH
COORDINATE
RESULT MAXIMUM LOAD
JOINT
X-DISP 0.713116E00 801
JCON685 Y-DISP 0.124141E01 802
J2180072 Z-DISP 0.105379E00 802
J2180128
SUMMARY OF MAXIMUM GLOBAL
DISPLACEMENTS SRSS VECTOR
LENGTHS
RESULT MAXIMUM LOAD
JOINT
XYZ-DISP 0.124452E01 802
J2180072 XY-DISP 0.124451E01 802
J2180072 XZ-DISP 0.713273E00 801
JCON685 YZ-DISP 0.124141E01 802
J2180072

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Results (Force in Spring Device)

• X-dir
  RS analysis results

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Results (Force in Spring Device)

• Y-dir
  RS analysis results

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Results (Force in Damper Device)

• Damper
  element force Calculation
• Each mode
  Vi Via-Vib
• By ABS method
  V
• Force
  F c V

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Results (Force in Damper Device)

• Damper
  element force Calculation

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Conclusion

• Spring device and damper device can be
  successfully modeled in GT STRUDL.
• Both methods give results consistent with each
  other.
• To achieve more accurate results, time history
  analysis needs to be performed.

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MathCad Application

• Benefits Efficiency and Automation
• Generate load combination input file from Excel
  file.
• Transform structural coordinates to move and
  rotate structure geometry.
• Offset mass distribution to create 5 torsional
  seismic effect for response spectrum analysis.

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Load Combination

• Example Input file (Excel file)

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Load Combination

• Example MathCad file

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Load Combination

• Example Output file (txt file)

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Transform Structure

• Modular Stair Tower.pps
• Coordinate Transformation Function.html
• Original purpose of using MathCAD to transform
  structure is to simulate the process of rigging
  and installing stair tower module. Same as the
  MOVE OBJECT command.
• (Why not use MOVE OBJECT ? )
• Later on, it is found this little program is very
  useful to transform any structure and combine
  structures in different orientation and origins
  together.

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Transform Structure

• 90 degree

• 75 degree

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Transform Structure

• 60 degree

• 45 degree

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Transform Structure

• 30 degree

• 15 degree

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Transform Structure

• Combine with TB

• Stairs Module

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Torsional seismic effect

• The objective is to redistribute the structure's
  mass such that the requirements for accidental
  torsion are met.
• At each level of the structure where it is
  desired to include accidental torsion, the mass
  will be re-distributed such that the new center
  of mass has been offset from its original
  position the required distance (normally 5 of
  the structures maximum dimension perpendicular to
  the direction of motion as code requirement).

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Torsional seismic effect

• SEISMIC LOAD.html
• Input
• JC2.xls
• MASS DEAD2.xls
• Output
• UBC-X-TOR.xls
• UBC-Y-TOR.xls

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Torsional seismic effect
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Acknowledgements

• The GT STRUDL analytical model used in this
  presentation is based on the Turbine Building for
  the Westinghouse AP1000 Advanced Passive Light
  Water Reactor Electric Power Generating Plant.
  Westinghouse Electric Company is the owner of the
  design. The original GT STRUDL analytical model
  was created by Toshiba Corporation/Obayashi
  Corporation in Japan. The design activity is
  being completed by Shaw under contract to
  Westinghouse.
• Dr. Michael Swanger
• Computer Aided Structural Engineering Center
  (GTSTRUDL)Structural Engineering, Mechanics, and
  MaterialsGeorgia Institute of Technology

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References

• GT STRUDL User Reference Manual
• NRC REGULATORY GUIDE 1.61
• Dynamics of Structures Theory and applications to
  Earthquake Engineering, Second Edition, Anil K.
  Chopra
• GTStrudl Damping Models for Dynamic Analysis,
  Michael H. Swanger, PhD
• Fundamentals of Earthquake Engineering, Elnashai,
  Amr, and Di Sarno, Luigi-Wiley 2008
• UBC-1997

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Question ?