streamlined process for soil-structure interaction analysis of nuclear facilities utilizing gtstrudl...
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Streamlined Process for Soil-Structure Interaction Analysis of Nuclear Facilities Utilizing GTSTRUDL
and MTR/SASSI
Wei Li, Michael Perez, Mansour Tabatabaie, and Basilio Sumodobila
June 23, 2011
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Introduction
• Key advantages of this streamlined process• Streamlined process for SSI:
– Development of structural FE model in GTSTRUDL– Conversion of structural FE model from GTSTRUDL to MTR/SASSI
– Verification of model conversion– Development of SSI model and SSI analysis using MTR/SASSI
– Seamless transfer of SSI analysis results to GTSTRUDL for post-processing/plotting
• Sample analysis results from two category I nuclear structures
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Key Advantages of this Streamlined Process
• GTSTRUDL and MTR/SASSI structural models are carbon copies– Single structural FE model
• Stress analysis using GTSTRUDL• SSI analysis using MTR/SASSI
– Same FE mesh, element numbering, node numbering, etc.– Allows efficient model development and refinement and for seamless
transfer of pre- and post-processing data and results between the two programs
– Simplifies transfer of results such as maximum nodal accelerations between the two programs
• Large scale structural FE model – Eliminates need for separate reduced model for SSI analysis– Captures out-of-plane floor and wall dynamic responses
• Allows large scale SSI models with over 100,000 nodes to be efficiently analyzed
• Simplifies QA process due to identical structural FE models
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GTSTRUDL - MTR/SASSI Streamlined Process
GTSTRUDL Users Group Meeting 2011 SC SOLUTIONS
Develop & QA GTSTRUDL structural model
Convert model “as is” to MTR/SASSI structural model
Perform fixed base static and dynamic analyses for verification of model conversion
Add excavated soil model & soil layers to complete SSI model
GTSTRUDL Structural FE
MODEL
MTR/SASSI Structural FE
MODEL
MTR/SASSI Structural FE
MODEL
MTR/SASSI EXCAVATED SOIL
FE MODEL
MTR/SASSI SOIL LAYERS
Perform SSI analysis and extract results for plotting using GTSTRUDL
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Development of FE model in GTSTRUDL
• Construct linear-elastic structural model– Use elements available in MTR/SASSI (shells, solids, beams, etc.)– Beam elements should be discretized into desired FE mesh– Include added masses, applied loads, and load combinations
• Structural FE model should satisfy passing frequency requirements for SSI analysis
• Perform fixed base static analysis– Obtain dead load reactions to verify model geometry, material
densities, and added masses– Obtain reactions for other load cases to verify applied loads
• Refine model as needed to capture target frequencies and design iterations
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Model Conversion: GTSTRUDL to MTR/SASSI
• Export structural model from GTSTRUDL database– Nodal coordinates– Elements – shells, solids, plates, etc
• Element connectivity• Material properties• Element thickness for shell elements
– Members (Beam elements)• Member connectivity• Material and section properties• Beta angles
– Springs• Spring connectivity• Spring stiffness and damping constants
– Other types of elements also available in MTR/SASSI– Nodal masses for added masses
• Masses for elements/members included in structural FE model by MTR/SASSI
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Model Conversion: GTSTRUDL to MTR/SASSI
GTSTRUDL Users Group Meeting 2011 SC SOLUTIONS
GTSTRUDL model
Export: GTSTRUDL database files (*.dbx): joints,
members, elements, materials, etc
Import: database files (*.dbx) files to
Excel for formatting into
MTR/SASSI syntax
Export/ Combine
into MTR/SASSI
HOUSE input file (_h.dat)
MTR/SASSI Structural FE
MODEL
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Verification of Model Conversion
• Structural FE models– GTSTRUDL model– MTR/SASSI model
• Fixed-base static analysis results– Compare reactions for all load cases considered
• Fixed-base dynamic analysis results– Identify nodes of interest (base mat, walls, roof, etc)– Extract acceleration time histories at selected nodes– Compute and plot acceleration response spectra at selected nodes
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Comparison of Acceleration Response Spectra – Wall
• Wall normal to X-axis (out of plane response)
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Comparison of Acceleration Response Spectra – Wall
• Wall normal to Y-axis (out of plane response)
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Comparison of Acceleration Response Spectra – Intermediate Floor
• Floor slab normal to Z-axis (out of plane response)
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Comparison of Acceleration Response Spectra – Beam
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• Development of SSI model– Add soil layers and properties– Define interaction nodes– Define excavated soil elements
• Perform time history SSI analysis and extract results
Add excavated soil model & soil layers to complete SSI model
MTR/SASSI Structural FE
MODEL
MTR/SASSI EXCAVATED SOIL
FE MODEL
MTR/SASSI SOIL LAYERS
SSI analysis using MTR/SASSI
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Interaction nodes
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Seamless Transfer of MTR/SASSI Analysis Results to GTSTRUDL
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MTR/SASSI SSI analysis results
1.Nodal forces and moments2.Nodal disps, velocities, and accelerations
(results extracted at each time step and maximum results)
GTSTRUDL1.Results plotting2.Additional post-processing3.Input for pseudo-static stress analysis
(Can be read directly by GTSTRUDL with proper GTSTRUDL commands since node numbers and models are identical)
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Typical SSI analysis results
• Results plotting– Maximum nodal acceleration and dynamic soil pressure contours– In-structure time histories (ISTH) of accelerations, velocities,
displacements, and dynamic soil pressures• Additional post-processing
– In-structure response spectra (ISRS)– Sliding and overturning stability analysis results– Base shears and moments– Inter-story forces and moments
• Input for stress analysis– Inertia forces from MTR/SASSI analysis can be imported to GTSTRUDL
for pseudo-static analysis to calculate member/element forces and stresses for structural design
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Streamlined procedure used to evaluate two category I nuclear structures
• Seismic SSI analysis of 2 category I structures in a nuclear power plant currently undergoing certification
• Linear-elastic structural FE models constructed using:– PLATE elements and SPACE FRAME members in GTSTRUDL– PLATE/SHELL and 3D BEAM elements in MTR/SASSI
• Live and dead loads including equipment weight• Added hydrodynamic masses• SSI analysis performed for combination of ground motions and soil
conditions
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• Near surface category I nuclear structure with shear keys
Example 1
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GTSTRUDL/MTR/SASSI Structural Model
GTSTRUDL/MTR/SASSI shear Key Model
MTR/SASSI Excavated Soil Model
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Structural model: 14420 nodesSSI model: 17887 nodes
Example 2
• Deeply-embedded category I nuclear structure
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MTR/SASSI Excavated Soil Model
GTSTRUDL/ MTR/SASSI Longitudinal Cut ViewGTSTRUDL/ MTR/SASSI Structural Model
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Structural model: 15275 nodesSSI model: 32133 nodes
Maximum Accelerations
• Table of maximum accelerations at key locations• Near surface structure
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Building Location Elevation (ft) Node No. Maximum Absolute Accelerations
X-Dir. Y-Dir. Z-Dir.
Basemat SW Corner -6.00 1001 0.422 0.376 0.464
Basemat NE Corner ˝ 1501 0.409 0.367 0.481
Basemat Center ˝ 5757 0.421 0.370 0.489
Basemat Equipment ˝ 1172 0.421 0.375 0.472 1395 0.415 0.379 0.436
Fan Room at Elevation of 51.5 feet
+50.50
3056 0.574 0.507 0.567 3396 0.579 0.486 0.464 3380 0.604 0.476 0.504 3040 0.586 0.498 0.480
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Plot of Maximum Accelerations (X-direction)
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Near surface structure
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Plot of Maximum Accelerations (Y-direction)
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Deeply-embedded structure
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Plot of Maximum Accelerations (Z-direction)
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Deeply-embedded structure
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In-Structure Spectral Acceleration Response: Base-mat
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0.0
0.5
1.0
1.5
2.0
0.1 1 10 100
Frequency (Hz)
X-S
pe
ctr
al A
cc
ele
rati
on
(g
's)
In-Structure
Reference Outcrop Motion
Damping = 5%
0.0
0.5
1.0
1.5
2.0
0.1 1 10 100
Frequency (Hz)
Y-S
pe
ctr
al A
cc
ele
rati
on
(g
's)
In-Structure
Reference Outcrop Motion
Damping = 5%
0.0
0.5
1.0
1.5
2.0
0.1 1 10 100
Frequency (Hz)
Z-S
pe
ctr
al A
cc
ele
rati
on
(g
's)
In-Structure
Reference Outcrop Motion
Damping = 5%• Near surface structure• Envelope accelerations
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In-Structure Spectral Acceleration Response: Wall Platform Supports
GTSTRUDL Users Group Meeting 2011 SC SOLUTIONS
0.0
1.0
2.0
3.0
4.0
0.1 1 10 100
Frequency (Hz)
X-S
pe
ctr
al A
cc
ele
rati
on
(g
's)
In-Structure
Reference Outcrop Motion
Damping = 5%
0.0
1.0
2.0
3.0
4.0
0.1 1 10 100
Frequency (Hz)
Y-S
pe
ctr
al A
cc
ele
rati
on
(g
's)
In-Structure
Reference Outcrop Motion
Damping = 5%
0.0
0.5
1.0
1.5
2.0
2.5
0.1 1 10 100
Frequency (Hz)
Z-S
pe
ctr
al A
cc
ele
rati
on
(g
's)
In-Structure
Reference Outcrop Motion
Damping = 5% • Deeply-embedded structure• Envelope accelerations
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Maximum Absolute Total Inter-story Dynamic X-Shear Force and YY-Overturning Moment Diagram
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-20
-10
0
10
20
30
40
50
60
70
80
0 10,000 20,000 30,000
Ele
vati
on
(ft
)
Vx (Kips)
Vx
Total Net
-20
-10
0
10
20
30
40
50
60
70
80
0 500,000 1,000,000 1,500,000
Ele
vati
on
(ft
)
My (K-ft)
My
Total Net
Near surface structure
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Maximum Absolute Total Inter-story Dynamic Y-Shear Force and XX-Overturning Moment Diagram
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-20
-10
0
10
20
30
40
50
60
70
80
0 5,000 10,000 15,000 20,000
Ele
vati
on
(ft
)
Vy (Kips)
Vy
Total Net
-20
-10
0
10
20
30
40
50
60
70
80
0 200,000 400,000 600,000 800,000
Ele
vati
on
(ft
)
Mx (K-ft)
Mx
Total Net
Near surface structure
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Sliding Stability Analysis
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• Near surface structure• D/C ratios and Factors of Safety
• Maximum values• Values at each time step
• Computes min base friction coefficient to meet F.S. = 1.1
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Overturning Stability Analysis
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• Deeply-embedded structure• D/C ratios and Factors of Safety
• Maximum values• Values at each time step
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Summary
• GTSTRUDL and MTR/SASSI structural models are carbon copies– Single structural FE model
• Stress analysis using GTSTRUDL• SSI analysis using MTR/SASSI
– Same FE mesh, element numbering, node numbering, etc.– Allows efficient model development and refinement and for seamless
transfer of pre- and post-processing data and results between the two programs
– Simplifies transfer of results such as maximum nodal accelerations between the two programs
• Large scale structural FE model – Eliminates need for separate reduced model for SSI analysis– Captures out-of-plane floor and wall dynamic responses
• Allows large scale SSI models with over 100,000 nodes to be efficiently analyzed
• Simplifies QA process due to identical structural FE models
GTSTRUDL Users Group Meeting 2011 SC SOLUTIONSCopyright © 2011 SC Solutions, Inc, All Rights Reserved
Questions?
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