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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Copyright © 2011 SC Solutions, Inc, All Rights Reserved 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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

GTSTRUDL - MTR/SASSI Streamlined Process 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 EXCAVATED SOIL FE MODEL MTR/SASSI SOIL LAYERS Perform SSI analysis and extract results for plotting using GTSTRUDL GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Model Conversion: GTSTRUDL to MTR/SASSI Export: GTSTRUDL database files (*.dbx): joints, members, elements, materials, etc GTSTRUDL model Export/ Combine into MTR/SASSI HOUSE input file (_h.dat) MTR/SASSI Structural FE MODEL Import: database files (*.dbx) files to Excel for formatting into MTR/SASSI syntax GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Comparison of Acceleration Response Spectra – Wall Wall normal to X-axis (out of plane response) GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Comparison of Acceleration Response Spectra – Wall Wall normal to Y-axis (out of plane response) GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Comparison of Acceleration Response Spectra – Intermediate Floor Floor slab normal to Z-axis (out of plane response) GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Comparison of Acceleration Response Spectra – Beam GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

SSI analysis using MTR/SASSI 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 Interaction nodes GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Seamless Transfer of MTR/SASSI Analysis Results to GTSTRUDL Nodal forces and moments Nodal disps, velocities, and accelerations (results extracted at each time step and maximum results) GTSTRUDL Results plotting Additional post-processing Input for pseudo-static stress analysis (Can be read directly by GTSTRUDL with proper GTSTRUDL commands since node numbers and models are identical) GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Copyright © 2011 SC Solutions, Inc, All Rights Reserved 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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Example 1 Near surface category I nuclear structure with shear keys GTSTRUDL/MTR/SASSI Structural Model GTSTRUDL/MTR/SASSI shear Key Model MTR/SASSI Excavated Soil Model Structural model: 14420 nodes SSI model: 17887 nodes GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Example 2 Deeply-embedded category I nuclear structure MTR/SASSI Excavated Soil Model GTSTRUDL/ MTR/SASSI Longitudinal Cut View GTSTRUDL/ MTR/SASSI Structural Model Structural model: 15275 nodes SSI model: 32133 nodes GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Maximum Accelerations Table of maximum accelerations at key locations Near surface structure GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Plot of Maximum Accelerations (X-direction) Near surface structure GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Plot of Maximum Accelerations (Y-direction) Deeply-embedded structure GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Plot of Maximum Accelerations (Z-direction) Deeply-embedded structure GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

In-Structure Spectral Acceleration Response: Base-mat Near surface structure Envelope accelerations GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

In-Structure Spectral Acceleration Response: Wall Platform Supports Deeply-embedded structure Envelope accelerations GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Copyright © 2011 SC Solutions, Inc, All Rights Reserved Maximum Absolute Total Inter-story Dynamic X-Shear Force and YY-Overturning Moment Diagram Near surface structure GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Copyright © 2011 SC Solutions, Inc, All Rights Reserved Maximum Absolute Total Inter-story Dynamic Y-Shear Force and XX-Overturning Moment Diagram Near surface structure GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Sliding Stability Analysis 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 GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Overturning Stability Analysis Deeply-embedded structure D/C ratios and Factors of Safety Maximum values Values at each time step GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Copyright © 2011 SC Solutions, Inc, All Rights Reserved 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 Copyright © 2011 SC Solutions, Inc, All Rights Reserved

Copyright © 2011 SC Solutions, Inc, All Rights Reserved Questions? GTSTRUDL Users Group Meeting 2011 Copyright © 2011 SC Solutions, Inc, All Rights Reserved