STRUSASSI: A Soil-Structure Interaction Analysis Tool Incorporating GTSTRUDL and SASSI 2000

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2. 2 STRUSASSI:A Soil-Structure Interaction Analysis Tool Incorporating GTSTRUDL and SASSI 2000 Andy Maham*, Jagdish Bhatt Ph.D. *, and Greg Mertz Ph.D.** Bechtel Savannah River, Inc.* Los Alamos National Laboratory** June 22-25, 2005 GTSTRUDL Users Group Meeting

3. 3 Presentation Outline Problem Statement Required Analysis Tools: Why STRUSASSI? SSI Substructure Technique SASSI 2000 and GTSTRUDL Features STRUSASSI Features Analysis using STRUSASSI Future Enhancements Questions?

4. 4 Problem Statement Evaluation of existing structures Process building Two-story shear wall structure with shallow embedment Sand filter building Shear wall structure with spread footings at different elevations Sand filter medium could significantly affect SSI response Equivalent Static EQ Analysis Obtain seismic base shear Generate In-Structure Response Spectra (ISRS)

5. 5 Process Building

6. 6 Process Building (2)

7. 7 Sand Filter Building

8. 8 Sand Filter Building (2)

9. 9 Sand Filter Building (3)

10. 10 Required Analysis Tools Graphical Modeler Develop 3-D model of complicated structures Soil-Structure Interaction SSI effects had to be investigated Effects of sand filter medium Design Results Fundamental frequencies Base Shear ISRS

11. 11 Required Analysis Tools (2) Available Tools GTSTRUDL Automatic mesh generator GENERATE command RESULTANT CUT command Eigenvalue Analysis SASSI 2000 SSI analysis of embedded structures ISRS STRUSASSI Incorporates aspects of both programs

12. 12 Required Analysis Tools (3) STRUSASSI Directly translates a GTSTRUDL model into a SASSI 2000 model Complies with SASSI 2000 requirements Interaction nodes Excavated soil elements and soil layers Lumped masses Plate, brick, and beam elements

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14. 14 SSI Substructure Technique

15. 15 SASSI 2000 Features SITE Module Establish soil layers HOUSE Module Forms mass and stiffness matrices Soil-structure boundary Excavated soil elements Brick, plate, and beam elements with beta reference joint Caution Input requires numerical, sequential numbering and FORTRAN column alignment Difficult for large models BLACK BOX! Mass and stiffness matrices are generated for both the structure and the excavated soil Lumped masses must be specified Interaction nodes define soil-structure boundary Note: the embedded nodes must lay on a soil layer. Therefore, must one-to-one correspondence between SITE file and House file - SASSI uses Beta Reference joint instead of Beta angle Mass and stiffness matrices are generated for both the structure and the excavated soil Lumped masses must be specified Interaction nodes define soil-structure boundary Note: the embedded nodes must lay on a soil layer. Therefore, must one-to-one correspondence between SITE file and House file - SASSI uses Beta Reference joint instead of Beta angle

16. 16 Sand Filter Structure Elevation View

17. 17 GTSTRUDL Features Finite Element Modeler GTMENU ‘GENERATE’ commands Dynamic Analysis Assembler ‘INERTIA OF JOINTS’ command Model Organization ‘GROUP’ command Database Management Model information easily retrievable Macros Manipulation of model information ‘Translate’ model from one form to another

18. 18 STRUSASSI Features GTSTRUDL database ? SASSI 2000

19. 19 STRUSASSI Features (2) GROUP ‘INTERACT’ ?Interaction nodes GROUP ‘EXCASOIL’ ? Excavated soil elements STRUSASSI reads ‘SITE’ file to retrieve layer number and properties Translates all: Structure properties Beta reference from beta angle Member releases ? ‘001001’ format Lumped masses Creates Management Filter Maintains node, element, and group IDs STRUSASSI reads from the database! If GROUP ‘INTERACT’ does not exist, SASSI will assume all nodes at or below ground elevation are interaction nodes If GROUP ‘EXCASOIL’ exists, STRUSASSI will read the ‘SITE’ module to determine which soil layer the element is one and the properties of the element. STRUSASSI Reading from the database allows the user to generate model with GTMENU or typical input fileIf GROUP ‘INTERACT’ does not exist, SASSI will assume all nodes at or below ground elevation are interaction nodes If GROUP ‘EXCASOIL’ exists, STRUSASSI will read the ‘SITE’ module to determine which soil layer the element is one and the properties of the element. STRUSASSI Reading from the database allows the user to generate model with GTMENU or typical input file

20. 20 STRUSASSI Features (3)

21. 21 STRUSASSI Filter

22. 22 SASSI ‘HOUSE’ Files A ‘Commented’ and ‘Uncommented’ House file are created A ‘Commented’ and ‘Uncommented’ House file are created

23. 23 Analysis using STRUSASSI Generate structure w/ GTSTRUDL Create ‘INTERACT’ and ‘EXCASOIL’ groups Specify lumped masses (i.e. 25% of live load) Run ‘STRUSASSI’ to create SASSI 2000 ‘HOUSE’ file Perform SSI analysis using SASSI 2000 Generate ISRS and obtain peak accelerations Perform Equivalent Static Analysis Use STRUSASSI filter to apply peak accelerations to GTSTRUDL model Take Section Cuts to obtain base shear

24. 24 Analysis using STRUSASSI

25. 25 Analysis using STRUSASSI

26. 26 Analysis using STRUSASSI

27. 27 Analysis using STRUSASSI

28. 28 Analysis using STRUSASSI

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30. 30 Analysis using STRUSASSI Perform SSI Analysis using SASSI 2000 Generate ISRS Obtain peak accelerations

31. 31 Analysis using STRUSASSI Perform Equivalent Static Analysis peak acc. x nodal mass = force or Perform Response Spectra Analysis envelope base node response spectra Take Section Cuts to determine Base Shear

32. 32 Future Enhancements SASSI – to – GTSTRUDL aspect Automated equivalent static load or response spectra load creation ‘NOTES’ feature? Establishing ground elevation Multiple Language Translator GTSTRUDL, SASSI 2000, SAP, STAAD, etc.

33. 33 QUESTIONS?