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Geotechnical Examples using OpenSees

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Presentation made by Prof. Pedro Arduino @ University of Porto during the OpenSees Days Portugal 2014 workshop

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Geotechnical Examples using OpenSees

  1. 1. Geotechnical Examples using OpenSees Pedro Arduino University of Washington, Seattle OpenSees Days Portugal 2014, Workshop on Multi-Hazard Analysis of Structures using OpenSees University of Porto, Porto, Portugal Thursday July 3, 2014
  2. 2. Outline Take advantage of tcl scripting!! OpenSees Wiki Geotechnical Examples Useful links Take advantage of pre- and post- processors GID, just one possible alternative  Some recent research projects completed using OpenSees Dynamic analysis of piles Analysis of complete bridge system 3D analysis of piles
  3. 3. Take advantage of tcl scripting!! tcl can be used to develop scripts for geotechnical applications. Possible applications: Laterally Loaded Pile Foundation – (similar to lpile) One-Dimensional Consolidation Total Stress Site Response Analysis of a Layered Soil Column- (similar to shake) Effective Stress Site Response Analysis of a layered Soil Column Dynamic Effective Stress Analysis of a Slope Excavation Supported by Cantelever Sheet Pile Wall Other ….
  4. 4. OpenSees Wiki Geotechnical Examples http://opensees.berkeley.edu/wiki/index.php/Examples
  5. 5. Pseudo-Static Pile Pushover Analysis The pile is modeled using the dispBeamColumn element with an elastic fiber section for linear elastic constitutive behavior. This example describes how to run a pushover analysis of a pile in OpenSees. The pile and spring nodes are tied together using the equalDOF command. The soil is represented by p-y, t-z, and Q-z springs using the PySimple1, TzSimple1, and QzSimple1 uniaxial materials with zeroLength elements. The model is created in 3D. Pile nodes have 6 DOF, and the soil nodes have 3 DOF.
  6. 6. Pseudo-Static Pile Pushover Analysis results of pushover analysis for a fixed-head pile
  7. 7. 1D Consolidation A column of soil is modeled in 2D using the 9_4_QuadUP element. This element has nine nodes. The nodes in the corners of the element have an additional degree-of-freedom for pore pressure. This example describes how to run a total 1D soil consolidation analysis in OpenSees. The surcharge load is applied as a constant timeseries inside of a plain load pattern. A transient analysis is conducted due to the time- dependent nature of consolidation.
  8. 8. 1D Consolidation excess pore pressure: double drainage single drainage other results: vertical effective stress vertical settlement
  9. 9. Total Stress Site Response Analysis A layered soil profile is modeled in 2D using nodes with 2 DOF. This example describes how to run a total stress site response analysis in OpenSees. The plane strain formulation of the 4-node quadrilateral element quad is used for the soil. Soil constitutive models include: PressureDependMultiYield PressureIndependMultiYield Periodic boundary conditions are enforced in horiz. direction using the equalDOF command A compliant base is considered using a viscous dashpot modeled using a zeroLength element and the viscous uniaxial material.
  10. 10. Total Stress Site Response Analysis Input motion surface response spectra comparison with other analytical methods surface acceleration surface response spectra
  11. 11. Effective Stress Site Response Analysis The approach is similar to the total stress analysis. A layered soil profile is modeled in 2D with periodic displacement boundary conditions enforced using the equalDOF command and a compliant base is considered using a viscous dashpot modeled using a zeroLength element and the viscous uniaxial material. This example describes how to run an effective stress site response analysis in OpenSees. The 9_4_QuadUP element is used to model the soil. This element considers the interaction between the pore fluid and the solid soil skeleton, allowing for phenomena such as liquefaction to be modeled. The PressureDependMultiYield02 constitutive model is used for the soil.
  12. 12. Effective Stress Site Response Analysis summary of soil behavior at three depths within the soil profile
  13. 13. 3D Effective Stress Site Response Analysis displacement of soil column during analysis with contours of excess pore pressure ratio
  14. 14. Dynamic Analysis of 2D Slope Model problem: This example presents a 2D effective stress analysis of a slope subject to an earthquake ground motion. The elements and constitutive models match those used in the site response analysis examples. The free-field soil response is applied to the model using free-field columns which are much more massive than the adjacent soil. Finite element mesh:
  15. 15. Dynamic Analysis of 2D Slope excess pore pressure ratio shear stress-strain lateral displacement excess pore pressure ratio contours near slope
  16. 16. Excavation Analysis This example presents a simulated excavation supported by a sheet pile wall using OpenSees. The InitialStateAnalysis feature is used to create the gravitational state of stress in the model without accompanying displacements. The plane strain formulation of the quad element is used for the soil with the PressureDependMultiYield nDMaterial for constitutive behavior. The sheet pile wall is modeled using the dispBeamColumn element with an elastic fiber section for linear elastic constitutive behavior. Soil elements to the right of the wall are progressively removed to simulate an excavation. The soil-wall interface is modeled using the BeamContact2D element.
  17. 17. Excavation Analysis Nodal displacement magnitude during the excavation analysis
  18. 18. Excavation Analysis shear and moment in the wall during the excavation analysis
  19. 19. Difficult to create tcl scripts for complex boundary value geotechnical problems. complex foundation configurations embankments wharves bridges 3-D analysis Need to use pre- and post processors to create meshes and visualize results GID, just one possible alternative  Take advantage of pre- and post- processors
  20. 20. GiD Problem Type for 2D Analysis Create geometry and select problemType Assign boundary conditions
  21. 21. GiD Problem Type Assign materials to the geometry Generate mesh and OpenSees input file
  22. 22. Some research projects completed using OpenSees Dynamic analysis of piles Analysis of complete bridge system 3D analysis of piles
  23. 23. Dynamic Analysis of Piles in OpenSees
  24. 24. SPSI modeling in OpenSees
  25. 25. Two-column Bent Northridge motion, amax = 0.25g Northridge motion, amax = 0.74g
  26. 26. Two-span bridge
  27. 27. Two-span bridge Bent-S Bent-L Bent-M
  28. 28. SPSI of a complete bridge system • Five-span bridge • pile group foundation • abutment • liquefiable soil / various layers • lateral spreading • earthquake intensities • uncertainties
  29. 29. • Five-span bridge • Approach embankments • Variable thickness of liquefiable soil SPSI of a complete bridge system
  30. 30. Bearing pad spring Pile cap passive earth pressure spring abutment reaction spring Pressure Independent Multi Yield material clay Pressure Dependent Multi Yield material liquefiable soil py (liquefiable) py spring (dry sand) py (stiff clay) Nonlinear fiber beam column Mackie & Stojadinovic (2003) C L SPSI of a complete bridge system
  31. 31. OpenSees model Bridge Idealization SPSI of a complete bridge system
  32. 32. Northridge motion (0.25g) time time Soil Strain Profile during shaking SPSI of a complete bridge system
  33. 33. Loma Prieta (1.19g) time time SPSI of a complete bridge system Soil Strain Profile during shaking
  34. 34. Erzincan, Turkey 1992 (amax = 0.70g) displacement ru 90 cm 20 cm SPSI of a complete bridge system Max. pile demand
  35. 35. 3D Pile Analysis Solid-Solid Model Beam-Solid Model
  36. 36. 3D Pile Analysis Axially Loaded Piles  Evaluation of pile forces and accumulation of side resistance Self-weight forces Zero friction under self-weight Applied force at pile head Force at pile toe Full friction mobilization Sticking interface behavior Qtotal Qtoe Qtotal = Qtoe + Qside Qside= pB S fc dz fc fc = sh(z) tan d
  37. 37. 3D Pile Analysis Laterally Loaded Piles (solid-beam contact element) Perform numerical load test Compare results 3x Magnification
  38. 38. The beam-solid contact elements enable the use of standard beam-column elements for the pile This allows for simple recovery of the shear force and bending moment demands placed upon the pile Additionally, the surface traction acting on the pile-soil interface can be recovered and resolved into the forces applied by the soil to the pile 3D Pile Analysis Lateral Spreading Effects
  39. 39. Pile Sections Soil Profile Conventional 1D Model 3D Finite Element Model Comparison Between 1D & 3D Application Numerical Modeling of Single Pile with high-strength reinforcement and casing
  40. 40. Application Analysis of piles socketed in Rock 3D bricks for pile and rock w/contact Beam for pile, 3D bricks for rock w/contact 푉 = 휏푧푥푑퐴
  41. 41. Application Numerical Analysis of Mataquito River bridge 1D Modeling Approach 3D Modeling Approach Prototype 2D Modeling Approach
  42. 42. Bridge deck spring Application Numerical Analysis of Mataquito River bridge Modeling the abutment and grouped shaft foundation
  43. 43. 3D Applied Kinematic Model Application Numerical Analysis of Mataquito River bridge 3D Applied Kinematic Model
  44. 44. Application Numerical Analysis of Mataquito River bridge 3D Applied Kinematic Model
  45. 45. Application Numerical Analysis of Mataquito River bridge 3D Applied Kinematic Model
  46. 46. Application Numerical Analysis of Mataquito River bridge 3D Applied Kinematic Model
  47. 47. Application Numerical Analysis of Mataquito River bridge 3D Applied Kinematic Model
  48. 48. Application Numerical Analysis of Mataquito River bridge Deformation of shafts with contact forces acting on their surfaces
  49. 49. Liquefiable Layer Gravel Medium Dense Sand Dense Sand Fill Embedded Pile Cap Application Numerical Analysis of Llacolen bridge
  50. 50. Kinematic Deformation x z x y Displacement in x-direction Application Numerical Analysis of Llacolen bridge
  51. 51. Thank You! Questions? Universidad Nacional de Cordoba

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