Minutes of AFF50 Geoseismic Subcommittee TRB ’06 MeetingDRAFT

24 January 2006

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Minutes of Subcommittee Meeting

Subcommittee AFF50(1) – Geoseismic Concerns

(Parent Committee AFF50 – Seismic Design of Bridges)

2005 Annual Meeting of TRB

Tuesday, January 24, 2006 1:00 – 3:15 pm

Congressional, Marriott Hotel

Washington, D.C.

  1. Attendance: List attached
  2. Agenda
  3. Opening remarks
  4. Self introductions
  5. AFF50 Sessions
  6. TRB Announcements
  7. FHWA Initiatives on geotechnical issues
  8. Update on NCHRP 12-70
  9. Discussion of Committee scope, research needs, and future sessions
  10. General Items of Record
  11. Next year’s (2007) TRB meeting is scheduled for January 21 – 25
  12. 2008 TRB meeting is scheduled for January 13 – 17
  13. Opening Remarks (Ed Kavazanjian, Chair)
  14. This is the first meeting of the “Geoseismic Concerns” subcommittee.
  15. The subcommittee’s parents are AFF50 (Seismic design of bridges) and AFS30 (Foundations of Bridges and Other Structures). This subcommittee will provide geotechnical input to these two parent committees.
  16. Sessions
  17. Sessions this year at TRB sponsored or co-sponsored by AFF50
  18. Session 583 – Effective stress site response analysis for liquefiable ground
  19. Session 658 – Seismic retrofitting and current seismic research
  20. AFF50 Committee meeting – Wednesday at 2 30 pm, Shoreham Exhibit Hall B
  21. FHWA Initiatives (Jerry DiMaggio & Peter Osborne, FHWA)
  22. Background for two major activities.
  23. MCEER retrofit manuals have been completed
  24. A new FHWA Reference Manual and NHI Training Course will be develop that combines structural and geotechnical issues with modules on Retrofit and on Design. The start of this activity is pending the outcome of AASHTO adoption of the new LRFD guidelines that are currently under revision. The activity will be a 2-step process:
  25. Step 1: Develop new manuals incorporating AASHTO LRFD guidelines. This effort includes updating Geotechnical Engineering Circular (GEC) Number 3 and incorporating information from the MCEER retrofit manual.
  26. Step 2: Developing the new training course.
  27. The subcommittee engaged in an extended discussion about the pending AASHTO LRFD guidelines regarding: (1) adopted/proposed probable levels of ground motion exceedance (i.e., earthquake return periods) [the next draft will apparently call for a single level of design earthquake with a 1000 year return period]; (2) the potential conflicts between the proposed design earthquake in the new draft guidelines and work done on NCHRP Projects 12-49 [which was based upon two design earthquake levels, with a 2500 year return period for the upper level] and 12-70 [work in progress] for geotechnical / geo seismic LRFD issues; and (3) the section of the new draft guidelines concerning liquefaction analyses. Concern was expressed over the suggestion that no liquefaction analyses would be required if the design earthquake magnitude was less than 6.5.
  28. Update on NCHRP 12-70: Seismic Design and Analysis of Retaining Walls, Buried Structures, Slopes and Embankments (Don Anderson – CH2M Hill)

a. NCHRP 12-70 is a three-year program to evaluate and improve DOT procedures for the seismic design of free-standing retaining walls, slopes and embankments, and buried structures. The project includes proposing specifications to be used in the AASHTO LRFD Bridge Design Specifications and developing design examples for these topics. Work is being performed by a Project Team consisting of CH2M Hill, Earth Mechanics, and Parsons Brinkerhoff. Dr. Anderson’s presentation will be posted to the committee web site.

b. The NCHRP 12-70 Project Team is making the proposed specifications compatible with those being developed under NCHRP Project 20-07. This second NCHRP Project is being conducted by Imbsen & Associates and involves updating the seismic provisions for bridge design in the current AAHTO LRFD Bridge Design Specifications. The final report for the NCHRP 20-07 Project is being completed. in the near future and will tentatively be voted upon by AASHTO in July of 2007 after a series of trial applications are conducted.

  1. Committee Scope (Ed Kavazanjian, Chair)
  2. Geoseismic issues that are considered within the scope of the sub-committee include:
  3. Seismic hazard analysis & seismic risk
  4. Site response (including nonlinear & effective stress based analyses)
  5. Dynamic soil properties
  6. Liquefaction (including triggering and consequences)
  7. Seismic design of deep and shallow foundations
  8. capacity and stiffness
  9. soil-structure interaction
  10. Seismic design of retaining walls & abutments
  11. Seismic design of bridge approaches
  12. embankments
  13. cuts and fills
  14. Additional issues discussed by committee members and guests as appropriate for the subcommittee included:
  15. Liquefaction mitigation
  16. Seismic design of buried structures
  17. Post-earthquake evaluation of bridges (geoseismic aspects/foundations)
  18. Response spectrum and return period issues (w.r.t. seismic hazard)
  19. Performance-based design
  20. Committee Research Needs
  21. Prior to the meeting, sub-committee members were asked to identified issues that could be the basis of a Research Needs statement developed by the sub-committee. The following suggestions were received:
  22. Teh Sung (NYDOT)
  23. guidelines for soil-pile-structure interaction analysis
  24. criteria for determining level of analysis
  25. appropriate analysis methods & software
  26. evaluation of geotechnical parameters
  27. lateral response of piles in liquefiable soils
  28. Bill Kramer (IDOT)
  29. return period for ULE
  30. dynamic stiffness of layered soil profiles
  31. impact of thin ( < 2.5 ft) liquefiable layers
  32. evolution of dynamic forces and pore pressures during shaking
  33. if peak dynamic force is early and liquefaction is later, do we need to analyze for both?
  34. Tom Cooling (URS)
  35. lateral spreading forces on large (100 ft+) caissons (with and without liquefiable crust)
  36. tolerable lateral movements for foundations subject to dynamic loads
  37. is AASHTO 1.5-inch limit appropriate and does it apply to static plus seismic movement?
  38. seismic design of auger-cast piles
  39. ductility and survivability
  40. detailing of pile head and pile cap connection
  41. Lee Marsh (ABAM)
  42. improved and simplified techniques to integrate structural and geotechnical phenomena
  43. rational methods to combine vibrational (shaking) response and ground deformation (e.g., lateral spreading)
  44. Ed Kavazanjian (ASU)
  45. evaluating residual shear strength of sandy soils
  46. predicting the impacts of liquefaction
  47. lateral spreading
  48. forces on piles
  49. settlement
  50. site response & dynamic forces
  51. performance of mitigation measures (e.g., stone columns, vertical drains, reinforced soil mats)
  52. Additional research needs discussed by committee members and guests
  53. Active fault displacements
  54. Near-field effects
  55. ground motions & fling effect
  56. liquefaction
  57. Shallow foundation design
  58. soil-foundation-structure interaction
  59. stiffness design (i.e., spring constants) in layered soils
  60. Response spectrum of soft soils (2-point method is unconservative for soft, coastal South Carolina soils)
  61. LRFD methods calibrated to average soil properties
  62. Site response of improved ground
  63. Residual shear strength & dynamic soil properties of silty sands
  64. Performance based geotechnical design criteria
  65. performance requirements
  66. allowable displacements & settlements
  67. performance during extreme events, e.g., vessel collision, wave forces, scour
  68. Priorities for Future Sessions, Recommended NCHRP Project Statements, and Recommended NCHRP Syntheses (Ed Kavazanjian, Chair)
  69. Performance of Foundations subject to Seismic and Other Extreme Loads
  70. Research statement with AFS30:
  71. Topics to include
  72. large diameter caissons subject to liquefaction
  73. performance based design criteria
  74. Evaluation of Residual Shear Strength
  75. Joint session with AFS30 and maybe AFP30
  76. Performance of Piles in Liquefiable Soil
  77. Proposed Synthesis report
  78. Soil Properties for Seismic Analysis
  79. Future effort
  80. Topics to include
  81. recommendations for laboratory and field testing
  82. LRFD calibration
  83. Seismic design of shallow foundations
  84. Future effort
  85. Topics to include
  86. methods of analysis
  87. soil properties
  88. LRFD calibration

Meeting adjourned at 3:15 pm.

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