Home

Subcommittee on GeoSeismic Considerations of the TRB Committee on Seismic Design of Bridges (AFF50)

AFF50 COMMITTEE ON SEISMIC DESIGN OF BRIDGES

AFF50(1) SUBCOMMITTEE ON GEOSEISMIC ISSUES

in cooperation with

AFS30 COMMITTEE ON DESIGN OF FOUNDATIONS FOR BRIDGES AND OTHER STURCTURES

CONTENTS:

JUSTIFICATION:

Geotechnical issues, including seismic hazard analyses, site response effects, characterization of strong ground motions, permanent ground deformation, and the dynamic stiffness and capacity of deep and shallow foundations, are important considerations in seismic design of bridges. While there is a TRB Committee on Foundations for Bridges and Other Structures, Committee AFS30, this committee is not explicitly concerned with seismic design issues. Furthermore, some of the geotechnical issues associated with the seismic design of bridge foundations, such as seismic hazard analysis, are not currently included in the scope of AFS30's activities. Therefore, the subcommittee will both serve as a bridge between AFS30 and the Seismic Design of Bridges committee (AFF50) and insure that the full scope of geotechnical issues associated with seismic design of bridges are accommodated within TRB.

SUBCOMMITTEE SCOPE

Technical issues that will be addressed by this subcommittee include:

  • Characterization of design ground motions, including the effect of local site conditions on intensity, frequency content, and duration.
  • Prediction of, design for, and mitigation of permanent ground displacement, including fault displacements, seismically-induced slope instability, and liquefaction flow failures.
  • Evaluation of dynamic stiffness coefficients for shallow and deep foundations.
  • Seismic design of embankments and retaining walls for bridge approaches and abutments, including lateral earth pressure, bearing capacity, pseudo-static limit equilibrium approaches, and seismic displacement evaluation.
  • Load and Resistance Factor Design (LRFD) methodologies for foundations, earth structures, and retaining walls.
  • Soil-Structure Interaction and the interface between geotechnical analysis and foundation design and structural analysis and superstructure design.

SUBCOMMITTEE ACTIVITIES

Activities of the subcommittee will include developing sessions and workshops jointly with the AFS30 committee for presentation at the annual TRB meeting, developing sessions for the FHWA Bridge Conferences, preparing research needs statements for consideration by NCHRP, and providing review comments on proposed AASHTO LRFD guide specifications for seismic design of bridges.
The potential for joint sessions between AFS30 and AFF50 was discussed at this years (2005) AFS30 meeting. It is proposed that a session on ""Changes in Site Response Due to Liquefaction - Design Approaches" be organized for the 2006 meeting. Other potential topics for joint sessions and workshops include:

  • "Modeling and Experimentation in the Design of Foundations for Dynamic Events,"
  • "Estimation of Permanent Ground Deformations Associated with Liquefaction,"
  • "Seismic Deformation Analysis of Embankments and Retaining Structures,"
  • "Liquefaction Impacts on Bridges," and
  • a Workshop for Volume 2 of the pending MCEER Seismic Retrofit Manual.

SUBCOMMITTEE TERM

The proposed term of the subcommittee is April 15, 2005 to April 14, 2008. Near the end of this term, an evaluation of the accomplishments of the subcommittee and of the need for additional work by the subcommittee will be conducted to determine if the subcommittee should apply for a second three-year term.

SUBCOMMITTEE RENEWAL

In December, 2007, a proposal was submitted to TRB to renew the term of the Geoseismic Issues subcommittee for another 3 years. The renewal proposal stated that the primary objective of the subcommittee over the three year renewal period would be to facilitate implementation of new AASHTO guide specifications for seismic design, including LRFD methods for seismic design of bridge foundations and appurtenant earth structures. The renewal proposal identified the following activities that the committee may undertake over that term:

  1. Prepare a statement on "Research Needs for LRFD Methods for Seismic Design of Bridge Foundations"

  2. Sponsor a workshop on the new NCHRP 12-70 report on "Seismic Analysis and Design of Retaining Walls, Buried Structures, Slopes, and Embankments" at the 2009 or 2010 TRB meeting

  3. Solicit papers for a session on "Effects of Pore Pressure Generation on
    Site Response - Practical Design Approaches" for the 2009 meeting

  4. Solicit papers for a session on "LRFD Methods in Geotechnical Earthquake Engineering" for the 2010 TRB meeting.

  5. Co-sponsor a workshop on the two new FHWA Seismic Design of Bridges
    training courses (on structural and geotechnical issues) currently
    under development for the 2011 TRB meeting.


Login