NCHRP Synthesis 428: Practices and Procedures for Site-Specific Evaluations of Earthquake Ground Motions (Matasovic and Hashash, 2011) revealed that 1D equivalent-linear analysis is the de facto standard for state DOT highway facilities at those locations where site-specific ground response analyses are conducted in accordance with provisions in the AASHTO LRFD Bridge Design Specifications (2014) and the AASHTO Design Guidelines for Seismic Bridge Design (2011). However, users have concerns about the applicability of equivalent-linear analyses for the cases for which site-specific response analyses are most useful (i.e., soft soil sites, liquefiable sites, and sites subjected to very strong shaking). While nonlinear 1D site response analyses are beginning to be used in practice to address these concerns, there is considerable uncertainty on how to employ and interpret the results of such analyses. To assist bridge and foundation designers, guidelines on the use and selection of 1D nonlinear software with pore water pressure generation and dissipation are needed for the effective and economical seismic design of all types of highway facilities.

Research was performed under NCHRP Project 12-114, “Guidance on Seismic Site Response Analysis with Pore Water Pressure Generation,” by Geo-Logic Associates, Inc. This research included developing guidelines for the selection and use of analytical methods for 1D nonlinear seismic site response analysis with pore water pressure generation to quantify the effects of site-specific conditions on earthquake ground response. The guidelines considered the following: (1) input parameters required for the analyses (e.g., site characterizations, seismic loading); (2) limitation, selection, and validation of analytical methods; (3) the process of model setup; and (4) how to review the models and use the results of the analytical methods.

In addition to NCHRP Research Report 1092, two deliverables are available on the National Academies Press website (nap.nationalacademies.org) by searching for NCHRP Research Report 1092: Seismic Site Response Analysis with Pore Water Pressure Generation: Guidelines.

The deliverables are as follows:

• NCHRP Web-Only Document 383: Seismic Site Response Analysis with Pore Water Pressure Generation: Resources for Evaluation, which contains the appendices to this report:
  • Appendix A: Literature Search
  • Appendix B: Field Exploration and Site Characterization.
  • Appendix C: Experiments and Advanced Laboratory Testing
  • Appendix D: Numerical Modeling – Element Tests
  • Appendix E: Numerical Modeling – Case Histories
• A plan that identifies mechanisms and channels for implementing this research.