Workshop on

Soil Structure Interaction (SSI) Knowledge and Effect on the Seismic Assessment of NPPs Structures and Components

Ottawa, Canada, 6-8 October 2010

Deadline for abstracts

Online abstract submittal

31 May 2010

Notification of accepted papers


25 June 2010

Deadline for full paper submission


10 September 2010

Deadline for registration
Online registration form
30 September 2010

Organisation and host

The NEA/CSNI-IAGE / IAEA ISSC workshop on ""Soil Structure Interaction (SSI) Knowledge and Effect on the Seismic Assessment of NPPs Structures and Components" will be held on 6-8 October 2010 in Ottawa, Canada, hosted by the Canadian Nuclear Safety Commission (CNSC). This first announcement is to inform you of this event and call for papers to be submitted for presentation at the workshop


Coordinated by NEA Committee on the Safety of Nuclear Installations (CSNI) and with the International Seismic Safety Centre (ISSC) of the International Atomic Energy Agency (IAEA), the objective of this workshop is to review and disseminate recent findings and issues in SSI knowledge and effect on the seismic assessment of nuclear power plant (NPP) structures and components as follows:

  1. A description of the state-of-the-art engineering practices, in different member states, regarding SSI analysis including consistent interface among various technical areas such as seismic hazard assessment, geotechnical engineering and foundation safety, and structural engineering.
  2. A description of the issues associated with SSI analysis such as addressing non linear behaviour of soil/backfill material, performance of deterministic SSI analysis consistent with PSHA, cracking of concrete, embedment effect, partial separation of foundation and soil, SSI analysis of pile foundations, interaction of heavy adjacent structures on SSI analysis, challenges for standard design to encompass a variety of soil and rock sites and a wide range of earthquake spectra including high frequency content (> 33 Hz) and consideration of incoherency of earthquake motions in the SSI analysis.
  3. A comparison of SSI analysis approaches: Frequency Domain versus Time Domain and SSI analysis software limitations.
  4. Site effect: Simplified (1D) analysis versus 3D analysis and SSI analysis software limitations.
  5. A discussion of SSI methodology used in different countries including the topic of base isolation and treatment of uncertainties related to SSI parameters.
  6. A comparison of SSI results to available structural response records produced by real earthquakes, especially for shift in fundamental frequency, NPP basement response, in-structure response spectra where records are available, to get an objective comparison and to improve the confidence in the current SSI analysis results.

Proposed papers should address one or more of the above topics.

The expected conclusions of the workshop should give better understanding of the current SSI analysis methods and practices and their effects on assessment of NPP structures and components.


The earthquake ground motion response spectra (GMRS) are defined in the "free-field," i.e., without the presence of structures, at the ground surface. Because of the deformability of the supporting media (rock or soil), the resulting motions at the foundation mat will differ from the corresponding free-field motions. This difference between the foundation mat motion and the free-field motion is known as the SSI effect. SSI is an important consideration in seismic analysis, design, and qualification of NPP structures and components. In general, it is manifested by decreasing structure frequencies, and modification of the foundation input motions and the resulting structural response and the floor response spectra. Progress in the understanding and modelling of this complex phenomenon is necessary for improvements of the structural analysis, design, and construction practices of NPP structures and components.

Scope, content and outline

The workshop will include an introductory session, technical sessions devoted to technical presentations by participants on the topics outlined in the objectives and a final session. The final session will summarise the discussions and develop conclusions and recommendations for possible further actions by the CSNI and the IAEA ISSC. All the participants are expected to take part in the discussion and in the formulation of conclusions in the final session.

Papers and case studies addressing the issues mentioned in the objectives of the workshop are welcomed. Several sessions with ample time for discussion will be defined accordingly to these topics.

Last reviewed: 10 September 2010