Principles of soil-structure interaction under seismic disturbance. Kinematic effects and seismic stability

An essential aspect in understanding the behavior of structures under seismic loads, kinematic interaction is one of the components of Soil-Structure Interaction (SSI).

Drawing on concepts at the crossroads of several disciplines, such as geotechnics, engineering seismology, soil and structural dynamics, soil-structure interaction (SSI) has become a real specialty.

In addition, under the impetus of the "Eurocode" reference texts and, in particular, Eurocodes 7 and 8 (EN 1997 and 1998 standards), a complete revision of documents relating to the soil and foundations of structures has begun. In particular, the latest generation of codes for dimensioning structures in seismic zones, such as Eurocode 8, encourages the practice of soil-structure interaction in static and dynamic conditions when dimensioning structures.

The approach proposed in this article, relating to kinematic effects, is to bring together, with that published under the reference [C251] for inertial effects, the basics of ISS in order to give the engineer the essential steps, as well as the successive levels of detail that he can bring to his analysis while identifying the parameters on which he can act during dimensioning.

To complement these aspects of soil-structure interaction, which can be described using the mechanics of elastic and/or viscoelastic media, it was deemed relevant to explore the boundary of structure stability under dynamic loading, such as the effects of overturning and sliding at the soil-structure interface.

This concludes the article with an approach to the design of retaining structures under seismic conditions, in particular through a calculation approach to failure.

The principles of wave propagation in terrestrial media are recalled to enable the presentation of soil eigenperiod evaluations for use in the engineering of surface structures. To this end, methods for calculating horizontal soil displacement profiles are reviewed for different cases of horizontally stratified soils. These displacements can be used to assess the forces developing in deep foundations.

In addition to the regulatory approaches to the stability of shallow foundations to sliding and overturning, we propose to develop the specific effects, which may be "beneficial", on the dimensioning of the detachment of a footing, as well as on its irreversible displacements.

The article is completed by a discussion of the stability of retaining structures under earthquakes, exploring the "Monobé-Okabé" method of failure usually used for frictional soils. However, the extension of the...