Abstract
This paper illustrates an original and simple method to predict earthquake-induced deformations of geotechnical systems. The method is an extension of static non-linear analysis, and is conceived to predict the behaviour of geotechnical systems, like supported and unsupported excavations, that during the seismic motion accumulate displacements in a single direction. The seismic capacity of the system is described by its capacity curve, obtained either from a numerical push-over analysis or through a simplified procedure. The corresponding seismic demand is described by a combination of the elastic response spectrum, including basic information on the maximum amplitudes of the seismic motion, and a cyclic demand spectrum, that provides additional information about the equivalent number of cycles that contribute to the accumulation of displacements. In the paper, the method is described in detail and is validated through different procedures, namely: comparisons with experimental results obtained in the geotechnical centrifuge; comparison with results of advanced numerical analyses; extensive comparison, using a large database of seismic records, with the results of non-linear time-domain analyses. In its final part, the paper provides guidance for the practical use of the method for design.
Highlights
When subjected to seismic actions, many geotechnical systems are characterised by a strongly asymmetric behaviour
When subjected to seismic actions, the geotechnical systems considered in this paper exhibit a strongly non-linear behaviour related to the progressive activation of their capacity, that in turn may produce a significant accumulation of displacements: the seismic performance for this category of constructions is expressed by a measure of its final, permanent deformation
Any type of time-domain analysis requires a representation of the seismic action through time histories, and for simple structures this represents a significant burden to the designer
Summary
When subjected to seismic actions, many geotechnical systems are characterised by a strongly asymmetric behaviour. A sliding-block approach implies the assumption of a rigid-perfectly plastic behaviour and neglects the dynamic response of the system under consideration To some extent this limitation can be addressed using decoupled procedures, like those originally proposed by Seed and Martin (1966) and by Chopra (1966) and further developed, for instance, by Rathje and Bray (1999) and Baziar et al (2012). In this decoupled approach the input signal used to integrate the equation of motion for a rigidperfectly plastic system is evaluated from a free-field ground response analysis that accounts for the deformability and non-linearity of the soil. The illustration of the method is preceded by a description of the typical dynamic response of the systems under consideration, that is addressed
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