Earthquake Geotechnical Case Histories for Performance-Based Design

Abstract

Performance-Based Design (PBD) is increasingly employed recently in structural design of buildings and infrastructural facilities in many countries. However, PBD has not yet been established sufficiently in geotechnical engineering practice. Seismically induced ground deformation essential to performance design is not easy to evaluate mainly because, in contrast to superstructures, the ground is a 3-dimensional continuum with tremendous spatial variability and its stress-strain relationship is strongly nonlinear with dilatancy effect. A rapid development and establishment of practical and reliable PBD is thus needed not only for foundation design but also for superstructures resting on incompetent soils. It is particularly true under circumstances where seismic ground motions observed during recent destructive earthquakes are getting larger. Such large motions often lead to intolerable results of foundation ground and superstructures resting on it, if they are designed by the conventional limit design methodologies. Thus, we are urged to reconsider how to design new buildings and new civil engineering structures properly and also how to retrofit existing structures from the viewpoint of their performance under increasing seismic loads. The first task toward this direction is to establish the performance criteria in the arena of earthquake geotechnical design to comply with the performance of buildings or civil engineering structures. The next major challenge for the geotechnical engineering community is to shift from the limit state design to the strain/deformation evaluation based on time/frequency-domain calculations not only in research front but also in engineering practice as well. More and more numerical analyses incorporating time-histories of input seismic motions and strong nonlinear response of soils are already in practice in this respect. However, in contrast to the conventional methods, uncertainties involved in the PBD become considerable in terms of seismic input, large-strain soil properties, variability of soil properties, optional parameters in numerical analyses, etc, which almost inevitably attracts designers’ attention from deterministic methods to probabilistic approaches. What we need in choosing appropriate input parameters and judging the reliability of analytical results is a sort of benchmark case histories with well-documented geotechnical and seismic conditions. As one of the activities of TC4, ISSMGE in the 2005–2009 term, it has been planned to publish a case history volume accommodating well-instrumented geotechnical and earthquake data of high qualities, so that international geotechnical researchers can refer it as a benchmark for developing performance-based design methodologies. The title of the Volume is “Earthquake Geotechnical Case Histories for Performance-Based Design”. Items to be addressed in this volume are;