طراحی مبتنی بر عملکرد در مهندسی ژئوتکنیک زمین لرزه
Abstract
1- Introduction
2- Sardis dam
3- Development of screening criteria for seismic stability of slopes
4- Mormon island auxiliary dam (miad)
5- Reliability of nonlinear analysis
6- Concluding remarks
References
Abstract
The key elements of performance-based design will be illustrated and discussed in the context of designing cost effective remedial measures for embankment dams with liquefiable materials in the foundation. This situation is considered one of the more challenging areas of performance based design. Some of the key elements that will be considered will be the selection of performance criteria, selection of an appropriately validated analysis program and calibrating the constitutive model to represent material properties in the field. Major elements of performance based seismic design will be explored using typical case histories from practice such as Sardis Dam in Mississippi, Mormon Island Auxiliary Dam in California, and Flood Protection Dikes in Hokkaido, Japan. A primary source of concern about performance based design based on the results of finite element or finite difference methods of analysis is the reliability of the analyses. Reliability is enhanced by due diligence in the selection of a well-validated program and an appropriately calibrated constituted constitutive model. These issues are discussed in the paper, but there remains a residual concern because there is no field response data on large dams by which our real capability can be assessed.
Introduction
Performance based design (PBD) is based on tolerable displacement criteria and has become part of practice in geotechnical earthquake engineering. It has been widely used for developing remediation strategies for embankment dams with foundations susceptible to liquefaction under design seismic loadings. There are two crucial requirements for implementing PBD: acceptable performance criteria and a reliable method of analysis. For embankment dams, the criterion of acceptable performance is usually specified by tolerable displacements of the crest, although additional criteria may also be imposed as will be shown later in the case of Mormon Island auxiliary Dam. A nonlinear analysis is essential for checking performance because soil behaves as a nonlinear solid under strong shaking. If significant seismic pore water pressures are developed during shaking, the analysis must be based on effective stresses. Nonlinear dynamic effective stress analysis has many forms and its safe use requires a good technical understanding of the mechanics of the constitutive model selected for use and knowledge of its validation history based on element test data, centrifuge test data and any evidence from case histories. It also requires an adequate understanding of how the computation procedure works. The elements of performance based design are explored by the following examples from practice; Sardis Dam in Mississippi, flood protection dikes in Hokkaido Japan and the Mormon Island Auxiliary Dam, Folsom, California and screening the seismic stability of slopes for residential development.