This paper presents the development of a comprehensive modeling-quality cyclic simple shear testi... more This paper presents the development of a comprehensive modeling-quality cyclic simple shear testing database composed of tests performed on fully-saturated samples of Monterey 0/30 sand. This newly developed database is composed of two series. The first consists of a comprehensive series of unidirectional tests incorporating a variety of relative densities and confining pressures. The second series consists of tests performed under a variety of multi-directional stress paths, including a number of stress paths never before examined in the laboratory. The bi-directional series is focused on soils that exhibit dilatant behavior (i.e. medium to high-density soils). The database is designed such that the unidirectional series serves as a comprehensive baseline against which to compare the results of the multidirectional series. Together, they represent an unmatched resource for both the development and calibration of 3-dimensional constitutive models and understanding the behavior of li...
A comprehensive testing database composed of modeling-quality multi-directional cyclic simple she... more A comprehensive testing database composed of modeling-quality multi-directional cyclic simple shear testing on medium to high relative density, fully-saturated samples of Monterey 0/30 sand has recently been developed. This testing program incorporated a variety of multi-directional stress paths, including a large number of stress paths never before examined. Results from these tests have proven useful for enhancing current understanding of liquefaction behavior by allowing for a more complete theory to emerge. This new 3-dimensional theory greatly expands current understanding of liquefaction behavior and elucidates some areas in which current theory—which has been based principally on uni-directional laboratory testing—can be misleading or unconservative. Of particular interest are the topics of pore pressure generation and softening, the relationship between pore pressure and strain capacity, and the dilational lock-up in medium density sands that acts to limit large free-flow ty...
A new nonlinear model for site response analysis was developed to more realistically simulate the... more A new nonlinear model for site response analysis was developed to more realistically simulate the observed soil nonlinearity in cyclic shear. The formulation is based on the Perfectly Hysteretic model with the tangent stiffness related to the most recent stress reversal only. The current (tangent) stiffness is expressed as a harmonic mean of the small strain and large strain stiffnesses with an additional component describing the maximum shear stiffness, Gmax, as a function of maximum shear stress ratio. The model has three material parameters which allows the nearly independently adjustment of the shear modulus and damping curves. As a result, the model is able to closely reproduce realistic shear modulus degradation and damping curves obtained experimentally for clays and sands, in contrast to other existing nonlinear models with the same degree of complexity. The proposed model has been implemented in a general dynamic finite element code and used to perform 1-D site response ana...
Journal of Geotechnical and Geoenvironmental Engineering, 2006
Using the recorded response at two vertical array sites, the SimSoil model presented in the compa... more Using the recorded response at two vertical array sites, the SimSoil model presented in the companion paper is evaluated. The SimSoil model, which describes the small strain nonlinear behavior of granular materials, is implemented as a material model in AMPLE2000, a nonlinear, one-dimensional site response analysis code. Shear wave velocity profiles and laboratory test data available for both the La Cienega site, which was instrumented over 250 m, and the Lotung site, which was instrumented over 47 m, were used to determine SimSoil model parameters. Predictions from AMPLE2000 are compared with the measured response at several elevations for earthquakes that resulted in both nonlinear and nearly linear soil behavior. Using the available laboratory data and known input motions, the predictions of the response at these sites matched the recorded response well for varied magnitudes of shaking with a single set of parameters for each site.
Journal of Geotechnical and Geoenvironmental Engineering, 2006
A simple formulation is presented that predicts the nonlinear small strain behavior of cemented a... more A simple formulation is presented that predicts the nonlinear small strain behavior of cemented and uncemented granular soils. Its performance is evaluated through the comparison of model predictions to results from laboratory tests. A companion paper evaluates the performance of this model implemented in a site response analysis code through comparison with the measured response at two sites. The formulation for the maximum shear modulus, Gmax , which is selected through the evaluation of existing formulations and data, is presented with the hysteretic model developed to describe the shear modulus reduction and damping increase with increasing strains. Few parameters are needed to predict the small strain response, and correlations between model parameters and index properties of granular materials are presented when possible. The model, SimSoil, is shown to capture the cyclic response for sands and gravels with varying densities over a wide range of pressures measured in laboratory tests, including case...
Journal of Geotechnical and Geoenvironmental Engineering, 2011
The authors are grateful to the discusser for his feedback on our paper and for sharing his obser... more The authors are grateful to the discusser for his feedback on our paper and for sharing his observations of the seismic performance of the two International Teleport Plaza (ITP) buildings during the 1989 Loma Prieta earthquake. We encourage the discusser to publish this case history with ...
This paper presents the development of a comprehensive modeling-quality cyclic simple shear testi... more This paper presents the development of a comprehensive modeling-quality cyclic simple shear testing database composed of tests performed on fully-saturated samples of Monterey 0/30 sand. This newly developed database is composed of two series. The first consists of a comprehensive series of unidirectional tests incorporating a variety of relative densities and confining pressures. The second series consists of tests performed under a variety of multi-directional stress paths, including a number of stress paths never before examined in the laboratory. The bi-directional series is focused on soils that exhibit dilatant behavior (i.e. medium to high-density soils). The database is designed such that the unidirectional series serves as a comprehensive baseline against which to compare the results of the multidirectional series. Together, they represent an unmatched resource for both the development and calibration of 3-dimensional constitutive models and understanding the behavior of li...
A comprehensive testing database composed of modeling-quality multi-directional cyclic simple she... more A comprehensive testing database composed of modeling-quality multi-directional cyclic simple shear testing on medium to high relative density, fully-saturated samples of Monterey 0/30 sand has recently been developed. This testing program incorporated a variety of multi-directional stress paths, including a large number of stress paths never before examined. Results from these tests have proven useful for enhancing current understanding of liquefaction behavior by allowing for a more complete theory to emerge. This new 3-dimensional theory greatly expands current understanding of liquefaction behavior and elucidates some areas in which current theory—which has been based principally on uni-directional laboratory testing—can be misleading or unconservative. Of particular interest are the topics of pore pressure generation and softening, the relationship between pore pressure and strain capacity, and the dilational lock-up in medium density sands that acts to limit large free-flow ty...
A new nonlinear model for site response analysis was developed to more realistically simulate the... more A new nonlinear model for site response analysis was developed to more realistically simulate the observed soil nonlinearity in cyclic shear. The formulation is based on the Perfectly Hysteretic model with the tangent stiffness related to the most recent stress reversal only. The current (tangent) stiffness is expressed as a harmonic mean of the small strain and large strain stiffnesses with an additional component describing the maximum shear stiffness, Gmax, as a function of maximum shear stress ratio. The model has three material parameters which allows the nearly independently adjustment of the shear modulus and damping curves. As a result, the model is able to closely reproduce realistic shear modulus degradation and damping curves obtained experimentally for clays and sands, in contrast to other existing nonlinear models with the same degree of complexity. The proposed model has been implemented in a general dynamic finite element code and used to perform 1-D site response ana...
Journal of Geotechnical and Geoenvironmental Engineering, 2006
Using the recorded response at two vertical array sites, the SimSoil model presented in the compa... more Using the recorded response at two vertical array sites, the SimSoil model presented in the companion paper is evaluated. The SimSoil model, which describes the small strain nonlinear behavior of granular materials, is implemented as a material model in AMPLE2000, a nonlinear, one-dimensional site response analysis code. Shear wave velocity profiles and laboratory test data available for both the La Cienega site, which was instrumented over 250 m, and the Lotung site, which was instrumented over 47 m, were used to determine SimSoil model parameters. Predictions from AMPLE2000 are compared with the measured response at several elevations for earthquakes that resulted in both nonlinear and nearly linear soil behavior. Using the available laboratory data and known input motions, the predictions of the response at these sites matched the recorded response well for varied magnitudes of shaking with a single set of parameters for each site.
Journal of Geotechnical and Geoenvironmental Engineering, 2006
A simple formulation is presented that predicts the nonlinear small strain behavior of cemented a... more A simple formulation is presented that predicts the nonlinear small strain behavior of cemented and uncemented granular soils. Its performance is evaluated through the comparison of model predictions to results from laboratory tests. A companion paper evaluates the performance of this model implemented in a site response analysis code through comparison with the measured response at two sites. The formulation for the maximum shear modulus, Gmax , which is selected through the evaluation of existing formulations and data, is presented with the hysteretic model developed to describe the shear modulus reduction and damping increase with increasing strains. Few parameters are needed to predict the small strain response, and correlations between model parameters and index properties of granular materials are presented when possible. The model, SimSoil, is shown to capture the cyclic response for sands and gravels with varying densities over a wide range of pressures measured in laboratory tests, including case...
Journal of Geotechnical and Geoenvironmental Engineering, 2011
The authors are grateful to the discusser for his feedback on our paper and for sharing his obser... more The authors are grateful to the discusser for his feedback on our paper and for sharing his observations of the seismic performance of the two International Teleport Plaza (ITP) buildings during the 1989 Loma Prieta earthquake. We encourage the discusser to publish this case history with ...
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Papers by Juan M Pestana