The Experts below are selected from a list of 1589685 Experts worldwide ranked by ideXlab platform
Youssef M. A. Hashash - One of the best experts on this subject based on the ideXlab platform.
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Recent Advances in Non-Linear Site Response Analysis
2010Co-Authors: Youssef M. A. Hashash, Camilo Phillips, David R. GroholskiAbstract:Studies of earthquakes over the last 50 years and the examination of dynamic soil behavior reveal that soil behavior is highly nonlinear and hysteretic even at small strains. Non-linear behavior of soils during a seismic event has a predominant role in current site Response Analysis. The pioneering work of H. B. Seed and I. M. Idriss during the late 1960’s introduced modern site Response Analysis techniques. Since then significant efforts have been made to more accurately represent the non-linear behavior of soils during earthquake loading. This paper reviews recent advances in the field of non-linear site Response Analysis with a focus on 1-D site Response Analysis commonly used in engineering practice. The paper describes developments of material models for both total and effective stress considerations as well as the challenges of capturing the measured small and large strain damping within these models. Finally, inverse Analysis approaches are reviewed in which measurements from vertical arrays are employed to improve material models. This includes parametric and non-parametric system identification approaches as well as the use of Self Learning Simulations to extract the underlying dynamic soil behavior unconstrained by prior assumptions of soil behavior.
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a novel framework integrating downhole array data and site Response Analysis to extract dynamic soil behavior
Soil Dynamics and Earthquake Engineering, 2008Co-Authors: Chichin Tsai, Youssef M. A. HashashAbstract:Seismic site Response Analysis is commonly used to predict ground Response due to local soil effects. An increasing number of downhole arrays are deployed to measure motions at the ground surface and within the soil profile and to provide a check on the accuracy of site Response Analysis models. Site Response Analysis models, however, cannot be readily calibrated to match field measurements. A novel inverse Analysis framework, self-learning simulations (SelfSim), to integrate site Response Analysis and field measurements is introduced. This framework uses downhole array measurements to extract the underlying soil behavior and develops a neural network-based constitutive model of the soil. The resulting soil model, used in a site Response Analysis, provides correct ground Response. The extracted cyclic soil behavior can be further enhanced using multiple earthquake events. The performance of the algorithm is successfully demonstrated using synthetically generated downhole array recordings.
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Rate-dependent soil behavior in seismic site Response Analysis
Canadian Geotechnical Journal, 2008Co-Authors: Duhee Parkd. Park, Youssef M. A. HashashAbstract:One-dimensional site Response Analysis is widely used in estimating local seismic site effects. The soil behavior in the Analysis is often assumed to be independent of the rate of seismic loading. Laboratory test results, on the other hand, indicate that cyclic cohesive soil behavior is influenced by the rate of loading. Three models of rate-dependent dynamic soil behavior were derived based on available laboratory data. The models were implemented and evaluated in a modified one-dimensional equivalent linear site Response Analysis approach. Results show that rate-dependent shear modulus and damping can have a pronounced influence on propagated weak ground motion but a secondary influence on propagated strong motion. Rate dependence of the damping ratio has a greater impact on the computed Response than rate dependence of the shear modulus. This paper highlights the relevance of the compatibility between frequencies at which dynamic soil properties are measured and their use in site Response Analysis.
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soil damping formulation in nonlinear time domain site Response Analysis
Journal of Earthquake Engineering, 2004Co-Authors: Duhee Park, Youssef M. A. HashashAbstract:Nonlinear time domain site Response Analysis is used to capture the soil hysteretic Response and nonlinearity due to medium and large ground motions. Soil damping is captured primarily through the hysteretic energy dissipating Response. Viscous damping, using the Rayleigh damping formulation, is often added to represent damping at very small strains where many soil models are primarily linear. The Rayleigh damping formulation results in frequency dependent damping, in contrast to experiments that show that the damping of soil is mostly frequency independent. Artificially high damping is introduced outside a limited frequency range that filters high frequency ground motion. The extended Rayleigh damping formulation is introduced to reduce the overdamping at high frequencies. The formulation reduces the filtering of high frequency motion content when examining the motion Fourier spectrum. With appropriate choice of frequency range, both formulations provide a similar Response when represented by the 5% damped elastic Response spectrum. The proposed formulations used in non-linear site Response Analysis show that the equivalent linear frequency domain solution commonly used to approximate non-linear site Response underestimates surface ground motion within a period range relevant to engineering applications. A new guideline is provided for the use of the proposed formulations in non-linear site Response Analysis.
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soil damping formulation in nonlinear time domain site Response Analysis
Journal of Earthquake Engineering, 2004Co-Authors: Duhee Park, Youssef M. A. HashashAbstract:Nonlinear time domain site Response Analysis is used to capture the soil hysteretic Response and nonlinearity due to medium and large ground motions. Soil damping is captured primarily through the ...
W. D. Liam Finn - One of the best experts on this subject based on the ideXlab platform.
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Seismic Response Analysis of Pile Foundations
Geotechnical and Geological Engineering, 2010Co-Authors: Thuraisamy Thavaraj, W. D. Liam FinnAbstract:A quasi-3D continuum method is presented for the dynamic nonlinear effective stress Analysis of pile foundation under earthquake excitation. The method was validated using data from centrifuge tests on single piles and pile groups in liquefiable soils conducted at the University of California at Davis. Some results from this validation studies are presented. The API approach to pile Response using p – y curves was evaluated using the quasi-3D method and the results from simulated earthquake tests on a model pile in a centrifuge. The recommended API stiffnesses appear to be much too high for seismic Response Analysis under strong shaking, but give very good estimates of elastic Response.
Thuraisamy Thavaraj - One of the best experts on this subject based on the ideXlab platform.
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Seismic Response Analysis of Pile Foundations
Geotechnical and Geological Engineering, 2010Co-Authors: Thuraisamy Thavaraj, W. D. Liam FinnAbstract:A quasi-3D continuum method is presented for the dynamic nonlinear effective stress Analysis of pile foundation under earthquake excitation. The method was validated using data from centrifuge tests on single piles and pile groups in liquefiable soils conducted at the University of California at Davis. Some results from this validation studies are presented. The API approach to pile Response using p – y curves was evaluated using the quasi-3D method and the results from simulated earthquake tests on a model pile in a centrifuge. The recommended API stiffnesses appear to be much too high for seismic Response Analysis under strong shaking, but give very good estimates of elastic Response.
Anastasios Anastasiadis - One of the best experts on this subject based on the ideXlab platform.
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Investigation on site-specific seismic Response Analysis for Bucharest (Romania)
Bulletin of Earthquake Engineering, 2020Co-Authors: Florin Pavel, Radu Vacareanu, Kyriazis Pitilakis, Anastasios AnastasiadisAbstract:In this study, the nonlinear seismic Response Analysis of five sites with deep boreholes in Bucharest (Romania) is performed. A ground motion database consisting of recordings obtained during several Vrancea intermediate-depth earthquakes is compiled for the analyses. The results of the nonlinear site Response Analysis show that significant long-period spectral amplifications occur for all five sites and that the level on input peak ground acceleration influences in a significant manner the spectral amplifications, both as median value and variability. In addition, the differences in terms of site amplification factors between the five analysed sites also increase with the level of the input peak ground acceleration levels. The median site amplifications decrease with the increase of the peak ground acceleration for spectral periods of up to 2.0 s, while for longer periods the median site amplifications increase. The results of the nonlinear site Response Analysis were also validated by using real ground motions recorded in the same area during recent Vrancea intermediate-depth earthquakes.
Jan Eric Larsson - One of the best experts on this subject based on the ideXlab platform.
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An expert system for frequency Response Analysis
IEEE Control Systems, 1994Co-Authors: Jan Eric LarssonAbstract:Frequency Response Analysis is a classical method for obtaining models of linear, time-invariant systems. However, the quality of the results strongly depends on the experiment design and choice of parameters. Likewise, different problems may demand a fault diagnosis. This article presents a knowledge-based system that guides the user through the planning and execution of a frequency Response experiment, and it also performs a fault diagnosis and suggests remedies for possible problems. >
