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Anil K. Chopra - One of the best experts on this subject based on the ideXlab platform.
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direct finite element method for nonlinear Analysis of semi unbounded dam water foundation rock systems
Earthquake Engineering & Structural Dynamics, 2017Co-Authors: Arnkjell Lokke, Anil K. ChopraAbstract:Summary A direct finite element method is presented for nonlinear earthquake Analysis of interacting dam–water–foundation rock systems. The Analysis Procedure applies viscous damper absorbing boundaries to truncate the semi-unbounded fluid and foundation-rock domains and specifies at these boundaries effective earthquake forces determined from the design ground motion defined at a control point on the free surface. The Analysis Procedure is validated numerically by computing the frequency response functions and transient response of an idealized dam–water–foundation rock system and comparing with results from the substructure method. Because the Analysis Procedure is applicable to nonlinear systems, it allows for modeling of concrete cracking, as well as sliding and separation at construction joints, lift joints, and at concrete–rock interfaces. Implementation of the Procedure is facilitated by commercial finite element software with nonlinear material models that permit modeling of viscous damper boundaries and specification of effective earthquake forces at these boundaries. Copyright © 2017 John Wiley & Sons, Ltd.
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approximate incremental dynamic Analysis using the modal pushover Analysis Procedure
Earthquake Engineering & Structural Dynamics, 2006Co-Authors: Sang Whan Han, Anil K. ChopraAbstract:Incremental dynamic Analysis (IDA)—a Procedure developed for accurate estimation of seismic demand and capacity of structures—requires non-linear response history Analysis of the structure for an ensemble of ground motions, each scaled to many intensity levels, selected to cover the entire range of structural response—all the way from elastic behaviour to global dynamic instability. Recognizing that IDA of practical structures is computationally extremely demanding, an approximate Procedure based on the modal pushover Analysis Procedure is developed. Presented are the IDA curves and limit state capacities for the SAC-Los Angeles 3-, 9-, and 20-storey buildings computed by the exact and approximate Procedures for an ensemble of 20 ground motions. These results demonstrate that the MPA-based approximate Procedure reduces the computational effort by a factor of 30 (for the 9-storey building), at the same time providing results to a useful degree of accuracy over the entire range of responses—all the way from elastic behaviour to global dynamic instability—provided a proper hysteretic model is selected for modal SDF systems. The accuracy of the approximate Procedure does not deteriorate for 9- and 20-storey buildings, although their dynamics is more complex, involving several ‘modes’ of vibration. For all three buildings, the accuracy of the MPA-based approximate Procedure is also satisfactory for estimating the structural capacities for the limit states of immediate occupancy, collapse prevention, and global dynamic instability. Copyright © 2006 John Wiley & Sons, Ltd.
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a modal pushover Analysis Procedure to estimate seismic demands for unsymmetric plan buildings
Earthquake Engineering & Structural Dynamics, 2004Co-Authors: Anil K. Chopra, Rakesh K. GoelAbstract:An Erratum has been published for this article in Earthquake Engng. Struct. Dyn. 2004; 33:1429. Based on structural dynamics theory, the modal pushover Analysis (MPA) Procedure retains the conceptual simplicity of current Procedures with invariant force distribution, now common in structural engineering practice. The MPA Procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MPA Procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by non-linear static Analysis using the inertia force distribution for each mode, which for unsymmetric buildings includes two lateral forces and torque at each floor level. These ‘modal’ demands due to the first few terms of the modal expansion are then combined by the CQC rule to obtain an estimate of the total seismic demand for inelastic systems. When applied to elastic systems, the MPA Procedure is equivalent to standard response spectrum Analysis (RSA). The MPA estimates of seismic demand for torsionally-stiff and torsionally-flexible unsymmetric systems are shown to be similarly accurate as they are for the symmetric building; however, the results deteriorate for a torsionally-similarly-stiff unsymmetric-plan system and the ground motion considered because (a) elastic modes are strongly coupled, and (b) roof displacement is underestimated by the CQC modal combination rule (which would also limit accuracy of RSA for linearly elastic systems). Copyright © 2004 John Wiley & Sons, Ltd.
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a modal pushover Analysis Procedure for estimating seismic demands for buildings
Earthquake Engineering & Structural Dynamics, 2002Co-Authors: Anil K. Chopra, Rakesh K. GoelAbstract:Developed herein is an improved pushover Analysis Procedure based on structural dynamics theory, which retains the conceptual simplicity and computational attractiveness of current Procedures with invariant force distribution. In this modal pushover Analysis (MPA), the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by a pushover Analysis using the inertia force distribution for each mode. Combining these ‘modal’ demands due to the first two or three terms of the expansion provides an estimate of the total seismic demand on inelastic systems. When applied to elastic systems, the MPA Procedure is shown to be equivalent to standard response spectrum Analysis (RSA). When the peak inelastic response of a 9-storey steel building determined by the approximate MPA Procedure is compared with rigorous non-linear response history Analysis, it is demonstrated that MPA estimates the response of buildings responding well into the inelastic range to a similar degree of accuracy as RSA in estimating peak response of elastic systems. Thus, the MPA Procedure is accurate enough for practical application in building evaluation and design. Copyright © 2001 John Wiley & Sons, Ltd.
K Van Bibber - One of the best experts on this subject based on the ideXlab platform.
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haystac axion search Analysis Procedure
Physical Review D, 2017Co-Authors: B M Brubaker, L Zhong, S K Lamoreaux, K W Lehnert, K Van BibberAbstract:We describe in detail the Analysis Procedure used to derive the first limits from the Haloscope at Yale Sensitive to Axion CDM (HAYSTAC), a microwave cavity search for cold dark matter (CDM) axions with masses above $20\ \mu\text{eV}$. We have introduced several significant innovations to the axion search Analysis pioneered by the Axion Dark Matter eXperiment (ADMX), including optimal filtering of the individual power spectra that constitute the axion search dataset and a consistent maximum likelihood Procedure for combining and rebinning these spectra. These innovations enable us to obtain the axion-photon coupling $|g_\gamma|$ excluded at any desired confidence level directly from the statistics of the combined data.
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haystac axion search Analysis Procedure
Physical Review D, 2017Co-Authors: B M Brubaker, L Zhong, S K Lamoreaux, K W Lehnert, K Van BibberAbstract:We describe in detail the Analysis Procedure used to derive the first limits from the Haloscope at Yale Sensitive to Axion CDM (HAYSTAC), a microwave cavity search for cold dark matter (CDM) axions with masses above $20\text{ }\text{ }\ensuremath{\mu}\mathrm{eV}$. We have introduced several significant innovations to the axion search Analysis pioneered by the Axion Dark Matter eXperiment (ADMX), including optimal filtering of the individual power spectra that constitute the axion search data set and a consistent maximum likelihood Procedure for combining and rebinning these spectra. These innovations enable us to obtain the axion-photon coupling $|{g}_{\ensuremath{\gamma}}|$ excluded at any desired confidence level directly from the statistics of the combined data.
Rakesh K. Goel - One of the best experts on this subject based on the ideXlab platform.
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a modal pushover Analysis Procedure to estimate seismic demands for unsymmetric plan buildings
Earthquake Engineering & Structural Dynamics, 2004Co-Authors: Anil K. Chopra, Rakesh K. GoelAbstract:An Erratum has been published for this article in Earthquake Engng. Struct. Dyn. 2004; 33:1429. Based on structural dynamics theory, the modal pushover Analysis (MPA) Procedure retains the conceptual simplicity of current Procedures with invariant force distribution, now common in structural engineering practice. The MPA Procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MPA Procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by non-linear static Analysis using the inertia force distribution for each mode, which for unsymmetric buildings includes two lateral forces and torque at each floor level. These ‘modal’ demands due to the first few terms of the modal expansion are then combined by the CQC rule to obtain an estimate of the total seismic demand for inelastic systems. When applied to elastic systems, the MPA Procedure is equivalent to standard response spectrum Analysis (RSA). The MPA estimates of seismic demand for torsionally-stiff and torsionally-flexible unsymmetric systems are shown to be similarly accurate as they are for the symmetric building; however, the results deteriorate for a torsionally-similarly-stiff unsymmetric-plan system and the ground motion considered because (a) elastic modes are strongly coupled, and (b) roof displacement is underestimated by the CQC modal combination rule (which would also limit accuracy of RSA for linearly elastic systems). Copyright © 2004 John Wiley & Sons, Ltd.
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a modal pushover Analysis Procedure for estimating seismic demands for buildings
Earthquake Engineering & Structural Dynamics, 2002Co-Authors: Anil K. Chopra, Rakesh K. GoelAbstract:Developed herein is an improved pushover Analysis Procedure based on structural dynamics theory, which retains the conceptual simplicity and computational attractiveness of current Procedures with invariant force distribution. In this modal pushover Analysis (MPA), the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by a pushover Analysis using the inertia force distribution for each mode. Combining these ‘modal’ demands due to the first two or three terms of the expansion provides an estimate of the total seismic demand on inelastic systems. When applied to elastic systems, the MPA Procedure is shown to be equivalent to standard response spectrum Analysis (RSA). When the peak inelastic response of a 9-storey steel building determined by the approximate MPA Procedure is compared with rigorous non-linear response history Analysis, it is demonstrated that MPA estimates the response of buildings responding well into the inelastic range to a similar degree of accuracy as RSA in estimating peak response of elastic systems. Thus, the MPA Procedure is accurate enough for practical application in building evaluation and design. Copyright © 2001 John Wiley & Sons, Ltd.
Philippe Charlier - One of the best experts on this subject based on the ideXlab platform.
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maori heads mokomokai the usefulness of a complete forensic Analysis Procedure
Forensic Science Medicine and Pathology, 2014Co-Authors: Philippe Charlier, Isabelle Huynhcharlier, Luc Brun, Julie Champagnat, Laetitia Laquay, Christian HerveAbstract:Based on an Analysis of 19 mummified Maori heads (mokomokai) referred to our forensic laboratory for anthropological Analysis prior to their official repatriation from France to New Zealand, and data from the anthropological and medical literature, we propose a complete forensic Procedure for the Analysis of such pieces. A list of 12 original morphological criteria was developed. Items included the sex, age at death, destruction of the skull base, the presence of argil deposits in the inner part of the skull, nostrils closed with exogenous material, sewing of eyelids and lips, pierced earlobes, ante-mortem and/or post-mortem tattoos, the presence of vegetal fibers within nasal cavities, and other pathological or anthropological anomalies. These criteria were tested for all 19 mokomokai repatriated to New Zealand by the French authorities. Further complementary analyses were limited to fiberscopic examination of the intracranial cavities because of the taboo on any sampling requested by the Maori authorities. In the context of global repatriation of human artifacts to native communities, this type of anthropological expertise is increasingly frequently requested of forensic anthropologists and other practitioners. We discuss the reasons for and against repatriating non-authentic artifacts to such communities and the role played by forensic anthropologists during the authentication process.
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shrunken head tsantsa a complete forensic Analysis Procedure
Forensic Science International, 2012Co-Authors: Philippe Charlier, Isabelle Huynhcharlier, Luc Brun, Christian Herve, Lorin G De La GrandmaisonAbstract:Based on the Analysis of shrunken heads referred to our forensic laboratory for anthropological expertise, and data from both anthropological and medical literature, we propose a complete forensic Procedure for the Analysis of such pieces. A list of 14 original morphological criteria has been developed, based on the global aspect, color, physical deformation, anatomical details, and eventual associated material (wood, vegetal fibers, sand, charcoals, etc.). Such criteria have been tested on a control sample of 20 tsantsa (i.e. shrunken heads from the Jivaro or Shuar tribes of South America). Further complementary analyses are described such as CT-scan and microscopic examination. Such expertise is more and more asked to forensic anthropologists and practitioners in a context of global repatriation of human artifacts to native communities.
Yansong Wang - One of the best experts on this subject based on the ideXlab platform.
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an efficient elastic displacement Analysis Procedure for simulating transient conformal contact elastohydrodynamic lubrication systems
Journal of Tribology-transactions of The Asme, 2010Co-Authors: Shangwu Xiong, Yansong Wang, Jane Q WangAbstract:A compliance operator is often utilized to evaluate the elastic displacement of surfaces in the simulation of transient and steady-state elastohydrodynamic lubrication of conformal-contact systems. The values of the compliance operator represent the elastic responses of all nodes when only one node is under a unit load. The accuracy of compliance operator values, computational cost, and storage size are important issues. Our study of steady-state conformal-contact elastohydrodynamic lubrication analyses suggests a method of selective-fine-mesh with selective-storage, as well as a special technique of the combined selective-fine-mesh with selective-storage mapping. These two techniques enable an efficient elasticity Procedure for the simulation of steady-state and transient conformal-contact elastohydrodynamic lubrication systems by means of the finite element method.
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an efficient elastic deformation Analysis Procedure for simulating conformal contact transient elastohydrodynamic lubrication systems
2008 STLE ASME International Joint Tribology Conference IJTC 2008, 2008Co-Authors: Shangwu Xiong, Jane Q Wang, Yansong WangAbstract:A compliance operator, Eji , is often utilized to evaluate elastic deformation in the simulation of transient and steady state elastohydrodynamic lubrication of conformal-contact systems. The values of the compliance operator represent the elastic responses of all nodes when only one node is under a unit load. The accuracy of compliance operator values, computational cost, and storage size are important issues. Based on our previous study on steady-state conformal-contact elastohydrodynamic lubrication systems, an advanced method of selective-fine-mesh with selective storage is suggested, and a special technique of combined selective-fine-mesh with selective storage mapping is proposed. These two techniques enable an efficient elasticity Procedure for the simulation of transient conformal-contact elastohydrodynamic lubrication systems.Copyright © 2008 by ASME
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an efficient elastic deformation Analysis Procedure for simulating conformal contact elastohydrodynamic lubrication systems
ASME STLE 2007 International Joint Tribology Conference Parts A and B, 2007Co-Authors: Shangwu Xiong, Jane Q Wang, Yansong WangAbstract:A compliance operator is often utilized to evaluate the elastic deformation during simulation of elastohydrodynamic lubrication of conformal-contact systems. The values of the compliance operator represent the elastic deformations of all nodes when only one node is under a unit external load. The accuracy of compliance operator values, computational cost, and storage size are important issues. It is found that values only in a small region surrounding the loading node should be used and those in other regions can be discarded. Moreover, the mesh refinement in thickness direction is found to be more important than that along the longitudinal and width directions. A simple formula is suggested as the relationship between the values of a compliance operator and refinement steps. These two approaches enable an efficient elasticity Procedure for the simulation of conformal-contact Elastohydrodynamic lubrication systems.Copyright © 2007 by ASME