The Experts below are selected from a list of 9159 Experts worldwide ranked by ideXlab platform
Billie F. Spencer - One of the best experts on this subject based on the ideXlab platform.
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Control of Wind-Induced Nonlinear Oscillations in Suspended Cables
Nonlinear Dynamics, 2004Co-Authors: Mohamed Abdel-rohman, Billie F. SpencerAbstract:In this paper, the along-wind and across-wind responses of suspended cables are studied. The mean wind direction is assumed to be perpendicular to the plane of the suspended cable. It is shown that the cable gallops in the across-wind direction, when the mean wind speed exceeds a critical wind speed. To control the galloping response, a vertical Viscous Damper, in the vertical plane of the cable, is introduced at a certain location on the cable to a near fixed platform such as a bridge deck. The efficiency of the vertical Viscous Damper and its location in controlling the galloping of the suspended cable is investigated.
M. C. Constantinou - One of the best experts on this subject based on the ideXlab platform.
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simulated bilinear elastic behavior in a sdof elastic structure using negative stiffness device experimental and analytical study
Journal of Structural Engineering-asce, 2014Co-Authors: D T R Pasala, M. C. Constantinou, Satish Nagarajaiah, A A Sarlis, A M Reinhorn, Douglas P TaylorAbstract:AbstractThe acceleration and base shear of structures during strong ground motion can be attenuated by achieving bilinear-elastic behavior without any permanent displacement—also referred to as “apparent weakening.” The negative stiffness device (NSD), used in this study, exhibits nonlinear-elastic negative stiffness behavior; by adding NSD to the elastic structure, the resulting structure-device assembly behaves like a bilinear-elastic structure. Peak acceleration and base shear experienced by the structures can be reduced by adding the negative stiffness device, and the additional deformations caused by the reduced stiffness can be contained by adding a Viscous Damper. This paper presents the experimental study on a three-story fixed-base structure (3SFS), acting as a single-degree-of-freedom (SDOF) system (because of bracing in the top two stories), that demonstrates the concept of apparent weakening in elastic structural systems. Two NSDs and a Viscous Damper are installed in the first story of 3SFS. ...
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Spring‐Viscous Damper systems for combined seismic and vibration isolation
Earthquake Engineering & Structural Dynamics, 2007Co-Authors: Nicos Makris, M. C. ConstantinouAbstract:SUMMARY The coupled lateral-vertical-rocking dynamic response of spring-Viscous Damper isolated structures is considered. The force-displacement relation of the Viscous Dampers is described by an experimentally calibrated fractional derivative viscoelasticity model. The equations of motion are derived and reduced to a form for direct solution by the discrete Fourier transform method. The validity and accuracy of the derived solution are demonstrated by comparison with shake table test results. The developed analysis procedure is employed in the seismic analysis of a recently constructed isolated structure. The analytical and experimental results demonstrate that spring-Viscous Damper isolation systems are capable of providing both effective seismic and vibration isolation.
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spring Viscous Damper systems for combined seismic and vibration isolation
Earthquake Engineering & Structural Dynamics, 1992Co-Authors: Nicos Makris, M. C. ConstantinouAbstract:SUMMARY The coupled lateral-vertical-rocking dynamic response of spring-Viscous Damper isolated structures is considered. The force-displacement relation of the Viscous Dampers is described by an experimentally calibrated fractional derivative viscoelasticity model. The equations of motion are derived and reduced to a form for direct solution by the discrete Fourier transform method. The validity and accuracy of the derived solution are demonstrated by comparison with shake table test results. The developed analysis procedure is employed in the seismic analysis of a recently constructed isolated structure. The analytical and experimental results demonstrate that spring-Viscous Damper isolation systems are capable of providing both effective seismic and vibration isolation.
Mohamed Abdel-rohman - One of the best experts on this subject based on the ideXlab platform.
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Control of Wind-Induced Nonlinear Oscillations in Suspended Cables
Nonlinear Dynamics, 2004Co-Authors: Mohamed Abdel-rohman, Billie F. SpencerAbstract:In this paper, the along-wind and across-wind responses of suspended cables are studied. The mean wind direction is assumed to be perpendicular to the plane of the suspended cable. It is shown that the cable gallops in the across-wind direction, when the mean wind speed exceeds a critical wind speed. To control the galloping response, a vertical Viscous Damper, in the vertical plane of the cable, is introduced at a certain location on the cable to a near fixed platform such as a bridge deck. The efficiency of the vertical Viscous Damper and its location in controlling the galloping of the suspended cable is investigated.
Chopra, Anil K. - One of the best experts on this subject based on the ideXlab platform.
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Direct finite element method for nonlinear earthquake analysis of 3‐dimensional semi‐unbounded dam–water–foundation rock systems
'Wiley', 2018Co-Authors: Løkke Arnkjell, Chopra, Anil K.Abstract:A direct finite element method for nonlinear earthquake analysis of 2‐dimensional dam–water–foundation rock systems has recently been presented. The analysis procedure uses standard Viscous‐Damper absorbing boundaries to model the semi‐unbounded foundation‐rock and fluid domains and specifies the seismic input as effective earthquake forces at these boundaries. Presented in this paper is a generalization of the direct finite element method with Viscous‐Damper boundaries to 3‐dimensional dam–water–foundation rock systems. Step‐by‐step procedures for determining the effective earthquake forces starting from a ground motion specified at a control point on the foundation‐rock surface is developed, and several numerical examples are computed and compared with independent benchmark solutions to demonstrate the effectiveness of the analysis procedure for modeling 3‐dimensional systems
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Direct finite element method for nonlinear earthquake analysis of 3‐dimensional semi‐unbounded dam–water–foundation rock systems
Wiley, 2018Co-Authors: Løkke Arnkjell, Chopra, Anil K.Abstract:A direct finite element method for nonlinear earthquake analysis of 2‐dimensional dam–water–foundation rock systems has recently been presented. The analysis procedure uses standard Viscous‐Damper absorbing boundaries to model the semi‐unbounded foundation‐rock and fluid domains and specifies the seismic input as effective earthquake forces at these boundaries. Presented in this paper is a generalization of the direct finite element method with Viscous‐Damper boundaries to 3‐dimensional dam–water–foundation rock systems. Step‐by‐step procedures for determining the effective earthquake forces starting from a ground motion specified at a control point on the foundation‐rock surface is developed, and several numerical examples are computed and compared with independent benchmark solutions to demonstrate the effectiveness of the analysis procedure for modeling 3‐dimensional systems.submittedVersionThis is the pre-peer reviewed version of an article, which has been published in final form at [https://doi.org/10.1002/eqe.3019]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
Satish Nagarajaiah - One of the best experts on this subject based on the ideXlab platform.
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cable with discrete negative stiffness device and Viscous Damper passive realization and general characteristics
Smart Structures and Systems, 2015Co-Authors: Lin Chen, Limin Sun, Satish NagarajaiahAbstract:Negative stiffness, previously emulated by active or semi-active control for cable vibration mitigation, is realized passively using a self-contained highly compressed spring, the negative stiffness device (NSD).The NSD installed in parallel with a Viscous Damper (VD) in the vicinity of cable anchorage, enables increment of Damper deformation during cable vibrations and hence increases the attainable cable damping. Considering the small cable displacement at the Damper location, even with the weakening device, the force provided by the NSD-VD assembly is approximately linear. Complex frequency analysis has thus been conducted to evaluate the damping effect of the assembly on the cable; the displacement-dependent negative stiffness is further accounted by numerical analysis, validating the accuracy of the linear approximation for practical ranges of cable and NSD configurations. The NSD is confirmed to be a practical and cost-effective solution to improve the modal damping of a cable provided by an external Damper, especially for super-long cables where the Damper location is particularly limited. Moreover, mathematically, a linear negative stiffness and Viscous damping assembly has proven capability to represent active or semi-active control for simplified cable vibration analysis as reported in the literature, while in these studies only the assembly located near cable anchorage has been addressed. It is of considerable interest to understand the general characteristics of a cable with the assembly relieving the location restriction, since it is quite practical to have an active controller installed at arbitrary location along the cable span such as by hanging an active tuned mass Damper. In this paper the cable frequency variations and damping evolutions with respect to the arbitrary assembly location are then evaluated and compared to those of a taut cable with a Viscous Damper at arbitrary location, and novel frequency shifts are observed. The characterized complex frequencies presented in this paper can be used for preliminary damping effect evaluation of an adaptive passive or semi-active or active device for cable vibration control.
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simulated bilinear elastic behavior in a sdof elastic structure using negative stiffness device experimental and analytical study
Journal of Structural Engineering-asce, 2014Co-Authors: D T R Pasala, M. C. Constantinou, Satish Nagarajaiah, A A Sarlis, A M Reinhorn, Douglas P TaylorAbstract:AbstractThe acceleration and base shear of structures during strong ground motion can be attenuated by achieving bilinear-elastic behavior without any permanent displacement—also referred to as “apparent weakening.” The negative stiffness device (NSD), used in this study, exhibits nonlinear-elastic negative stiffness behavior; by adding NSD to the elastic structure, the resulting structure-device assembly behaves like a bilinear-elastic structure. Peak acceleration and base shear experienced by the structures can be reduced by adding the negative stiffness device, and the additional deformations caused by the reduced stiffness can be contained by adding a Viscous Damper. This paper presents the experimental study on a three-story fixed-base structure (3SFS), acting as a single-degree-of-freedom (SDOF) system (because of bracing in the top two stories), that demonstrates the concept of apparent weakening in elastic structural systems. Two NSDs and a Viscous Damper are installed in the first story of 3SFS. ...
