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Kuo-chun Chang - One of the best experts on this subject based on the ideXlab platform.
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shaking table study on displacement based design for seismic retrofit of existing buildings using nonlinear viscous Dampers
Journal of Structural Engineering-asce, 2008Co-Authors: Kuo-chun Chang, Yuyuan Lin, Changyu ChenAbstract:This paper presents the experimental and analytical results of a shaking-table study on the elastic and inelastic behavior of a 2/3-scale three-story steel structure retrofitted by the nonlinear viscous Dampers. The properties of the Dampers used in the test are designed based on the displacement-based design procedure. The retrofitted frame exhibits moderate inelastic behavior under the design ground motion of the 275% El Centro earthquake. The lateral floor displacements, story drifts, floor accelerations, story shears, and Damper axial forces measured from the frame tested are compared with those obtained from the displacement-based method as well as the nonlinear time-history analysis. It is shown from the study that the addition of nonlinear viscous Dampers to the structure results in displacement and force reduction by about 68 to 80% under the 30% El Centro earthquake (PGA ≈ 0.1 g). Higher-mode responses are significantly diminished. In addition, the displacement and acceleration responses of the structure with Dampers are appropriately captured by analytical models in the elastic range. The differences between the experimental and analytical results become noticeable in the inelastic range. The displacement-based evaluation procedure tends to underestimate the responses of the damped structure in the elastic range and overestimate them in the inelastic range.
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Higher-mode effect on the seismic responses of buildings with viscoelastic Dampers
Earthquake Engineering and Engineering Vibration, 2002Co-Authors: Meng-hao Tsai, Kuo-chun ChangAbstract:In conventional modal analysis procedures, usually only a few dominant modes are required to describe the dynamic behavior of multi-degrees-of-freedom buildings. The number of modes needed in the dynamic analysis depends on the higher-mode contribution to the structural response, which is called the higher-mode effect. The modal analysis approach, however, may not be directly applied to the dynamic analysis of viscoelastically damped buildings. This is because the dynamic properties of the viscoelastic Dampers depend on their vibration frequency. Therefore, the structural stiffness and damping contributed from those Dampers would be different for each mode. In this study, the higher-mode effect is referred to as the response difference induced by the frequency-dependent property of viscoelastic Dampers at higher modes. Modal analysis procedures for buildings with viscoelastic Dampers distributed proportionally and non-proportionally to the stiffness of the buildings are developed to consider the higher-mode effect. Numerical studies on shear-type viscoelastically damped building models are conducted to examine the accuracy of the proposed procedures and to investigate the significance of the higher-mode effect on their seismic response. Two Damper models are used to estimate the peak Damper forces in the proposed procedures. Study results reveal that the higher-mode effect is significant for long-period viscoelastically damped buildings. The higher-mode effect on base shear is less significant than on story acceleration response. Maximum difference of the seismic response usually occurs at the top story. Also, the higher-mode effect may not be reduced by decreasing the damping ratio provided by the viscoelastic Dampers. For practical application, it is realized that the linear viscous damping model without considering the higher-mode effect may predict larger Damper forces and hence, is on the conservative side.
Changyu Chen - One of the best experts on this subject based on the ideXlab platform.
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shaking table study on displacement based design for seismic retrofit of existing buildings using nonlinear viscous Dampers
Journal of Structural Engineering-asce, 2008Co-Authors: Kuo-chun Chang, Yuyuan Lin, Changyu ChenAbstract:This paper presents the experimental and analytical results of a shaking-table study on the elastic and inelastic behavior of a 2/3-scale three-story steel structure retrofitted by the nonlinear viscous Dampers. The properties of the Dampers used in the test are designed based on the displacement-based design procedure. The retrofitted frame exhibits moderate inelastic behavior under the design ground motion of the 275% El Centro earthquake. The lateral floor displacements, story drifts, floor accelerations, story shears, and Damper axial forces measured from the frame tested are compared with those obtained from the displacement-based method as well as the nonlinear time-history analysis. It is shown from the study that the addition of nonlinear viscous Dampers to the structure results in displacement and force reduction by about 68 to 80% under the 30% El Centro earthquake (PGA ≈ 0.1 g). Higher-mode responses are significantly diminished. In addition, the displacement and acceleration responses of the structure with Dampers are appropriately captured by analytical models in the elastic range. The differences between the experimental and analytical results become noticeable in the inelastic range. The displacement-based evaluation procedure tends to underestimate the responses of the damped structure in the elastic range and overestimate them in the inelastic range.
Y. L. Xu - One of the best experts on this subject based on the ideXlab platform.
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Adjustable fluid Damper with SMA actuators
Smart Materials and Structures, 2006Co-Authors: Z. Q. Li, Y. L. Xu, L. M. ZhouAbstract:The passive fluid Damper is one of most widely used control devices for mitigating the vibration of stay cables in a cable-stayed bridge in practice. However, each stay cable features unique dynamic characteristics and requires a specific Damper to achieve the best vibration mitigation, which engenders much trouble in the manufacture, implementation and maintenance of Dampers. In this study, a novel adjustable fluid Damper with shape memory alloy (SMA) actuators was developed. Instead of the fixed number of orifices in the piston head of a common fluid Damper, SMA actuators were installed inside the piston head to control the number of orifices so as to change the Damper parameters for the best control of a group of stay cables. The principle and design issues of the adjustable fluid Damper are introduced. An adjustable fluid Damper, which has ten orifices in the piston head, eight of them being controllable for achieving changes in damping at nine levels, was designed and manufactured. The performance tests of the Dampers were carried out within a range of frequencies and amplitudes and for a number of open orifices and different sizes of orifice. The experimental results provide a data base for the Maxwell model of the Damper and show that such a Damper can provide a wide range of forces and energy dissipation capacity. © 2006 IOP Publishing Ltd.
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seismic response control of frame structures using magnetorheological electrorheological Dampers
Earthquake Engineering & Structural Dynamics, 2000Co-Authors: Y. L. Xu, W L Qu, J M KoAbstract:Semi-active control of buildings and structures for earthquake hazard mitigation represents a relatively new research area. Two optimal displacement control strategies for semi-active control of seismic response of frame structures using magnetorheological (MR) Dampers or electrorheological (ER) Dampers are proposed in this study. The efficacy of these displacement control strategies is compared with the optimal force control strategy. The stiffness of brace system supporting the smart Damper is also taken into consideration. An extensive parameter study is carried out to find the optimal parameters of MR or ER fluids, by which the maximum reduction of seismic response may be achieved, and to assess the effects of earthquake intensity and brace stiffness on Damper performance. The work on example buildings showed that the installation of the smart Dampers with proper parameters and proper control strategy could significantly reduce seismic responses of structures, and the performance of the smart Damper is better than that of the common brace or the passive devices. The optimal parameters of the Damper and the proper control strategy could be identified through a parameter study. Copyright © 2000 John Wiley & Sons, Ltd.
J M Ko - One of the best experts on this subject based on the ideXlab platform.
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seismic response control of frame structures using magnetorheological electrorheological Dampers
Earthquake Engineering & Structural Dynamics, 2000Co-Authors: Y. L. Xu, W L Qu, J M KoAbstract:Semi-active control of buildings and structures for earthquake hazard mitigation represents a relatively new research area. Two optimal displacement control strategies for semi-active control of seismic response of frame structures using magnetorheological (MR) Dampers or electrorheological (ER) Dampers are proposed in this study. The efficacy of these displacement control strategies is compared with the optimal force control strategy. The stiffness of brace system supporting the smart Damper is also taken into consideration. An extensive parameter study is carried out to find the optimal parameters of MR or ER fluids, by which the maximum reduction of seismic response may be achieved, and to assess the effects of earthquake intensity and brace stiffness on Damper performance. The work on example buildings showed that the installation of the smart Dampers with proper parameters and proper control strategy could significantly reduce seismic responses of structures, and the performance of the smart Damper is better than that of the common brace or the passive devices. The optimal parameters of the Damper and the proper control strategy could be identified through a parameter study. Copyright © 2000 John Wiley & Sons, Ltd.
Yuyuan Lin - One of the best experts on this subject based on the ideXlab platform.
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shaking table study on displacement based design for seismic retrofit of existing buildings using nonlinear viscous Dampers
Journal of Structural Engineering-asce, 2008Co-Authors: Kuo-chun Chang, Yuyuan Lin, Changyu ChenAbstract:This paper presents the experimental and analytical results of a shaking-table study on the elastic and inelastic behavior of a 2/3-scale three-story steel structure retrofitted by the nonlinear viscous Dampers. The properties of the Dampers used in the test are designed based on the displacement-based design procedure. The retrofitted frame exhibits moderate inelastic behavior under the design ground motion of the 275% El Centro earthquake. The lateral floor displacements, story drifts, floor accelerations, story shears, and Damper axial forces measured from the frame tested are compared with those obtained from the displacement-based method as well as the nonlinear time-history analysis. It is shown from the study that the addition of nonlinear viscous Dampers to the structure results in displacement and force reduction by about 68 to 80% under the 30% El Centro earthquake (PGA ≈ 0.1 g). Higher-mode responses are significantly diminished. In addition, the displacement and acceleration responses of the structure with Dampers are appropriately captured by analytical models in the elastic range. The differences between the experimental and analytical results become noticeable in the inelastic range. The displacement-based evaluation procedure tends to underestimate the responses of the damped structure in the elastic range and overestimate them in the inelastic range.
