New approaches for non-classically damped system eigenanalysis

Khanlari, Karen; Ghafory‐Ashtiany, Mohsen

doi:10.1002/eqe.467

Cited by 16 publications

(6 citation statements)

References 7 publications

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“…The resulting equivalent sti ness is applied to the isolation layer elements only, while the superstructure remains elastic. To keep the simplicity of the method and to prevent complex eigenvalue calculations [37,38], the equivalent damping is applied globally, in addition to existing viscous damping.…”

Section: Equivalent Linearizationmentioning

confidence: 99%

Simplified methods for design of base‐isolated structures in the long‐period high‐damping range

Weitzmann

Ohsaki

Nakashima

2005

Earthq Engng Struct Dyn

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SUMMARYA recent trend in the design of base-isolated structures is the extension of the natural period and the incorporation of high damping. This paper shows that the existing simpliÿed methods perform less accurately in this ÿeld of application, mainly due to inappropriate use of spectral data and insu ciently adjusted equivalent models. The paper proposes new period-dependent concepts to reduce pseudo-acceleration spectra and to transform these values into total accelerations with respect to the viscous damping ratio. The model of equivalent damping is adjusted to re ect several period-dependent e ects. The estimation of the accelerations in MDOF systems is based on additional period shifts. All modiÿcations are derived for a simpliÿed linear approach based on eigenforms, and a non-linear approach based on pushover and capacity spectrum analysis. To illustrate observed problems and to demonstrate the capabilities of the proposed concepts, example structures are studied in detail. Furthermore, intensive statistical tests prove the e ectiveness of the modiÿcations in a wide parameter range and show considerable improvements over traditional approaches.

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Section: Equivalent Linearizationmentioning

confidence: 99%

Simplified methods for design of base‐isolated structures in the long‐period high‐damping range

Weitzmann

Ohsaki

Nakashima

2005

Earthq Engng Struct Dyn

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“…Equation (5) can be extended as equation (6) (Khanlari and Ghafory-Ashtiany, 2005)…”

Section: Proposed Approach Conceptmentioning

confidence: 99%

A novel approach of active control of structures based on the critically damped condition

Rashidi

Khanlari

Zarfam

et al. 2020

Journal of Vibration and Control

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In this research, the active control of structures based on the critically damped condition was proposed for reducing displacements and drifts of structures under seismic loading. In this approach, the second-order dynamic equation is converted into a first-order dynamic equation and a first-order derivative operator with the same constants, which satisfy critically damped conditions of the system. Based on this concept and using the defined performance index, the feedback gain matrix of the structural velocity is obtained. In the method of active control of structures based on the critically damped condition, the control force, which is the linear definition of the feedback gain matrix and the structural velocity, is exerted on the structure in each time step. Four types of numerical examples are examined to the comparison verification of active control of structures based on the critically damped condition with the classical linear optimal control, standard model predictive control, and other methods proposed in several references. Programming and calculations are done by Mathcad prime mathematical software.

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“…Studies of dynamic characterization are extremely important in formulating predictive models for seismic response of hybrid cable-stayed bridge structures subjected to earthquake loadings [8][9][10]. Characterization of damping forces in a vibrating structure has long been an active area of research in structural dynamics [5,6,[11][12][13][14][15][16][17][18]. There are many situations in which the un-damped and classically damped assumptions are invalid.…”

Section: Introductionmentioning

confidence: 99%

Exploring damping characteristics of composite tower of cable-stayed bridges

Raheem

2016

Sādhanā

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The damping characterization is important in making accurate predictions of the seismic response of the hybrid structures dominated by different damping mechanisms. Different damping characteristics arise from the construction of the tower with different materials: steel for the upper part; reinforced concrete for the lower main part and interaction with supporting soil. The process of modeling damping matrices and experimental verification is challenging because damping cannot be determined via static tests as mass and stiffness can be. The assumption of classical damping is not appropriate if the system to be analyzed consists of two or more parts with significantly different levels of damping. The dynamic response of structures is critically determined by the damping mechanisms, and its value is very important for the design and analysis of vibrating structures. An analytical approach that is capable of evaluating the equivalent modal damping ratio from structural components is desirable for improving seismic design. Two approaches are considered to define and investigate dynamic characteristics of a composite tower of cable-stayed bridges: The first approach makes use of a simplified approximation of two lumped masses to investigate the structure irregularity effects including damping of different material, mass ratio, frequency ratio on dynamic characteristics and modal damping. The second approach employs a detailed numerical step-by-step integration procedure.

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New approaches for non-classically damped system eigenanalysis

Cited by 16 publications

References 7 publications

Simplified methods for design of base‐isolated structures in the long‐period high‐damping range

Simplified methods for design of base‐isolated structures in the long‐period high‐damping range

A novel approach of active control of structures based on the critically damped condition

Exploring damping characteristics of composite tower of cable-stayed bridges

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