Papers by Keyword: Passive Control

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Authors: Tao Wang, Xi Chen, Rui Teng
Abstract: Proposed in this study is a type of friction damper characterized a continuously variable post-sliding stiffness, which provides an increasing post-sliding force with the accretion of the deformation. It is possible to adjust the output force according to the performance targets at different earthquake levels, thus enlightening a practical approach to the explicit structure control to satisfy all of the required performance objectives. The proposed damper consists of a piston, a rubber layer, friction plates and the jacket. The friction plates and the inside of the jacket constitute the contact pair, or the sliding surface. The friction plates are fixed on the piston through the rubber layer which provides the normal pressure on the sliding surface. The radius of sliding surface varies continuously along the axis of the jacket. Both analyses and experiments reveal that the parabola shape of sliding surface would introduce a cubic force-displacement relationship, thus being helpful to prevent a structure from collapse.
Authors: Tao Wang, Xi Chen, Rui Teng
Abstract: Proposed in this study is a type of friction damper characterized a continuously variable post-sliding stiffness, which provides an increasing post-sliding force with the accretion of the deformation. It is possible to adjust the output force according to the performance targets at different earthquake levels, thus enlightening a practical approach to the explicit structure control to satisfy all of the required performance objectives. Theoretical analyses reveal that the parabola shape of the sliding surface would introduce a cubic force-displacement relationship, which was also demonstrated by sophisticated finite element models. The typical mechanic model was then incorporated into the source code of OpenSEES. The dynamic analysis gave reasonable results and experimental results also demonstrated that the proposed friction damper is able to reduce the displacement response and more important, is helpful to prevent a structure from collapse.
Authors: Satish Nagarajaiah, Dharma T.R. Pasala, Andrei Reinhorn, Michael Constantinou, Apostolos A. Sirilis, Douglas Taylor
Abstract: Yielding can be emulated in a structural system by adding an adaptive “negative stiffness device” (NSD) and shifting the “yielding” away from the main structural system-leading to the new idea of “apparent weakening” that occurs ensuring structural stability at all displacement amplitudes. This is achieved through an adaptive negative stiffness system (ANSS), a combination of NSD and a viscous damper. By engaging the NSD at an appropriate displacement (apparent yield displacement that is well below the actual yield displacement of the structural system) the composite structure-device assembly behaves like a yielding structure. The combined NSD-structure system presented in this study has a re-centering mechanism thereby avoids permanent deformation in the composite structure-device assembly unless, the main structure itself yields. Essentially, a yielding-structure is “mimicked” without any, or with minimal permanent deformation or yielding in the main structure. As a result, the main structural system suffers less accelerations, less displacements and less base shear, while the ANSS “absorbs” them. This paper presents comprehensive details on development and study of the ANSS/NSD. Through numerical simulations, the effectiveness and the superior performance of the ANSS/NSD as compared to a structural system with supplemental passive dampers is presented. A companion paper presents the NSD and its mechanics in detail.
Authors: Xi Chen, Fu You Xu, Wen Liang Qiu, Zhe Zhang
Abstract: Active Mass Damper has been proven to be efficient in suppressing structure vibration. Previous studies of AMD have been concentrated on the vibration control of buildings under earthquake excitation, whereas few investigation of wind-induced bridge vibration control has been conducted. In consideration of the characteristics of one suspension pipeline bridge which behaves dramatic lateral and torsional response under fluctuating wind action, a two-DOFs TMD/AMD system for suppressing both lateral and torsional responses was proposed. The bridge is modeled using Ansys and the buffeting responses of the bridge under TMD, AMD control are respectively simulated and analyzed by MATLAB/Simulink. The efficiency of different control system has been studied. The results show that two-DOFs AMD system has a better performance in suppressing the buffeting response of lateral bending and torsion. In addition, AMD system can be applicable to a wider range of frequency and therefore manifests the more stable performance than TMD under fluctuating wind loads which contain various frequency components.
Authors: Mario Di Paola, Francesco Lo Iacono, Giacomo Navarra
Abstract: Mitigation of structural damage due to earthquake ground motion may be performed by inserting dampers in the structure. In order to enhance the damping effect various toggle brace configurations have been recently proposed. In this paper these equipments are analyzed in detail and compared with a new one here proposed. The analysis is performed by taking into account the inherent nonlinearities of the damper by means of stochastic analysis and validated by using time histories of recorder accelerograms and by the stochastic analysis using spectrum consistent power spectral density.
Authors: Hui Hong Feng, Yu Chen
Abstract: The cost management for construction enterprises is an important link of whole process engineering cost control in project construction. This article elaborates the details and procedures of the construction enterprises’ cost management in the construction stage. In the paper, it will be divided into three steps which are the stage of preparing, implementation and completion of project, and construction enterprises will separately use the methods of pre-control, control in process and afterwards control in each step for the cost management.
Authors: L.S. Leao, Maurício Vicente Donadon, A.M.G. de Lima, A.G.C. Filho
Abstract: This paper presents a numerical study on the influence of multimodal shunt circuit parameters in the flutter velocity of a typical section under an unsteady airflow. Flutter on typical sections is a kind of self-excited oscillation which can occur due to the interaction with the airflow. In the flutter point, when the critical dynamic pressure is reached, the vibrations of the typical section become unstable and increase fast and significantly in time. As a result, it can lead the structure to failure. Thus, it becomes important to investigate the possibility of reducing the effects of flutter in order to increase the reliability of composite structures during service. In this work, the aero-electromechanical dynamic model formulation is based on the Hamilton principle. The unsteady aerodynamic forces are calculated based on the linearized thin-airfoil theory, proposed by Theodorsen. The passive element responsible for the energy dissipation is a multimodal resonant shunt circuit in series topology, attached to a piezoelectric patch. An iterative solution algorithm is proposed to solve the resultant nonlinear eigenvalue problem. The optimum shunt tuning is firstly performed using Hagood and Flotow’s propositions; then, it is used an heuristic optimization algorithm, based on Differential Evolution. The preliminary results indicate that the flutter speed can be affected by the passive control, both in its mechanical aspect as electrical.
Authors: Wei Wei Bian, Liang Ming Wang, Yang Zhong
Abstract: In order to increase the density of guided rockets, a passive control method was proposed to reduce the trajectory dispersion caused by initial disturbances, thrust misalignment, vertical wind, etc. at the end of boost phase. The basic principle of passive control method was introduced briefly, and then the disturbance motion equations for the rocket projectile were established. The effective conditions to implement passive control on guided rockets were put forward. A technical scheme of installing elastic sabots on rocket projectile was proposed to realize passive control and a simulation was conducted. The simulation results indicate that the passive control scheme can effectively decrease the velocity direction deviation caused by various disturbances factors at the end of boost phase.
Authors: Young Won Chang, Olga Kostiyukova, Kil To Chong
Abstract: Bilateral teleoperation systems connected to computer networks such as the internet have to deal with varying time delays depending on several factors such as congestion, bandwidth, or distance. Such systems can easily become unstable due to irregular or varying time delays. A passivity concept has been used as the framework to solve the stability problem in bilateral control of teleoperation systems and we demonstrate in this paper how to recover both passivity and tracking performance using a novel control architecture that incorporates time varying gains into the transmission path, feedforward, and feedback position control. Simulation results for a single-degree of freedom master/ slave system are presented which demonstrates the performance of the resulting control architecture.
Authors: Jin He Gao, Hiroshi Tagawa
Abstract: This paper presents a new energy dissipation device for earthquake protection of structures. The proposed device, which uses a quasi-linear motion mechanism, achieves dissipation of seismic energy into the structure through yielding of U-shaped steel dampers. Consequently bracing members are subjected to only tensile force. Cyclic loading tests of the portal moment frames with the proposed device are conducted. Results and discussions are presented with emphasis on key features which affect energy dissipation capability. The lateral load and story drift angle relationships show that the proposed device provides stable and reasonably large energy dissipation capability. The effect of pre-tension applied to the bracing members is also examined through the brace axial strain and lateral load relationship.
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