• Journal of Drive and Control
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• v.14 no.1
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• pp.8-13
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• 2017

This paper proposes a hydraulic circuit for a Magnetorheological (MR) damper that can be used for semi-active and active controls. Methods are presented for obtaining reliable damping force displacement and velocity data, and hysteresis loop data corresponding to applied current. In order to get reliable data, analysis using electric and electronic software, a series of tests. and comparative evaluations are required. A hydraulic circuit model is proposed that can be applied to analyze a MR damper without any assumptions where the yield stress data according to the applied current are known. Analysis results of the proposed hydraulic circuit are confirmed by experimental results within acceptable tolerance. This hydraulic circuit model can be applied to various MR dampers and systems.

• Steel and Composite Structures
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• v.45 no.6
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• pp.865-876
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• 2022

The slit members have lower strength and lower stiffness, which might lead to lower energy dissipation. In order to improve the seismic performance of the slit members, the paper proposes the shear lead damper, which has stable performance and small deformation energy dissipation capacity. Therefore, the shear lead damper can set in the vertical silts of the slit member to transmit the shear force and improve energy dissipation, which is suitable for the slit member. Initially, the symmetrical teeth-shaped lead damper was tested and analyzed. Then the staggered teeth-shaped lead dampers were developed and analyzed, based on the defect analysis and build improvements of the symmetrical specimen. Based on the parameter analysis, the main influence factors of hysteretic performance are the internal teeth, the steel baffles, and the width and length of damper. Finally, the theoretical analysis was presented on the hysteretic curve. And the skeleton curve and hysteresis path were identified. Based on the above theoretical analysis, the design method was proposed, including the damping force, the hysteresis model and the design recommendations.

• Journal of Korean Association for Spatial Structures
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• v.20 no.1
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• pp.79-86
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• 2020

The performance enhancement of various damping systems from natural hazards has become an highly important issue in engineering field. In this paper, ENTA hysteretic dampers were tested under cyclic loadings to evaluate their performance in terms of ductility and energy dissipation. The test results showed that the hysteretic dampers are effective damping systems to enhance the buildings performance for remodeling and retrofit of buildings. Also, the hysteretic dampers were modeled in FEM(Finite Element Method) structural analysis program. As comparing the computer modeling and the experiment, this study model reflects the nonlinear behavior of steel and derives the hysteresis loop.

• Smart Structures and Systems
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• v.24 no.3
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• pp.303-317
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• 2019

Magneto-rheological fluid (MRF) rotatory dampers are normally used for controlling the constant rotation of machines and engines. In this research, such a device is proposed to act as variable stiffness device to alleviate the rotational oscillation existing in the many engineering applications, such as motor. Under such thought, the main purpose of this work is to characterize the nonlinear torque-angular displacement/angular velocity responses of an MRF based variable stiffness device in oscillatory motion. A rotational hysteresis model, consisting of a rotatory spring, a rotatory viscous damping element and an error function-based hysteresis element, is proposed, which is capable of describing the unique dynamical characteristics of this smart device. To estimate the optimal model parameters, a modified whale optimization algorithm (MWOA) is employed on the captured experimental data of torque, angular displacement and angular velocity under various excitation conditions. In MWOA, a nonlinear algorithm parameter updating mechanism is adopted to replace the traditional linear one, enhancing the global search ability initially and the local search ability at the later stage of the algorithm evolution. Additionally, the immune operation is introduced in the whale individual selection, improving the identification accuracy of solution. Finally, the dynamic testing results are used to validate the performance of the proposed model and the effectiveness of the proposed optimization algorithm.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.351-360
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• 2014

The purpose of this research is to introduce the simplified equivalent frame model for the equivalent lateral force procedure, the response spectrum procedure and nonlinear procedure according to ASCE7-10 in order to reduce the time of performance and reasonably evaluate the effect of applying the damping system with the various conditions for the analysis and the variable. In this research, the seismic performance assessment and the design of the damping system were conducted through the nonlinear time history analysis based on the performance based seismic design in ASCE7-10 in regard to applying the damping system to apartment buildings which is lately issued. The optimal design based on the 75% of seismic base shear was performed for an apartment building. The seismic performance assessment were conducted to check the safety of the building, and the economic evaluation was performed by comparing the amount of resource for the optimal designed building with the amount of resource for the original building. In addition, hysteresis dampers was applied to the apartment building, and the suggested equivalent frame model was performed using the damping system design in ASCE7-10, then its control effects were proved in the full scale model of the apartment building which was used in this research.

• Smart Structures and Systems
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• v.2 no.3
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• pp.209-224
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• 2006

The use of smart dampers to optimally control the response of structures is on the increase. To maximize the potential use of such damper systems, their accurate modeling and assessment of their performance is of vital interest. In this study, the performance of a controllable fluid dashpot damper, in terms of damper forces, damper dynamic range and damping force hysteretic loops, respectively, is studied mathematically. The study employs a damper Bingham-Maxwell (BingMax) model whose mathematical formulation is developed using a Fourier series technique. The technique treats this one-dimensional Navier-Stokes's momentum equation as a linear superposition of initial-boundary value problems (IBVPs): boundary conditions, viscous term, constant Direct Current (DC) induced fluid plug and fluid inertial term. To hold the formulation applicable, the DC current level to the damper is supplied as discrete constants. The formulation and subsequent simulation are validated with experimental results of a commercially available magneto rheological (MR) dashpot damper (Lord model No's RD-1005-3) subjected to a sinusoidal stroke motion using a 'SCHENK' material testing machine in the Materials Laboratory at the University of Technology, Sydney.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1103-1120
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• 2015

A self-sensing magnetorheological (MR) damper with embedded piezoelectric force sensor has recently been devised to facilitate real-time close-looped control of structural vibration in a simple and reliable manner. The development and characterization of the self-sensing MR damper are presented based on experimental work, which demonstrates its reliable force sensing and controllable damping capabilities. With the use of experimental data acquired under harmonic loading, a nonparametric dynamic model is formulated to portray the nonlinear behaviors of the self-sensing MR damper based on NARX modeling and neural network techniques. The Bayesian regularization is adopted in the network training procedure to eschew overfitting problem and enhance generalization. Verification results indicate that the developed NARX network model accurately describes the forward dynamics of the self-sensing MR damper and has superior prediction performance and generalization capability over a Bouc-Wen parametric model.

• International Journal of Concrete Structures and Materials
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• v.9 no.1
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• pp.89-118
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• 2015

The geometric nonlinearity of off-diagonal bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model's pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.3
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• pp.292-301
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• 2008

A linearized model for hysteretic acoustic nonlinearity of imperfectly joined interface is proposed and analyzed by using Coulomb damping to investigate the characteristics of the reflection and transmission coefficients for harmonic waves at the contact interface. Closed crack is modeled as non welded interface that has nonlinear discontinuity condition in displacement across its boundary. Based on the hysteretic contact stiffness of the contact interface, the reflected and transmitted waves are determined by deriving the tractions on both sides of the interface in terms of the discontinuous displacements across the interface. It is found that the amplitudes of the reflected and transmitted waves are dependent on the frequency and the hysteretic stiffness. As the frequency of the incident wave increases, the higher reflection and lower transmission are obtained. It also shows that the hysteresis of the interface increases the reflection coefficient, but reduces the transmission coefficient. A fatigue crack is also made in aluminum specimen to demonstrate these characteristics of the reflection and transmission of contact interfaces.

• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.809-821
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• 2016

Concentric-tube continuum robots have formed an active field of research in robotics because of their manipulative exquisiteness essential to facilitate delicate surgical procedures. A set of concentric tubes with designed initial curvatures comprises a robot whose workspace can be controlled by relative translations and rotations of the tubes. Kinematic models have been widely used to predict the movement of the robot, but they are incapable of describing its time-dependent hysteretic behaviors accurately particularly when snapping occurs. To overcome this limitation, here we present a finite element modeling approach to investigating the dynamics of concentric-tube continuum robots. In our model, each tube is discretized using MITC shell elements and its transient responses are computed implicitly using the Bathe time integration method. Inter-tube contacts, the key actuation mechanism of this robot, are modeled using the constraint function method with contact damping to capture the hysteresis in robot trajectories. Performance of the proposed method is demonstrated by analyzing three specifications of two-tube robots including the one exhibiting snapping phenomena while the method can be applied to multiple-tube robots as well.