• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.687-702
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• 2015

A method based on derivatives of eigen-parameters is presented for damage detection in discrete systems with dampers. The damage is simulated by decrease on the stiffness coefficient and increase of the damping coefficient. In the forward analysis, the derivatives of eigen-parameters are derived for the discrete system. In the inverse analysis, a derivative of eigen-parameters based model updating approach is used to identify damages in frequency domain. Two numerical examples are investigated to illustrate efficiency and accuracy of the proposed method. Studies in this paper indicate that the proposed method is efficient and robust for both single and multiple damages and is insensitive to measurement noise. And satisfactory identified results can be obtained from few numbers of iterations.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.681-685
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• 2004

A media-feeding (or media-transport) system is a key component in daily consumer systems such as printers, copiers and ATM's. The role of the media-transport system is to feed a medium, which is usually in the form of a thin film, to the main process in a uniform and repeatable manner. Even small slippage between the media and the feeding rollers could significantly degrade the performance of the entire system. The slippage between the medium and the feeding rollers is determined by many parameters which include the friction coefficient between the feeding rollers and the medium material, the angular velocity of the feeding rollers, and the normal force applied by feeding rollers on the medium. This paper investigates the effect of the normal force and the angular velocity of feeding rollers on the slippage of the medium. Authors have constructed a test bed for experiments, which consists of a feeding module and various measuring devices. Using regular paper as media being fed, the authors experimentally measured the slippage of the medium under various normal forces and angular velocities of driving feeding roller. Also the authors developed a novel two-dimensional simulation model for the media-transport system. The paper medium is modeled as a set of multiple rigid bodies interconnected by revolute joints and rotational springs and dampers. Simulations were executed using a multi-body dynamic analysis tool called RecurDy $n^{ⓡ}$. The slippage obtained by the simulation is compared to experimental results.ults.

• Wind and Structures
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• v.7 no.4
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• pp.251-264
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• 2004

The effects of a class of nonlinear Tuned Mass Dampers on the aeroelastic behavior of SDOF systems are investigated. Unlike classical linear TMDs, nonlinear constitutive laws of the internal damping acting between the primary oscillator and the TMD are considered, while the elastic properties are keept linear. The perturbative Multiple Scale Method is applied to derive a set of bifurcation equations in the amplitude and phase and a parametric analysis is performed to describe the postcritical scenario of the system. Both cubic- and van der Pol-type dampings are considered and the dependence of the limit-cycle amplitudes on the system parameters is studied. These new results, compared with the previously obtained bifurcation scenario of a SDOF aeroelastic oscillator equipped with a linear TMD, show a detrimental effect on the maximum limit-cycle amplitude reduction of the nonlinear TMD. However, the analyses evidence that in the parameter region away from the perfect tuning condition the nonlinear connection can be used to tune the system with an enhancement of the limit-cycle amplitude reduction.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.451-458
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• 2006

The goal of many researchers in the field of structural engineering is to reduce both damage to building structures and discomfort of their inhabitants during strong motion seismic events. The present paper reports on analytical work conducted with this aim in mind as a prior research of experimental study. A four-story, 6.4 m tall, laboratory model of a building is employed as a example structure. The laboratory structure has graphite epoxy columns and each floor is equipped with a chevron brace that serves to resist inter-story drift with the installation of a magnetorheological (MR) damper. An artificial excitation has been generated with a robust range of seismic characteristics. A series of numerical simulations demonstrates that an optimized fuzzy controller is capable of robust performance for a variety of seismic base motions. Optimization of the fuzzy controller is achieved using multi-objective genetic algorithm(MOGA), i.e. NSGA-II. Multiple objective functions are used in order to reduce both peak and root-means-squared displacement and accelerations at the floor levels of the building.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.600-605
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• 2012

In this paper, the acoustic performance of a shipboard large-sized room unit is studied. The room unit is a kind of rectangular absorptive chamber with a partition whose surface absorptive material with fabric skin is attached to. The room unit has one inlet and three outlet. At the inlet, a plane damper is installed to control the flow rate. The acoustic performance of a prototype room unit is measured using a HVAC mock-up. It is shown that its insertion loss is comparable with that of a commercially-used room unit but the developed room unit generates flow noise higher than the other one. The major source of flow noise is analyzed by NADS-R, the noise analysis program for room unit. Cone-shaped dampers are proposed to be used as the damper of a room unit to reduce flow noise. It is shown that the cone-shaped damper decrease flow noise remarkably.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.5
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• pp.468-473
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• 2012

In this paper, the acoustic performance of a shipboard large-sized room unit is studied. The room unit is a kind of rectangular absorptive chamber with a partition whose surface absorptive material with fabric skin is attached to. The room unit has one inlet and three outlets. At the inlet, a plane damper is installed to control the flow rate. The acoustic performance of a prototype room unit is measured using a HVAC mock-up. It is shown that its insertion loss is comparable with that of a commercially-used room unit but the developed room unit generates flow noise higher than the other one. The major source of flow noise is analyzed by NADS-R, the noise analysis program for room unit. Cone-shaped dampers are proposed to be used as the damper of a room unit to reduce flow noise. It is shown that the cone-shaped damper decrease flow noise remarkably.

• Earthquakes and Structures
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• v.14 no.6
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• pp.567-576
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• 2018

This manuscript introduces a new damping device which is composed of a water tank and a pendulum. The new damping device can be tuned to multiple frequencies. In addition, it has a higher energy dissipation capacity when compared with the conventional Tuned Liquid Dampers (TLDs). In order to evaluate the efficiency of this new damping device a series of free vibration and forced vibration tests were conducted on a scaled down single-story one-bay steel frame. Two different configurations were studied for the mass of the pendulum that included a completely and a partially submerged mass. It was observed that the completely submerged configuration led to 44% higher damping ratio when compared with the conventional TLD. In addition, the completely submerged configuration reduced the peak displacement response of the structure 1.6 times more than the conventional TLD. The peak acceleration response of the structure equipped with the new damping device was reduced twice more than the conventional TLD. It was also found that, when the excitation frequency is lower than the resonance frequency, the conventional TLD performs better than the partially submerged configuration of the new damping device.

• Steel and Composite Structures
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• v.48 no.4
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• pp.475-483
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• 2023

In this paper, a new energy-efficient semi-active hybrid bulk damper is developed that is cost-effective for use in structural applications. In this work, the possibility of active and semi-active component configurations combined with suitable control algorithms, especially vibration control methods, is explored. The equations of motion for a container bridge equipped with an MDOF Mass Tuned Damper (M-TMD) system are established, and the combination of excitation, adhesion, and control effects are performed by a proprietary package and commercial custom submodel software. Systematic methods for the synthesis of structural components and active systems have been used in many applications because of the main interest in designing efficient devices and high-performance structural systems. A rational strategy can be established by properly controlling the master injection frequency parameter. Simulation results show that the multiscale model approach is achieved and meets accuracy with high computational efficiency. The M-TMD system can significantly improve the overall response of constrained structures by modestly reducing the critical stress amplitude of the frame. This design can be believed to build affordable, safe, environmentally friendly, resilient, sustainable infrastructure and transportation.

• Earthquakes and Structures
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• v.11 no.6
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• pp.1123-1141
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• 2016

To explore the application of traditional tuned mass dampers (TMDs) to the earthquake induced vibration control problem, a pounding tuned mass damper (PTMD) is proposed by adding a viscoelastic limitation to the traditional TMD. In the proposed PTMD, the vibration energy can be further dissipated through the impact between the attached mass and the viscoelastic layer. More energy dissipation modes can guarantee better control effectiveness under a suite of excitations. To further reduce mass ratio and enhance the implementation of the PTMD control, multiple PTMDs (MPTMD) control is then presented. After the experimental validation of the proposed improved Hertz based pounding model, the basic equations of the MPTMD controlled system are obtained. Numerical simulation is conducted on the benchmark model of the Canton Tower. The control effectiveness of the PTMD and the MPTMD is analyzed and compared under different earthquake inputs. The sensitivity and the optimization of the design parameters are also investigated. It is demonstrated that PTMDs have better control efficiency over the traditional TMDs, especially under more severe excitation. The control performance can be further improved with MPTMD control. The robustness can be enhanced while the attached mass for each PTMD can be greatly reduced. It is also demonstrated through the simulation that a non-uniformly distributed MPTMD has better control performance than the uniformly distributed one. Parameter study is carried out for both the PTMD and the MPTMD systems. Finally, the optimization of the design parameters, including mass ratio, initial gap value, and number of PTMD in the MPTMD system, is performed for control improvement.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.11-19
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• 2007

This paper proposes an optimal design method of distribution and capacities of linear viscous dampers for vibration control of two adjacent buildings. The previous researches have dealt with suboptimal design problem under the assumption that linear viscous dampers are distributed uniformly or proportionally to the sensitivity of the modal damping ratio according to floors, whereas this study deals with global optimization problem in which the damping capacities of each floor are independently selected as design parameters. For this purpose, genetic algorithm to effectively search multiple design variables in large searching domains is adopted and objective function leading to the global optimal solutions is established through the comparison of several optimal design values obtained from different objective functions with control performance and damping capacity. The effectiveness of the proposed method is investigated by comparing the control performance and total damping capacity designed by the proposed method with those of the previous method. In addition, the time history analyses are performed by using three historical earthquakes with different frequency contents, and the simulation results demonstrate that the proposed method is an effective seismic design method for the vibration control of the adjacent structures.