• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.15-23
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• 2010

To reduce the vibration levels, additional dissipation elements such as dry friction dampers are sometimes integrated into bladed disk assembly. In this study, forced response analysis systems for a tuned bladed disk with friction dampers were developed and verified. For the efficient nonlinear vibration analysis, multi-harmonic balanced method and cyclic boundary condition were used. Also, mode shapes obtained using fictitious mass method were used to describe the motion of the structures with the concentrated structural nonlinearity, friction damper. The relative convergence of fictitious mass and traditional unconstrained modes were compared.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.435-443
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• 2010

This study presents key parameters for the structure installed with MR controller in reducing its responses. MR controller is regarded as Bingham model of which control forces are frictional and viscous ones. The parameters are identified as friction force ratios, $R_f$ and $R_h$ which are, respectively, ratio of MR controller friction force to static restoring force for free vibration and ratio of the friction force to amplitude of harmonic force. Structure-MR controller system shows nonlinear response behavior due to friction force. Energy balance strategy is adopted to transform the behavior to linear one with equivalent damping ratio. Finally, proposed equivalent linear process is compared to the nonlinear one, which turns out to give acceptably good results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.6
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• pp.589-596
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• 2008

This study introduces the design of a bi-directional damper using a tuned mass damper(TMD) and a tuned liquid column damper(TLCD) and presents experimental verifications to confirm its control performance. The damper used in this study behaves as a TMD in a specific translational direction and acts as a TLCD in the other orthogonal direction. First, shaking table test is performed to investigate the coupled effect of control forces produced by TMD and TLCD. Then, the parameters that affect to dynamic characteristics of the proposed damper are quantitatively evaluated based on the experimental results. Testing results shows that the damper used in this study produces control forces coupled by TLCD and TMD, as it is excited by waves with an incident angle. Also, it is observed that the damper can be used to reduce bi-directional responses of building structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.17-24
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• 2003

The main objective of this paper is to evaluate the control performance of a coulomb friction damper(CFD) for controlling the inelastic behavior of seismically excited structures, The seismic performances of various buildings are evaluated using capacity spectrum method(CSM), and the additional dampings are calculated If the evaluated performance levels of the buildings are below the target level. Maximum friction force of the CFD to achieve additional damping is provided using the concept of equivalent viscous damping, Numerical simulations for single degree of freedom(SDOF) systems with various structural periods and post yield stiffness ratios demonstrate the effectiveness of the proposed procedure.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.369-373
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• 2016

Accurate identification of damping matrix in structures is very important for predicting vibration responses and estimating parameters or other characteristics affected by energy dissipation. In this paper, damping matrix identification method that use normal frequency response functions, which were estimated from complex frequency response functions, is proposed. The complex frequency response functions were obtained from the experimental data of the structure. The nonproportional damping matrix was identified through the proposed method. Two numerical examples (lumped-mass model and cantilever beam model) were considered to verify the performance of the proposed method. As a result, the damping matrix of the nonproportional system was accurately identified.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.351-358
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• 2020

This paper presents a tuned mass damper (TMD) utilizing a parametric design technique to reduce the dynamic responses to seismic loads of retractable large spatial structures. An artificial intelligence algorithm was developed to automatically search for the installation position of the damping device. This enables confirming the dynamic response of the structure in real time while finding the optimum position for the damping device. Further, the optimum mass of the damping device is determined from among several alternatives, and a design that can be effectively applied to both open and closed conditions of the roof is obtained.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.239-245
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• 2006

In this paper, the performance of a toggle brace-MR damper system is evaluated for the control of the structure excited by earthquake load and the non-linearity of the toggle system is investigated. Considering that the control force of MR damper described by Bingham model is a function of velocity, velocity amplification factor by the toggle brace system is calculated and the effect of toggle configuration on the amplification factor is also evaluated. Numerical results show that the control performance can be largely enhanced using toggle brace system especially for the case that the MR damper installed with conventional brace system such as Chevron and diagonal cannot provide enough control force under severe earthquake load.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.135-142
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• 2020

In the case of a concrete structure, vibration problems occur under various conditions because of its low damping performance. To solve this problem, a study on the high damping performance of the polymer concrete with hybrid damper has recently been increased. Since water is not used in polymer concrete, the curing time is short. Also, the physical properties and dynamic properties of polymer concrete are quite excellent. So polymer concrete is widely expected to be used for structural materials. The hybrid damper is the structural system that consists of steel balls and viscous fluid inside the pipe which is embedded in polymer concrete. It can reduce the structural vibrations through the energy dissipation mechanism of viscous fluid and steel balls. In this study, the physical and dynamic properties of polymer concrete with hybrid damper were compared with ordinary concrete. As a result, the elasticity coefficient and the strength of the polymer concrete with hybrid damper were so much excellent. In particular, the tensile strength was 6.5 to 10 times higher than ordinary concrete. The frequency response function and damping ratio were also compared. As a result, the dynamic Stiffness of the polymer concrete was 25% greater than that of ordinary concrete. The damping ratio of the polymer concrete was approximately 3 times higher than that of ordinary concrete. Although the dynamic stiffness of the hybrid damper showed similar tendency, the damping ratio was 3.5 times higher than that of ordinary concrete. Therefore, the polymer concrete with hybrid damper was superior to ordinary concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.70-78
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• 2023

The ordinary concentrically braced frame has an advantage of having simple design procedure. For this reason, it has been widely used for the small-sized frame structures subject to moderate or lower magnitude earthquake, even though its seismic performance against the earthquake load is not much effective compared to that of other frame systems. To enhance seismic performance of the ordinary concentrically braced frame where the bracing has a weakness for compressive behavior under lateral earthquake, seismic retrofitting by viscous damper has been commonly introduced. However, the viscous damper, itself, generally does not have stiffness for restoring the structure to the original position. This may cause residual displacement to the structure. In this paper, a self-centering viscous damper system in which upper and lower beams having flexural rigidity play a role as a nonlinear-elastic spring, restoring the spring-damper system subject to external displacement history to its original location, is developed. The numerical analysis for a simplified frame structure shows how including the developed self-centering viscous damper system leads to an enhanced seismic performance of the frame structure through energy dissipation during earthquake excitation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.172-180
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• 2009

Normally in order to build a semi-active control system equipped with MR damper, the dynamic modeling of the damper is required to numerically predict its dynamic damping force and also its behavioral characteristics. For the dynamic modeling of the MR damper, this paper attempts to predict and evaluate its dynamic behavior by applying specifically both a power model and a Bingham model. Dynamic loading tests were performed on the squeeze type of damper specially designed for this research, and force-displacement hysteresis loops confirmed the effectiveness of the damper as a semi-active control device. In the meantime, in order to evaluate the effectiveness of each model applied, the model parameter for each model was identified. On the basis of the parameter, we derived the error ratio of the force-velocity relationship curve and the dynamic damping force, which was contrasted and compared with the experimental results of the squeeze type of damper. Finally, the squeeze type of MR damper developed in this research was proved to be valid as a semi-active control device, and also the evaluation of the two dynamic models showed they were working fine so that they were likely to be easily utilized to numerically predict the dynamic characteristics of any dampers with MR fluid as well as the squeeze type of MR damper.