• Steel and Composite Structures
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• v.25 no.4
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• pp.473-484
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• 2017

In this study a seismic retrofit scheme for a building structure was presented using steel plate slit dampers. The energy dissipation capacity of the slit damper used in the retrofit was verified by cyclic loading test. Genetic algorithm was applied to find out the optimum locations of the slit dampers satisfying the target displacement. The seismic retrofit of the model structure using the slit dampers was compared with the retrofit with enlarging shear walls. A simple damper distribution method was proposed using the capacity spectrum method along with the damper distribution pattern proportional to the inter-story drifts. The validity of the simple story-wise damper distribution procedure was verified by comparing the results of genetic algorithm. It was observed that the capacity-spectrum method combined with the simple damper distribution pattern leaded to satisfactory story-wise distribution of dampers compatible with the optimum solution obtained from genetic algorithm.

• Earthquakes and Structures
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• v.11 no.1
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• pp.25-43
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• 2016

The uneven distribution of rolling friction coefficient may lead to great uncertainty in the structural seismic isolation performance. This paper attempts to improve the isolation performance of a spring-damper-rolling isolation system by artificially making the uneven friction distribution to be concave. The rolling friction coefficient gradually increases when the isolator rolls away from the original position during an earthquake. After the spring-damper-rolling isolation system under different ground motions was calculated by a numerical analysis method, the system obtained more regular results than that of random uneven friction distributions. Results shows that the concave friction distribution can not only dissipate the earthquake energy, but also change the structural natural period. These functions improve the seismic isolation efficiency of the spring-damper-rolling isolation system in comparison with the random uneven distribution of rolling friction coefficient, and always lead to a relatively acceptable isolation state even if the actual earthquake significantly differs from the design earthquake.

• Earthquakes and Structures
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• v.16 no.6
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• pp.679-690
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• 2019

This paper presents machine learning methods using Support Vector Machine (SVM) and Multilayer Perceptron (MLP) to analyze optimal damper distribution for structural vibration control. Regarding different building structures, a genetic algorithm based optimization method is used to determine optimal damper distributions that are further used as training samples. The structural features, the objective function, the number of dampers, etc. are used as input features, and the distribution of dampers is taken as an output result. In the case of a few number of damper distributions, multi-class prediction can be performed using SVM and MLP respectively. Moreover, MLP can be used for regression prediction in the case where the distribution scheme is uncountable. After suitable post-processing, good results can be obtained. Numerical results show that the proposed method can obtain the optimized damper distributions for different structures under different objective functions, which achieves better control effect than the traditional uniform distribution and greatly improves the optimization efficiency.

• Earthquakes and Structures
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• v.13 no.6
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• pp.551-559
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• 2017

A large number of isolation systems are designed without considering the non-uniform friction distribution in space. In order to analyze the effects of non-uniform friction distribution on the structural response of isolation system, this paper presented a simplified rolling-damper-spring isolation system and analyzed the structural responses under earthquakes. The numerical results indicate that the calculation errors related to the peak values of structural acceleration, relative displacement and residual displacement are sequentially growing because of the ignorance of non-uniform friction distribution. However, the influence rule may be weakened by the spring and damper actions, and the unreasonable spring constant may lead to the sympathetic vibration of isolation system. In the case when the friction variability is large and the damper action is little, the non-uniform friction distribution should be taken into consideration during the calculation process of the peak values of structural acceleration and relative displacement. The non-uniform friction distribution should be taken into full consideration regardless of friction variability degree in calculating the residual displacement of isolation system.

• Smart Structures and Systems
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• v.4 no.5
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• pp.685-696
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• 2008

This paper deals with the numerical model of a bracing-friction damper system and its deployment using the optimal slip load distribution for the seismic retrofitting of a damaged building. The Slotted Bolted Connection (SBC) type friction damper system was tested to investigate its energy dissipation characteristic. Test results coincided with the numerical ones using the conventional model of a bracing-friction damper system. The placement of this device was numerically explored to apply it to the assumed damaged-building and to evaluate its efficiency. It was found by distributing the slip load that minimizes the given performance indicies based on structural response. Numerical results for the damaged building retrofitted with this slip load distribution showed that the seismic design of the bracing-friction damper system under consideration is effective for the structural response reduction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.9
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• pp.581-589
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• 2008

The pulverized coal combustion behavior in the utility boiler is very complex since so many physical and chemical processes happen in it, simultaneously. The mixing of pulverized coal with combustion air plays an important role in achieving the efficient combustion and stable boiler operation. The distribution of combustion air supplied to the furnace through the windbox damper system has not been clearly known since the individual measurements of air flow for each air nozzle were not possible, yet. The present study describes the CFD modelling of windbox damper system and aims to obtain the air flow rates and pressure loss coefficients across the present five damper systems, respectively. The one dimensional flow network model has been also established to get air flow distributions across the windbox damper, and applied to the actual plant operation condition. Compared with the designed air flow distribution, the modelled one gives a reasonable agreement. For the actual plant operation, the predicted air flow distribution at each air nozzle is differed with the designed data and strongly affected by the individual opening angle.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.561-567
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• 2007

This paper deals with the numerical model of a bracing-friction damper system and its deployment using the optimal slip load distribution for the seismic retrofitting of a damaged building. The Slotted Bolted Connection (SBC) type friction damper system was tested to investigate its energy dissipation characteristic. Test results coincided with the numerical ones using the conventional model of a bracing-friction damper system. The placement of this device was numerically explored to apply it to the assumed damaged-building and to evaluate its efficiency. It was found by distributing the slip load that minimizes the given performance indicies based on structural response. Numerical results for the damaged building retrofitted with this slip load distribution showed that the seismic design of the bracing-friction damper system under consideration is effective for the structural response reduction.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.641-647
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• 2004

Characteristics of the high frequency pulsatile flow have been investigated experimentally to understand the flow phenomena in the hydraulic system. The accumulator in high frequency hydraulic system but that is not effective all frequency zone. Therefore, a hydraulic damper used with accumulator is suggested to reduce the high frequency pulsatile where the accumulator is not effective. The pulsating pressure obtained by Pressure measurement system are analyzed to power spectral density distribution. According to the variations of pump input pressure and actuator acceleration frequency, the pressure is measured with or without an accumulator or pulsatile damper The amplitude of pressure with damper is very lower than those without accumulator or damper due to absorbing function of damper. As the frequency of actuator acceleration is increased, the effect of damper becomes very important to decrease the amplitude of pulsatile Pressure waveform with high frequencies.

• Fire Science and Engineering
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• v.27 no.1
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• pp.31-38
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• 2013

The pressurized smoke control system is important for fire safety in building because it is directly concerned with egress time of people. Even though the damper plays an essential role in the pressurized smoke control system, the phenomena of backflow smoke occurs for a certain the damper position. The research for a position of damper effects on distribution of air flow at the fire door is not performed. In this study, numerical simulation using FDS 5.5 was carried out to analyze the effect of the position of damper on flow distribution at the fire door. To simulate real situation, effects of opening and closing of fire door was considered. As a result, when HRR was between 200 kW and 400 kW, in the case which the damper was on the opposite wall of the fire door, the back flow to the vestibules was large compared to the two other cases of damper position. But when HRR was above 400 kW, Effect on damper position was not occurred.

• Steel and Composite Structures
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• v.27 no.5
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• pp.633-646
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• 2018

This study investigated the seismic performance of a hybrid damper composed of a steel slit plate and friction pads, and an optimum retrofit scheme was developed based on life cycle cost. A sample hybrid damper was tested under cyclic loading to confirm its validity as a damping device and to construct its nonlinear analysis model. The effectiveness of the optimum damper distribution schemes was investigated by comparing the seismic fragility and the life cycle costs of the model structure before and after the retrofit. The test results showed that the damper behaved stably throughout the loading history. Numerical analysis results showed that the slit-friction hybrid dampers optimally distributed based on life cycle cost proved to be effective in minimizing the failure probability and the repair cost after earthquakes.