• Earthquakes and Structures
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• v.3 no.1
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• pp.59-81
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• 2012

A ductility inverse-mapping method for SDOF systems including passive dampers is proposed which enables one to find the maximum acceleration of ground motion for the prescribed maximum response deformation. In the conventional capacity spectrum method, the maximum response deformation is computed through iterative procedures for the prescribed maximum acceleration of ground motion. This is because the equivalent linear model for response evaluation is described in terms of unknown maximum deformation. While successive calculations are needed, no numerically unstable iterative procedure is required in the proposed method. This ductility inverse-mapping method is applied to an SDOF model of bilinear hysteresis. The SDOF models without and with passive dampers (viscous, viscoelastic and hysteretic dampers) are taken into account to investigate the effectiveness of passive dampers for seismic retrofitting of building structures. Since the maximum response deformation is the principal parameter and specified sequentially, the proposed ductility inverse-mapping method is suitable for the implementation of the performance-based design.

• Journal of Korean Society of Steel Construction
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• v.15 no.4 s.65
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• pp.447-456
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• 2003

In this study, the proper shape of dampers was determined when the outside frame formed a rectangle. The proper shape of dampers is rectangular, having the same ratio as the outside frame. The design was based on the impact energy dissipated by the seismic performance of the mainly rectangular dampers. This study sought to compare both strength and energy dissipation between nonlinear analysis data and experimental data through load-displacement curves. The use of the ANSYS FEM software was suggested to analyze the nonlinear behavior of rectangular dampers subjected to cyclic loading. The target of this study was to determine what shape was efficient for rectangular tensile brace dampers. The safety of the developed rectangular dampers was also checked for better fabrication.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.980-985
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• 2008

This paper presents vehicle road test of a semi-active suspension system equipped with continuously controllable magnetorheological (MR) dampers. As a first step, front and rear MR dampers are designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial middle-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the MR dampers, the test vehicle is prepared for road test by integrating current suppliers, real-time data acquisition system and numerous sensors such as accelerometer and gyroscope. Subsequently, the manufactured four MR dampers (two for front parts and two for rear parts) are incorporated with the test vehicle and a skyhook control algorithm is formulated and realized in the data acquisition system. In order to emphasize practical aspect of the proposed MR suspension system, road tests are undertaken on proving grounds: bump and paved roads. The control responses are evaluated in both time and frequency domains by activating the MR dampers.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.5
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• pp.403-410
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• 2009

In this paper, damping coefficients and effective masses of tuned liquid-type column dampers were quantitatively evaluated based on experimental results by using system identification technique. First, shaking table tests were performed for two types of tuned liquid-type column dampers. Then, the dynamic characteristics of dampers used in this study were experimentally grasped from harmonic wave excitation testing results of the dampers with various water level. Finally, damping ratios and effective masses of the dampers with varying water level were quantitatively evaluated from minimizing the errors between numerical and experimental results. It was confirmed from system identification results that damping ratio and effective mass are decreased as the water level of dampers is increased.

• Steel and Composite Structures
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• v.26 no.3
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• pp.289-301
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• 2018

The rigid steel connections were suffered severe damage because of low rotational capacity during earthquakes. Hence, many investigations have been conducted on the connections of steel structures. As a solution, steel slit dampers were employed at the connections to prevent brittle failure of connections and damage of main structural members. Slit damper is a plate or a standard section with a number of slits in the web. The objective of this paper is to improve the seismic performance of steel slit dampers in the beam-to-column connection using finite element modeling. With reviewing the previous investigations, it is observed that slit dampers were commonly fractured in the end parts of the struts. This may be due to the low participation of struts middle parts in the energy dissipation. Thus, in the present study slit damper with elliptic slits is proposed in such a way that end parts of struts have more energy absorption area than struts middle parts. A parametric study is conducted to investigate the effects of geometric parameters of elliptic slit damper such as strut width, strut height and plate thickness on the seismic performance of the beam-to-column connection. The stress distribution is improved along the struts in the proposed slit damper with elliptic slits and the stress concentration is decreased in the end parts of struts. The average contributions of elliptic slit dampers, beam and other sections to the energy dissipation are about 97.19%, 2.12% and 0.69%, respectively.

• Smart Structures and Systems
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• v.21 no.5
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• pp.669-675
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• 2018

Under braking forces of a freight train, there are great longitudinal structural responses of a large freight railway cable-stayed bridge. To alleviate such adverse reactions, viscous dampers are required, whose parametric selection is one of important and arduous researches. Based on the longitudinal dynamics vehicle model, responses of a cable-stayed bridge are investigated under various cases. It shows that there is a notable effect of initial braking speeds and locations of a freight train on the structural responses. Under the most unfavorable braking condition, the parameter sensitivity analyses of viscous dampers are systematically performed. Meanwhile, a mixing method called BPNN-NSGA-II, combining the Back Propagation neural network (BPNN) and Non-Dominated Sorting Genetic Algorithm With Elitist Strategy (NSGA-II), is employed to optimize parameters of viscous dampers. The result shows that: 1. the relationships between the parameters of viscous dampers and the key longitudinal responses of the bridge are high nonlinear, which are completely different from each other; 2. the longitudinal displacement of the bridge main girder significantly decreases by the optimized viscous dampers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.3
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• pp.235-242
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• 2009

This paper presents vehicle road test of a semi-active suspension system equipped with continuously controllable magnetorheological(MR) dampers. As a first step, front and rear MR dampers are designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial middle-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the MR dampers, the test vehicle is prepared for road test by integrating current suppliers, real-time data acquisition system and numerous sensors such as accelerometer and gyroscope. Subsequently, the manufactured four MR dampers(two for front parts and two for rear parts) are incorporated with the test vehicle and a skyhook control algorithm is formulated and realized in the data acquisition system. In order to emphasize practical aspect of the proposed MR suspension system, road tests are undertaken on proving grounds: bump and paved roads. The control responses are evaluated in both time and frequency domains by activating the MR dampers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.1
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• pp.109-119
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• 2004

A design procedure for velocity-dependent supplemental dampers, such as viscous or viscoelastic dampers, required to meet the desired performance objectives was developed using displacement spectra. The amount of supplemental damping required to satisfy given performance limit state was obtained first from the nonlinear static procedure using displacement spectra, then dampers were appropriately distributed throughout the stories to realize the required damping. The proposed method was applied to multi-story steel frames, and the structures were analyzed by time history analysis to validate the accuracy of the design procedure. According to the analysis results the maximum displacements of the model structures retrofitted by the supplemental dampers turned out to be restrained well within the given target values.

• Steel and Composite Structures
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• v.19 no.2
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• pp.309-325
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• 2015

A convenient procedure for seismic retrofit of existing buildings is to use passive control methods, like using friction dampers in steel frames with bracing systems. In this method, reduction of seismic demand and increase of ductility generally improve seismic performance of the structures. Some of its advantages are development of a stable rectangular hysteresis loop and independence on environmental conditions such as temperature and loading rate. In addition to friction dampers, masonry-infill panels improve the seismic resistance of steel structures by increasing lateral strength and stiffness and reducing story drifts. In this study, the effect of masonry-infill panels on seismic performance of a three-span four-story steel frame with Pall friction dampers is investigated. The results show that friction dampers in the steel frame increase the ductility and decrease the drift (to less than 1%). The infill panels fulfill their function during the imposed drift and increase structural strength. It can be concluded that infill panels together with friction dampers, reduced structural dynamic response. These infill panels dissipated input earthquake energy from 4% to 10%, depending on their thickness.

• International journal of steel structures
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• v.18 no.4
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• pp.1107-1124
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• 2018

The structural behavior of reinforced concrete coupled shear wall structures is greatly influenced by the behavior of their coupling beams. This paper presents a process of the seismic analysis of reinforced concrete coupled shear wall-frame system linked by hysteretic dampers at each floor. The hysteretic dampers are located at the middle portion of the linked beams which most of the inelastic damage would be concentrated. This study concerned particularly with wall-frame structures that do not twist. The proposed method, which is based on the energy equilibrium method, offers an important design method by the result of increasing energy dissipation capacity and reducing damage to the wall's base. The optimum distribution of yield shear force coefficients is to evenly distribute the damage at dampers over the structural height based on the cumulative plastic deformation ratio of the dissipation device. Nonlinear dynamic analysis indicates that, with a proper set of damping parameters, the wall's dynamic responses can be well controlled. Finally, based on the total plastic strain energy and its trend through the height of the buildings, a prediction equation is suggested.