• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.851-856
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• 2007

Recently, the matter controlling lateral drift is important in high rise buildings, In particular, seismic control dampers, such as mass damper and hysteretic damper, are emerging in the field of actively reducing drift. But. seismic control dampers have weak points with the lack of quantitative analysis and maintenance of the device. Accordingly, in this study we examine the structural characteristic of Steel Elasto-Plastic Hysteretic Damper, which is needless of maintenance, and then consider the basic conditions in the design and construction of the optimal seismic control effect which uses this device.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.378-382
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• 2005

The opening of high speed railway upgraded our land transportation speed limit, causing lots of changes including living and culture and also paving the way for stepping up the railway technology. However, it is also true that we had a limit to adopt the existing railway system structured for 150km/h to the new structure requiring a higher speed of approximate 300km/h due to technological, based on the time and experience. More importantly, heading toward a step of operating such a high speed railway system, it has been practically and quickly proposed that the railway needs high speed railway engineering, maintenance technology of parts of the vehicles to have a stable maintenance foundation and localization of major parts. Therefore, this study was intended to research the actual displacement characteristics in runningg on an actual track for the purpose of developing the protective and maintenance technology of springs and dampers, which are core parts among suspension elements of a high speed railway vehicle. For this, it was researched the actual vehicle test and its interpretation centered on primary spring, which is used for the suspension system of a bogie, body-body dampers and body-bogie yaw damper. Also, to analyze the displacement characteristics of suspension system in the actual conditions of high speed railway vehicles, a vehicle‘s dynamic characteristics was analyzed and interpreted. At the same time, a tester for measuring the actual displacement of such suspension elements was designed and attached to actual vehicles, to measure the displacements that occur in running it on the Seoul-Busan line, one of major lines serviced by KTX. The displacement data gained from the test with actual vehicles was analyzed for its displacement distribution depending on the service sections and frequency, with which the valuable data necessary for any potential breakdown or maintenance in the future could be obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.619-627
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• 2014

An optimization method is proposed for the simultaneous design of structural and control systems using the equivalent static loads. In the past researches, the control parameters of such feedback gains are obtained to improve some performance in the steady-state. However, the actuators which have position and velocity feedback gains should be designed to exhibit a good performance in the time domain. In other words, the system analysis should be conducted for the transient-state in dynamic manner. In this research, a new equivalent static loads method is presented to treat the control variables as the design variables. The equivalent static loads (ESLs) set is defined as a static load set which generates the same displacement field as that from dynamic loads at a certain time. The calculated sets of ESLs are applied as multiple loading conditions in the optimization process. Several examples are solved to validate the proposed method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.55-63
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• 2013

In this study, seismic performance was evaluated considering the deterioration level for the low-rise and moderate buildings with non-seismic details which are most common in Korea. Evaluation results showed that the deterioration condition is relatively good even after 24 years of construction but the seismic performance did not satisfy the protection index in the first and second evaluation. In case of the third evaluation, the goal performance was satisfied based on the interstory drift ratio but reinforcement is found to be necessary. Seismic performance was evaluated after the target buildings were reinforced in the walls, bracing, and damper. Results showed the interstory drift ratio drastically reduced regardless of reinforcement methods and satisfied the level of immediate occupancy. In case of wall reinforcement, however, base shear increased more than double which requires review on the existing foundation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.82-88
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• 2018

This study investigated the structure of an 8-pole 8-slot linear generator, which acts as an electromagnetic damper by combining the structure of an electromagnetic suspension device capable of generating electrical energy through energy harvesting by absorbing the vibration energy from the road surface while driving. To compare the energy harvesting effect of the electromagnetic suspension according to the actual road surface, a driving road test was simulated for two actual road conditions, an asphalt road surface and unpacked road surface condition, using a civilian combined vehicle model in conjunction with a vehicle simulation program, Carsim and Simulink. As a result, the relative displacements of the suspensions on the asphalt road surface and the unpaved road were 8 mm and 13 mm, respectively. By applying the suspension displacement value derived by modeling the linear generator coupled to the electromagnetic suspension, the simulation was then performed for an analysis time of 0.3s by applying the same analytical conditions using the commercial electromagnetic analysis program, ANSYS MAXWELL, The average power generation on the unpacked roads and asphalt roads was 198.6W and 98.7W respectively, which was 103.7% higher for unpackaged roads. Finally, to compare the sensitivity of the road surface frequency and the suspension input displacement to the power generation output, the sensitivity of the two variables was 1.725 and 1.283, respectively, and the road surface frequency had a 34.5% higher effect on the average power generation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.1-8
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• 2009

Stay cable is easily exposed to vibration induced rainy wind effects. There are some problems for not only unexpected vibration but also well-known vibration. An outbreak of displacement by the said effects brings damages such as over-tension of cables and barriers, fatigue of anchorages and dampers, and additional shear force variation of stiffening girders. This study suggests analytic methodology for dynamic tension variation of cables and shear force variation of stiffening girders. Additionally this study announces with dynamic problems for cable stayed bridge briefly. To realize this subject, we divide restoring force into chord component and normal component and then make up the differential equations which can satisfy physical phenomenon for each component. Finally we apply adequate functions such as sinusoidal and parabola in order to reduce these differential equations. Therefore we can meet with good results through a series of above process. As a remarkable result, CIP recommendations (2002) give inadequate solution with over 10% error. However it gives very good solution if parts of our study are reflected at the said recommendations. The fact means that CIP recommendations (2002) well-known as international standard of stay cables are not even concern about this subject yet. For verification of this study, F.E. analysis using E.C.C. with external forces was fulfilled, and the accuracy and conciseness of this study were shown.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.61-68
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• 1991

The system such as railway bridge can be modelled as the restrained beam with intermediate supports. This kind of structures are subject to the moving load, which has a great effect on dynamic stresses and can cause sever motions, especially at high velocities. Therefore, to analyze the dynamic characteristics of the system due to the moving load is very important. In this paper, the governing equation of motion of a restrained beam subjected to the moving load is derived by using the Hamilton's principle. The orthogonal polynomial functions, which are trial functions and satisfying the geometric and dynamic boundary conditions, are obtained through simple procedure. The dynamic response of the system subjected to the moving loads is obtained by using the Galerkin's method and the numerical time integration technique. The numerical tests for various constraint, velocity and boundary conditions were preformed. Furthermore, the effects of mass of the moving load are studied in detail.

• The Journal of the Acoustical Society of Korea
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• v.14 no.5
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• pp.36-43
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• 1995

This paper presents the lousing characteristics and the time. response of ultrasonic focusing transducer which is a coupled system with an electromechanical and an acoustical component. The Finite Element Method and the Hybrid Type Infinite Element Method are applied for the analysis. The position of the focal points and the resolutions is obtained from the loosing characteristics and the time response. It is found that the transducer with the damper, which stabilizes the displacement of the radiation surface, gives a better resolution. In conclusion, the results could be applied to the design and the performance analysis of the ultrasonic focusing transducer.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.7
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• pp.489-498
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• 2019

The airloads and structural loads of Light Civil Helicopter (LCH) rotor are investigated using a loose CFD/CSD coupling. The structural dynamics model for LCH 5-bladed rotor cwith elastomeric bearing and inter-bladed damper is constructed using CAMRAD-II. Either isolated rotor or rotor-fuselage model is used to identify the effect of the fuselage on the aeromechanics behavior at a cruise speed of 0.28. The fuselage effect is shown to be marginal on the aeromechanics predictions of LCH rotor, though the effect can be non-negligible for the tail structure due to the prevailing root vortices strengthened by the fuselage upwash. A lifting-line based comprehensive analysis is also conducted to verify the CFD/CSD coupled analysis. The comparison study shows that the comprehensive analysis predictions are generally in good agreements with CFD/CSD coupled results. However, the predicted comprehensive analysis results underestimate peak-to-peak values of blade section airloads and elastic motions due to the limitation of unsteady aerodynamic predictions. Particularly, significant discrepancies appear in the structural loads with apparent phase differences.

• Journal of the Korean Society for Railway
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• v.14 no.1
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• pp.11-18
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• 2011

This paper proposed a new 2-D multi-body dynamic modeling technique to analyze overriding behaviors taking place during train collision. This dynamic model is composed of nonlinear springs, dampers and masses by considering the deformable characteristics of carbodies as well as energy absorbing structures and components. By solving this dynamic model for rollingstock, energy absorbing capacities of collision elements, accelerations of passenger sections, impact forces applied to interconnecting devices, and overriding displacements can be well estimated. For a case study, we chose KHST (Korean High Speed Train), obtained crush characteristic data of each carbody section from 3-D finite element analysis, and established a 2-D multi-body dynamic model. This 2-D dynamic model was simulated under the train-to-train collision scenarios, and evaluated with 3-D virtual testing model. It was founded from the simulation results that this 2-D dynamic model could well predict overriding behaviors, and the modeling technique of carbody deformation was very important in overriding estimation.