• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.492-498
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• 2005

A linear motor damper based on the linear motor principle is developed to suppress structural vibration. This paper deals with the design, analysis, and manufacture of the linear motor damper. It is designed to be able to move the auxiliary mass of 1500kg, up to $\pm250mm$ stroke. The control algorithm was designed based on LQG control logic with acceleration feedback. Through performance tests, it was confirmed that the developed hybrid mass damper has reliable feasibility as a control device for structural control. In addition, the linear motor damper is more economical than both hydraulic and electric motor driving mass damper with respect to simple structure and low maintenance cost. A series of performance tests of the linear motor damper system were carried out on the full-scale steel frame structure in UNISON Corporation. Through the performance tests, it was confirmed that acceleration levels are reduced down 10dB for first mode of structure

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.96-102
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• 2017

The highest fatal accident ratio was recorded in the construction industry. According to the industrial insurance premium rate & business type example, among the construction industry, the architectural work has the highest fatal and loss time accident ratio. Previous literature has investigated various aspects of accident occurrence and prevention in architectural work. However, those studied were limited in that they only focused on the fatal accident without considering the loss time accident. But non fatal accidents were recorded more than 50 times of fatal accidents. Therefore non fatal accidents must be controlled to lessen industrial accidents. Based on this, the goal of this study was to investigate the nature of the loss time accident and derive the risk index of work type in architectural work. In this study, opinions of safety experts were gathered and the risk index of work type was derived using AHP(Analytic Hierarchy Process). And verification was accomplished by comparing the results of this study with the risk index derived by analysis of accident records. Results showed that the risk index of work type was significantly higher in steel frame work, temporary installation work, earth & foundation work, facilities work, concrete work. And statistical analysis for verification showed that coefficient of Pearson correlation was 0.686 and P-value was 0.001.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.757-771
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• 2013

We present a semi-rigid connection estimation method by using cross modal strain energy method. While rigid or pinned assumptions are adopted for steel frames in traditional modeling via finite element method, the actual behavior of the connections is usually neither. Semi-rigid joints enable connections to be modeled as partially restrained, which improves the quality of the model. To identify the connection stiffness and update the FE model, a newly-developed cross modal strain energy (CMSE) method is extended to incorporate the connection stiffness estimation. Meanwhile, the relations between the correction coefficients for the CMSE method are derived, which enables less modal information to be used in the estimation procedure. To illustrate the capability of the proposed parameter estimation algorithm, a four-story frame structure is demonstrated in the numerical studies. Several cases, including Semi-rigid joint(s) on single connection and on multi-connections, without and with measurement noise, are investigated. Numerical results indicate that an excellent updating is achievable and the connection stiffness can be estimated by CMSE method.

• Steel and Composite Structures
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• v.25 no.5
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• pp.617-624
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• 2017

In this study, a new empirical method is presented to obtain Dynamic Increase Factor (DIF) in nonlinear static analysis of structures against sudden removal of a gravity load-bearing element. In this method, DIF is defined as a function of minimum ratio of difference between maximum moment capacity ($M_u$) and moment demand ($M_d$) to plastic moment capacity ($M_p$) under unamplified gravity loads of elements. This function determines the residual strength of a damaged building before amplified gravity loads. For each column removal location, a nonlinear dynamic analysis and a step-by-step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived, which correspond to the ratio min $[(M_u-M_d)/M_p]$ of beams in the bays immediately adjacent to the removed column, and at all floors above it. Therefore, the new DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of a moment frame structure. The proposed DIF formulas can estimate the real residual strength of a structure based on critical member.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1093-1101
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• 2005

Hybrid mass damper systems have recently been introduced as a dynamic vibration absorber to exploit the benefits of both the conventional tuned mass damper system and the active control system. A hybrid system is programmed to function as either a conventional TMD or as an active system according to the wind conditions and the resultant building and damper mass vibration characteristics. This paper deals with the design of the robust controller for the control of the flexible box structure. The control algorithm was devised based on $H_2$(LQG) robust control logic with acceleration feedback and to improve the capability of the controller Kalman Filter was accepted for the system. To test the ability of the robust controller using the linear motor damper system, performance tests and simulations were carried out on the full-scale steel frame structure. Through the performance tests, it was confirmed that acceleration levels are reduced down.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.502-506
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• 2006

For advanced construction safety, there frequently are repeated accident. Most of them are serious disasters which are continually concerned. But technical method of Safety organizations for construction project is still short, simple and unscientific. We suggest FMEA(Failure Mode and Effect Analysis) process on the safety management. The purpose of study is an establishment of safety system focused on scientific method by selecting priority unit and by figuring importance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.3
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• pp.46-52
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• 2018

Detail development and performance tests were conducted for the purpose of developing a damper system capable of lateral displacement control of existing frame structures. The development details are 1) ALD designed to prevent deformation of beams between columns and 2) AWD designed to control inter-story displacement. The non-reinforced BF specimen was used as a comparative study. The evaluation variables are failure mode, load-displacement curve, envelope curve, maximum strength, stiffness degradation and energy dissipation capacity. As a result, the seismic strengthening effect of ALD and AWD was confirmed. Also, it was confirmed that the method of restraining the column with the aramid sheet is superior to the improvement of the seismic performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.171-176
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• 2011

The purposes of the research were to evaluate system performance and response of building structure under external load for full scale modal-testing-tower applied toggle bracing and lead rubber damper(LRD). The dynamic properties of the structure were measured before and after installing damper under harmonic excitation using the AMD and the results were compared. The harmonic excitation condition is to increase 0.01Hz sine sweep signal from 0.49Hz to 0.63Hz. As a result of measuring resonant frequency, before installing damper is 0.55Hz and after installing damper is 0.62Hz. The experimental results after installing damper were also distinguished from simulation results and the main cause of this results is temperature dependency property of rubber material.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1427-1435
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• 2001

Air movement in wokplaces, whether resulting from a forced ventilation system or naturally occurring airflow, has a significant impact on occupational health. In a huge shipbuilding factory building, typical harmful factors such as fume or vaporized gas from welding and cutting of steel plates, and dusts from grinding give unpleasant feeling. From field data survey, the yearly dominant, wind directions for the shipbuilding factory building tested were northwest, northeast and southeast Among the three wind directions, the ventilation improvement was the worst for the northeastern wind. This study was focused on location of the opening vents in order to utilize the natural ventilation effectively. Instantaneous velocity fields inside the 1/1000 scale-down factory building model were measured using a 2-frame PIV system. The factory building model was embedded in an atmospheric boundary layer simulated in a wind tunnel. The modified vents improve the internal Ventilation flow with increasing the flow speed more than two times, compared with that of present vents.

• Journal of the Korean Society of Food Culture
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• v.18 no.6
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• pp.491-505
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• 2003

Yeolgujatang is traditional casserole with meat, fish and vegetables in special pot. Name of Yeolgujatang was in 1800s, as yeolgujatang, yeolgujatangbang, yeolguja, in 1900s, Yeolgujatang, royal feast food in Yi Dynasty was yeolgujatang, Meon-sinseolro, tangsinseolro. Yeolgujatang frame has legs and a lid, and a cylinder that can contain charcoal at the center of its rounded pot. with this charcoal, food can be cooked. Its material has changed from brazier to brassware, stainless steel, and silver. Nowdays electric sinseolro was also launched, which uses electric power instead of charcoal. Materials in yeolgujatang are beef, intestines, pork, chicken, pheasant, fish, sea bream, abalone, shrimps, vegetables, mushroom, ddock, guksu, cooked rice, seasening and garnish. Nutrition of Yeolgujatang per capita contains 221.5kal of calory, 17.3g of protein, 16.5g of fat, 6.1g of carbobydrates, 2g of fiber, 57.6mg of calcium, 208mg of phosphorus, 4.3mg of ferrum, $2177{\mu}gRE$ of vitaminA, 1.58mg of vitamin $B_1$, 0.3mg vitamin $B_2$, 6.6mg of vitaminC and 5.26mgNE of niacin. Yeolgujatang is excellent in nutrition, except for calcium and vitaminC.