• Journal of Industrial Technology
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• v.9
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• pp.29-41
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• 1989

A general study on the upgrading of mica minerals which are mainly found in pegmatite deposits was carried out for the purpose of developing a technique for recovering mica in form of comercial grade products. By the way the grade one of about 5~6% $K_2O$ still is not developed. The target of this research work is to be establish a process for the efficient concentration of muscovite, containing more than 10% $K_2O$. The tests are applied to incraese the recovery and grade of concentrates in term of variations of conditions. The test sample consists of mainly muscovite and gangue mineral such as quartz, pyrite and chlorite. Decantation and shaking table tests were ineffective to up-grade this low grade one, but flotation method gave satisfactory result. By means of grade one, but flotation method gave satisfactory result. By means of grindability tests, an optimum result could be obtained from the sample ground to -48mesh feed size. The flotation result indicates that the dodecyl ammonium chloride used as a cationic collector is effective on the negatively charged surface, while the sodium dodecyl sulfate as an anionic collector is effective on the positively charged surface. Muscovite was floated by petroleum sulfonate as well as amine type collector, it also floated by MIBC as well as pine oil frother under well condition. Fine muscovite concentrates of about 10.68% $K_2O$ was obtained with 22.4% yield, by decantation, the muscovite concentrates of 10.10% $K_2O$ was obtained with 23.54% yield, by table concentration, the muscovite concentrates of 11.51% $K_2O$ was obtained with 23.0% yield by flotation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.39-48
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• 2022

In earthquake situations, broadcasting and communication services are directly linked to rapid on-site rescue and effective restoration works. Recently, a variety of base isolation devices are widely introduced on building floors to avoid critical seismic damages of telecommunication facilities. However, in buildings with long fundamental periods, those devices may have undesirable amplification of seismic responses due to resonance effect between the building floors and base isolation devices. This study performs the seismic safety evaluation of two types of base isolation devices deployed for telecommunication facilities in mid- and high-rise buildings through numerical and experimental approaches. It is found that mid- and high-rise buildings can have low-frequency dynamic responses at the top floor when being subjected to design basis earthquake loading. Furthermore, bi-directional shake table testing demonstrated that the selected base isolation devices can exhibit unstable dynamic behaviors under such low-frequency excitations of the floor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.194-202
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• 1996

An approach to increase the seismic resistance of large structures is to reduce the seismic forces, to which structures are subjected by base isolation systems. The anti-seismic performance of base-isolated beatings has been verified experimentally by shaking table tests. However, it may be difficult to perform the tests for the full-scale beatings of base-isolated structures. Therefore, the test program was designed to evaluate the reliability and properties of the beatings under a range of loading conditions including axial stress, loading frequency and direction, and temperature. The effects of scale were also evaluated by comparing the results of the 1/4-scale beatings with those from the full-scale bearings, and the ultimate behavior of both types of bearings with evaluated through a series of roll-out tests. This report draws comparisons among the different tests and bearings to determine the importance of various factors including load history, axial stress, and frequency. Comparisons between the 1/4-scale bearings were difficult because of the scaling effects in manufacturing and thermal radiation, but qualitative results from the 1/4-scale bearings can certainly be extrapolated the full-scale bearings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.465-470
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• 2007

In this paper, a two-way tuned liquid mass damper(TLMD) using a tuned liquid column damper(TLCD) and a rubber-bearing-type tuned mass damper(TMD) was manufactured for controlling two-way direction acceleration responses of a high-rise building structure. The proposed controlling device behaves as a tuned liquid column damper in one direction and as a tuned mass damper in the other direction. In this study, Performance evaluation of the downscaled model is conducted. The results show that the two-way controllability is behaved independently each other and realscale TLMD applicable to the high-rise building can be designed.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.15-21
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• 2000

액상화되기 쉬운 모래지반 위에 축조된 제방의 지진시 거동을 조사하고 액상화 경감을 위한 대책공법의 효과를 비교하기 위하여 12가지 경우에 대해 진돈대 시험을 수행하였다. 본 시험에는 널말뚝, 자갈배수재, 모래다짐 말뚝과 강관말뚝 등의 대책공법이 적용되었다. 진동대 시험에 사용된 투명토조의 길이는 194cm이고 폭은 44cm 그리고 높이는 60cm이다. 기초지반은 포화된 모래이며 수중침강법을 적용하여 상대밀도 약 30%로 조성되었다. 이 포화된 느슨한 모래지만 위에 15cm 높이의 제방이 경사 1:1.5로 축조되었다. 진동대 시험시 제방과 기초지반의 거동을 측정하기 위해서 간극수압계 12개, 가속도계 4개 및 LVDT 2개가 시험모델에 설치되었다. 진동대의 크기는 2m$\times$2m이며, 진동시의 입력가속도는 0.1g에서 시작하여 최고 0.4g까지 증가시켰다. 본 모델에 적용된 공법 모두가 일반적인 진동법위에서 액상화 발생을 억제시키는데 유용한 것으로 증명이 되었으며, 그 중에서 모래다짐말뚝이 액상화로 인한 피해를 감소시키는데 가장 효과적인 것으로 나타났다. 또한 각각의 대책공법에 대한 최적 배치안의 본 연구에서 제시되었다.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.201-204
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• 2010

Earthquake load to design a structure has been calculated from a fixed base SDOF model using amplified surface accelerations along soft soil layers. But the method dose not consider a soil-structure interaction. Centrifugal experiments that were consisted of soil, a shallow foundation and a structure were performed to find the effects of soil-structure interaction. The experiments showed that mass and stiffness of the foundation affected a response of the structure and nonlinear behavior of soil near the foundation. And a rocking displacement caused by overturning moment affected the response and increases a damping effect. In this study, the centrifugal experiment was simulated as a two dimensional finite element model. The finite element model was used for nonlinear time domain analysis of the OpenSees program. The numerical model accurately evaluated the behaviors of soil and the foundation, but the rocking effect and the behavior of structure were not described.

• Smart Structures and Systems
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• v.15 no.6
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• pp.1481-1501
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• 2015

MR-TLCD (Magneto-Rheological Tuned Liquid Column Damper) is a new developed vibration control device, which combines the traditional passive control property with active controllability advantage. Based on traditional TLCD governing equation, this study further considers MR-fluid viscosity in the equation and by transforming the non-linear damping term into an equivalent linear damping, a solution can be obtained. In order to find a countable set of parameters for the design of the MR-TLCD system and also to realize its applicability to structures, a series of experimental test were designed and carried out. The testing programs include the basic material properties of the MR-fluid, the damping ratio of a MR-TLCD and the dynamic responses for a frame structure equipped with the MR-TLCD system subjected to strong ground excitations. In both the analytical and experimental results of this study, it is found that the accurately tuned MR-TLCD system could effectively reduce the dynamic response of a structural system.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.129-139
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• 2000

The liquefaction of reclaimed land generally caused the harbor facilities to hazards. In Korea, the major harbor quay walls are gravity type and the gravity quay wall is not a good earthquake resistant structure. Recently, various earthquake resistant quay walls have been suggested, but the study on the efficiency of reinforced quay wall was not much performed. In this study, numerical analysis is carried out for performance evaluation of easily adoptable earthquake resistant quay walls. The results of numerical analysis are compared with shaking table test that is performed at the same cross-section.

• Smart Structures and Systems
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• v.25 no.5
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• pp.531-541
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• 2020

This paper demonstrates the possibility of evaluating the safety of a building right after an earthquake using consumer-grade surveillance cameras installed in the building. Two cameras are used in each story to extract the time history of interstory drift during the earthquake based on camera calibration, stereo triangulation, and image template matching techniques. The interstory drift of several markers on the rigid floor are used to estimate the motion of the geometric center using the least square approach, then the horizontal interstory drift of any location on the floor can be estimated. A shaking table collapse test of a steel building was conducted to verify the proposed approach. The results indicate that the accuracy of the interstory drift measured by the cameras is high enough to estimate the damage state of the building based on the fragility curve of the interstory drift ratio. On the other hand, the interstory drift measured by an accelerometer tends to underestimate the damage state when residual interstory drift occurs because the low frequency content of the displacement signal is eliminated when high-pass filtering is employed for baseline correction.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.6
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• pp.7-15
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• 2002

In this paper, the nonlinear parameter estimation method using the estimated hysteresis of each structural members was studied for the purpose of efficient seismic damage prediction and estimation of MDOF nonlinear structural model in the shaking table test. The hysteresis of each structural members can be obtained by the conversion of measured response histories into relative motions of each structural members and member forces. These hysteresis can be used to evaluate various kinds of damage indices of each structural members. The MDOF nonlinear structural model for further analysis(re-analysis) can be easily reconstructed using estimated nonlinear structural parameters of each structural members. To demonstrate the proposed techniques, several numerical and experimental example analyses are carried out. The results indicate that the proposed method can be very useful to assess local seismic damages of structures.