• Journal of Korean Association for Spatial Structures
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• v.8 no.4
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• pp.91-100
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• 2008

In this study, the vibration control performance of high-rise building structures connected by a sky-bridge has been investigated. The philosophy of vibration control using sky-bridges is to allow structures with different dynamic characteristics to exert control forces upon one another through sky-bridges to reduce the overall responses of the system. The the high-rise building structure connected by sky-bridge with 49 and 42 stories was used in this study to investigate the displacement, acceleration, reaction of bearings and stress of sky-bridge by analytical methods. To this end, historical earthquakes, an artificial earthquake and wind force time histories obtained from wind tunnel tests were used. Based on the analytial results, the use of sky-bridge can be effective in reducing the structural responses of high-rise buildings against wind and seismic loads.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.6
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• pp.597-605
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• 2008

The feasibility study of a newly proposed smart base isolation system employing magneto-rheological elastomers(MREs) has been carried out. MREs belong to a class of smart materials whose elastic modulus or stiffness can be adjusted by varying the magnitude of the magnetic field. The base isolation systems are considered as one of the most effective devices for vibration mitigation of civil engineering structures such as bridges and buildings in the event of earthquakes. The proposed base isolation system strives to enhance the performance of the conventional base isolation system by improving the robustness of the system wide stiffness range controllable of MREs, which improves the adaptability and helps in better vibration control. To validate the effectiveness of the MRE-based isolation system, an extensive numerical simulation study has been performed using both single-story and five-story building structures employing base isolated devices under several historical earthquake excitations. The results show that the proposed system outperformed the conventional system in reducing the responses of the structure in all the seismic excitations considered in the study.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.187-197
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• 2010

The paleoseismological study in Korea has begun along the Yangsan fault zone (YFZ) and Ulsan fault zone (UFZ) since 1994. Some evidences related to late Quaternary movement are found at only some part of the YFZ, such as Pyonghae, Yuge, and Eonyang-Tongdosa areas. However, it is found along the most of the UFZ except the northen and southern ends of the fault. The dominant time span of faulting events along the YFZ and UFZ are quite different, and 500 ka to 200 ka and 300 ka to recent time, respectively. The dominant faulting senses of the YFZ and UFZ are right-lateral strike slip and reverse, respectively. These senses correspond well with the focal mechanism of recent occurring earthquakes along these two fault zones. If we evaluate the intensity of the activity of the YFZ from the average slip rate, which is 0.1~0.04 m/ka, it is comparable with the faults of higher C class in Japan. The slip rate of UFZ, which is 0.2~0.06 m/ka, is comparable with the faults of lower B to higher C class. Based on the relationship between maximum displacement and magnitude, the maximum earthquake magnitude is evaluated to be 6.8 and 7.0 in the YFZ and UFZ, respectively. An intensive studies are needed to clarify the problems such as segmentation of faults, return period, and geological evidences related to historical earthquakes.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.325-336
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• 2012

Smart base isolation systems developed for structures in high seismic regions cannot be directly applied to structures in regions of low-to-moderate seismicity, such as Korea. Therefore, the problems that occur by applying the smart base isolation system for high seismic regions to the structures in regions of low-to-moderate seismicity have been investigated in this study. To this end, a five-story building is used as an example, and an MR damper and low damping elastomeric bearings were used to compose a smart base isolation system. Artificial earthquakes are simulated for ground motions in regions of high and low-to-moderate seismicity. Based on numerical simulation results, the MR damper capacity that can provide good control is quite different among regions of high and low-to-moderate seismicity. Moreover, it is noted that the properties of a smart base isolation system for the regions of low-to-moderate seismicity should be carefully designed because the base isolation effects of the smart base isolation system for high seismic regions deteriorate when it is applied to the structures in regions of low-to-moderate seismicity.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1995.10a
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• pp.157-159
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• 1995

지난 1995년 7월 30일 칠리 북측해안(23.4$^{\circ}$S, 70.2$^{\circ}$W)에서 발생한 진도 8.2(Mw = 8.2 $\pm$ 0.16)의 지진에 의한 쓰나미는 태평양을 가로질러 일본해안까지 전파되어 다시 한번 일본에서 원지 쓰나미의 내습에 따른 해안재해의 경각심을 일으켰다. 본 연구에서는 역사적으로 큰 피해를 유발시킨 1883년의 크라카토아 화산 폭발에 의한 쓰나미, 1960년 칠리 발파라이소 해역의 쓰나미, 1964년 알라스카 Prince William Sound에서의 쓰나미의 외양전파(trans-oceanic propagation)를 쓰나미 수치 시뮬레이션 모형에 의해 산정하고, 그 결과를 과학가시화 기법에 의해 정연한 컴퓨터 그래픽 비디오 애니메이션으로서 작성하였다. (중략)

• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.649-652
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• 2004

자연재해나 인위적 재난은 발생자체를 막을 수는 없으나 인위적 재난일 경우에는 노력여하에 따라 재난의 발생과 피해정도를 줄일 수 있다. 또한, 홍수 태풍 지진과 같은 자연재해도 사전에 막을수는 없으나 효율적인 대응체계와 방재정보시스템을 갖춘다면 피해정도를 많이 줄일 수 있을 것이다. 따라서 본 연구에서는 재해${\cdot}$재난에 관한 연구의 역사가 길고 효율적인 방재정보시스템으로 각종 재해${\cdot}$재난에 대응하고 있는 미국과 일본의 방재정보시스템을 비교${\cdot}$검토해 봄으로써 우리나라의 실정에 맞는 방재정보시스템의 구축에 도움을 주고자 한다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.1-13
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• 2009

Liquefaction is a significant threat to structures on loose saturated sandy soil deposits in the event of an earthquake, and can often cause catastrophic damage, economic loss, and loss of life. Nevertheless, the Korean peninsula has for a long time been recognized as a safe region with respect to the hazard of liquefaction, as the peninsula is located in a moderate seismicity region, and there have been no reports of liquefaction, with the exception of references in some historical documents. However, some earthquakes that have recently occurred in different parts of the world have led to liquefaction in non-plastic silty soils, a soil type that can be found in many of the western coastal areas of Korea. In this study, we first present procedures for evaluating the liquefaction potential, and calculate the liquefaction potential index (LPI) distribution at two western coastal sites using both piezocone penetration test (CPTu) data and standard penetration test (SPT) data. The LPI is computed by integrating liquefaction potential over a depth of 20m, and provides an estimate of liquefaction-related surface damage. In addition, we compared the LPI values obtained from CPTu and SPT, respectively. Our research found that the CRR values from CPTu were lower than those from the SPT, particularly in the range between 40 and 120 for the corrected tip resistance, (qc1N)CS, from the CPTu, or in the range of CRR less than 0.23, resulting in relatively high LPI values. Moreover, it was observed that the differences in the CRR between the two methods were relatively higher for soils with high fine contents.

• Korean Journal of Heritage: History & Science
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• v.38
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• pp.305-327
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• 2005

Although the stone pagoda in Mireuk Temple site, Iksan, Cholla Province has been collapsed long time ago, few historical record has clearly explained the reason why the pagoda was collapsed and when. The west side of the pagoda have been destroyed from top to the sixth floor and the broken or damaged stone materials have been piled up in disorder. the lower part in the west was reinforced and enclosed by a stone embankment levelled to the height of the first storey of the pagoda. With no record informing the historical fact when it was made and by whom, it is only presumed that the embankment may have been built long time ago in order to prevent remains from further destruction. In the second chapter of the study, it has been tried to restore a reasonable historical background of the pagoda based on records or comments found in literatures such as traditional poetry and essays in chronological order. The collapsed slope in the west side, just above the embankment surrounding the lower part of the pagoda, was concreted in 1915 during the Japanese colonial period. Then in 1998, the Jeollabukdo has examined the structural safety of the pagoda. The Cultural Properties Committee has decided have the concrete layer removed and moreover to take apart the whole pagoda. It is also included that the disassembled stone materials should be given proper conservation treatments before being put into the place where they were in the reassembling process. The front view of the collapsed phase of the pagoda was revealed when the concrete-covered layer was removed. A hypothesis was built that there may be as many different appearances of collapsed pagoda depending on natural causes such as earthquake, sunken foundation, flood and typhoon. In chapter three, characteristic features were classified by examining various images of pagodas destroyed by different natural reasons mentioned in historical records. The chapter four dealt with comparison and analysis on the conditions shown in the stone pagoda in Mireuk Temple site and other examples studied in advance. The result of the study revealed that though having been made higher than the ground surface, the podium or the base of the pagoda actually has been eroded by rain and water. The erosion is supposed not only to have been proceeded for a long time without break but also to have caused the first storey body stone in the west inclined to outward. It has come to a conclusion that the pagoda may have been lead to collapse when the first storey body stone, supporting the whole weight from the upper storeys, became out of upright position and lost its balance. However, no such distinctive features of structural changes shown in pagodas collapsed by natural causes like earthquake, typhoon or sunken basement, have been found in the stone pagoda in Mireuk Temple site.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.27-35
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• 2010

This paper presents the vibration control performance of the smart passive control system to suppress the undesired vibration of the structure subjected to the earthquake loadings. Smart passive control system is the MR damper-based control system augmented with electromagnetic induction(EMI) device which consists of permanent magnets and solenoid coils. According to the Faraday's law of electromagnetic induction, an EMI device produces electrical energy from the mechanical energy due to the reciprocal motions of the structure and provide it to the MR damper. The smart passive control system can be the simple and easy to implement and maintain control system by replacing the feedback control system including sensors, controllers and external power sources of the conventional MR damper-based semiactive control system with the EMI device. The control performance of the smart passive control system is evaluated through the set of shaking table test considering the various historical earthquake loadings.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.11-19
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• 2007

This paper proposes an optimal design method of distribution and capacities of linear viscous dampers for vibration control of two adjacent buildings. The previous researches have dealt with suboptimal design problem under the assumption that linear viscous dampers are distributed uniformly or proportionally to the sensitivity of the modal damping ratio according to floors, whereas this study deals with global optimization problem in which the damping capacities of each floor are independently selected as design parameters. For this purpose, genetic algorithm to effectively search multiple design variables in large searching domains is adopted and objective function leading to the global optimal solutions is established through the comparison of several optimal design values obtained from different objective functions with control performance and damping capacity. The effectiveness of the proposed method is investigated by comparing the control performance and total damping capacity designed by the proposed method with those of the previous method. In addition, the time history analyses are performed by using three historical earthquakes with different frequency contents, and the simulation results demonstrate that the proposed method is an effective seismic design method for the vibration control of the adjacent structures.