• Earthquakes and Structures
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• 제14권4호
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• pp.337-347
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• 2018

This paper presents some shaking table tests conducted on a 1/4-scaled model with 5-story steel reinforced concrete (SRC) spatial frame with irregular section columns under a series of base excitations with gradually increasing acceleration peaks. The test frame was subjected to a sequence of seismic simulation tests including 10 white noise vibrations and 51 seismic simulations. Each seismic simulation was associated with a different level of seismic disaster. Dynamic characteristic, strain response, acceleration response, displacement response, base shear and hysteretic behavior were analyzed. The test results demonstrate that at the end of the loading process, the failure mechanism of SRC frame with irregular section columns is the beam-hinged failure mechanism, which satisfies the seismic code of "strong column-weak beam". With the increase of acceleration peaks, accumulated damage of the frame increases gradually, which induces that the intrinsic frequency decreases whereas the damping ratio increases, and the peaks of acceleration and displacement occur later. During the loading process, torsion deformation appears and the base shear grows fast firstly and then slowly. The hysteretic curves are symmetric and plump, which shows a good capacity of energy dissipation. In summary, SRC frame with irregular section columns can satisfy the seismic requirements of "no collapse under seldom earthquake", which indicates that this structural system is suitable for the construction in the high seismic intensity zone.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권2호
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• pp.369-390
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• 2023

Technologies for disaster management are highly sought areas for research and commercial deployment. Landslides, Flood, cyclones, earthquakes, forest fires and road/train accidents are some causes of disasters. Capturing video and accessing data in real time from the disaster site can help first responders make split second decisions which may save human lives and valuable resource destructions. In this context the communication technologies performing the task should have high bandwidth and low latency which only 5G can deliver. But unfortunately in India, deployment of the 5G mobile communication systems is yet to give a shape and again in remote areas unavailability of 4G signals is still severe. In this situation the authors have proposed, simulated and experimented a 4G-5G communication scheme where from the disaster site the signals will be transmitted by a 5G terminal to a nearby 4G-5G gateway installed in a mobile vehicle. The received 5G signal will be further relayed by the 4G-5G gateway to the fixed 4G base station for onward transmission towards the disaster management station for decision making, deployment and relief monitoring. The 4G-5G gateway acts as a relay and converter of 5G signal to 4G signal and vice versa. This relayed system can be further mounted on a vehicle mounted relay (VMR) as proposed by 3GPP in Release 18. The scheme is also in the same line of context with Verizon's, "Tactical Humanitarian Operations Response" (THOR) vehicle concept. The performance of the link is studied in different channel conditions, the throughput achieved is superb. The authors have implemented the above mentioned system towards smart campus networking and monitoring landslides activities which are common in their regions.

• Earthquakes and Structures
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• 제17권3호
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• pp.245-256
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• 2019

An experimental study was conducted to evaluate the dynamic behavior of a free-standing frame equipped with a movable base system using cast iron and mortar as the bearing materials. The preliminary friction test indicated that a graphite layer developed on the interface and exhibited stable friction behavior. The friction coefficient ranged from 0.33 to 0.36 when the applied normal compression stress ranged from 2.6 to 5.2 MPa. The effect of the variation of normal compression stress would be small. Shaking table tests on the free-standing frame showed that rock, slide, and rock-slide responses occurred. The cumulative slide distance reached 381 mm under JMA Kobe wave excitation; however, only a few cyclic slides occurred at the same locations along the moving track. Most surfaces sustained single slides. Similar results can be observed in other shaking conditions. The insufficient cyclic sliding and significant rocking resulted in a few graphite layers on the mortar surfaces. Friction coefficients were generally similar to those obtained in the preliminary friction tests; however, the values fluctuated when the rocking became significant. The collisions due to rocking caused strong horizontal acceleration responses and resulted in high friction coefficient. In addition, the strong horizontal acceleration responses caused by the collisions made the freestanding specimen unable to reduce the input horizontal acceleration notably, even when slippage occurred. Compared with the counterpart fixed-base specimen, the specimen equipped with the iron-mortar base could reduce the horizontal acceleration amplification response and the structural deformation, whereas the vertical acceleration response was doubled due to collisions from rocking.

• 대한공간정보학회지
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• 제21권2호
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• pp.71-83
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• 2013

최근 자연재해의 발생빈도가 높아지고 그 규모가 점차 대형화되고 있어, 방재에 대한 관심이 높아지고 있다. 우리나라의 대표적인 자연재해는 태풍과 호우로, 강도가 증가하는 추세에 있으며 이에 따라 매년 발생하는 피해의 규모도 커지고 있다. 자연재해 피해발생시 지자체가 상시적으로 보유하고 있는 방재자원으로는 그 피해 규모를 감당하기 어려운 실정이다. 따라서 대규모 재난발생시 피해 특성에 맞는 장비와 인력을 신속하게 동원, 배분할 수 있도록 지역 특성에 맞는 방재자원 공동 활용체계를 구축할 필요가 있다. 본 논문에서는 전국 각 지역의 특성을 분석하고 이에 따라 '재난 공동 대응을 위한 지자체 컨소시엄 구성 방안'을 제안하였다. 먼저, GIS를 이용하여 2002년에서 2011년까지의 재해연보에 수록된 지자체별 피해액을 나타낸 재해지도를 제작하였다. 다음, 전국을 행정구역에 따라 크게 5개 권역으로 구분하고, 각 권역의 지형적, 인문적 특성 및 태풍과 호우에 의한 피해 규모를 분석하여 다시 12개의 클러스터로 세분하였다. 마지막으로 각 권역의 재난대책거점을 선정하였다. 본 연구의 피해 분석자료는 방재대책 수립시 참고자료로 활용될 수 있을 것이다.

• 한국가스학회지
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• 제25권3호
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• pp.46-52
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• 2021

본 연구는 스마트폰 Wi-Fi AP를 이용한 건축물내 구조대상자 위치정보 수집을 통해서 사고 현장대응에 활용할 수 있는 방안을 제안하고 그 효용성에 대해 분석하였다. 8개 건축물 지점에서 평균 30회 이상 Wi-Fi AP 네이밍 위치 확인 및 전파세기를 측정하도록 위치 측위 서버에 요청하고, 수신된 측위 결과 좌표값을 분석하는 방식으로 위치정보의 정확도와 오차범위를 확인하였다. 기존 기지국 기반 위치 오차값 263m에 대비해 최대 93% 이상 범위를 축소할 수 있었고, 8개 지점의 최소·최대 오차값은 4.137m ~ 14.037m, 평균오차는 9.525m로 확인되었다. 위치정보 유무에 따라 인명구조에 소요되는 시간을 3가지 상황에 대해 비교한 결과, 화재진압 및 인명구조에 소요되는 측정시간 결과는 위치정보가 정확하게 소방대원에게 제공되었을 경우 구조활동에 소요되는 시간이 10분 50초로 나타났으나, 위치정보가 전혀 없는 경우 45분 이상 소요되었다. 스마트폰 Wi-Fi AP을 이용하여 건축물 내 구조대상자 위치정보를 정확하게 구조대원에게 제공함을 통해, 사고 현장에서 탐색에 소요되는 시간을 단축시킴으로써, 인명구조 및 골든타임 확보에 제안 시스템이 효과적인 것으로 분석되었다.

• 한국재난정보학회 논문집
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• 제10권2호
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• pp.200-207
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• 2014

이 연구에서는 '기계경비 112신고 기준'인 감독명령 제2013-1호를 분석하고 정책적 과제를 제시하였다. 이 감독명령은 기계경비업체의 출동대응의무 등 독자적인 범죄예방 능력 확보와 통계기반 구축을 위해 확인신고를 원칙으로 하고 긴급신고의 대상을 특정하는 선별신고 제도의 시행을 규정하고 있다. 선별신고제도의 목적을 달성하기 위한 정책적 과제로 첫째, 통계기반의 구축을 위한 오경보와 오신고, 비상버튼과 감지신호에 대한 용어의 정립과 기계경비원을 대체할 적절한 용어의 개발이 필요하다. 둘째, 기계경비업체는 이 감독명령의 112신고 기준을 준수하기 위한 대응체제를 구축하여야 한다. 셋째, 경찰은 선별신고제도의 긴급신고 대상 설정에 대한 재검토가 있어야 한다. 넷째, 이 감독명령을 엄정하게 시행하기 위한 행정규제와 감독의 강화가 요구된다.

• Structural Engineering and Mechanics
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• 제62권2호
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• pp.197-208
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• 2017

Among various retrofitting strategies, use of semi-active control for retrofitting a building structure has gained momentum in recent years. One of the techniques for such retrofitting is to connect a weaker building to an adjacent stronger building by semi-active devices, so that performances of a weaker building are significantly improved for seismic forces. In this paper, a ten storey weaker building is connected to an adjacent stronger building using magneto-rheological (MR) dampers, for primarily improving the performance of the weaker building in terms of displacement, drift and base shear. For this, a fuzzy logic controller is specifically developed by fuzzyfying the responses of the coupled system. The performance of the control strategy is compared with the passive-on and passive-off controls. Pounding Mitigation between the two buildings is also investigated using all three control strategies. The results show that there exists a fundamental frequency ratio between the two buildings for which maximum control of the weaker building response takes place with no penalty on the stronger building. There exists also a fundamental frequency ratio where control of the weaker building response is achieved at the expense of the amplification of the stronger building. However, coupling strategy always improves the possibility of pounding mitigation.

• Smart Structures and Systems
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• 제17권3호
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• pp.471-489
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• 2016

Modal identification based on ambient vibration data has attracted extensive attention in the past few decades. Since the excitation for ambient vibration tests is mainly from the environmental effects such as wind and traffic loading and no artificial excitation is applied, the signal to noise (s/n) ratio of the data acquired plays an important role in mode identifiability. Under ambient vibration conditions, certain modes may not be identifiable due to a low s/n ratio. This paper presents a study on the mode identifiability of an instrumented cable-stayed bridge with the use of acceleration response data measured by a long-term structural health monitoring system. A recently developed fast Bayesian FFT method is utilized to perform output-only modal identification. In addition to identifying the most probable values (MPVs) of modal parameters, the associated posterior uncertainties can be obtained by this method. Likewise, the power spectral density of modal force can be identified, and thus it is possible to obtain the modal s/n ratio. This provides an efficient way to investigate the mode identifiability. Three groups of data are utilized in this study: the first one is 10 data sets including six collected under normal wind conditions and four collected during typhoons; the second one is three data sets with wind speeds of about 7.5 m/s; and the third one is some blind data. The first two groups of data are used to perform ambient modal identification and help to estimate a critical value of the s/n ratio above which the deficient mode is identifiable, while the third group of data is used to perform verification. A couple of fundamental modes are identified, including the ones in the vertical and transverse directions respectively and coupled in both directions. The uncertainty and s/n ratio of the deficient mode are investigated and discussed. A critical value of the modal s/n ratio is suggested to evaluate the mode identifiability of the deficient mode. The work presented in this paper could provide a base for the vibration-based condition assessment in future.

• Structural Engineering and Mechanics
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• 제52권3호
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• pp.485-505
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• 2014

This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.

• 한국재난정보학회 논문집
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• 제13권4호
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• pp.442-454
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• 2017

생물테러에 사용되는 생물무기는 세균과 바이러스, 리켓치아, 곰팡이 등을 가공하여 만들어지며, 화학작용제, 방사능작용제와 함께 대량살상무기(Weapons of Mass Destruction, WMD)로 분류되어진다. 생물무기는 다른 대량살상무기들에 비하여 개발과 생산의 용이성, 저렴한 비용, 은닉살포가 가능하다는 운용상 이점들이 존재한다. 본 논문은 생물무기 개발이 이루어진 역사와 현존하는 생물학적 위협에 대해 분석하고, 생물작용제의 물리적 특성과 인체내 감염기작을 기초로 생물무기 공격으로 인한 사회적 영향을 예측하였다. 스벨드롭스크 탄저균유출사고, 아랄스크 두창발생, 2001년 탄저테러 등 생물무기관련 역사적 사례들에서 사고 인지형태, 작용제 오염확산범위와 피해자의 질병특성을 분석한 결과, 생물테러는 공격 즉시 인지가 어렵고, 광범위한 확산이 가능하여 대규모 노출자를 발생시키며, 호흡기관련 중증질환을 일으켜 보건 의료기관에 막대한 부담을 일으킬 것이라는 사실을 발견하였다. 이를 토대로 생물테러에 효과적으로 대응하기 위해서 요구되는 보건대응역량을 제시하였다. 효과적인 증후군감시체계 및 관련질병 보고체계를 운영하여 신속히 이상징후를 파악해야하며, 실험실진단체계를 통해 병원체의 확진을 실시하여야한다. 또한 보건기관은 역학조사 시 수사기관과의 공조를 통해 잠재적노출자를 명확히 규명하여야 하며, 마지막으로 인적 물적 자원을 효율적으로 운용하여 집단예방조치가 효과적으로 이루어지도록 되어야할 것이다. 이러한 보건대응역량을 지속적으로 강화한다면 생물테러위협에 성공적으로 대응할 수 있을 것이다.