• 대한안전경영과학회지
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• 제9권1호
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• pp.37-49
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• 2007

The tower cranes are widely used in very useful construction machine the sites of constructing high-structure and have a structural sensitiveness. Therefore, the accidents have often happened due to the deficiency of laborer's understanding and lack of safety of structure. Till now, as we have research and studied above, we can properly protect accidents by construction equipments particularly crane as well as most disasters which occur frequently in construction site. The goal of this study is the safety inspection model of the tower crane a construction site, which preventible the collapse accident of tower crane which is constructed by using the correcting frame. In order to accomplish the goal of this study, the field survey, the reference investigation and the structure analysis were performed for the collapse accident of tower crane using the correcting data. This study will be proposed a build-up solutions about operating and release of safety constructions and researched about software safety estimation. Also, preventing safety problems of Tower Crane Construction site as applying safety estimation program and laws and regulations. As a result, The real time control of tower crane inspection system is implemented by to illustrate the application of the adopted optimal design model.

• Advances in concrete construction
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• 제1권1호
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• pp.29-44
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• 2013

Post earthquake fire (PEF) can lead to the collapse of buildings that are partially damaged in a prior ground-motion that occurred immediately before the fire. The majority of standards and codes for the design of structures against earthquake ignore the possibility of PEF and thus buildings designed with those codes could be too weak when subjected to a fire after an earthquake. An investigation based on sequential analysis inspired by FEMA356 is performed here on the Life-Safety performance level of structures designed to the ACI 318-08 code after they are subjected to two different earthquake levels with PGA of 0.35 g and 0.25 g. This is followed by a four-hour fire analysis of the weakened structure, from which the time it takes for the weakened structure to collapse is calculated. As a benchmark, the fire analysis is also performed for undamaged structure and before occurrence of earthquake. The results show that the vulnerability of structures increases dramatically when a previously damaged structure is exposed to PEF. The results also show the damaging effects of post earthquake fire are exacerbated when initiated from second and third floor. Whilst the investigation is for a certain class of structures (regular building, intermediate reinforced structure, 3 stories), the results confirm the need for the incorporation of post earthquake fire in the process of analysis and design and provides some quantitative measures on the level of associated effects.

• Earthquakes and Structures
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• 제22권6호
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• pp.571-584
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• 2022

The residual displacement ratio (RDRs) response spectra have been generally used as an important means to evaluate the post-earthquake repairability, and the ratios of residual to maximum inelastic displacement are considered to be more appropriate for development of the spectra. This methodology, however, assumes that the expected residual displacement can be computed as the product of the RDRs and maximum inelastic displacement, without considering the correlation between these two variables, which inevitably introduces potential systematic error. For providing an adequately accurate estimate of residual displacement, while accounting for the collapse resistance performance prior to the repairability evaluation, a probability-based procedure to estimate the residual displacement demands using the nonlinear static analysis (NSA) is developed for single-degree-of-freedom (SDOF) systems. To this end, the energy-based equivalent damping ratio used for NSA is revised to obtain the maximum displacement coincident with the nonlinear time history analysis (NTHA) results in the mean sense. Then, the possible systematic error resulted from RDRs spectra methodology is examined based on the NTHA results of SDOF systems. Finally, the statistical relation between the residual displacement and the NSA-based maximum displacement is established. The results indicate that the energy-based equivalent damping ratio will underestimate the damping for short period ranges, and overestimate the damping for longer period ranges. The RDRs spectra methodology generally leads to the results being non-conservative, depending on post-yield stiffness. The proposed approach emphasizes that the repairability evaluation should be based on the premise of no collapse, which matches with the current performance-based seismic assessment procedure.

• International Journal of Advanced Culture Technology
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• 제10권4호
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• pp.511-517
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• 2022

Recently, due to rapid climate change, the population of honey bees has decreased, posing a great threat to the existence of the Earth's ecosystem. In particular, the colony collapse phenomenon in which bees disappeared nationwide in early 2022 had devastating consequences for beekeepers. In order to solve the problems of beekeeping due to climate change, it is urgent to develop a system that can monitor the situation inside the hive through various IoT sensors. This paper develops a system that can measure the activity of bees inside the hive and uses it to measure the number of times of entry and exit of the hive. The data measured by the developed system can be monitored in real time on a smartphone through the cloud server. The system developed in this paper can monitor the ecology of bees according to climate change and measure internal and external bee activities. Using this method, it is possible to check in advance for the colony collapse phenomenon in which bees disappeared in early 2022. This is very meaningful in that it presents an alternative that can identify the cause of the problem through early detection.

• Steel and Composite Structures
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• 제41권5호
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• pp.713-730
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• 2021

The seismic performance of rigid steel frames is widely investigated, but that of semi-rigid (SR) steel frames are not studied extensively, especially for near-field earthquakes. In this paper, the performances of five and ten-story steel SR frames having different degrees of semi-rigidity are evaluated at four performance points in the four different deformation states, namely, the elastic, elasto-plastic, plastic, and near collapse states. The performances of the SR frames are measured by the response parameters including the maximum values of the top floor displacement, base shear, inter-story drift ratio, number of plastic hinges, and SRSS of plastic hinge rotations. These response parameters are obtained by the capacity spectrum method (CSM) using pushover analysis. The validity of the response parameters determined by the CSM is evaluated by the results of the nonlinear time history analysis (NLTHA) for both near and far-field earthquakes at different PGA levels, which are consistent with the performance points. Results of the study show that the plastic hinges of SR frame significantly increase in the range of plastic to near-collapse states for both near and far-field earthquakes. The effect of the degree of semi-rigidity is pronounced only at higher degrees of semi-rigidity. The predictions of the CSM are fairly well in comparison to the NLTHA.

• Computers and Concrete
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• 제31권5호
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• pp.371-384
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• 2023

Precast roofing systems employing prestressed elements often serve as smart structural solutions for the construction of industrial buildings. The precast concrete elements usually employed are highly engineered, and often consist in thin-walled members, characterised by a complex behaviour in fire. The present study was carried out after a fire event damaged a precast industrial building made with prestressed beam and roof elements, and non-prestressed curved barrel vault elements interposed in between the spaced roof elements. As a consequence of the exposure to the fire, the main elements were found standing, although some locally damaged and distorted, and the local collapse of few curved barrel vault elements was observed in one edge row only. In order to understand and interpret the observed structural performance of the roof system under fire, a full fire safety engineering process was carried out according to the following steps: (a) realistic temperature-time curves acting on the structural elements were simulated through computational fluid dynamics, (b) temperature distribution within the concrete elements was obtained with non-linear thermal analysis in variable regime, (c) strength and deformation of the concrete elements were checked with non-linear thermal-mechanical analysis. The analysis of the results allowed to identify the causes of the local collapses occurred, attributable to the distortion caused by temperature to the elements causing loss of support in early fire stage rather than to the material strength reduction due to the progressive exposure of the elements to fire. Finally, practical hints are provided to avoid such a phenomenon to occur when designing similar structures.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.175-176
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• 2023

The masonry structure is constructed by cement mortar binding material of brick objects and uses reinforced hardware(connected hardware or wall tie) together when building. However, over time, the corrosion of reinforced steel and the deterioration of joint mortar as well as bricks cause the risk of collapse. In particular, when the externally decorated brick wall is installed on the concrete girder for each floor, the angle bracket is not constructed or corroded, the full-layer weight load is applied to the wall of 0.5B, which is an example of full-scale or collapse. As a result of the evaluation, it was confirmed that the performance was improved compared to the existing bracket, and we plan to carry out a real-life test and long-term performance review of the building using the bracket in the future.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.509-512
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• 2003

Dehydration and micro crack thermal expansion occur in cement hydrates of concrete structure heated by fire for a long time. The characteristic of concrete exposed to high temperature can be analyzed from distribution of porosity and pore size. Porosity showed a tendency to increase irrespective of specimen types. This is due to both the outbreak of collapse of gel comprising the cement and a micro crack by heating. Porosity did not affect the variety of specimen and increased with the same tendency throughout every specimen. In addition, the deteriorate of compressive strength resulted from increase in porosity

• 한국수자원학회논문집
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• 제41권11호
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• pp.1135-1142
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• 2008

하천제방의 붕괴 요인중 구조물(배수통문) 주변 제방의 붕괴는 전체 요인의 l0% 이상을 차지하고 있으며, 특히 2002년 홍수시 낙동강에서 발생한 제방 유실 지점은 거의 배수통문 주위에서 발생하였다. 이러한 제방 파괴는 이질 재료인 통문 구조물과 제체 접합부 사이에 공극이나 공동이 형성된 후 홍수시 내부 침식으로 인해 공동이 확대되어 발생하는 파괴구조를 가지고 있다. 이러한 상황에서 하천제방의 안전관리를 위해 배수통문 주변의 공동발생 여부 혹은 공동내의 흐름 인지 등을 목적으로 한 연구가 진행되고 있으며, 본 연구에서는 Flex센서와 Fiber bragg grating 센서의 변이 계측에 대한 실험을 통해 두 센서의 특징을 파악하고, 하천제방의 안전관리를 위해 보다 적합한 센서의 결정이 가능하도록 하였다. 실험결과 현 시점에서 변이 계측과 관련하여 계측치의 일관성, 미소변이 계측 등 Flex센서의 단점을 보완할 수 있는 FBG센서의 여러 특징을 확인할 수 있었다.

• 지질공학
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• 제24권4호
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• pp.501-510
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• 2014

화구호를 가지고 있는 화산에서 분화는 단순히 화산분출물에 의한 피해와 더불어 칼데라 호수에 저장된 많은 양의 물이 방류하여 대규모의 재해를 유발한다. 최근 백두산 분화의 전조가 관측되고 있고 백두산의 분화 시 천지칼데라호로 인해 예상되는 화산성 홍수의 피해를 추정하고 화산 재해에 대비하여 사회적, 경제, 문화, 정치적 파급 효과에 대한 정보와 적절한 대응방안의 마련이 필요하다. 백두산의 화산활동으로 인하여 천지의 외륜산이 붕괴되고 천지에 저장된 물이 방류될 경우를 가정하여 2차원 평면 흐름 수치모형을 이용하여 잠재적 홍수피해 위험지역을 파악하였다. 방류되는 물의 양은 외륜산 붕괴 메커니즘을 표현하는 미분방정식을 풀어 시간의 함수로 유량곡선을 작성하였다. 구성된 유량곡선을 수치모형의 상류부 경계조건으로 하였고, 하류부 경계조건은 백산수고의 수위를 설정하여 10일 동안 송화강 유역으로 흐르는 홍수피해 지역을 모의하였다. 지형자료는 USGS의 SRTM3 수치 표고 자료를 바탕으로 $100m{\times}100m$의 격자(Grid)를 생성하였다. 지표면 특성은 인공위성 MODIS자료를 사용하여 유출곡선지수와 조도계수를 산정하였다. FLO-2D로 모의한 침수지역을 위성영상과 중첩하여 침수면적을 계산한 결과, 외륜산(outer rim) 붕괴가 발생하고 붕괴율이 10 m/hr인 경우 이도백하부근 도심지 면적 $22.4km^2$ 중 80%정도가 침수되며, 붕괴율이 100 m/hr인 경우 98%의 지역이 침수되는 것으로 나타났다.