• Wind and Structures
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• 제29권5호
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• pp.339-359
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• 2019

Pre-stressed concrete poles are among the supporting systems used to support transmission lines. It is essential to protect transmission line systems from harsh environmental attacks such as downburst wind events. Typically, these poles are designed to resist synoptic wind loading as current codes do not address high wind events in the form of downbursts. In the current study, the behavior of guyed pre-stressed concrete Transmission lines is studied under downburst loads. To the best of the authors' knowledge, this study is the first investigation to assess the behaviour of guyed pre-stressed concrete poles under downburst events. Due to the localized nature of those events, identifying the critical locations and parameters leading to peak forces on the poles is a challenging task. To overcome this challenge, an in-house built numerical model is developed incorporating the following: (1) a three-dimensional downburst wind field previously developed and validated using computational fluid dynamics simulations; (2) a computationally efficient analytical technique previously developed and validated to predict the non-linear behaviour of the conductors including the effects of the pretension force, sagging, insulator's stiffness and the non-uniform distribution of wind loads, and (3) a non-linear finite element model utilized to simulate the structural behaviour of the guyed pre-stressed concrete pole considering material nonlinearity. A parametric study is conducted by varying the downbursts locations relative to the guyed pole while considering three different span values. The results of this parametric study are utilized to identify critical downburst configurations leading to peak straining actions on the pole and the guys. This is followed by comparing the obtained critical load cases to new load cases proposed to ASCE-74 loading committee. A non-linear failure analysis is then conducted for the three considered guyed pre-stressed concrete transmission line systems to determine the downburst jet velocity at which the pole systems fail.

• 한국해안·해양공학회논문집
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• 제35권3호
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• pp.57-66
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• 2023

본 논문에서는 해상풍력발전단지의 경제성을 파악하고자 발전단가 측면에서 해상풍력 지지구조물 형식 및 시공 방법에 따른 균등화발전비용(levelized cost of energy, LCOE)의 차이를 분석하고 LCOE의 주요 구성 요소에 따른 민감도 분석을 실시하였다. 연구대상 현장으로 국내 서남해 해상풍력실증단지를 선정하였으며, 설치 기수에 따른 공사비를 분석하였다. LCOE 민감도 분석 결과 설비이용률, 터빈 관련 비용, 가중평균자본비용 그리고 BOS(balance of system) 관련 비용의 순서로 LCOE에 대한 민감도가 높은 것으로 나타났다. 아울러 국내 해상풍력 지지구조물로 주로 적용되었던 포스트파일링(post-piling) 재킷 공법을 기본안으로 선정하여 공사비를 산출한 후, 시공 방법을 프리파일링(pre-piling)으로 변경한 재킷 공법과 트라이포드(tripod) 공법의 초기투자비용을 비교하였다. 그에 따른 LCOE를 분석한 결과, 프리파일링 재킷 공법의 경우 고가의 템플릿이 필요하지만, 강재 소모량이 적고, 설치규모가 대형화할수록 시공 기간이 단축되어 전체 공사비 및 LCOE가 낮아지며 경제성이 향상되는 것을 확인하였다.

• 대한지역사회영양학회지
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• 제18권3호
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• pp.243-256
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• 2013

The purpose of this study was to evaluate the effectiveness of Centers for Child-care Foodservice Management (CCFSM)'s support on menu management in child-care centers and kindergartens by comparing two perspectives of pre-support vs. post-support and established vs. non-established. To evaluate dietary variety, we used methods that considered both Dietary Diversity Score (DDS) and Dietary Variety Score (DVS). For surveying pre-support and post-support state by CCFSM, we collected and analyzed menus of June and September, 2012, targeting 7 CCFSM supported institutions. Meanwhile, for surveying state in CCFSM established and non-established areas, we collected and analyzed menus of June, 2012, which were implemented in institutions in CCFSM established (181 places) and non-established (106 places) areas. The results of evaluation on the dietary support by CCFSM showed that post-supporting state by CCFSM (95.3%) was significantly higher than pre-supporting state (77.2%) (p < 0.001) and established areas (87.4%) were significantly higher than non-established ones (77.2%) (p < 0.05) on 'Meeting the DRI for infant'. Evaluation of dietary variety between pre- and post-support state by CCFSM showed that post-support state (total 77.3 point) was higher than pre-support state (total 76.4 point). Evaluation of dietary variety between established and non-established areas showed that established areas (total 81.1 point) were significantly higher than non-established ones (total 77.1 point) (p < 0.001). Therefore, it is considered that dietary support service conducted by CCFSM contributes to improve variety level of diet provided by child-care centers and kindergartens.

• 터널과지하공간
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• 제15권1호
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• pp.39-46
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• 2005

터널 단층대에서 수평시추로 조사한 막장전방의 암반 상태를 공학적 암반분류법인 RMR값으로 평가하였고 이를 터널 굴착 후 막장을 관찰하여 결정한 RMR값과 비교 분석하였다. 수평시추로 예측한 RMR값은 비교적 정확하여 터널 굴진 후 막장을 관찰하여 구한 RMR값과 큰 차이가 없었다. 그러나 일부 구간에서는 수평시추와 막장관찰로 구한 RMR값의 차이가 약 50까지 발생하였고 이를 RMR 평가항목으로 분석한 결과 불연속면의 상태에 대한 평점에서 24의 차이가 나타났고 암질지수와 단축압축강도 평점에서 각각 15와 13의 차이로 나타났다. 두 방법에서 평가한 RMR값의 차이를 줄이기 위해서는 터널 내 수평시추공의 위치를 터널의 안정성에 가장 큰 영향을 줄 수 있는 곳으로 선정하고 불연속면의 상태에 대한 평가는 불연속면의 연속성, 분리 틈, 풍화도 등 5개의 소항목 각각에 대해 5단계로 구분한 세부평점을 적용하여야 할 것이다.

• International Journal of Railway
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• 제5권4호
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• pp.144-147
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• 2012

New transport technologies have been rapidly developed and various transport systems are ready to introduce. However, there no exists effective decision making tools for pre-feasibility studies on transport systems. The pre-feasibility studies should provide reliable solutions about whether a certain transport system is feasible or not by cost-benefit analysis and effectiveness test of enhancing regional economy. This study introduces the smart transport investment/information system (SMARTIS) for supporting decision making with ease, fast and reliable methods. The SMARTIS incorporates travel demand estimates into the process of feasibility studies with automatic data processing methods to give reliable solutions quickly. The SMARTIS is expected to be informative for transit agencies, planners, and operators.

• Earthquakes and Structures
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• 제8권3호
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• pp.801-820
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• 2015

The seismic sequence which hit the Northern Italian territory in 2012 produced extensive damage to reinforced concrete (RC) precast buildings typically adopted as industrial facilities. The considered damaged buildings are constituted by one-storey precast structures with RC columns connected to the ground by means of isolated socket foundations. The roof structural layout is composed of pre-stressed RC beams supporting pre-stressed RC floor elements, both designed as simply supported beams. The observed damage pattern, already highlighted in previous earthquakes, is mainly related to insufficient connection strength and ductility or to the absence of mechanical devices, being the connections designed neglecting seismic loads or neglecting displacement and rotation compatibility between adjacent elements. Following the vulnerabilities emerged in past seismic events, the paper investigates the seismic performance of industrial facilities typical of the Italian territory. The European building code seismic assessment methodologies are presented and discussed, as well as the retrofit interventions required to achieve an appropriate level of seismic capacity. The assessment procedure and retrofit solutions are applied to a selected case study.

• Journal of information and communication convergence engineering
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• 제7권4호
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• pp.480-488
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• 2009

A channel-shared modified accelerative pre-allocation wavelength division multiple access (CMAP-WDMA) media access control (MAC) has been proposed for metro-WDMA networks, as an extension of modified pre-allocation wavelength division multiple access (MAP-WDMA) MAC protocol. Similarly, CAP WDMA as an extension of accelerative pre-allocation wavelength division multiple access (AP-WDMA) MAC protocol. Performance of CMAP- and CAP-WDMA was extensively investigated under several channel sharing methods (CSMs), asymmetric traffic load patterns (TLPs), and non-uniform traffic distribution patterns (TDPs). The result showed that the channel utilization of the CMAP-WDMA always outperforms that of CAP-WDMA at the expense of longer channel access delay for channel shared case while CMAP-WDMA provided higher channel utilization at specific network conditions but always shorter channel access delay than CAP-WDMA for non-channel shared case. Additionally both for CMAP- and CAP-WDMA, determining an effective CSM is a critical design issue because TDPs and TLPs can be neither managed nor expected while CSM is manageable, and the CSM supporting the best channel utilization can be recommended.

• 대한수학교육학회지:수학교육학연구
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• 제27권1호
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• pp.137-156
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• 2017

본 연구는 테크놀로지 활용 지원체계의 확대, 교사의 지식과 신념, 교사교육 프로그램의 분석 틀의 문헌연구를 기초로 국내 수학교육과의 관련 교육의 현황과 현안, 발전 방향을 탐색하였다. 강좌개설 및 운영 자료는 설문조사와 강의계획서로 수집한 결과 강의는 수업의 향상을 목적으로 하며 전체 학과의 1/3에 수학교육관련 ICT 강의가 개설되지 않았다. 테크놀로지 통합 예비 중등수학교사교육을 위하여 국가적으로 교육과정의 방향과 세부내용의 부조화, 소프트웨어와 교과서 등 지원 부족 문제 해결을 통한 교육현장 개선과 교사교육의 포괄적, 세부적 방향설정이 중요하며 무엇보다도 테크놀로지 활용 관련 비전의 공유가 필요하다.

• 한국조사연구학회지:조사연구
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• 제12권1호
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• pp.1-30
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• 2011

본 연구의 목적은 선거여론조사에서 유권자의 사전 태도 및 투표 의향과 실제 투표 행동간의 상관성을 분석함으로써 투표결과에 대한 선거여론조사의 예측력을 높이는 방법을 탐색하는 것이다. 지지 후보, 정치적 자기 신뢰와 효능감 및 현재의 이슈에 대한 입장을 통해 사전 태도를 측정하고 투표 참여와 관련하여 투표 의향, 과거 선거에서 투표 참여 및 선거에 대한 관심 정도를 측정했다. 실제 투표행동은 개표 후 사후조사에서 투표 참여 여부와 투표 후보를 질문했고 사전조사와 투표 행동 간의 상관성을 분석하기 위해서 동일인을 대상으로 사전, 사후조사를 실시했다. 사전조사의 투표 의향, 선거 관심도와 과거 투표 참여 등이 실제 투표 참여와 상관성이 컸으며 사전조사의 지지 후보와 실제 투표후보 간에는 변동이 거의 없었다. 또한 인구 특성과 현안에 대한 태도를 통해 지지 후보 무응답자의 투표행동을 예측할 수 있음을 입증했다.

• Coupled systems mechanics
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• 제9권2호
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• pp.147-161
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• 2020

Constructive merging of "basic" systems of different behavior creates hybrid systems. In doing so, the structural elements are grouped according to the behavior in carrying the load into a geometric order that provides sufficient load and structure functionality and optimization of the material consumption. Applicable in all materializations and logical geometric forms is a transparent system suitable for the optimization of load-bearing structures. Research by individual authors gave insight into suitable system constellations from the aspect of load capacity and the approximatemethod of estimating the participation of partialstiffnesswithin the rigidity ofthe hybrid system. The obtained terms will continue to be the basisfor our own research of the influence of variable parameters on the behavior of hybrid systemsformed of glued laminated girder and cable of different geometric shapes. Previous research has shown that by applying the strut-type hybrid systems can increase the load capacity and reduce the deformability ofthe free girder.The implemented parametric analysis pointsto the basic parameterin the behavior of these systems-the rigidity ofindividual elements and the overallstiffnessofthe system.The basic idea ofpre-stressing is that, in the load system or individual load-bearing element, prior to application of the exploitation load, artificially challenge the forcesthatshould optimize the finalsystembehaviorin the overall load. Pre-stressing is possible only if the supporting system orsystem's element possesssufficientstrength orstiffness, orreaction to the imposed forces of pre-stressing. In this paper will be presented own research of the relationship of partial stiffness of strut-type hybrid systemsofdifferentgeometric forms.Conducted parametric analysisofhybridsystemswithandwithoutpre-stressing, and on the example of the glulam-steel strut-type hybrid system under realistic conditions of change in the moisture content ofthe wooden girder,resulted in accurate expressions and diagramssuitable for application in practice.