• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.5
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• pp.453-461
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• 2015

In order to manage the deflection of a curved PCT girder bridge during construction, a GPS receiver was installed at the spot predicted to be the weak point during the incremental launching so as to measure the deflection at each construction stage. The deflections obtained in the experiment were compared with those derived from the monitoring of stress, temperature and inclination. The comparative analysis of the GPS measurement and analytical values obtained from finite element modeling with respect to the launching distance showed that the measured values differ by 0.6 to 1.6 times to the analytical results. This difference could be significantly reduced by thermal calibration. From the analysis of the behavioral pattern of the bridge, deflection occurred during construction in the concrete tip due to the deflection at the head of the nose at the 95m and 75m-spots, and compression and tension developed respectively at the compression weak zone and tension weak zone. The application of GPS appeared to enable more efficient management of the deflection during the erection of the curved PCT girder bridge and is expected to be helpful for the prediction and management of the behavior in future ILM construction sites.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.125-131
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• 2011

This research aims to investigate the cause of the occurrence of a weak road drainage section scientifically and specifically through a site survey for a poorly drained section occurring due to rainfalls during road operation. This paper deeply reviewed the existing research results and current situation data on the poorly drained sections accumulated in Korea Expressway Corporation in order to investigate the cause of the occurrence of a weak road drainage section, and deeply verified and analyzed the weak sections for the road surface drainage facilities and the other road drainage facilities by visiting the expressway controlled by the 6 local headquarters and 33 branches of Korea Expressway Corporation. As a result of site surveys for the weak road drainage sections, i) in a road surface section, occurrence of ponding in the road shoulder pavement due to slope changes, bad collection of water in the collecting well at a median strip, shortage of road shoulder dike height, and inferior construction, etc. was analyzed to be the main cause of the occurrence of poorly drained sections, and ii) in a road neighborhood section, the occurrence of pavement height difference in a main road and shoulder section due to inferior ditches on a slope and the bad drain age at the inlet and outlet of a culvert due to soil deposits, debris, etc. were analyzed to be the main cause of the occurrence of weak sections. Proposed as a plan to improve the poorly drainage section of road were i)calculation of capacity through material changes at the ditch, enhancement of vertical sections and hydraulic analysis in terms of construction and other aspects, ii)derivation of a combined slope considering a slope and a vertical linearity and maintenance of proper distance between drainage structures in a vertical concave section in terms of geometrical structure, and iii)calculation of the drainage facility installation interval using a minutely rainfall intensity formula and a non-uniform flow analysis technique in terms of hydraulics and hydrologics and prompt removal of rainfalls from the road surface according to a linear drainage method.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.248-248
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• 2018

새만금 종합개발계획(정부, 2011)에 따른 내부개발의 완료시점은 2030년이며, 방수제 공사와 준설 등과 같이 만경강 및 동진강 유역 내 흐름을 변화시킬 수 있는 공사를 포함하고 있으므로 현재와 2030년의 하천 및 호의 수리특성은 다를 것이라 예상된다. 2030년까지 준설상황 등을 예측하여 반영하는 것은 사실상 불가능하기 때문에 새만금 종합개발계획에서 제시하고 있는 내부개발의 완료시점을 기준으로 홍수사상을 모의하였다. 새만금 호의 물리적인 변화는 수리특성의 변화로 이어질 수 있으며, 이는 상류지역으로 전파가 될 수 있으므로 호내 뿐만 아니라 만경강과 동진강 전역에 대한 홍수시의 수리특성을 검토하였다. 새만금 호와 연결된 만경강과 동진강의 설계홍수량은 대부분의 구간에서 100년 빈도이기 때문에 본 연구에서는 100년 빈도 홍수사상에 대한 분석을 기초로 홍수위 검토를 수행하였고, RCP8.5 시나리오를 적용한 100년 빈도 홍수량과 500년 빈도 홍수량에 대한 추가적인 연구를 수행하였으며, 이 결과를 토대로 취약지구 분석 및 대책 등을 제시하였다. 수치모의는 Delft3D를 이용하였으며, 새만금 유역의 동진강 지구의 실측치와 비교함으로써 모델의 적용성을 검증하였다. 서해안 조위 특성상 새만금 방조제는 조위 영향이 크므로, 이에 본 연구에서는 외조위의 특성을 고려하기 위해 새만금 유역 주변의 12개 조화상수(tidal harmonic constant)를 이용하여 조위에 대한 모의를 별도로 수행하고, 이 결과를 배수갑문의 경계조건으로 이용하였다. 상류 경계조건은 하천기본계획상에 제시된 하천은 이를 이용하였으며, 그 외의 소하천은 유역면적을 이용한 계산법을 사용하여, 선형적 면적 비유량(Specific Discharge, SD) 방법을 적용하여 본류의 유량에 부가하는 방식으로 수행하였다. 수치해석 결과, 준설 구간의 수위는 전반적으로 저하되었으며, 거리에 따른 수면의 경사를 분석한 결과 기존의 하천구역이 준설 등으로 인하여 호수의 특성으로 변화된 것으로 확인하였다. 본 연구에서 취약지구는 홍수위가 제방고의 약 80% 이상 되는 지역으로 결정하였으며, 이를 토대로 취약지구 분석을 수행한 결과 기존 100년 빈도에서 1지점, RCP 8.5 시나리오가 적용된 100년 빈도에서 88지점, 500년 빈도에서 125지점이 잠재적인 치수 위험이 있는 것으로 파악되었다. 기존의 1차원 연구결과와는 차이가 있는 부분은, 다수의 취약지구가 만곡부 또는 합류부 인근에 위치한 것이다. 향후 이러한 상대적인 치수 취약지점에 대해 정밀하고 국부적인 연구를 수행하여 정확한 홍수위 예측을 수행해야 할 것이다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2023.11a
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• pp.105-106
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• 2023

본연구는 콘크리트 타설과정에서 반복되는 펌프카 사고를 예방하기 위해서 설계 및 제작의 품질관리와 현(現))정기검사 기준을 개선해야 한다는 점을 제안하며, Booms 파단 사고 예방대책 제시가 목적이고, 최근 1~2년 사이에 발생한 펌프카 기계적 결함 사고의 현황조사와 사고 특징을 분석하고, 펌프카 장비의 검사기준 및 조정원의 자격과 기능교육 기준 마련의 필요성 확인한다. 붐대의 안전성 확인하기 위해서는 선행연구의 구조적 안전성 평가와 최대응력 부위에 대한 선행연구의 유한요소 해석모델 자료를 재분석하고, 2단 붐이 타설중 가장 많은 힘을 받는지와 파괴 가능성을 확인한다. Booms의 유한요소 모델 해석 결과 펌프카는 타설 과정에서 진동으로 피로 하중을 받을 수 있다는 동적해석과 정적해석 재검토 결과 가장 취약한 부위는 2단 붐이었으며, 2st 붐은 제작단계에서 부재 두께를 증가시키고, 상단부에 철판 보강을 권장한다. 펌프카 사고를 방지하기 위해서는 제조사는 생산단계에서 2st Boom 상단에 보강판 부착이 필요하고, 정기검사 비용 현실화와 비파괴 검사를 의무 검사로 반영이 필요하다고 제언한다.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.470-481
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• 2003

Exterior plate-column connection has an unsymmetrical critical section for eccentric shear of which perimeter is less than that of interior connection, and hence, around the connection, unbalanced moment and eccentric shear are developed by both gravity load and lateral loads. Therefore, exterior connection is susceptible to punching shear failure. Current design provision cannot accurately explain strength of existing experiments, partly due to the complexity in the behavior of exterior plate-column connection, or partly due to the theoretical deficiency of the strength analysis model adopted. In the present study, nonlinear finite element analyses were performed for exterior connections belonging to continuous flat plate. For each direction of lateral load, the behavior and strength of exterior plate-column connection were quite different. Based on the numerical result, strength prediction model for exterior connection was proposed for each direction of lateral load. Compared with existing experiments, the proposed method was verified.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.110-118
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• 2018

Due to recent earthquakes, there is a growing awareness that Korea is not a safe zone for earthquakes any more. Therefore, the review of various aspects of the seismic safety of the infrastructures are being carried out. Because of the characteristics of the underground structure buried in the ground, the electric power utility tunnels must be considered not only for the inertia and load capacity of the structure itself but also the characteristics of the surrounding soils. An extensive and accurate numerical analysis is inevitably required in order to consider the interaction with the ground, but it is difficult to apply the soil-structure interaction analyses, which generally requires high cost and extensive time, to all electric power utility tunnel structures. In this study, the major design variables including soil characteristics are considered as independent variables, and the seismic safety factor, which is the result of the numerical analysis, is considered as a dependent variable. Thus, a method is proposed to select vulnerable electric power utility tunnels with low seismic safety factor while excluding costly and time-consuming numerical analyses through the direct correlation analysis between independent and dependent variables. Equations of boundary limits were derived based on the distribution of the seismic safety factor and the cover depth and rebar amounts with high correlation relationship. Consequently, a very efficient and simple approach is proposed to select vulnerable electric power utility tunnels without intensive numerical analyses. Among the 108 electric power utility tunnels that were investigated in this paper, 30% were screened as fragile structures, and it is confirmed that the screening method is valid by checking the safety factors of the fragile structure. The approach is relatively very simple to use and easy to expand, and can be conveniently applied to additional data to be obtained in the future.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.165-172
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• 2013

Power generating unit structures are designed and built to meet standard to secure its safety for expected life time. As the structures have been exposed to combined environment, degradation of structure material is accelerated and it can cause unexpected damage; evaluating precise mechanical properties of weak site like welded area is an essential research area as it is directly connected to safety issues. Existing measuring technique like tensile test requires specific size in testing specimen yet it is destructive method which is hard to apply on running structures. To overcome above mentioned limitation, IIT is getting limelight as it is non-destructive and simple method. In this study, latest technique is introduced to evaluate tensile property and residual stress by analyzing stress field occurs under the indenter while IIT is performed. Test on welded area, the weak site of nuclear structures have been practiced and confirmed that IIT can be usefully applied to evaluate integrity in industry.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.159-160
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• 2015

현재 한국 전력계통의 경우 신재생전원의 보급 확대 및 전력수요의 증대에 따라, 국가적으로 대정전 사태 사전방지 등 신뢰도 높은 전력전송을 위한 노력으로서 HVDC 송전기술 도입이 폭넓게 검토되고 있다. 우리나라 전력 계통은 송전망 건설이 지연되고 있는 상황에서 수도권 부하는 증가하고, 발전 단지는 대규모화되고 있어 전력 계통 사고 및 그 파급이 점점 대형화되고 있다. 증가하는 전력수요에 대응하여 발전소를 건설해도 송전망 건설이 어려워 전력전송 능력이 점점 취약해지고 있다. 초대형화된 발전단지와 취약해진 송전망은 송전선의 혼잡을 증가시켜 불시에 기능정지가 될 경우, 사고의 영향력은 광역 정전으로 발전될 만큼 매우 커질 수 있다. 따라서 제 6차 전력수급 기본계획에 신규 반영되는 대규모 발전소의 계통 연계방안과 계통 신뢰도 측면으로 고려하여 장거리 전력 전송을 위한 HVDC 적용이 검토 됨에 따라 국내 HVDC 적용의 신규 시장이 될 가능성이 높다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.843-850
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• 2020

The purpose of this study is to evaluate the structural risk and weakness of a railway tank car through nonlinear collision analysis according to overseas collision safety standards. The goal is to propose a crash safety design guideline for railway tank cars for transporting dangerous goods in Korea. We analyzed the buffer impact test procedure of railway freight cars prescribed in EN 12663-2 and the tank puncture test criteria prescribed in 49CFR179. A nonlinear finite element model according to each standard was modeled using LS-DYNA, a commercial finite element analysis solver. As a result of the buffing impact test simulation, it was predicted that plastic deformation would not occur at a collision speed of 6 km/h or less. However, plastic deformation was detected at the rear of the center sill and at the tank center supporting the structure at a collision speed of 8 km/h or more. As a result of a head-on test simulation of tank puncture, the outer tank shell was destroyed at the corner of the tank head when 4% of the kinetic energy of the impacter was absorbed. The tank shell was destroyed in the area of contact with the impacter in the test mode analysis of tank shell puncture when the kinetic energy of the moving vehicle was reduced by 30%. Therefore, the simulation results of the puncture test show that fracture at the tank shell and leakage of the internal material is expected. Consequently, protection and structural design reinforcement are required on railway tank cars in Korea.

• Journal of the Korean Institute of Gas
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• v.16 no.1
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• pp.46-50
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• 2012

The performance of the Type3 hydrogen composite cylinder whose pressure is 70 MPa using hydrostatic cycling test equipment was evaluted in this study. It also includes the finite element method analysis on the performance of the cylinder when the pressure is applied. As a result, cylinder body parts of the Type3 hydrogen composite cylinder, which draws attention with its safe status and the lightness, was ruptured first and the same result has been found out through the finite element method. The dome knuckle and the cylinder body were proved as the weakest parts since the cylinder body parts was expanded under the pressure.