• Smart Structures and Systems
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• 제11권2호
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• pp.135-161
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• 2013

This work presents a test platform for the assessment and benchmarking of modern actuators which have been specifically developed for the new field and service robotics applications. This versatile platform has been designed for the comparative analysis of actuators of dissimilar technology and operating conditions. It combines a modular design to adapt to linear and rotational actuators of different sizes, shapes and functions, as well as those with different load capacities, power and displacement. This test platform emulates the kinematics of robotic joints while an adaptive antagonist-load actuator allows reproducing the variable dynamic loads that actuators used in real robotics applications will be subjected to. A data acquisition system is used for monitoring and analyzing test actuator performance. The test platform combines hardware and software in the loop to allow actuator performance characterization. The use of the proposed test platform is demonstrated through the characterization and benchmarking of three controllable impedance actuators recently being incorporated into modern robotics.

• Structural Engineering and Mechanics
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• 제15권3호
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• pp.345-365
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• 2003

The adoption of fibre reinforced polymer (FRP) rebars (whose behaviour is elastic-brittle) in reinforced concrete (RC) cross sections requires the assessment of the influence of time-dependent behaviour of concrete on the load-carrying capacity of these sections. This paper presents a method of computing the load-carrying capacity of sections that are at first submitted to a constant long-term service load and then overloaded up to ultimate load. The method solves first a non-linear visco-elastic problem, and then a non-linear instantaneous analysis up to ultimate load that takes into account the self-equilibrated stress distribution previously computed. This method is then adopted to perform a parametric analysis that shows that creep and shrinkage of concrete increase the load-carrying capacity of the cross section reinforced with FRP and allows for the suggestion of simple design rules.

• 대한교통학회지
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• 제35권2호
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• pp.91-104
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• 2017

본 연구에서는 통합모형인 GCAM을 활용한 국내수송부문을 모델링에 대해 논의한다. GCAM은 IPCC 5차 보고서 평가에도 활용된, 국제적으로 널리 쓰이는 모형이다. 그럼에도 불구하고 이를 국내수송부문에 그대로 적용하는 데 상당한 문제가 있다. 첫째, GCAM의 기준년도(2010년) 수송 서비스수요가 국가통계와 일치하지 않다는 점. 둘째, 수송부문 시뮬레이션 결과가 관련 부문별 서비스수요의 과거추이를 제대로 반영하고 못하고 있다는 점이다. GCAM을 활용한 국내 수송부문 모델링에서 가장 중요하게 영향을 미치는 수송서비스수요 항등식을 상세히 점검함으로써, 기준년도의 서비스수요를 국가통계와 일치시키도록 노력하였다. 또 GCAM의 시뮬레이션 결과가 과거 통계추이를 제대로 반영할 수 있도록 기존모형을 점검, 수정하였다. 점검 및 수정결과, 기존 GCAM의 시뮬레이션 결과와 어떤 부분에서 문제가 있는지, 또 수송부문별 과거 서비스 수요의 추이가 어떻게 제대로 반영되고 있는지를 상세히 보고하였다. 본 연구는 향후 수송부문의 정책, 기술평가 및 온실가스저감 대책 마련 등을 위한 시나리오 분석의 기본분석도구로 유용하게 쓰일 수 있을 것으로 보인다.

• 대한기계학회논문집A
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• 제30권8호
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• pp.993-1000
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• 2006

Operating experience of steam generators has shown that cracks of various morphology frequently occur in the steam generator tubes. These cracked tubes can stay in service if it is proved that the tubes have sufficient safety margin to preclude the risk of burst and leak. Therefore, integrity assessment using exact limit load solutions is very important for safe operation of the steam generators. This paper provides global and local limit load solutions for surface cracks in the steam generator tubes. Such solutions are developed based on three-dimensional (3-D) finite element analyses assuming elastic-perfectly plastic material behavior. For the crack location, both axial and circumferential surface cracks, and for each case, both external and internal cracks are considered. The resulting global and local limit load solutions are given in polynomial forms, and thus can be simply used in practical integrity assessment of the steam generator tubes.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.187-188
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• 2016

The purpose of this study is to develop a method of evaluating eco-efficiency of concrete based on environmental load emission, manufacturing cost, and durability in the concrete production process. Eco-efficiency is an advanced concept used to evaluate eco-friendliness of concrete. This technique intends to produce environment-friendly and highly durable concrete while minimizing environmental load on the ecosystem and manufacturing cost based on the results of service life assessment on concrete. This technique can be utilized to efficiently evaluate sustainability of concrete and find methods to improve it. Furthermore, the vision of this study is to contribute to implementation of environment-friendly concrete and construction industry.

• 한국해양공학회지
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• 제29권1호
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• pp.100-110
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• 2015

To meet the increasing demand for energy around the world, offshore and subsea energy development is constantly being conducted. This trend is accompanied by an increasing demand for pipeline installation, which brings numerous problems, including those related to accessibility, high pressure, and corrosion. Among these, corrosion is a primary factor in pipeline fractures, and can cause severe environmental and industrial damage. Hence, accurate corrosion assessment for corroded pipelines is very important. For this reason, the present study investigated the mechanical behavior of an idealized corroded subsea pipeline with an internal/external pressure load using the commercial FEA code ABAQUS. Then, the analysis result was compared with corrosion assessment codes such as ASME B31G, DNV RP F101, ABS. Finally, a fitness-for-service assessment was conducted.

• 대한환경공학회지
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• 제29권6호
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• pp.722-727
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• 2007

전과정평가(Life Cycle Assessment; LCA)는 전과정에 걸친 투입과 산출을 정량화하고, 잠재적인 환경 영향을 평가하는 도구이다. 기존 LCA 방법은 시간을 명확하게 고려하지 않는다는 결함이 있다. 또한 정규화(normalization)단계에서도 시간 경계에 관한 문제가 존재한다. 본 연구의 목적은 시간이 고려된 새로운 LCA 방법을 제안하는 것이다. 본 연구에서 제안하는 새로운 LCA 방법론인 '시간-부하 LCA'는 각각의 전과정단계에서 발생하는 환경 부하를 해당 전과정단계에서 소요되는 시간으로 나누는 것이다. 전과정평가에서 시간 고려를 명확히 함으로써 제품 시스템의 환경 영향에 대한 새로운 관점을 제공할 수 있을 뿐만 아니라 정규화 단계의 시간 단위 불일치를 보완할 수 있다. 시간-부하 LCA의 기본 전제는 같은 양의 환경 부하라 하더라도 짧은 시간 동안 발생하는 환경부하가 긴 시간 동안 발생하는 환경 영향보다 더 튼 환경 영향을 미칠 수 있다는 것이다. 그러므로 목록 파라미터가 환경에 미치는 영향을 평가할 때 시간 당 부하를 고려할 필요가 있다.

• 한국강구조학회 논문집
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• 제24권5호
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• pp.595-603
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• 2012

본 연구에서는 재하시험에 의하여 얻어지는 측정데이터를 적극적으로 활용하고 다양한 방법을 통하여 내하력을 평가하기 위하여 탄성지점을 적용하였다. 스프링력에 의한 구조해석의 적정성을 확인하고 실험결과의 신뢰도를 향상시키기 위하여 내민보로 제작한 탄성빔을 대상으로 처짐시험을 실시하였으며 이를 토대로 공용중인 교량의 내하력 평가 방법의 개선을 위하여 실제 공용중인 교량에 대한 정밀안전진단을 통한 검증을 실시하였다. 휨시험 결과 기존방법에 의하여 계산된 처짐보다 탄성지점을 적용하여 구한 처짐이 실측한 처짐과 근접한 것으로 나타났다. 준공 직후 초기점검 대상인 3경간 연속 강박스형교에 대한 내하력을 평가한 결과 탄성지점에 의한 내하력이 기존의 방법에 의한 내하력보다 최대 9.7% 작게 평가되었다. 본 연구는 기존 방법에 따라 교량의 내하력을 평가할 경우 응력보정계수의 적용과 같이 지침에 명확하게 제시되지 않은 부분으로 인하여 공학자에 따라 내하력이 상이하게 평가되는 경우가 빈번하므로 이에 대한 연구가 더욱 활발해 져야 한다는 취지에서 수행하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.269-274
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• 2008

For fitness-for-service analyses of underground natural gas pipelines, engineering assessment methods against possible defects need to be developed. The assessment methods for high pressure pipeline of KOGAS, was developed using the full size pipe burst tests and the finite element analysis. It included the defect assessment methods for a single and multi-corrosion, corrosion in girth welding part, corrosion in seam welding part, the mechanical damage defects as dent and gouge, crack and large plastic deformation of API 5L X65 pipe. In addition, we developed method to assess pipeline integrity by internal and external load to buried pipeline. Evaluation results were compared with other methods currently being applied to the gas pipeline. The program of Windows environment is made for easily using assessment methods. It provides a consistent user interface, so non-professional technician can easily and friendly use the FFS program from company intranet. Several evaluation programs is easily installed using one installer. Each program constitutes a common input interface and the output configuration program, and evaluation result store and can be recalled at any time. The FFS program based on independent evaluation method is used to evaluate the integrity and safety of KOGAS pipeline, and greatly contribute to safe and efficient operation of pipeline. This paper presents experimental, analytical and numerical investigations to develop the FFS methods for KOGAS pipeline, used as high pressure natural gas transmission pipeline within KOREA. Also, it includes the description of the integrated program for FFS methods.

• Structural Engineering and Mechanics
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• 제85권4호
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• pp.531-543
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• 2023

The existing concrete bridges are time-varying working systems, where the maintenance strategy should be planned according to the time-varying performance of the bridge. This work proposes a time-dependent residual capacity assessment procedure, which considers the non-stationary bridge load effects under growing traffic and non-stationary structural deterioration owing to material degradations. Lifetime bridge load effects under traffic growth are predicated by the non-stationary peaks-over-threshold (POT) method using time-dependent generalized Pareto distribution (GPD) models. The non-stationary structural resistance owing to material degradation is modeled by incorporating the Gamma deterioration process and field inspection data. A three-span continuous box-girder bridge is illustrated as an example to demonstrate the application of the proposed procedure, and the time-varying reliability indexes of the bridge girder are calculated. The accuracy of the proposed non-stationary POT method is verified through numerical examples, where the shape parameter of the time-varying GPD model is constant but the threshold and scale parameters are polynomial functions increasing with time. The case study illustrates that the residual flexural capacities show a degradation trend from a slow decrease to an accelerated decrease under traffic growth and material degradation. The reliability index for the mid-span cross-section reduces from 4.91 to 4.55 after being in service for 100 years, and the value is from 4.96 to 4.75 for the mid-support cross-section. The studied bridge shows no safety risk under traffic growth and structural deterioration owing to its high design safety reserve. However, applying the proposed numerical approach to analyze the degradation of residual bearing capacity for bridge structures with low safety reserves is of great significance for management and maintenance.