• 한국건설관리학회논문집
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• 제17권2호
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• pp.80-89
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• 2016

최근 인프라 투자는 신규 건설 중심에서 기 시공된 시설의 효율적인 운영과 유지관리로 패러다임이 전환되고 있다. 이와 함께 시설물 노후화에 따른 안전에 대한 국민적 관심이 증폭되고 있다. 본 연구에서는 한국시설안전공단의 시설물관리종합정보시스템에 등록되어 있는 1994년부터 2014년까지의 시설물 유지관리 관련 데이터를 바탕으로 점검진단지수와 보수보강지수 등의 정량적 분석 방법론을 적용하여 유지관리 활동의 성과를 평가하였다. 또한 과거에 비해 현재 시설물의 안전도가 어느 정도 향상되었는지 안전등급 데이터를 토대로 분석을 실시하였다. 분석 결과 우리나라 시설물의 안전성은 과거 대비 크게 향상된 것으로 나타났으며 안전성이 향상된 요인으로는 정기적인 안전점검과 그에 따른 보수 보강 활동의 결과로 추정해 볼 수 있다. 본 연구를 통해 도출 된 결과는 향후 시설물의 유지관리 정책 및 전략 수립에서 기초적 자료로 활용이 가능할 것으로 판단된다.

• Ecology and Resilient Infrastructure
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• 제3권2호
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• pp.80-91
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• 2016

도시홍수, 가뭄, 폭염과 열대야 등 다양한 기상재해가 빈번히 발생하고 있어 인명과 재산 피해는 물론 도시의 자연환경보전에 어려움을 겪고 있다. 다양한 기상재해를 최소화 하고 기후변화에 적응하면서 보다 쾌적한 도시환경을 다음 세대에게 넘겨주기 위한 목적으로 저영향개발 또는 그린인프라가 주목 받고 있다. 한국의 저영향개발 및 그린인프라 기술은 현재 보육(incubating) 또는 시연 (demonstrating) 단계에 있다. 중앙정부 및 지방정부의 노력으로 법률 정비가 빠르게 이루어지고 있다. 이를 통해 물을 이용만 하는 회색인프라 (Gray Infrastructure)로 구성된 회색도시 (Gray City)에서 물을 관리하는 그린인프라(Green Infrastructure)로 구성된 녹색도시 (Green City)로 변모하기 시작했다. 보다 체계적인 확산과 보급을 위해서는 한국형 신기술의 개발, 기술의 검증, 기술 기준의 정비, 다분야의 협력과 협업, 교육과 홍보 그리고 시민들의 참여가 요구된다.

• Smart Structures and Systems
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• 제6권5_6호
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• pp.481-504
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• 2010

Wireless smart sensor networks (WSSNs) have been proposed by a number of researchers to evaluate the current condition of civil infrastructure, offering improved understanding of dynamic response through dense instrumentation. As focus moves from laboratory testing to full-scale implementation, the need for multi-hop communication to address issues associated with the large size of civil infrastructure and their limited radio power has become apparent. Multi-hop communication protocols allow sensors to cooperate to reliably deliver data between nodes outside of direct communication range. However, application specific requirements, such as high sampling rates, vast amounts of data to be collected, precise internodal synchronization, and reliable communication, are quite challenging to achieve with generic multi-hop communication protocols. This paper proposes two complementary reliable multi-hop communication solutions for monitoring of civil infrastructure. In the first approach, termed herein General Purpose Multi-hop (GPMH), the wide variety of communication patterns involved in structural health monitoring, particularly in decentralized implementations, are acknowledged to develop a flexible and adaptable any-to-any communication protocol. In the second approach, termed herein Single-Sink Multi-hop (SSMH), an efficient many-to-one protocol utilizing all available RF channels is designed to minimize the time required to collect the large amounts of data generated by dense arrays of sensor nodes. Both protocols adopt the Ad-hoc On-demand Distance Vector (AODV) routing protocol, which provides any-to-any routing and multi-cast capability, and supports a broad range of communication patterns. The proposed implementations refine the routing metric by considering the stability of links, exclude functionality unnecessary in mostly-static WSSNs, and integrate a reliable communication layer with the AODV protocol. These customizations have resulted in robust realizations of multi-hop reliable communication that meet the demands of structural health monitoring.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2012년도 춘계학술논문집 2부
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• pp.593-596
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• 2012

본 논문에서는 형식 조립식 하수관거 기초의 상재하중과 외압에 따른 거동을 범용 구조해석 프로그램인 ABAQUS 2009의 CAE 기능과 범용 CAD 프로그램인 Auto CAD Mechanical 2011의 3D 모델링을 통해 실제 실험결과와 비교하여 복잡한 구조의 구조물에서의 해석 정당성과 방법을 제안하고자 한다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.163-170
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• 2004

The main objective of this research is to determine the optimal sections of infrastructure (the pier and foundation) for orthotropic steel decks which is a part of prefabricated passenger car overpasses. Since the bridge to be designed allows only passenger cars, design loads are determined according to this condition. The total volume of the infrastructure is formulated as the objective function and the design constraints are based on the 'Korean Bridge Design Code' and 'Design Manual of Steel Framed Pier'. The programs used in this research are MATLAB 6.5 and MIDAS CIVIL.

• Ecology and Resilient Infrastructure
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• 제2권4호
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• pp.345-350
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• 2015

The toxicity of red mud (RM) pellets for water purification was evaluated using Pseudokirchneriella subcapitata and Daphnia magna in a lab-scale experiment. According to the algal growth inhibition test, both specific growth rates and relative growth rates of P. subcapitata decreased, and the growth inhibition rates increased ($R^2=0.97$, p<0.001) as the concentration of RM pellets in the aqueous solution increased (>1.6 g/L). Also, based on the acute toxicity evaluation test on D. magna, toxic unit (TU) values ranged between 0.00 and 2.83, and increased with an increase in the concentration of RM pellets in the aqueous solution. A correlation analysis indicated that the pH of RM pellets was statistically correlated with TU values ($R^2=0.77$, p=0.02). The environmental implication from this study is that the concentration of RM pellets in an aqueous solution needs to be lower than 4.4 g/L to keep the maximum permissible TU value less than 1.0.

• Smart Structures and Systems
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• 제18권5호
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• pp.885-909
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• 2016

Advances in low-cost wireless sensing have made instrumentation of large civil infrastructure systems with dense arrays of wireless sensors possible. A critical issue with regard to effective use of the information harvested from these sensors is synchronized sensing. Although a number of synchronization methods have been developed, most provide only clock synchronization. Synchronized sensing requires not only clock synchronization among wireless nodes, but also synchronization of the data. Existing synchronization protocols are generally limited to networks of modest size in which all sensor nodes are within a limited distance from a central base station. The scale of civil infrastructure is often too large to be covered by a single wireless sensor network. Multiple independent networks have been installed, and post-facto synchronization schemes have been developed and applied with some success. In this paper, we present a new approach to achieving synchronized sensing among multiple networks using the Pulse-Per-Second signals from low-cost GPS receivers. The method is implemented and verified on the Imote2 sensor platform using TinyOS to achieve $50{\mu}s$ synchronization accuracy of the measured data for multiple networks. These results demonstrate that the proposed approach is highly-scalable, realizing precise synchronized sensing that is necessary for effective structural health monitoring.

• Ecology and Resilient Infrastructure
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• 제3권4호
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• pp.215-220
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• 2016

A new immobilization technique of nanoscale $TiO_2$ powder to expanded polystyrene (EPS) balls with temperature-controlled melting method was developed, and the photocatalytic activity of $TiO_2$ powder-embedded EPS balls were evaluated using methylene blue (MB) solution under ultraviolet irradiation (${\lambda}=254nm$). Based on the scanning electron microscope (SEM) images and associated energy-dispersive X-ray spectroscopy (EDX) analysis, the components of the intact EPS balls were mainly carbon and oxygen, whereas those of $TiO_2$-immobilized EPS balls were carbon, oxygen, and titanium, indicating that relatively homogenous patches of $TiO_2$ and glycerin film were coated on the surface of EPS balls. Based on the comparison of degradation efficiencies of MB between intact and $TiO_2$-immobilized EPS balls under UVC illumination, the degradation efficiencies of MB can be significantly improved using $TiO_2$-immobilized EPS balls, and surface reactions in heterogeneous photocatalysis were more dominant than photo-induced radical reactions in aqueous solutions. Thus, $TiO_2$-immobilized EPS balls were found to be an effective photocatalyst for photodegradation of organic compounds in aqueous solutions without further processes (i.e., separation, recycling, and regeneration of $TiO_2$ powder). Further study is in progress to evaluate the feasibility for usage of buoyant $TiO_2$-immobilized EPS to inhibit the excessive growth of algae in rivers and lakes.

• 한국산학기술학회논문지
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• 제18권2호
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• pp.38-46
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• 2017

본 연구에서는 Industry Foundation Classes (IFC)를 기반으로 토목 시설물 정보 모델을 생성하는 경우에 발생할 수 있는 정보 검색 및 모델 재생성의 어려운 점을 보완할 수 있는 질의어를 개발하였다. 이를 위하여 첫번째로, IFC에서 구조물을 나타내기 위한 요소와 속성을 다루는 부분, 그리고 이들을 연결해주는 요소의 관계를 분석하고 이에 따른 흐름을 분석하였다. 이를 통해 최종 사용자의 입장에서 IFC 파일 내에서의 속성, 객체 및 그에 따르는 연결에 대한 접근 및 파악이 매우 힘들 수 있음을 확인하였다. 둘째, 기존 Building Information Model Query Language (BimQL)의 방법을 참고하여 IfcPropertySet 중심의 질의 방식을 제시하고 이를 적용할 수 있는 독립 모듈을 개발하였다. 마지막으로 제시한 방법을 철도의 궤도 및 침목에 적용하여 사용자가 의도한 대로 효과적인 정보 추출 및 모델 재생성이 가능함을 확인하였다. 이러한 접근방법의 장점은 IFC 파일만을 대상으로 효과적인 정보의 검색이 가능하다는 점으로, 정보의 상호운용성의 이점을 극대화할 수 있다.

• Smart Structures and Systems
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• 제29권1호
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• pp.181-193
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• 2022

Data-driven structural health monitoring (SHM) of civil infrastructure can be used to continuously assess the state of a structure, allowing preemptive safety measures to be carried out. Long-term monitoring of large-scale civil infrastructure often involves data-collection using a network of numerous sensors of various types. Malfunctioning sensors in the network are common, which can disrupt the condition assessment and even lead to false-negative indications of damage. The overwhelming size of the data collected renders manual approaches to ensure data quality intractable. The task of detecting and classifying an anomaly in the raw data is non-trivial. We propose an approach to automate this task, improving upon the previously developed technique of image-based pre-processing on one-dimensional (1D) data by enriching the features of the neural network input data with multiple channels. In particular, feature engineering is employed to convert the measured time histories into a 3-channel image comprised of (i) the time history, (ii) the spectrogram, and (iii) the probability density function representation of the signal. To demonstrate this approach, a CNN model is designed and trained on a dataset consisting of acceleration records of sensors installed on a long-span bridge, with the goal of fault detection and classification. The effect of imbalance in anomaly patterns observed is studied to better account for unseen test cases. The proposed framework achieves high overall accuracy and recall even when tested on an unseen dataset that is much larger than the samples used for training, offering a viable solution for implementation on full-scale structures where limited labeled-training data is available.