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엄준식 ( Eom Jun-sik ),( Andrzej S. Nowak ),노병철 ( Lho Byeong-cheol ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 논문집 Vol.7 No.2
The objective of this work is to verify the Code specified girder distribution factors for short and medium span bridges. To accomplish this objective, field tests were carried out on seventeen simply supported highway bridges. This paper presents the procedure and results of field tests that were performed to verify girder distribution factors. Finite Element analyses previously performed at the University of Michigan indicated that in most cases currently used girder distribution factors specified in AASHTO Codes are too conservative. However, these studies also showed that for short spans and short girder spacings, the girder distribution factors can be too permissive. Therefore, this paper focused on experimental evaluation of girder distribution factors for short and medium span steel girder bridges. The results were compared with the distribution factors specified by AASHTO Standard (2000) and AASHTO LRFD Code (1998). It has been found that the measured girder distribution factors are lower than AASHTO values in most cases, and sometimes the code specified values are overly conservative. The research work involved formulation of the testing procedure, selection of structure, installation of equipment, measurements, and interpretation of the results.
노병철 ( Lho Byeong-cheol ),엄준식 ( Eom Jun-sik ),최규형 ( Choi Kyu-hyung ),이복규 ( Lee Bok-kyu ),최종대 ( Choi Chong-dae ) 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.12 No.2
BWIM (Bridge Weigh-in-Motion) System can be used to monitor real time traffic information for bridges, such as number of overloaded vehicles, and their axle weights, which can in turn used for citations for illegal overloading. Bridge health monitoring is currently very important issue for bridge owners, since illegally loaded trucks can accelerate the deterioration of bridges currently in service. This study aims to develop a sensor package that can be easily installed under existing bridges. The strain data recorded under real traffic then can be converted to the axle weight information. In this paper, currently used sensors are studied, and their characteristics are analyzed. Finally, an improved sensor package is proposed and its practicality and applicability is tested under real time traffic.
기지하중을 받는 교량구조물의 현장 계측 및 해석에 따른 응력분포 연구
엄준식 ( Eom Jun-sik ),노병철 ( Lho Byeong-cheol ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 논문집 Vol.7 No.3
본 연구는 기지하중을 이용하여 교량의 효율적 평가를 하기 위한 것이다. 계산상 내하력이 부족한 것으로 평가된 교량의 하중저항능력은 기존의 방법에 의한 평가능력을 상회하는 경우가 일반적이다. 기지하중을 이용한 실험은 미지의 저항능력을 평가할 수 있으며, 따라서 대상교량의 하중저항능력을 정확히 검증할 수 있다. 실험을 위한 기지하중은 일반적인 통행하중보다 큰 것을 사용하여야 한다. 따라서 본 연구에서는 미시간 주에서는 법적으로 허용된 11축 트럭 하중(685kN)을 고려하여, 두 대의 군용탱크와 두 대의 11축 트럭을 이용하였으며, 실험의 안전을 위하여 재하하중의 크기를 점진적으로 증가하면서 계측을 실시하였다. 실험에 의한 대상 교량의 응력수준은 계산에 의한 값보다 다소 작게 측정되었으며, 이는 부적절한 재료강도의 예측, 파라펫이나 가드레일과 같은 비구조요소의 기여, 지지조건의 변화 등에 기인한 것으로 분석되었다. The objective of the presented study is to develop an efficient procedure of proof load testing for existing bridges. By analytical methods, some of these bridges are not adequate to carry normal highway traffic. However, the actual load carrying capacity is often much higher than what can be determined by conventional analysis. Proof load testing can reveal the hidden strength reserve and thus verify the adequacy of the tested bridge. Proof load level required for meaningful tests should be sufficiently higher than legal load. In the state of Michigan, the legal 11-axle truck can weigh up to 685 kN. In this study, a combination of two military tanks and two Michigan 11-axle trucks was used. The proof loads were gradually increased to ensure the safety of the test. After each move, measurements were taken. For the considered bridge, stress levels were rather low compared to pre-test analysis results. This is due to incorrect material strength, structural contribution of nonstructural components such as parapets and railings, and partially fixed supports.
솔더범프와 TiW/Cu/electroplating Cu UBM 층과의 금속간 화합물 형성과 범프 전단력에 관한 연구
장의구,김남훈,김남규,엄준철 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.3
The joint strength and fracture surface of Sn-Pb solder bump in photo diode packages after isothermal aging testing were studied experimentally. Cu/Sn-Pb solders were adopted, and aged for up to 900 hours at 12$0^{\circ}C$ and 17$0^{\circ}C$ to analyze the effect of intermetallic compound(IMC). In 900-hour aging experiments, the maximum shea strength of Sn-Pb solder decreased by 20% and 9%. The diffraction patterns of Cu$_{6}$Sn$_{5}$, scallop-shape IMC, and planar-shape Cu$_3$Sn were observed by Transmission Electron Microscopy (TEM).EM).
한지수 ( Han Ji-soo ),엄준식 ( Eom Jun-sik ),노병철 ( Lho Byeong-cheol ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.7 No.2
This paper is to propose an enhanced impact echo technique that can reduce some problems of impact echo test and develop a Virtual Instrument for the application via a thickness evaluation technique which has same technical background to find deterioration in concrete structures. In the proposed technique, transfer function from dual channel system analysis is used, and coherence is improved to achieve reliable data. Also an averaged signal -ensemble- is used to achieve more reliable results. From the analysis of transfer function, the thickness is effectively identified.
최종대 ( Choi Chong-dae ),노병철 ( No Byung-cheol ),엄준식 ( Eom Jun-sik ),이우용 ( Lee Woo-yong ),권동근 ( Kwom Dong-keun ) 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.12 No.1
Accurate estimation of load is very important for bridge diagnostics to verify the remaining service life and to schedule required maintenance. The major truck parameters include load information, such as gross vehicle weight, axle weight, and axle configuration, speed, and dynamic characteristics. Also important are site condition, such as distance between passing trucks, ratio of fully-loaded trucks. These parameters can be measured using weigh-in-motion (WIM) technique. In this study, bridge weigh-in-motion (BWIM), which is invisible to truck drivers (to avoid bias), was used to collect unbiased truck information based on Moses’ previous study. In this study, BWIM equipment was installed in Mun-Mak Bridge to verify the accuracy and applicability of the system. Further study is planned on the various types of bridges to standardize the site-specific truck data, and rational fatigue load calculation.