• 한국구조물진단유지관리공학회 논문집
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• 제5권3호
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• pp.131-139
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• 2001

Experimental programs were accomplished to improve and evaluate the structural performance of RC frame structures with masonry infilled wall, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. Test variables are restraining factors of frame, with or without masonry infilled wall, and masonry method. Six reinforced concrete rigid frame and masonry infilled wall were tested and constructed in one-third scale size under vertical and cyclic loads simultaneously. Based on the test results, the following conclusions can be made. For masonry infilled wall with restraining factors of frame(IFWB-1~3), cumulated energy dissipation capacities were increased by 1.35~1.60 times in comparision with that of masonry infilled wall(IFB-1) at final stage of testing. For masonry infilled wall with restraining factors of frame, maximum horizontal capacities were increased by 1.91~2.24 times in comparision with that of rigid frame.

• 한국구조물진단유지관리공학회 논문집
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• 제4권1호
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• pp.147-155
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• 2000

Five reinforced concrete rigid frame and masonry infilled wall and cut off type masonry infilled wall were tesed during vertical and cyclic loads simultaneously. Experimental programs were accomplished to improve and evaluate the structural performance of test specimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. Test variables are hoop reinforcement ratio, with or without masonry infilled wall, and masonry method. All the specimens were constructed in one-third scale size. Based on the test results, the following conclusions can be made. For masonry infilled wall(IFB-1), maximum horizontal capacity was increased by 1.45 time in comparision with that of rigid frame(FB-0). For cut off masonry infilled wall (IFBC-1~3), maximum horizontal capacity was increased by 1.73~1.98 time in comparision with that of rigid frame(FB-0). For cut off masonry infilled wall(IFBG-1~3), ductility was increased by 1.48~2.08 time in comparision with that of masonry infilled wall (IFB-1).

• Structural Engineering and Mechanics
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• 제57권5호
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• pp.937-949
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• 2016

Fiber reinforced polymer (FRP) applications in the structural engineering field include concrete-FRP composite systems, where FRP components are either attached to or embedded into concrete structures to improve their structural performance. This paper presents the results of an analytical study conducted using finite element model (FEM) to simulate the behavior of three-points load beam reinforced with GFRP and/or steel bars. To calibrate the FEM, a small-scale experimental program was carried out using six reinforced concrete beams with $200{\times}200mm$ cross section and 1000 mm length cast and tested under three point bending load. The six beams were divided into three groups, each group contained two beams. The first group was a reference beams which was cast without any reinforcement, the second group concrete beams was reinforced using GFRP, and the third group concrete beams was reinforced with steel bars. Nonlinear finite element simulations were executed using ANSYS software package. The difference between the theoretical and experimental results of beams vertical deflection and beams crack shapes were within acceptable degree of accuracy. Parametric study using the calibrated model was carried out to evaluate two parameters (1) effect of number and position of longitudinal main bars on beam behavior; (2) performance of concrete beam with composite longitudinal reinforcement steel and GFRP bars.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• 한국건축시공학회지
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• 제21권1호
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• pp.87-95
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• 2021

본 연구에서는 현재 건설신기술로 지정된 복합계방수공법 7개사(A~G)를 대상으로 KS F 2622:멤브레인 방수층 성능평가 시험방법 중 현장 적용조건과 유사성이 큰 평가항목을 선정하여 평가한 결과, 모든 시험체가 기본 물성평가에서 KS 기준을 상회하는 성능을 확보했음에도 불구하고, 내피로(균열 거동) 시험을 제외한 방수성(수밀성) 시험, 처짐 저항성 시험, 부풂 저항성 시험에서 점착 도막 계열로 이루어진 공법의 접합부와 수직부 등 취약부위의 현장품질 성능을 확보하기 어려운 것으로 확인하였다.

• 한국안전학회지
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• 제37권6호
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• pp.81-88
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• 2022

It is necessary to better understand the effect of age-related degradation on the performance of reinforced concrete shear walls in nuclear power plants in order to ensure their structural safety in the event of earthquakes. Therefore, this paper studies seismic fragility of the typical shear wall in nuclear power plants under earthquake excitation Reinforced concrete shear wall is composed of wall, horizontal and vertical flanges. Due to characteristics of its geometry, it is difficult to predict the ultimate behavior of shear wall under earthquake excitation. In this study, for more realistic numerical simulation, the Latin Hyper-Cube (LHC) simulation technique was used to generate uncertain variables for the material properties of concrete shear walls. The effects of crack, characteristics of inelastic behavior of concrete, and loss of cross section were considered in the nonlinear finite element analysis. The effects of aging-related deterioration were investigated on the performance of reinforced concrete shear walls through analysis of undegraded concrete shear walls and degraded concrete shear walls. The resulting seismic fragility curves present the change of performance of concrete shear wall due to age-related degradation.

• Applied Microscopy
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• 제50권
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• pp.25.1-25.11
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• 2020

Scanning acoustic microscopy (SAM) or Acoustic Micro Imaging (AMI) is a powerful, non-destructive technique that can detect hidden defects in elastic and biological samples as well as non-transparent hard materials. By monitoring the internal features of a sample in three-dimensional integration, this technique can efficiently find physical defects such as cracks, voids, and delamination with high sensitivity. In recent years, advanced techniques such as ultrasound impedance microscopy, ultrasound speed microscopy, and scanning acoustic gigahertz microscopy have been developed for applications in industries and in the medical field to provide additional information on the internal stress, viscoelastic, and anisotropic, or nonlinear properties. X-ray, magnetic resonance, and infrared techniques are the other competitive and widely used methods. However, they have their own advantages and limitations owing to their inherent properties such as different light sources and sensors. This paper provides an overview of the principle of SAM and presents a few results to demonstrate the applications of modern acoustic imaging technology. A variety of inspection modes, such as vertical, horizontal, and diagonal cross-sections have been presented by employing the focus pathway and image reconstruction algorithm. Images have been reconstructed from the reflected echoes resulting from the change in the acoustic impedance at the interface of the material layers or defects. The results described in this paper indicate that the novel acoustic technology can expand the scope of SAM as a versatile diagnostic tool requiring less time and having a high efficiency.

• Earthquakes and Structures
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• 제24권3호
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• pp.205-215
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• 2023

Currently, many studies are underway at home and abroad on the seismic performance evaluation and dry construction method of the masonry structure. In this study, a dry stack masonry wall system without mortar using concrete blocks is proposed, and investigate the seismic performance of dry filling wall frames through experimental studies. First, two types of standard blocks and key blocks were designed to assemble dry walls of concrete blocks. And then, three types of experiments were manufactured, including pure frame, 1/2 height filling wall frame, and full height filling wall frame, and cyclic load experiments in horizontal direction were performed to analyze crack patterns, load displacement history, rebar deformation yield, effective stiffness change, displacement ductility, and energy dissipation capacity. According to the experimental results, the full height filling wall frame had the largest horizontal resistance against the earthquake load and showed a high energy dissipation capacity. However, the 1/2 height filling wall frame requires attention because the filling wall constrains the effective span of the column, limiting the horizontal displacement of the frame. In addition, the concrete block was firmly assembled in the vertical direction of the wall as the horizontal movement between the concrete blocks was allowed within installation margin, and there was no dropping of the assembled concrete block.

• 한국전산구조공학회논문집
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• 제30권6호
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• pp.541-547
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• 2017

기후변화에 따른 자연재해의 증가하고 있다. 이에 자연재해에 의한 토목구조물의 피해 및 붕괴를 예방하기 위하여 처짐 및 균열을 지속적인 관리가 필요하다. 이에 효과적인 구조물 관리를 위해 광학 이미지 기술이 유지관리 기술에 적용되고 있다. 하지만 광학이미지 기술은 촬영에 따른 주변 조건의 영향이 크며, 그 때문에 촬영조건에 대한 검증이 필요하다. 이를 위해 본 논문에서 촬영조건으로 자연광, 촬영매수, 촬영거리를 따른 수직변위 추정값의 정확도에 대해 검증하였다. 실험을 통해 확인한 결과 자연광이 수직변위를 추정하는데 자연광이 가장 큰 영향을 미치는 것을 확인할 수 있었고, 촬영거리 또한 수직변위를 검토하는데 주요한 영향을 미치는 것을 확인할 수 있었다. 본 결과를 통해서 외부환경에서 촬영하는데 활용하여 변위 추정 시 발생하는 오차를 최소화할 수 있으며, 이러한 과정을 통해 구조물 유지관리에 적용할 수 있다.

• 한국강구조학회 논문집
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• 제10권3호통권36호
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• pp.423-435
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• 1998

본 연구에서는 기존의 강교에서 흔하게 발견되고 있는 맞대기 용접부의 용입불량으로 인한 부재의 피로강도 저하도를 정량적으로 평가하고자 하였다. 이를 위하여 강교량의 재료로 널리 사용되고 있는 SWS490강으로 제작된 완전용입 및 용입깊이가 서로 다른 불완전용입 맞대기 용접시험편을 대상으로 일정진폭하중시험을 수행하여 S-N선도를 산출하고 이를 비교 검토하였으며, 파괴역학적 방법을 이용하여 불완전용입 용접재의 피로수명을 계산하였다. 본 연구의 결과로서, 완전용입 용접재의 경우 AASHTO의 피로강도등급선도와의 비교에서 피로한도값은 A등급보다 높은 값을 보였고, S-N선도의 기울기는 5.57로 매우 높게 나타났다. 불완전용입 용접재의 경우 불완전용입깊이 D가 증가함에 따라 피로강도가 감소하는데, D=14.7mm인 경우 AASHTO의 E'등급보다 낮게 나타난다. 불완전용입 용접재의 파손거동에서 피로균열은 내부 용접루트 선단부에서 a/c가 매우 작은 반타원형 표면균열의 형태로 발생하고, 시험체의 두께방향으로 진전하여 최종파손을 유발한다. 파괴역학적 방법을 이용한 불완전용입 용접재의 피로수명을 평가하기 위하여 3차원 반타원형 균열형상에 대한 응력확대계수 K를 유한요소해석으로 구하였다. 여기서 얻어진 K값과 실험으로 얻어진 Paris식의 상수를 이용하여 불완전용입 용접재의 피로수명을 계산하여 비교하였다. 그리고 실제 불완전용입 맞대기용접부의 파손으로 붕괴사고가 발생한 성수대교의 수직재에 본 연구결과를 적용하여 피로수명을 계산해 보았다.