• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.121-129
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• 2006

This study look into the mechanisms of growth and magnification of the cracks and delamination in the pre-cracked RC beams repaired with carbon fiber sheets. The experimental parameters were loading type, loading speed and crack. In the experiments, it was confirmed that a failure of beams began with development and propagation of the stepped delamination in the below the loading point due to the rapid change of shear force, but mechanisms of the failure were not influenced with loading type, loading speed and pre-cracks. Particularly, in the case of beams having the pre-cracks, growth of crack concentrated at the special crack below the loading point and led to failure of the beam by delamination due to magnification of crack.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.52-54
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• 2002

저온균열은, 대한용접학회에서 발간한 '용접.접합용어사전'에 의하면, '용접 후 용접부의 온도가 대체로 $200^{\circ}C$ 이하의 저온에서 발생하는 균열을 총칭한다. 경우에 따라서는 실온까지 냉각한 후 일정한 기간이 경과한 후에 발생하기도 하며, 이러한 균열을 지연균열(delayed cracking)이라고 한다'로 되어 있다. 이들 저온균열의 발생에는 주로 구속응력과 경화조직 및 확산성수소가 영향을 미치고 있으며, 그 종류는 위에서 언급한 지연균열 외에 라멜라 테어링, 변형균열, 칭균열형 저온균열 등이 있다. 본 기술강좌에서는 용접부의 저온균열에 대하여 지연균열과 그 외의 저온균열로 나누어 2회에 걸쳐 소개하기로 한다.하기로 한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.191-195
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• 2009

After developing the pre-crack to simulate a damaged reinforced concrete beam, fatigue test was conducted on the beam repaired by GFRP Bar and GSP embedded method. In the result of fatigue test, most residual displacement and crack of the experimental beams occurs in the early loading cycle and an increasing rate of these due to number of cycles were insignificant. Comparing with a non-repaired beam, a static strength of the repaired beam greatly increased, but fatigue strength decreased. In S-N curves, fatigue strength of the beam repaired by GFRP Bar and GSP was 58%, 52% of the static strength respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.153-159
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• 2007

This paper is experimental investigation for failure characteristics and performance of a RC beams strengthened with GFSP which were developed for improvement of the early debonding problems in the externally bonded FRP systems. To represent damages and load conditions of the existing beam, pre-cracks and repeating loads are adopted for experimental parameters. In this experiment, it is confirmed that strengthening with GFSP is a very effective strengthening method for an increase in strength, a decrease in deflection, a control of the crack. But it shown that the design of the beams to be strengthened with GFSP should be consider a brittle behavior of the grass fiber on the flexural capacity.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.827-829
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• 2021

현대사회의 시설물 중 다수가 콘크리트를 사용하여 건설되었고, 재료적 성질로 인해 균열, 박락, 백태 등의 손상이 발생하고 있고 시설물 관리가 요구되고 있다. 하지만, 현재 시설물 관리는 사람의 육안 점검을 정기적으로 수행하고 있으나, 높은 시설물이나 맨눈으로 확인할 수 없는 시설물의 경우 관리가 어렵다. 이에 본 논문에서는 다양한 영상장비를 활용해 시설물의 이미지에서 균열을 분류하는 알고리즘을 제안한다. 균열 분류 알고리즘은 산업 이상 감지 데이터 세트인 MVTec AD 데이터 세트를 사전 학습하고 L2 auto-encoder를 사용하여 균열을 분류한다. MVTec AD 데이터 세트를 사전학습시킴으로써 균열, 박락, 백태 등의 특징을 학습시킬 수 있을 것으로 기대한다.

• Magazine of the Korea Concrete Institute
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• v.14 no.1
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• pp.53-60
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• 2002

매스 콘크리트 구조물에서는 콘크리트 타설 후 시멘트의 수화열로 인한 온도응력에 의해서 온도균열의 발생 가능성이 매우 높다. 따라서, 매스 콘크리트 시공시, 온도균열을 구조물의 내구성 관점에서 최대한 억제시킬 필요가 있다. 최근에는 국내에서도 단위시멘트량이 많은 배합을 이용하는 고강도 콘크리트 구조물의 시공이 증가되고 있다. 이와 같은 매스 콘크리트 구조물은 단위시멘트량이 많기 때문에 부재내 수화열에 의한 온도의 상승 속도가 빠르기 때문에 시공에 앞서 사전에 설계, 재료 및 시공 측면에서 온도균열 제어 대책을 검토할 필요가 있다.(중략)

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.11
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• pp.19-26
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• 2018

This paper presents the shear strengthening effect of externally post-tensioning (EPT) method using high-strength steel rod in pre-cracked reinforced concrete (RC) beams. Three- and four-point bending tests were performed on a total of 8 specimens by adjusting the strengthening depths in the deviator position of EPT. The effective strengthening depths were 435, 535, and 610 mm. The pre-loading up to about 2/3 of ultimate load capacity measured in unstrengthened RC beam were applied in the beam to be post-tensioned. The EPT method was then applied to the pre-damaged RC beams and re-loading was added until the end of the test. EPT restored deflections of 3 mm or more, which account for about 40% of deflection when the pre-loading was applied. The shear strengthening increases more than 3 times and 36~107% in terms of the stiffness and load-carrying capacity compared to unstrengthening RC beams. The increased load-carrying capacities of the post-tensioned beam with strengthening depths of 435 and 535 mm are almost the same as 36~61%, and those of 610 mm are 84~107%, which shows the greatest shear strengthening effect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.40-47
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• 2022

The present study aimed to examine the effectiveness of different techniques for controlling the diagonal cracks at the corners of openings on the strength, deformation, and crack propagation in reinforced concrete walls. The crack control strip proposed in this study, the conventional diagonal steel reinforcing bars, and stress-dispersion curved plates were investigated for controlling the diagonal cracks at the opening corners. An additional crack self-healing function was also considered for the crack control strip. To evaluate the volume change ratio and crack width propagation around the opening, downsized wall specimens with a opening were tested under the diagonal shear force at the opening corner. Test result showed that the proposed crack control strip was more effective in reducing the volume change and controlling the crack width around the opening when compared to the conventional previous methods. The crack control strip with crack healing feature displayed the superior performance in improving the strength of the wall and reducing the crack width while healing cracks occurred in the previous tests.

• Proceedings of the Korean Society of Computer Information Conference
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• 2021.07a
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• pp.649-652
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• 2021

본 논문에서는 노후화된 목조·석조 건축물의 균열을 탐지하는 기법을 소개한다. 본 기법의 목적은 석조·목조 문화재의 시간의 흐름에 따른 관리 소홀, 균열(벌레, 날씨, 기온 등), 배부름 현상에 의한 문화재의 손상을 사전에 방지하기 위함이다. 기존에 존재하는 목조·석조 건축물의 균열, 노후, 배부름 등 다양한 결함과 변형의 탐지 방법은 접촉식 센서를 이용하여 탐지를 해왔지만, 문화재 자체의 미관을 해칠 뿐 아니라 문화재를 추가로 훼손할 가능성이 있다는 문제점이 제시되었다. 이 문제를 해결하기 위해 문화재 비 접촉형 탐지 기법을 사용한다. CCTV 및 DSLR과 같은 관측장비로 촬영한 영상정보를 기반으로 문화재의 결함과 변형을 AI 영상분석 기반 방법으로 판단하는 문제를 제안한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5844-5853
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• 2014

This paper presents the results of experimental investigations on the shear failure behaviors of reinforced concrete beams using ductile fiber reinforced cementitious composite (DFRCC). Total 10 RC beams of $150{\times}300{\times}1,000mm$ size were tested by 4-point bending under the displacement control. The main parameters of the experiment are surface treatment by grinding and preloading to the cracking point in the repair process. The load-displacement curves, diagonal tension cracking load, flexural cracking load, and shear strength were obtained. The test results showed that the DFRCC can be used effectively for restoring the shear strength approximately 99% to the original value under the condition that the appropriate thickness and surface treatment like grinding are assured. For further research, the specimens taken from real deteriorated structures will need to be tested after being repaired with DFRCC.