• Title, Summary, Keyword: 균열조사

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A Study on Survey of Carbonation for Sound, Cracked, and Joint Concrete in RC Column in Metropolitan City (국내 도심지 콘크리트 교각 취약부의 탄산화 조사에 대한 연구)

  • Kwon, Seung Jun;Park, Sang Sun;Nam, Sang Hyuk;Cho, Ho Jin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.11 no.3
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    • pp.116-122
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    • 2007
  • The concrete structures in Metropolitan city are usually exposed to carbonation and corrosion of embedded steel occurs due to the carbonation. In inspection and diagnosis of concrete structures, carbonation depth in sound concrete is mainly evaluated and service life for concrete structure is predicted based on the result. Generally, however, mass concrete structures such as columns have construction joint for suitable placing and also have cracks in early-age. In this study, carbonation depth in RC columns used for 20 years in metropolitan city is evaluated and also analyzed by considering the local conditions like sound, cracked, and joint area. The carbonation depth in cracked and joint area is more rapid than that in sound area, and it is thought to be more desirable to consider this effect in concrete structures with small cover depth. Furthermore, the technique for carbonation prediction in cracked concrete is derived in terms of crack width and the results from this technique are verified by comparing those from previous research.

An Experimental Study on Structural Characteristics of Reinforced Concrete Beams with the Perforative Opening (철근콘크리트 개방형 유공보의 구조적 특성에대한 실험적 연구)

  • 구해식
    • Magazine of the Korea Concrete Institute
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    • v.9 no.6
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    • pp.225-232
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    • 1997
  • 철근콘크리트 유공보에 있어서 기존 유공보의 연구는 유공위치를 보춤의 중앙에 위치하여 연구하였으나 철근코크리트 보의 역학적 특성활용과 시공상의 편의성을 위해 사각형 유공의 위치를 보춤 하단에 설치하여 개방형 유공보로 변형하였다. 본 연구에서는 사각형 유공보에 대한 유공크기의 세로길이를 보춤의 0.3배로 하고 가로길이를 세로길의의 1~3배로 변화시켜 보강 및 무보강 상태의 사각형 유공보와 이의 사각형 유공하부 콘크리트를 제외시킨 개방형 유공보에 있어서 총 10개의 시험체를 대상으로 하는 실험을 실시하여 시험체의 최대내력, 유공주위에서의 전단균열과 시험체의 휨인장균열, 주요위치의 변위조사, 주근 및 유공주위의 콘크리트와 보강철근의 변형도조사, 시험체의균열을 조사하여 상호변화를 비교.분석하였다. 이 연구결과로부터 개방형유공보의 유공주위 응력변형상태, 파괴메카니즘, 적절한 개방형 유공크기,설계시 고려사항을 제시하여 차후의 개방형 유공보의 계속적인 연구에 기여하고자 한다.

Ultrasonic evaluation of small surface fatigue cracks initiating in residual stress zone (잔류응력 영역에서 발생한 작은 피로균열의 초음파 평가)

  • Kang Kae-Myung;Kim Jin-Yeon
    • Journal of the Korean Institute of Gas
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    • v.4 no.1
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    • pp.55-62
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    • 2000
  • A surface acoustic wave method for the evaluation of small fatigue crack initiated from a pit-type surface flaw is presented. In-situ ultrasonic experiments are performed for aluminum 2024-T3 alloy samples under the fatigue test. During the fatigue test, the surface acoustic wave reflection signal from the pit and crack is measured under different hold-stress levels. From the measured and predicted surface wave reflections the depths of fully and partially open cracks are determined and results are verified by comparing with SEM fractography The crack opening behavior of the fatigue crack is evaluated from the predicted effective crack depths. The method developed in this study can be applied to monitor and characterize crack initiation and propagation from pit-type surface flaws in the early stage of fatigue life.

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Study on the discharge of soil particles and ground collapse through cracks in underground structures (지중구조물 균열을 통한 토립자 유출 및 지반함몰 특성 연구)

  • Kim, Ho-Jong;Kim, Kang-Hyun;Shin, Jong-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.5
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    • pp.699-715
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    • 2019
  • Recently, in urban areas, cavities and ground collapse adjacent to underground structures are frequently reported. Several studies on the cavity generation by structure cracks have been made, however they are focused on the cause of cracks and settlement of the ground. In this paper, soil particle and groundwater discharge through pipe cracks and cavity generation mechanism are investigated. The theoretical analysis of the groundwater, which is the main factor of the drainage of the soil particles, and the particle transport mechanism and flow characteristics were investigated. An experimental model test was carried out to identify the mechanism of cavity generation by underground buried pipe cracks. The soil particle weight of discharge through the cracks, and the movement characteristics of the particles were analyzed using PIV. In this study, it is clearly identified that soil particle movements, cavity generation and ground collapse that occur in the ground are basically caused by the movement of groundwater.

A Modification of the $C^*$ Integral Considering the Effect of Crack Growth (균열 진전의 효과를 고려한 $C^*$ 적분의 수정)

  • 최영환;방종명;염윤용;송지호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.13 no.1
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    • pp.77-86
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    • 1989
  • A modified $C^{*}$ integral as load parameter in creep fracture is proposed considering the effect of crack growth. It is shown that the parameter does not depend on crack velocity. By performing experiment using STS 304 stainless steel at 600.deg.C the validity of the parameter is investigated. The results show that the parameter is a good measure as a load parameter in creep fracture and the rate of crack tip opening displacement can also be a creep load parameter for STS 304 at 600.deg. C.C.

Propagation of Crack in Concrete Subjected to Dynamic Loading (동적하중(動的荷重)을 받는 콘크리트의 구열(龜裂)성장)

  • Kang, Sung Hoo;Kim, Woo
    • Journal of The Korean Society of Civil Engineers
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    • v.8 no.2
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    • pp.135-145
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    • 1988
  • This study deals with the prediction of crack propagation in concrete mortar subjected to static and dynamic load. Total 54 CLWL-DCB(Crack-line-loaded-double-cantilever beam) concrete mortar specimens were tested to measure crack growth using ASTM 561-80. Main variables were sand to cement ratio and water to cement ratio. The resulting load(P)-COD(Crack Opening Displacement; $2V_1$) curves and COD-CTOD (Crack Tip Opening Displacement; $2V_2$) curves were analyzed to calculate effective crack length and physical crack length by way of ASTM 561-80 proposed. Replica crack length were also obtained directly during the test. The differences in crack propagation between under static load and under dynamic load were investigated.

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Surface Crack Evaluation Method in Concrete Structures (콘크리트 구조물의 표면 균열 평가 기법)

  • Lee, Bang-Yeon;Yi, Seong-Tae;Kim, Jin-Keun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.2
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    • pp.173-182
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    • 2007
  • Cracks in concrete structures should be measured to periodically assess potential problems in durability and serviceability. Conventional crack measurement systems depend on visual inspections and manual measurements of the crack features such as width, length, and direction using microscope and crack gage. However, conventional methods take long time as well as manpower, and lack quantitative objectivity resulted by inspectors. In this study, an evaluation technique for concrete surface cracks is developed using image processing and artificial neural network. Developed technique consists of three major parts: (1) crack detection (2) crack analysis and (3) pattern recognition. To examine validity of the technique developed in this study, crack analyzing tests were performed on the images obtained from various types of concrete surface cracks. The test results revealed that the system is highly effective in automatically analyzing concrete surface cracks in terms of features and patterns of cracks.

Performance Evaluation of Asphalt Pavement Reinforced with Glass Fiber Sheet Type of Geosynthetics (유리섬유시트 형태의 토목섬유로 보강된 아스팔트 포장의 공용성 평가)

  • Cho, Sam-Deok;Lee, Dae-Young
    • Journal of the Korean Geosynthetics Society
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    • v.10 no.3
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    • pp.1-8
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    • 2011
  • This paper presents the performance evaluation of asphalt pavement reinforced with fiber sheet type of geosynthetics and observations conducted to evaluate the practical efficiencies and performance of overlay asphalt pavement reinforced with geosynthetics. In this study, performance evaluation were performed for the six section of construction site. The performance indcators of asphalt pavement reinforced with geosynthetics has been collected Automatic Road Analyzer (ARAN), Falling Weight Deflectometer (FWD) and have been analyzed for rutting, cracking ratio, falling weight and international roughness index. As a result of performance evaluations, geosynthetics reinforced asphalt pavement is sigficant effect on increasing a cracking resistance than the non-reinfroced asphalt pavement, also rutting and crak is slowly increase as incerasingly performance period.

Description of crack growth behavior of SB41 steel in terms of J integral (J적분에 의한 SB41강의 피로균열 진전 특성 평가)

  • 배원호;김상태;이택순
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.6
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    • pp.1568-1575
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    • 1990
  • Fatigue crack growth behavior was investigated in the center cracked plate of KS SB41 steel and the relation between the crack growth rate and various mechanical parameters was studied at small scale yielding, large scale yielding and full scale yielding. The crack opening ratio U was about 0.6-0.8 and had the larger value in the case of load control than that of strain control. Effective stress intensity factor range, .DELTA.K$_{eff}$ and J integral range, .DELTA.J were obtained from the notion of crack opening, and the crack growth rate was expressed with these values. The value of J integral range increased rapidly at stress ratio, R=0 in full scale yielding of load control test. COD value also increased rapidly with the increase of ligament net stress at large scale yielding of load control test.t.

Standardization of Injection System by Inorganic Materialfor Crack Repair of Tunnel Concrete Structures (터널 콘크리트 구조물의 보수를 위한 무기계 균열주입기술의 표준화 연구)

  • Bae, Kee-Sun;Gwak, Su-Jung;Baek, Jong-Myeong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.6
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    • pp.191-197
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    • 2006
  • This study is to establish a standardization of injection system by inorganic material for crack repair of tunnel concrete structures. For this various surveys and experiments were carried out as followed. The first we surveyed capability of injection and crack pattern of concrete structures in site. and second we analyzed the relationship between crack width and volume of injection, and decided pressure and volume of injection. Finally we evaluated the relationship between crack width and volume of injection with kind of concrete structures, and between required time for injection and crack width with thickness of structure. From these surveys and experiments, we cleared the relationship between crack patterns and injection technologies such as volume, pressure of injection and required time for injection with kind of structure.