• Title, Summary, Keyword: 균열조사

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Analysis of Cracking Characteristics with Indenter Geometry Using Cohesive Zone Model (Cohesive Zone Model을 이용한 압입자 형상에 따른 균열특성분석)

  • Hyun, Hong Chul;Lee, Jin Haeng;Lee, Hyungyil;Kim, Dae Hyun;Hahn, Jun Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.12
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    • pp.1453-1463
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    • 2013
  • In this study, we investigated the effect of the indenter geometry on the crack characteristics by indentation cracking test and FEA. We conducted various cohesive finite element simulations based on the findings of Lee et al. (2012), who examined the effect of cohesive model parameters on crack size and formulated conditions for crack initiation and propagation. First, we verified the FE model through comparisons with experimental results that were obtained from Berkovich and Vickers indentations. We observed whether nonsymmetrical cracks formed beneath the surface during Berkovich indentation via FEA. Finally, we examined the relation between the crack size and the number of cracks. Based on this relation and the effect of the indenter angle on the crack size, we can predict from the crack size obtained with an indenter of one shape (such as Berkovich or Vickers) the crack size for an indenter of different shape.

Service Life Evaluation of RC Column Exposed to Carbonation Considering Time-dependent Crack Pattern (시간의존성 균열 패턴을 고려한 탄산화에 노출된 콘크리트의 확률론적 내구수명 평가)

  • Kwon, Seung-Jun
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.4 no.1
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    • pp.10-18
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    • 2016
  • RC(Reinfored Concrete) structures exposed to carbonation in urban city have durability degradation with extended service life and cracks in concrete causes a local accelerated carbonation. In the present work, crack effect on carbonation depth is investigated and the service life of RC structure is evaluated considering cracks from early age and time-dependent cracks based on the previous field investigation. DFP(Durability Failure Probability), safety index, and the related service life are calculated considering the time to crack width reaches to maximum crack width(0.3mm). The results with time effect on crack width show lower DFP and longer service life, which seems to be reasonable compared with conservative results from crack effect from initial stage. Furthermore, crack effect is evaluated to be insignificant on DFP and service life. The technique with time-dependent crack effect on carbonation can be effectively used for RC structure containing cracking in use.

Crack Example and Crack Control Method of Very-Early Strength Latex-Modified Concrete (초속경 라텍스개질 콘크리트의 균열발생 사례 및 억제방안)

  • Choi, Pan-Gil;Yun, Kyong-Ku;Lee, Bong-Hak
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.3
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    • pp.173-180
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    • 2009
  • Very-early strength latex-modified concrete(below ; VES-LMC) was developed for possible early-opening-to-traffic after overlay of bridge deck concrete. The purpose of this study is to analyze the cause of map, transverse and longitudinal cracking in VES-LMC and to provide a control method for minimizing occurrence of cracking. The proposed prevention method against map and transverse cracking was verified by field data. VES cement was modified as the unit cement content was reduced from 390kg/$m^3$ to 360kg/$m^3$. The maximum size of coarse aggregate was increased from 13mm to 19mm. The wire mesh and steel fiber were adopted in concrete mixture. From the results, the proposed prevention method against map and transverse cracking was verified since structural cracking was not occurred until 3 years after overlay.

Influences of Post Weld Heat Treatment on Fatigue Crack Growth Behavior of Transverse TIG Welded Al6013-T4 Aluminum Alloy Joint (횡방향 TIG 용접된 Al6013-T4알루미늄 합금 용접부의 피로균열전파거동에 미치는 PWHT의 영향)

  • Haryadi, Gunawan Dwi;Kim, Seon Jin
    • Journal of Power System Engineering
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    • v.16 no.4
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    • pp.66-73
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    • 2012
  • 본 연구는 횡방향 TIG 용접된 Al6013-T4 알루미늄 합금 용접부의 피로균열전파거동에 미치는 용접후열처리(PWHT)의 영향을 조사하는 것이 주목적이다. 기초적으로 인장시험, 경도 및 미세조직이 조사되었으며, 피로균열전파거동을 고찰하기 위한 피로 시험은 모두 중앙균열인장(CCT) 시험편에 대하여 수행되었다. T82열처리에 있어서 시효시간은 피로균열전파율, 인장강도 및 경도에 대단히 민감함을 나타내었으며, 모재와 열영향부재의 경우가 용접재보다 기계적 성질이 우수하였다. 횡방향 TIG 용접한 Al6013-T4 시험재의 용접후열처리 조건에 따라서 피로균열전파 저항에는 차이가 나타났으며, 본 실험의 조건하에서 24시간 인공시효 PWHT-82 시험편이 피로균열전파 저항이 가장 우수한 결과를 나타내었다.

Joint Behavior of Concrete Pavements Using Joint Crack Inducer (줄눈균열 유도장치를 사용한 콘크리트 포장의 줄눈거동)

  • Park, Moon Gil;Choi, Ki Hyo;Nam, Young Kug;Jeong, Jin Hoon
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.1D
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    • pp.57-65
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    • 2008
  • Joint of concrete pavement contributes to improvement of pavement performance by preventing occurrence of random cracking due to drying shrinkage and temperature changes of concrete slabs at early age. However, saw-cutting operations performed prior to sufficient concrete hardening develop micro-cracking of the concrete near the joints, which may develop to long-term distresses due to repetitious traffic and environmental loadings. To reduce the distresses, the joint crack inducers with heights of 100 mm, 150 mm, and 220 mm and the joint cracking slots with various depth were installed at a test section to investigate occurrence of the joint cracks and their behaviors over 5 months. As the results, higher efficiency of the crack inducing and larger behavior of the joint cracks were observed for the taller joint crack inducer. Higher efficiency of the crack inducing and improvement of the joint performance are warranted by additional investigation and reformation of the joint crack inducer.

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Line Laser Image Processing for Automated Crack Detection of Concrete Structures (콘크리트 구조물의 자동화 균열탐지를 위한 라인 레이저 영상분석)

  • Kim, Junhee;Shin, Yoon-Soo;Min, Kyung-Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.3
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    • pp.147-153
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    • 2018
  • Cracking in concrete structure must be examined according to appropriate methods, to ensure structural serviceability and to prevent structural deterioration, since cracks opened wide for a long time expedite corrosion of rebar. A site investigation is conducted in a regular basis to monitor structural deterioration by tracking growing cracks. However, the visual inspection are labor intensive. and judgment are subject. To overcome the limit of the on-site visual investigation image processing for identifying the cracks of concrete structures by analyzing 2D images has been developed. This study develops a unique 3D technique utilizing a line laser and its projection image onto concrete surfaces. Automated process of crack detection is developed by the algorithms of automatizing crack map generation and image data acquisition. Performance of the developed method is experimentally evaluated.

철근콘크리트 건물외벽의 수축균열의 실태와 그 대책

  • Lee, Lee-Hyeong
    • Journal of the Korea Construction Safety Engineering Association
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    • v.2 no.1
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    • pp.65-77
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    • 1992
  • 철근콘크리트 건물에 발생하는 균열은 그 원인이 크게 표1과 같이 콘크리트의 재료성질과 시공 그리고 외적요인과 하중으로 분류되고 있다. 그중 외벽에 발생하는 균열의 원인은 콘크리트 수축에 기인하는 것외에 다짐불량에 의한 코올드 조인트와 철근 부식 등에 의한 팽창균열 등 여러가지가 있다. 본고는 특히 중요한 수축균열에 한정하여 그 실태와 대책의 동향을 설명한다.「수축에 의해 발생하는 균열」의 원인은 콘크리트의 건조수축, 수화열에 의한 열수축 및 외기온의 변동에 의한 온도수축으로 대별될 수 있다. 실제의 건물 외벽균열은 이들이 복합적으로 작용하여 발생한다. 따라서 본 고에서는 이러한 종류의 균열실태에 대해 조사사례와 연구보고를 소개함과 동시에 균열 메카니즘. 방지대책 등에 대해 이해를 돕기 위한 자료를 제공한다. 본고는 1992년 2월에 소유가 발표한 일본 콘크리트 공학의 "RC건물외벽의 수축균열의 실태와 그 대책"을 중심으로 요약한 내용이다.

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Durability Evaluation and Defect Pattern Analysis in Railway Bridge Through Field Investigation (현장조사를 통한 철도 고가교 구조물의 내구성 평가 및 결함 패턴 분석)

  • Kwon, Seung Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.1
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    • pp.10-20
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    • 2013
  • Because of the defect in design, damage in using period, and deterioration in long term exposure to severe environmental condition, degradation of performance in RC (Reinforced Concrete) structures has occurred. This paper contains durability performance evaluation in railway bridges which covers eight districts through field investigation. For the target structures, durability performance is evaluated and the critical problems in use are derived. Additionally, service lifes for the deteriorated structures are evaluated through Durability-Environment index method based on the results from field investigation, and the results are compared with those from the condition assuming the structures without defect, damage, and deterioration. The target structures which consist of RC T girder, PSC girder, RC box, and Rahmen are investigated and the critical damage patterns are derived. They are evaluated to be cracks in PSC girder end, flexural cracks in PSC girder, crack around EPT anchor, and flexural cracks in RC T girder and RC box. The reasons for the critical patterns are also investigated. This study can be utilized for the repair planning considering the different district and the structure types.

Influence of Exposure Environmental Conditions on the Crack Healing Performance of Self-healing Repair Mortar Specimens (노출환경 조건이 자기치유형 보수 모르타르 시험체의 균열 치유성능에 미치는 영향)

  • Lee, Woong-Jong;Lee, Hyun-Ho;Ahn, Sang-Wook;Lee, Kwang-Myong
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.6 no.4
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    • pp.283-288
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    • 2018
  • Since the crack self-healing materials are activated according to the exposure environmental conditions from the time of crack occurrence, it is very important to clarify the relationship between the healing performance and the exposure environmental conditions of the crack surface. In this paper, the influence of the exposure environmental conditions on the crack healing performance of self-healing repair mortar was investigated through the water permeability test. The influence of temperature and humidity on the crack width of cracked specimens was evaluated. As a result of measuring the change of the crack width, the effect of curing temperature was negligible but it was confirmed that crack-closing occurred due to the change of dry-wet condition. The healing materials produced on the crack surface of the specimens was identified as calcite minerals. Since the minerals with high density are precipitated under the influence of gravity, the healing performance is somewhat different according to the direction of the crack surface, and the healing performance was significantly improved in the wet exposure condition than the air exposure condition.

A study on analysis of vibration and crack measurement data on granite-bed rock (화강암 지반에서 진동 및 크랙측정치 분석에 관한 연구)

  • Han, Dong-Hun;Ahn, Myung-Seog;Lee, Kwang-Yeol;Oh, Byung-Sam;Kang, Moon-Gu
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.3
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    • pp.251-260
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    • 2003
  • Tunnel blasting has been performed with V-cut to investigate the characteristics. Blasting vibrations were measured at two directions, the proceed direction and side direction. Propagation characteristics were determined by regression analysis; square root scaled distance and cube root scaled distance with maximum charge per delay of the blast. Testing result, The cross point was 62m in the allowable vibration velocity of 3mm/sec and 46m in 5mm/sec. Also, vibration level with measuring point was highest and decayed fastest, adapting to cube root scaled distance, for the proceed direction on ground.

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