• 대한토목학회논문집
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• 제26권4D호
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• pp.609-615
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• 2006

균열 및 안치공법은 노후화된 콘크리트 슬래브의 줄눈 및 균열부의 과도한 움직임으로 인하여 아스팔트 덧씌우기층에 발생되는 반사균열을 억제하기 위해 기존의 노후화된 콘크리트 포장에 적정 간격의 불연속면을 형성시켜서 각각의 불연속면에서의 움직임을 작게 유지하는 공법으로 미국 등에서는 널리 사용되고 있다. 본 연구에서는 LTPP Data를 이용하여 균열 및 안치 공법 적용 후 IRI과 포장 파손 추이를 분석하여 공법 사용에 의한 공용성 변화에 미치는 영향을 고찰하였다.

• 산업기술연구
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• 제22권A호
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• pp.185-192
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• 2002

The performance of old and the new concrete construction depends upon bond strength between old and the new concrete. Current adhesive and strength measurement method ignores the effect of stress concentration from shape of specimens. Therefore, this research calculates stress concentration coefficient as the ratio of drilling depth to drilling diameter($h_s/D$), the ratio of overlay thickness to drilling diameter($h_0/D$), the ratio of steel disk thickness to drilling diameter(t/D), the ratio of overlay elastic modulus to substrate modulus($E_1/E_0$), the distance from core to corner border(L_$_{corner}$) and the distance between cores(L_$_{coic}$) vary. The finite element method is adapted to analysis The results from 'the F.E.M analysis are as follows. The stress concentration effects can be minimized when the ratio of drilling depth to drilling diameter($h_s/D$) is 0.20~0.25, the elastic modulus ratio($E_1/E_0$) is 06~1.0, and the ratio of steel disk thickness to drilling diameter(t/D) is 3.0. The overlay thickness, the distance from specimens to corner border(L_$_{corner}$), the distance between cores(L_$_{coic}$) almost do not affect to the stress concentration.

• Structural Monitoring and Maintenance
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• 제1권3호
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• pp.273-292
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• 2014

The effectiveness of a retrofitting method for concrete columns with particular weaknesses is experimentally evaluated and presented in this paper. Structural deficiencies namely the inadequacy of transverse reinforcement and short length of lap splices are very common in columns found in structures built prior to the 1960s and 1970s. Recent earthquakes worldwide have caused severe damages and collapses of these structures. Nevertheless, the importance of improving the load transfer capacity between the deficiently lap-spliced bars is usually underestimated during the strengthening procedures applied in old buildings, though critical for the safety of the residents' lives. Thus, the seismic performance of the enhanced columns is frequently overestimated. The retrofitting approach presented herein involves reinforced concrete jacketing of the column sub-assemblages and welding of the lap-spliced bars to prevent the splice failure and conform to the provisions of modern design Codes. The cyclic lateral loading response of poorly confined original column specimens with insufficient lap splices and the seismic behavior of the retrofitted columns are compared. Test results clearly demonstrate that the retrofitting procedure followed is an effective way of significantly improving the seismic performance of substandard columns found in old buildings.

• 한국지진공학회논문집
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• 제27권6호
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• pp.331-337
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• 2023

Due to the aging of a building, 38.8% (about 2.82 million buildings) of the total buildings are old for more than 30 years after completion and are located in a blind spot for an inspection, except for buildings subject to regular legal inspection (about 3%). Such existing buildings require users to self-inspect themselves and make efforts to take preemptive risks. The scope of this study was defined as the general public's visual self-inspection of buildings and was limited to structural members that affect the structural stability of old buildings. This study categorized possible damage to reinforced concrete to check the structural safety of buildings and proposed a checklist to prevent the damage. A damage assessment methodology was presented during the inspection, and a self-inspection scenario was tested through a chatbot connection. It is believed that it can increase the accessibility and convenience of non-experts and induce equalized results when performing inspections, according to the chatbot guide.

• 한국방재학회 논문집
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• 제9권6호
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• pp.41-49
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• 2009

콘크리트 포장 확장공사시 하부지반의 다짐도 부족과 이로 인한 강성 및 지내력 발생차이는 접속부에서의 벌어짐, 단차, 밀림 등을 발생시키지만 이들 상호간의 연관성에 대한 국내연구는 매우 부족하였다. 본 연구에서는 평판재하시험(PBT)과 공내재하시험(PMT)을 이용하여 확장부 및 기존포장부에서 하부기초 강성측정을 각각 시도하고 그 시험결과를 바탕으로 확장부 및 기존도로부의 강성차이의 크기발생 차이를 분석하였으며 아울러 확장구간과 기존구간의 지내력과 강성 차이 및 접속부의 처리방안의 차이에 의한 포장슬래브의 거동을 평가하기 위해 고안된 변위계를 현장에 설치하여 벌어짐, 단차, 밀림의 발생현상을 관찰하고 이들 사이의 상호연관성과 발생 원인을 분석하여 그 원인을 규명하였다.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.701-721
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• 2014

In the assessment of existing RC buildings, the reliable appraisal of the compressive strength of in-situ concrete is a fundamental step. Unfortunately, the data that can be obtained by the available testing methods are typically affected by a high level of uncertainty. Moreover, in order to derive indications about the degradation and ageing of the materials by on site tests, it is necessary to have the proper terms of comparison, that is to say, to know the reference data measured during the construction phases, that are often unavailable when the building is old. In the cases when such a comparison can be done, the in situ strength values typically turn out to be lower than the reference strength values (tests performed on taken samples during the construction). At this point, it is crucial to discern and quantify the specific effect induced by different factors: ageing of the materials; poor quality of the placement, consolidation or cure of the concrete during the construction phases; damage due to drilling. This paper presents a procedure for correlating the destructive compressive tests and non-destructive tests (ultrasonic pulse velocity tests) with the data documenting the compressive strength tested during the construction phases. The research work is aimed at identifying the factors that induce the difference between the in-situ strength and cubes taken from the concrete casting, and providing, so, useful information for the assessment procedure of the building.

• 터널과지하공간
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• 제7권3호
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• pp.230-237
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• 1997

As concrete structure is getting old and decrepit, its inspection and diagnosis is getting important. Therefore, it is necessary to estimate the soundness of structure using non-destructive tests for effective repairs and maintenances. But, applications of non-destructive tests in tunnel have been used restrictively, due to accessibility only from one side in tunnel lining and presence of tunnel installations. Recently, the various non-destructive techniques have been studied. Especially, ground penetrating radar(GPR) and impact echo (IE) methods have been researched for tunnel inspection. In this study, the applicability of impact echo test in tunnel lining inspection has been investigated. This paper described the tunnel inspection for lining thickness and internal flaw using impact echo tests. Model tests were carried out using impact echo test systems on two concrete models, Model I is measuring for lining thickness, Model II is detecting for internal flaw. Also, the test were applied for lining inspections in a tunnel constructed by NATM. From the results of impact echo tests, we have concluded that impact echo test is a very useful and effective technique for inspecting the concrete tunnel linings.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.286-289
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• 2006

Headed bars have used to the anchoring of the tension or compression longitudinal bars and of the shear reinforcing bars. Recently, lap splices of headed bars are attempted to the joints of precast concrete members and to the connections between old and new concrete members. Previous Michael's experimental research showed that confinement details had an effect on the lap splice performances of headed bars. In this study, the lap splice performances of headed bars(D25) with lap length and confinement details are evaluated through the experimental works. Four specimens, of which variables were the lap length of headed bar and the type of confine details, were tested for the performance evaluation on lap splice. Test results show that the lap length confinement reinforcement improve the performance of lap splice.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.829-841
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• 2014

The main purpose of this study is to determine the effect of overlay on the crack propagation. In order to simplify the problem, a cement concrete pavement is modeled as an elastic plate on Winkler foundation. To derive the singular integral equations, the Fourier transform and dislocation density function are used. Lobatto-Chebyshev integration formula, as a numerical method, is used to solve the singular integral equations. The numerical solution of stress intensity factor at the crack tip is derived. In order to examine the effect of overlay for resisting crack propagation, numerical analyses are carried out for a cement concrete pavement with an embedded crack and a concrete pavement with an asphalt overlay. Results show the significant factors that influence the crack propagation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1133-1138
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• 2000

The interface necessarily exists in joints using cement mortar, UP(Unsaturated Polyester : UP) mortar and SBR(SBR-latex) mortar. Characteristics of shear transfer in joint interface consisting of different materials are studied with experimental and analytical methods. The uniaxial compressive shear experiments are accomplished with various angle of inclination (35, 45, 55, 65, 75°), materials of old and new-cast mortar. In this study, The results are as follows ① Mohr-coulomb's slip theory be applied to the interface consisting different materials ② The cohesion of UP mortar is superior to that f cement mortar, SBR mortar.