• 한국지반신소재학회논문집
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• 제2권2호
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• pp.33-38
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• 2003

부직포와 결합한 보강용폴리에스터 직포 지오텍스타일을 제조한 다음 크리프 시험결과로 부터 허용인장강도를 구하였다. 설계 및 시공을 고려한 안전율로 부터 장기설계인장강도를 구하였고 보강기능을 조사하기 위하여 지오그리드와 복합 직포 지오텍스타일의 장기거동을 비교하였다. 실험결과로 부터 보강용 직포 지오텍스타일이 지오그리드와 같은 충분한 보강성능이 있음을 확인할 수 있었고, 향후 추가실험을 통하여 복합 직포 지오텍스타일의 우수한 보강성능이 지속적으로 검증되어야 할 것으로 생각된다.

• 한국지반공학회논문집
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• 제20권3호
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• pp.119-128
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• 2004

본 연구에서는 지반 보강재로 폐타이어를 사용함에 있어서 환경적인 영향에 대하여 고찰하였다. 시험은 12개의 침출수 발생장치 속에 모래와 타이어조각들을 섞은 후 세 가지 조건의 용액을 각각 순환시킨 침출수에 대하여 화학적분석과 생물학적 독성영향을 조사하였다. 연구결과, 검출된 모든 금속원소의 오염농도는 우리나라 먹는물 수질기준치보다 훨씬 낮았고, 철을 제외한 모든 금속원소의 농도가 시간이 지남에 따라 줄어드는 것으로 나타났다. 선행된 시험과 비교한 결과 노출되는 금속의 비표면적이 클수록 즉, 타이어칩, 타이어조각, 전체타이어의 순서로 오염물질의 농도가 크게 검출되었다. 형광성 박테리아를 이용한 독성검사의 결과에서는 독성이 발견되는 경향을 보이지 않아 폐타이어에서 나오는 침출수가 유기체에 유해한 영향을 미치지 않는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제16권4호
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• pp.391-404
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• 2003

Local reinforcement in dowel type timber joints is essential to improve ductility, to increase load carrying capacity and to reduce the risk of brittle failure, especially in the case of using solid dowel. In many types of reinforcing materials available today, DVW (densified veneer wood) has been demonstrated to be the most advantages in terms of compatibility, embedding performance and ductility. Preliminary studies show that using appropriately sized DVW discs bonded into the timber interfaces may be an effective way to reinforce the connection. In this paper, non-linear 3-dimensional finite element models, incorporating orthotropic and non-linear material behaviour, have been developed to simulate structural performance of the timber joints locally reinforced by DVW discs. Different contact algorithms were applied to simulate contact conditions in the joints. The models were validated by the corresponding structural tests. Correlation between the experimental results and the finite element simulations is reasonably good. Using validated finite element models, parametric studies were undertaken to investigate effects of the DVW disc sizes and the end distances on shear stresses and normal stresses in a possible failure plane in the joint.

• Computers and Concrete
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• 제15권2호
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• pp.305-319
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• 2015

On mesoscopic level, concrete can be treated as a three-phase composite material consisting of mortar, aggregates and interfacial transition zone (ITZ) between mortar and aggregate. A lot of research has confirmed that ITZ plays a crucial role in the mechanical fracture process of concrete. The aim of the present study is to propose a numerical method on mesoscale to analyze the failure mechanism of reinforced concrete (RC) structures under mechanical loading, and then it will help precisely predict the damage or the cracking initiation and propagation of concrete. Concrete is meshed by means of the Rigid Body Spring Model (RBSM) concept, while the reinforcing steel bars are modeled as beam-type elements. Two kinds of RC members, i.e. subjected to uniaxial tension and beams under bending, the fracture process of concrete and the distribution of cracks, as well as the load-deflection relationships are investigated and compared with the available test results. It is found that the numerical results are in good agreement with the experimental observations, indicating that the model can successfully simulate the failure process of the RC members.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.425-431
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• 2001

In order to take account of the statistical properties of probability variables used in the structural analysis, the conventional approach using the safety factor based on past experience usually estimated the safety of a structure. The real structures could only be analyzed with the error in estimation of loads, material characters and the dimensions of the members. But the errors should be considered systematically in the structural analysis. Structural safety could not precisely be appraised by the traditional structural design concept. Recently, new approach based on the probability concept has been applied to the assessment of structural safety using the reliability concept. In this study, safety of structures will estimated by the reliability analysis with commercial structural software that has the tools of nonlinear elastic-plastic 3-D analysis. Experimental test result is compared to results from this research and Coan/sup 1)/ In this paper, AFOSM(Advanced First-Order Second Moment method) is applied with von Mises, Tresca and Mohr-Coulomb failure criterions. The reliability index β and probability of failure P/sub f/ can be obtained by following this practical procedure as judgement a safety of structures and necessity of reinforcing.

• 한국시스템다이내믹스연구
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• 제7권1호
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• pp.91-118
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• 2006

The purpose of this study is to find what factors are directly related to the delay of public projects, usually going beyond the planned deadline and budget. From a series of System Dynamics simulation works applied to the Cheongju Cremation Project, the research finds that the negative externalities originated from the adjacent location of the LULU(locally unwanted land use) facilities have exerted significant influence on dynamic perceptions of key stakeholders, typically resulting in project delay. As shown repeated experiments, the proposed negotiation-based models would produce relatively higher planning performance level than the typical approaches hinged on the administrative-expediency tactics. Even though the former may require more human and material resources in the very beginning stage, as they have to deal with diverse grievances raised by major stake-holders, most of them would bound for strengthening reinforcing loops within the complex structure. These results also imply that negotiation or consensus-building approaches would enhance mutual agreement among stake-holders, upgrading the overall quality of project management.

• 한국구조물진단유지관리공학회 논문집
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• 제5권1호
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• pp.195-205
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• 2001

An analytical finite element approach to nonlinear behavior of reinforced concrete shear walls with opening under monotonic loading was presented in this paper. In order to achieve the objectives of present paper, the orthogonal anisotropic models for cracked reinforced concrete element based on smeared crack concept were used as the nonlinear material models of biaxial state of stress. The stiffness of cracked concrete was evaluated through the combined use of tension and compression stiffness models in and parallel directions of crack, respectively and shear transfer effect due to the aggregate interlocking at crack surface. The stress and strain of reinforcement in concrete was evaluated using the average stress and average strain relation with bond effect. based on smeared crack concept. The diagonal reinforcing bar was modeled using truss element with bond effect. A special significance of diagonal reinforcement near opening was given to the shear wall with opening and an effective distribution of diagonal reinforcement was presented in order to give an ultimate strength increment as well as a crack control.

• 산업기술연구
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• 제27권A호
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• pp.103-110
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• 2007

Concrete is a material that will crack during its service life by its very nature. For bridge decks this is especially significant as these cracks allow accelerated ingress of chlorides and the subsequent corrosion of the reinforcing steel and deck deterioration. Very-early strength latex-modified concrete (below ; VES-LMC) was developed in order to realize early-opening-to-traffic bridge deck concrete. Although there has been little research to document the degree of cracking in VES-LMC overlay, there has been a general perception among highway agencies that overlay cracking of VES-LMC, particularly early-age cracking, is a one of problems which should be solved. The purpose of this study was to analyze the cause of map, transverse and longitudinal cracking in VES-LMC and to provide a control methods for minimizing the occurrence of cracks. The proposed prevention against map and transverse cracking was verified by field applications. VES cement was modified, the unit cement contents was reduced into $360kg/m^3$ from $390kg/m^3$, the maximum size of coarse aggregate was increase into 19mm from 13mm, wire mesh and steel fibers were incorporated in concrete mixture.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.797-800
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• 2008

시멘트 사용량을 줄이기 위한 방법으로 포졸란 반응재료들이 혼화재로 사용되고 있다. 우리나라 전역에 널리 매장되어 있는 황토는 친환경 재료로서, 포졸란 반응을 하는 활성황토는 콘크리트의 혼화재로 활용성이 증가하고 있다. 또한 PET보강섬유는 폐 PET병을 재활용하여 만든 친환경재료로서 콘크리트에 혼입되어 미세균열을 제어하는 역할을 한다. 하지만 보강섬유를 혼입한 콘크리트에 대한 연구는 아직도 미비한 실정이고 황토를 혼화재로 사용한 콘크리트의 경우 황토 혼화재의 포졸란 반응과 보강섬유의 보강효과가 복합적으로 나타날 것으로 판단된다. 따라서 본 연구에서는 황토와 PET보강섬유를 혼입한 콘크리트 거동 특성을 분석하기 위하여 건조수축 시험을 통해 황토와 PET보강섬유를 혼입한 콘크리트의 재료특성을 평가하였다.

• 한국입자에어로졸학회지
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• 제13권4호
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• pp.183-189
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• 2017

Potassium hexatitanate ($K_2Ti_6O_{13}$) with high thermal insulating capacity, good mechanical properties, and excellent chemical stability are promising functional materials in the field of reinforcing material, heat insulating paints and automotive brake linings. In this study, we successfully synthesized rod-shaped potassium hexatitanate ($K_2Ti_6O_{13}$) by aerosol spray drying and post heat treatment as an eco-friendly process. The $KHCO_3-TiO_2$ porous particles were firstly synthesized from a colloidal mixture of $K_2CO_3$ and $TiO_2$ via aerosol spray drying. Size of $KHCO_3-TiO_2$ porous particles was ranged from $1{\mu}m$ to $5{\mu}m$. The porous particles were then heated to fabricate rod-type $K_2Ti_6O_{13}$. The length and width of rod-type composites were affected by temperature and heating time. The length and width of $K_2Ti_6O_{13}$ were increased by 830 nm and 500 nm, respectively, as the reaction temperature and time increased.