• Macromolecular Research
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• 제17권10호
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• pp.797-806
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• 2009

The mechanical and thermal behaviors of polyamide-6/clay nanocomposites were studied using the continuum-based, micromechanical models such as Mori-Tanaka, Halpin-Tsai and shear lag. Mechanic-based model prediction provides a better understanding regarding the dependence of the nanocomposites' reinforcement efficiency on conventional filler structural parameters such as filler aspect ratio ($\alpha$), filler orientation (S), filler weight fraction (${\Psi}_f$), and filler/matrix stiffness ratio ($E_f/E_m$). For an intercalated and exfoliated nanocomposite, an effective, filler-based, micromechanical model that includes effective filler structural parameters, the number of platelets per stack (n) and the silicate inter-layer spacing ($d_{001}$), is proposed to describe the mesoscopic intercalated filler and the nanoscopic exfoliated filler. The proposed model nicely captures the experimental modulus behaviors for both intercalated and exfoliated nanocomposites. In addition, the model prediction of the heat distortion temperature is examined for nanocomposites with different filler aspect ratio. The predicted heat distortion temperature appears to be reasonable compared to the heat distortion temperature obtained by experimental tests. Based on both the experimental results and model prediction, the reinforcement efficiency and heat resistance of the polyamide-6/clay nanocomposites definitely depend on both conventional (${\alpha},\;S,\;{\Psi}_f,\;E_f/E_m$) and effective (n, $d_{001}$) filler structural parameters.

• 한국지반신소재학회논문집
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• 제20권2호
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• pp.1-11
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• 2021

본 연구에서는 산업부산물인 고로슬래그와 순환유동층 보일러의 연소재를 주재료로 사용하여 시멘트와 유사한 경화반응을 유도하도록 개발된 친환경 지반안정재를 약액주입재로 사용하기 위한 실내시험과 시험시공에 관련된 연구가 진행되었다. 이를 위해 실내시험에서는 규산소다 및 실리카졸을 A액, 친환경 지반안정재(또는 OPC)를 B액으로 사용하여 시편을 제작하고, 실내시험을 실시하여 공학적·환경적 성능을 분석하였다. 그리고 실제 노후저수지에 시험시공을 실시하고, 현장에서의 투수시험, 전기비저항탐사를 실시하여 적용성을 분석하였다. 실내시험 결과, 친환경 지반안정재를 B액으로 사용한 약액주입재의 호모겔 압축강도는 보통 포틀랜드 시멘트와 비교하여 약 2.88~3.23배 큰 값을 나타내었다. 또한 대부분의 중금속 용출량이 보통 포틀랜드 시멘트와 비교하여 적고, 어독성 시험에서의 생존율도 100%로 나타났다. 따라서 실내시험 결과를 토대로 판단할 때 OPC에 비해 강도적, 환경적으로도 우수한 것으로 분석되었다. 노후 저수지에서의 시험시공 결과에서는 친환경 지반안정재를 약액주입재의 B액으로 사용하여 보강한 경우, 저수지 내부에서의 투수계수는 1/50 수준까지 감소하였다. 그리고 전기비저항 탐사결과 노후 저수지 내부의 전기비저항은 시간이 경과함에 따라 증가하여 포화대는 사라졌으며, 전반적으로 보강되는 것으로 분석되었다.

• 한국환경과학회지
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• 제17권2호
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• pp.135-140
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• 2008

Steel net gabion is eco-friendly retaining wall structure showing favorable ability to overcome construction and environmental restriction and also to resist corrosion, chemical attack and degradation. This paper is dealt with the applicability of gabion metal net as a substitution of existing strengthening material. Pull out test was carried out to verify the applicability of gabion metal net. According to results, the increase of surcharge loading and horizontal load resulted in a yield of metal net. The stress at the time of yield was in the range of elasticity. Accordingly, gabion metal net can be substituted for existing geogrid and there is a need for experiment and analysis of arrangement direction and durability of gabion steel net.

• 한국산업융합학회 논문집
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• 제16권1호
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• pp.14-20
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• 2013

In this study, characteristic of new materials for repairing/reinforcement of sea and underwater structures using urethane were studied experimentally. As a results, following their good result was obtained. Materials and construction methods due to a chemical reaction, so no seams, shape or form, regardless of the variety of civil engineering in the field can be applied. Fast workability, hardening existing concrete compared with 80% in shortening. Than the existing large concrete pouring construction cost could be reduced by more than 30%.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권2호
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• pp.71-80
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• 2009

This paper discusses the service life prediction methods for CFRP bar for concrete reinforcement using accelerated degradation tests. The relationship between performance degradation and the rate of a failure-causing chemical reaction is assumed for the temperature accelerated degradation tests. Methods of obtaining acceleration factors and predicting service life of the CFRP bar using the degradation model are presented.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.269-274
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• 1997

Recently, premature reinforcement corrosion in concrete structures exposed to chloride containing environments has an important problem. This is due to an increasing use of marine aggregate of chloride containing admixture a the mixing stage and due to an increase of concrete construction in marine environments. In this study, the behavior of chloride ions introduced into concrete from concrete surface by a marine environment was modeled. The physicochemcial processes including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction of chloride ion with solid phase were analyzed by using the finite element method. The results of this study may be used to predict the onset of reinforcement corrosion, and identify the maximum limit of chloride ions contained in admixtures.

• 건축역사연구
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• 제23권6호
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• pp.39-46
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• 2014

In this study, we evaluated the chemical and physical properties of structural steel, which is the most basic material for steel structures and reinforcement concrete structures in modern period. We theorized the technical data for the research of technical history of modern heritage structures by analyzing the product system and its quality control of structural steel used in modern historical heritages. The results of this study are as follow; first, the rounded bars were used in most of modern heritage structures. But in the case of Waegwan railroad bridge, the deformed bars were used in spit of not using in Japan after the great earthquake of Kantou. Second, the structural steel was good in terms of quality control, but It has brittle properties because it was not manufactured by heat treatment process.

• Wind and Structures
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• 제31권5호
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• pp.381-392
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• 2020

Despite that the failure of sign structure may not have disastrous consequence, its sheer number still ensures the need for rigorous safety standard to regulate their maintenance and construction. During its service life, a sign structure is subject to extensive wind load, sometimes well over its permissible design load. A fragility analysis of a sign structure offers a tool for rational decision making and safety evaluation by using a probabilistic framework to consider the various sources of uncertainty that affect its performance. Wind fragility analysis was used to determine the performance of sign structure based on the performance of its connection components. In this study, basic wind fragility concepts and data required to support the fragility analysis of the sign structure such as sign panel's parameters, connection component's parameters, as well as wind load parameters were presented. Fragility and compound fragility analysis showed disparity between connection component. Additionally, reinforcement of the connection system was introduced as an example of the utilization of wind fragility results in the retrofit decision making.

• Computers and Concrete
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• 제19권2호
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• pp.161-169
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• 2017

Chloride induced reinforcement corrosion is widely accepted to be the most frequent mechanism causing premature degradation of reinforced concrete structures. The electrochemical impedance of reinforcing steel in diatomite- and zeolite-containing concrete exposed to sodium chloride was assessed. Chemical, physical and mineralogical properties of three concrete samples (20% diatomite, 20% zeolite, and a reference containing neither) were correlated with corrosion investigations. The steel-reinforced samples were exposed to 3.5% NaCl solution for 500 days, and measured every 15 days via EIS method. Results indicated that porosity and capillary spaces increase the diffusion rate of water and electrolytes throughout the concrete, making it more susceptible to cracking. Reinforcement in the reference concrete was the most corroded compare to the zeolite and the diatomite samples.

• 한국지반공학회논문집
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• 제34권12호
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• pp.71-82
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• 2018

본 연구는 측방이동으로 인한 구조물의 안정성에 영향을 주는 각 인자(성토 높이, 성토부로부터 지하매설물까지의 이격 거리, 연약지반의 깊이, 연약지반의 압축지수 및 팽창지수)별에 대한 합리적이고 경제성 있는 보강길이를 제시하였다. 이러한 결과들을 토대로 각 인자들의 영향 정도를 파악하고, 어떠한 인자가 측방이동에 가장 영향을 미치는가를 파악하였다. 유한요소 해석프로그램을 이용하여 연약지반 상에 성토가 이루어지는 경우의 단면을 모델링하여 해석을 수행하였으며, 연약지반의 보강은 심층혼합공법(DCM)을 이용하였다. 그 결과 성토 높이 증가에 따른 보강길이의 증가율은 약 9~50%, 연약지반 심도 증가에 따른 보강길이의 증가율은 약 13~30%, 성토부로부터 지하 매설물의 이격 거리 감소에 따른 보강길이의 증가율은 약 7~25%, 압축지수 증가에 따른 보강길이의 증가율은 약 3~25%로 나타났다. 또한 각 인자별로 서로에 대한 영향성을 분석하였다. 그 결과 연약지반 심도의 보강길이 최대 최소 기울기비는 이격거리 변화에 큰 영향을 받았으며 이외의 인자들은 연약지반 심도의 변화에 따라 최대 최소 기울기 비가 큰 영향을 받았다. 한편 연약지반의 심도가 깊어질수록 성토높이에 따른 보강길이의 최대-최소기울기의 비는 3.75, 이격 거리에 따른 보강길이의 최대-최소기울기의 비는 4.3, 압축지수에 따른 최대-최소기울기의 비는 2.5로 나타났다. 이를 통해 세 개의 인자는 연약지반의 심도에 대한 영향을 크게 받는 것으로 확인되었다.