• 대한토목학회논문집
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• 제26권1A호
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• pp.75-89
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• 2006

본 논문에서는 생애주기동안 발생하는 부식이나 일평균교통량 및 중차량의 통행량와 같은 사용환경에 의존하는 강교의 생애신뢰성에 기초한 생애주기비용(Life-Cycle Cost: 이하 LCC) 최적설계 방법론을 제안하였다. 강교 최적설계를 위한 LCC는 초기비용, 생애주기 기대유지관리비용, 생애주기 기대직접복구비용과 인적 혹은 물적손실비용, 도로이용자비용, 그리고 사회-경제 손실비용을 포함하는 간접복구비용을 현재가치의 합으로 정식화하였다. 이러한 LCC비용항목 중에서 생애주기 복구비용의 산정을 위해서는 하중과 저항이력에 의존하는 누적손상확률로부터 산정되는 연파손확률이 고려되어야한다. 이를 위해 본 논문에서는 Nowak의 활하중 모델(1993)과 부식개시, 부식률, 그리고 재도장영향을 고려한 수정된 부식모델을 제안하였다. 이와같이 본 연구에서 제안된 LCC 최적설계 방법론은 3 경간연속(40 m+50 m+40 m=130 m)의 실제 강박스거더교에 적용되었고, 강재종류, 부식환경, 교통량 및 할인율에 따른 LCC의 효율성에 대해 비교 고찰하였다. 적용예를 통해 부식환경, 일평균교통량, 그리고 중차량의 통행량, 할인율 등은 강교 LCC최적설계에 매우 중요한 영향을 미칠 수 있음을 알 수 있었으며, 이러한 교량의 사용환경인자들은 경우에 따라 LCC 최적설계에 대한 주요 변수로 고려되어야 할 것으로 판단된다.

• 한국도로학회논문집
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• 제7권4호
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• pp.113-123
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• 2005

본 연구에서는 기존의 염화물계 제설제인 염화칼슘$(CaCl_2)$ 및 염화나트륨(NaCl)과 비염화물계 제설제(NS 100) 초산화합물 함유 염화물 제설제(NS 40), 그리고 이들 제설제를 중량대비 일정비율로 혼합$(NaCl\;70%+CaCl_2\;30%,\;NS\;40\;70%+CaCl_2\;30%,\;NaCl\;70%+NS\;40\;30%,\;NS\;40\;70%+NaCl\;30%)$하였을 때 제설성 능과 특성, 콘크리트의 동결융해저항성 및 강재의 부식에 미치는 영향을 실내시험을 통하여 비교 검토하였다. 이상의 시험결과를 바탕으로 동절기 구조물이 동해를 받을 수 있는 지역에서 염화물계 제설제를 사용할 경우 제설성능 및 효과, 강재의 부식성 콘크리트의 동결융해저항성 및 스켈링저항성에 미치는 영향을 고려해 볼 때 하나의 제석제를 사용하기 보다는 두가지 제설제를 적정 비율로 혼합하여 사용하는 것이 바람직한 방법임을 알 수 있었다. 혼합 사용시에는 제설성능 강재 및 콘크리트에 미치는 영향을 고려해 볼 때 NS40(70%)+염화칼슘(30%)이 가장 효과적인 것으로 나타났다.

• 한국해양공학회지
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• 제6권2호
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• pp.76-84
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• 1992

In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane behavior of base metal (BM) and heat affected zone (HAZ) of SAPH45. The main results obtained are as follows: 1) The more aspect ratio (b/t) of corner crack decreases, the more aspect ratio (b/a) takes greatly effect by corrosion. 2) The correlation between the stress intensity factor range ($\Delta$k) and crack growth rate (da/dN) for weldment in seawater is given by Paris rule as follow: da/dN=C($\Delta$K) super(m). Where m is constant, and the value is 3.82-3.84. 3) The accelerative factor ($\alpha$) of BM and HAZ under seawater is about 1.1-1.9, and ($\alpha$) of HAZ increases more and more under the low $\Delta$K region. 4) HAZ is more susceptible to corrowion than BM because of potential of electrode (E sub(c)) of HAZ becomes more less noble potential than that of BM.

• Corrosion Science and Technology
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• 제14권5호
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• pp.232-238
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• 2015

Corrosion is of greatest concern for metallic materials exposed to corrosive seawater or aggressive marine atmospheres. Marine structures and components made of metallic materials incur an initial cost and additional large costs for corrosion control and maintenance. There have been worldwide efforts to minimize marine corrosion and extend service life of the materials. It is believed that various factors are associated with corrosion of marine grade metallic materials, particularly the temperature of the solution affecting the corrosion rate by changing dissolved oxygen solubility and concentrations of chloride. In the present study, the electrochemical characteristics of S355ML steel are investigated to identify corrosion acceleration tendencies with changes in solution temperature under marine environments. It was found that increasing seawater temperature, promoted not only activation of chloride ion transfer, but also the formation of porous $Fe(OH)_3$ or $Fe_2O_3$, leading to the acceleration of corrosion.

• Corrosion Science and Technology
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• 제20권5호
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• pp.295-307
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• 2021

Effects of ε-carbide (Fe_2.4C) on corrosion and hydrogen diffusion behaviors of ultra-strong steel sheets for automotive application were investigated using a number of experimental and analytical methods. Results of this study showed that the type of iron carbide precipitated during tempering treatments conducted at below A₁ temperatures had a significant influence on corrosion kinetics. Compared to a steel sample with cementite (Fe₃C), a steel sample with ε-carbide (Fe_2.4C) showed higher corrosion resistance during a long-term exposure to a neutral aqueous solution. In addition, the diffusion kinetics of hydrogen atoms formed by electrochemical corrosion reactions in the steel matrix with ε-carbide were slower than the steel matrix with cementite because of a comparatively higher binding energy of hydrogen with ε-carbide. These results suggest that designing steels with fine ε-carbide distributed uniformly throughout the matrix can be an effective technical strategy to ensure high resistance to hydrogen embrittlement induced by aqueous corrosion.

• Corrosion Science and Technology
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• 제18권3호
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• pp.102-109
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• 2019

The hydrogen diffusion and trapping model with a numerical finite difference method (FDM) was modified and extended to accommodate $H_2S$ corrosion and scale forming processes of high-strength steel under tensile stress condition. The newly proposed diffusion model makes it possible to clearly understand combined effect of tensile stress and $H_2S$ corrosion process on hydrogen diffusion behaviors. The core concept of this theoretical approach is that overall diffusion behavior is separated into diffusion process through two respective layers: an outer sulfide scale and an inner steel matrix. Diffusion coefficient values determined by curve-fitting permeation data reported previously with the newly proposed diffusion model indicate that the application of tensile stress can contribute to continual increase in the diffusivity in the sulfide scale with a high density of defect. This suggests that the scale with a lower stability under the stress condition can be a key parameter to enhance hydrogen influx in the steel matrix. Consequently, resistance to hydrogen assisted cracking of the steel under tensile stress can be decreased significantly.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.81-82
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• 2022

Al and Zn are used to protect the steel structures from corrosion. In the present studies, 15Al-85Zn alloy wires has been used for the deposition of coating by arc thermal spray process. Moreover, this process of coating exhibited severe defects formation, therefore, this coating was post-treated with different concentrations i.e. 0.05, 0.1 and 0.5M sodium hexa meta phosphate (Na6[(PO3)6]: SHMP) to fill to defects of deposited coatings and assessed their corrosion resistance in 3.5 wt.% NaCl solution with exposure periods. After the treatment, the porosity of the coating reduced significantly by formation of composite oxide films onto the coating surface. Initially, 0.5 M SHMP treated coating exhibited highest in total impedance due to significant reduction of porosity but once the exposure periods are extended, the composite oxides are dissolved, thus, total impedance is decreased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.59-60
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• 2023

The corrosion of steel rebar embedded in the coastal areas is corroding once the chloride ions ingress through the pores of the concrete. Therefore, in the present study, a 100 ㎛ thick Al and Zn coating was deposited by an arc thermal spray process onto the steel. The corrosion studies of these deposited coatings were assessed in 3.5 wt.% NaCl contaminated concrete pore (CP) solution with immersion periods. The results show that the Al coating is more corrosion resistance compared to the Zn coating attributed to the formation of gibbsite (γ-Al(OH)₃) whereas Zn coating exhibits Zn(OH)₂ onto the coating surface as passive layer. The Zn(OH)₂ is readily soluble in an alkaline solution. Alternatively, γ-Al(OH)₃ on the Al coating surface is less solubility in the alkaline pH, which further provides barrier protection against corrosion.

• Corrosion Science and Technology
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• 제22권5호
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• pp.387-392
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• 2023

The objective of this study was to evaluate corrosion resistance of Zn-Al-Mg alloy coated steel in residential water with trace quantities of Cl^-. Comparative evaluations were performed using two commercial coated steel products, GI and Galvalume, as reference samples. Examination of corrosion morphology and measurement of weight loss revealed that the Zn-Al-Mg alloy coated steel exhibited higher corrosion resistance than reference samples. This finding suggests that the alloy coated steel possesses long-term corrosion resistance not only in highly Cl^- concentrated environments such as seawater, but also in environments with extremely low levels of Cl^- found in residential water. The primary factor contributing to the superior corrosion resistance of the Zn-Al-Mg alloy coated steel in residential water is the formation of an inhibiting corrosion product composed primarily of two phases: Zn₅(OH)₆(CO₃)₂ and Zn₅(OH)₈Cl₂·H₂O. The preferential dissolution of Mg from the corroded coating layer can increase alkalinity, which might enhance the thermodynamical stability of Zn₅(OH)₆(CO₃)₂.

• 한국구조물진단유지관리공학회 논문집
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• 제18권2호
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• pp.47-53
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• 2014

이 연구에서는 중소지간 합성형 강거더교량에 대한 신뢰성 해석을 위해 강거더와 콘크리트슬래브의 강성을 토대로 처짐을 고려한 한계 함수를 구축하여 신뢰성해석을 수행하였다. 확률적 하중과 저항모델을 통해 처짐을 예측하기 위해 계산에 필요한 변수들을 확률변수로 고려하였다. 강재의 부식에 의한 단면의 감소, 그리고 콘크리트의 크리프는 합성형교의 처짐에 많은 영향을 미친다. 따라서 이 연구에서는 AASHTO LRFD 기준으로 설계된 교량에 대해 시간에 따른 변수를 고려하여 강재단면의 감소와 크리프의 영향을 통계적 모델에 반영하기 위해 몬테-카를로 시뮬레이션 기법을 이용하였으며, 처짐과 사용성을 고려하여 다양한 지간과 거더간격을 가진 교량에 신뢰성 해석을 수행하였다. 그 결과, 장지간 교량의 경우, 단지간 교량과 비교해 보았을 때 상대적으로 크리프와 강재단면감소의 처짐에 대한 영향이 작았으며, 이에 반해 단지간 거더 교량의 경우 크리프의 진행에 따라 처짐에 많은 영향을 미친다는 것을 알 수 있었다.