• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.181-184
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• 2006

Traditional durability analysis is not possible to provide a controlled durability and long-term performance of concrete structures. Recently, research works have shown that probabilistic approach based on the theory of structural reliability, would be very valuable for durability analysis. In this study, the probabilistic durability analysis based on a Monte Carlo Simulation was carried out using sample data selected from detailed field investigation. The probabilistic properties of some design variables, such as diffusion coefficients of concrete and surface chloride concentration, were newly determined using some experimental data. By applying a probabilistic durability analysis to an integral structural design, the durability performance of concrete structures would be remarkably improved.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.46-52
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• 2017

Recently durability design based on deterministic or probabilistic method has been attempted since service life evaluation in RC(Reinforced Concrete) structure exposed to chloride attack is important. The deterministic durability design contains a reasonable method with time effect on surface chloride content and diffusion coefficient, however the probabilistic design procedure has no consideration of time effect on both. In the paper, a technique on PDF(Probability of Durability Failure) evaluation is proposed considering time effect on diffusion and surface chloride content through equivalent surface chloride content which has same induced chloride content within a given period and cover depth. With varying period to built-up from 10 to 30 years and maximum surface chloride content from $5.0kg/m^3$ to $10.0kg/m^3$, the changing PDF and the related service life are derived. The proposed method can be reasonably applied to actual durability design with preventing conservative design parameters and considering the same analysis conditions of the deterministic method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.343-352
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• 2010

Recently, many researchers have been carried out to estimate more controlled service life and long-term performance of carbonated concrete structures. Durability analysis and design based on probability have been induced to new concrete structures for design. This paper provides a carbonation prediction model based on the Fick's 1st law of diffusion using statistic data of carbonated concrete structures and the probabilistic analysis of the durability performance has been carried out by using a Bayes' theorem. The influence of concerned design parameters such as $CO_2$ diffusion coefficient, atmospheric $CO_2$ concentration, absorption quantity of $CO_2$ and the degree of hydration was investigated. Using a monitoring data, this model which was based on probabilistic approach was predicted a carbonation depth and a remaining service life at a variety of environmental concrete structures. Form the result, the application method using a realistic carbonation prediction model can be to estimate erosion-open-time, controlled durability and to determine a making decision for suitable repair and maintenance of carbonated concrete structures.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.137-143
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• 2008

In recent years, much research work has been performed on durability design and long-term performance of concrete structures in marine environments. In particular, the development of new procedures for probability-based durability design has been shown to provide a more realistic basis for the analysis. This approach has been successfully applied to several new concrete structures, where requirements for a more controlled durability and service life have been specified. For reinforced concrete structures in a marine environment, it is commonly assumed that the dominant degradation mechanism is the corrosion of the reinforcement due to the presence of chlorides. The design approach is based on the verification of durability limit states, examples of which are: depassivation of reinforcement, cracking and spalling due to corrosion, and collapse due to cross section loss of reinforcement. With this design approach the probability of failure can be determined as a function of time. In the present paper, a probability-based durability performance analysis is used in order to demonstrate the importance of the durability design approach of concrete structures in marine environments. In addition, the sensitivity of the various durability parameters affecting and controlling the durability of concrete structures in a marine environment is studied. Results show that the potential of this approach to assist durability design decisions making process is great. Based the crucial information generated, it is possible to prolong the service life of structures while simultaneously optimizing the final design solution.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.831-849
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• 2022

One of the most prevalent causes of reinforced concrete (RC) structural deterioration is chloride-induced corrosion. This paper aims to provide a comprehensive insight into the environmental effect of RC's chloride ingress process. The first step is to investigate how relative humidity, temperature, and wind influence chloride ingress into concrete. The probability of initiation time of chloride-induced corrosion is predicted using a probabilistic model that considers these aspects. Parametric analysis is conducted on several factors impacting the corrosion process, including the depth of concrete cover, surface chloride concentration, relative humidity, and temperature to expose environmental features. According to the findings, environmental factors such as surface chloride concentration, relative humidity and temperature substantially impact on the time to corrosion initiation. The long- and short-distance impacts are also examined. The meteorological data from the National Meteorological Center of China are collected and used to analyze the environmental characteristics of the chloride ingress issue for structures along China's coastline. Finally, various recommendations are made for improving durability design against chloride attacks.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.276-285
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• 2020

In this study, accelerated chloride diffusion tests were performed on OPC(Ordinary Portland Cement) and FA(Fly Ash) concrete considering three levels o f W/B(Water to Binder) ratio o n 1,095 curing days. The accelerated chloride diffusion coefficient and the passed charge were evaluated in accordance with Tang's method and ASTM C 1202, and the resistance performance to chloride attack improved over time. FA concrete showed excellent resistance performance against chloride penetration with help of pozzolanic reaction. As the result of the passed charge, FA concrete showed durability improvement, "low" grade to "very low" grade, but OPC concrete changed "moderate" grade to "low" grade at 1,095 curing days. After assuming the design variables used for durability design as normal distribution functions, the service life of each case was evaluated by the probabilistic analysis method based on MCS(Monte Carlo Simulation). In FA concrete, the increase of probability of durability failure was lower than that of OPC concrete with increasing time, because the time-dependent coefficient of FA concrete was up to 3.2 times higher than OPC concrete. In addition, the service life by probabilistic analysis was evaluated lower than the service life by deterministic analysis, since the target probability of durability failure was set to 10%. It is considered that more economical durability design will be possible if the mo re suitable target probability of durability failure is set for various structures through researches on actual conditions and indoor tests under various circumstances.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.497-500
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• 2008

In order to prevent deterioration of reinforced concrete structures exposed to marine environment, performance based durability design than the design by conventional deemed-to-satisfy rule should be concerned. For example, even though chloride threshold level, which is a major parameter for durability design, is defined as a 1.2 $kg/m^3$ in the Korean concrete specification, it shows that the chloride threshold level leads to over design in its real application so that realistic value should be determined for the performance design. In this paper, not only the probabilistic properties of chloride threshold level obtained from published data are taken into account, but also the experimental results of the probabilistic properties using surface chloride content, diffusion coefficient, cover depth are considered in the assessment utilizing the concept of performance based durability design. In computation, the Monte Carlo Simulation (MCS) is used to perform an assessment due to chloride attack for a target submerged tunnel box. This study found that the specification on current chloride threshold level should be modified for more rational and accurate assessment and design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1041-1048
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• 2006

The pulley is one of core mechanical elements in the power steering system for vehicles. The pulley operates under both the compressive loading and the torque. Therefore, to assure the safety of the power steering system, it is very important to investigate the durability and the optimization of the pulley. In this study, the applied stress distribution of the pulley under high tension and torsion loads was obtained by using finite element analysis. Based on these results the fatigue life of the pulley with the variation of the fatigue strength was evaluated by a durability analysis simulator. The results at 50% and 1% for the failure probability were compared with respect to the fatigue life. In addition to the optimum design for the fatigue life is obtained by the response surface method. The response function utilizes the function of the life and weight factors. Within range for design life condition the minimization of the weight, one of the formulation, is obtained by the optimal design. Moreover the optimum design by considering its durability and validity is verified by the durability test.

• Computers and Concrete
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• v.19 no.3
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• pp.305-313
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• 2017

A robust finite element based reinforced concrete bridge deck corrosion initiation model is applied for time-dependent probabilistic sensitivity analysis. The model is focused on uncertainties in the governing parameters that include variation of high performance concrete (HPC) diffusion coefficients, concrete cover depth, surface chloride concentration, holidays in reinforcements, coatings and critical chloride threshold level in several steel reinforcements. The corrosion initiation risk is expressed in the form of probability over intended life span of the bridge deck. Conducted study shows the time-dependent sensitivity analysis to evaluate the significance of governing parameters on chloride ingress rate, various steel reinforcement protection and the corrosion initiation likelihood. Results from this probabilistic analysis provide better insight into the effect of input parameters variation on the estimate of the corrosion initiation risk for the design of concrete structures in harsh chloride environments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.67-74
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• 2015

RC (Reinforced Concrete) structures are considered as cost-benefit and durable however performances of structural safety and durability are degraded due to steel corrosion. Service life in RC structure is differently evaluated due to different local environmental conditions even if it is exposed to the same chloride attack. In the paper, 25 concrete cores from field investigation are obtained from 4 RC columns with duration of 3.5~4.5 years exposed to sea water. Through total chloride content measurement, surface chloride contents and apparent diffusion coefficients are evaluated. Service life of the target structure is estimated through deterministic method based on Fick's $2^{nd}$ Law and probabilistic method based on durability failure probability, respectively. Probability method is evaluated to be more conservative and relatively decreased service life is evaluated in tidal zone and splash zone over 40.0 m. Chloride penetration behavior with coring location from sea level and the present limitations of durability design method are investigated in the paper.