• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.532-539
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• 1996

Existing assessment methodologies present a considerable problem because of fuzzy situation of deterioration mechanism of concrete bridges; namely, qualitative, subjective or inconsistent. This paper discusses current assessment methods in aspect of uncertainty. The expert system, COBDA, is developed for consistent and fast assessment of deteriorantion of concrete bridges. Briefly introduced in this paper are the structure of expert system and several methodologies for decision making of deterioration situation and providing repair option. COBDA is configured by PROLOG for logic approach and expert system shell based on Bayesian subjective probability. The methodologies are illustrated and discussed by comparison of condition assessment results in a case study.

• Structural Engineering and Mechanics
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• v.53 no.6
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• pp.1183-1200
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• 2015

Reinforcement corrosion can cause serious safety deterioration to aging concrete structures exposed in aggressive environments. This paper presents an approach for reliability analyses of deteriorating reinforced concrete structures affected by reinforcement corrosion on the basis of the representative symptoms identified during the deterioration process. The concrete cracking growth and rebar bond strength evolution due to reinforcement corrosion are chosen as key symptoms for the performance deterioration of concrete structures. The crack width at concrete cover surface largely depends on the corrosion penetration of rebar due to the expansive rust layer at the bond interface generated by reinforcement corrosion. The bond strength of rebar in the concrete correlates well with concrete crack width and decays steadily with crack width growth. The estimates of cracking development and bond strength deterioration are examined by experimental data available from various sources, and then matched with symptom-based lifetime Weibull model. The symptom reliability and remaining useful life are predicted from the predictive lifetime Weibull model for deteriorating concrete structures. Finally, a numerical example is provided to demonstrate the applicability of the proposed approach for forecasting the performance of concrete structures subject to reinforcement corrosion. The results show that the corrosion rate has significant impact on the reliability associated with serviceability and load bearing capacity of reinforced concrete structures during their service life.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.146-147
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• 2021

In this study, the deterioration of concrete subjected to high temperature was evaluated using harmonics. When concrete is exposed to high temperatures, its mechanical properties deteriorate. In order to evaluate this deterioration, a method of analyzing the waveform of elastic waves was applied. As the heating temperature increased, the fundamental wave of the 50 kHz elastic wave passing through the concrete decreased. In addition, harmonics were generated at each temperature, and the higher the heating temperature, the greater the ratio of harmonics. The higher the compressive strength, the greater the amplitude of the fundamental wave, and this phenomenon is thought to be due to the internal structure of concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.82-92
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• 2012

This study proposed a new non-destructive evaluation method for concrete bridge deck deterioration using ground penetrating radar (GPR). To calculate dielectric constant of the concrete bridge deck, an extended common mid-point (XCMP) method was developed for a two-layered structure using an air-coupled GPR antenna setup. The deterioration conditions of the concrete bridge deck such as deterioration depth was evaluated based on the dielectric constant and surface-to-average dielectric constant ratio of the concrete bridge deck. A GPR field test was conducted on an old concrete bridge with asphalt concrete surfacing to validate the new evaluation method. The test results showed that the newly proposed method estimated pavement thickness and deterioration depth of the concrete deck in a reasonable level.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.158-161
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• 1991

By applying the newly developed techniques of polymer impregnated concrete (PIC) severely deteriorated and low quality concrete can be restored to an adequate structural material. Early deterioration of concrete causes severe problems for bridge deck concrete, pavement concrete for highways and airports, hydraulic structures and buiilding structures. Deterioration has its orgin in cracks on concrete surface, scaling of spalling due to freezing and thawing, neutralization of concrete, penetrations of water, salt, and calcium chloride. The objective of this study is to develope the new surface impregnants and strengthening techniques for them. It is found that the new impregnants and strengthening techniques developed in this study can retian the charecteristics of the existing concrete and decrease deterioration, and also increase durability, chemical resistance, strength, stiffness and ductility of the existing concrete.

• Structural Engineering and Mechanics
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• v.54 no.2
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• pp.319-336
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• 2015

Life cycle performance of corrosion affected RC structures is an important and challenging issue for effective infrastructure management. The accurate condition assessment of corroded RC structures mainly depends on the effective evaluation of deterioration occurring in the structures. Structural performance deterioration caused by reinforcement corrosion is a complex phenomenon which is generally uncertain and non-decreasing. Therefore, a stochastic modelling such as the gamma process can be an effective tool to consider the temporal uncertainty associated with performance deterioration. This paper presents a time-dependent reliability analysis of corrosion affected RC structures associated bond strength degradation. Initially, an analytical model to evaluate cracking in the concrete cover and the associated loss of bond between the corroded steel and the surrounding cracked concrete is developed. The analytical results of cover surface cracking and bond strength deterioration are examined by experimental data available. Then the verified analytical results are used for the stochastic deterioration modelling, presented here as gamma process. The application of the proposed approach is illustrated with a numerical example. The results from the illustrative example show that the proposed approach is capable of assessing performance of the bond strength of concrete structures affected by reinforcement corrosion during their lifecycle.

• Corrosion Science and Technology
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• v.6 no.4
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• pp.177-185
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• 2007

The purpose of this study is to evaluate freezing-thawing and surface scaling resistance in order to examine the frost durability of concrete in a chloride-inherent environment. The mixing design for this study is as follows: 3 water binder ratios of 0.37, 0.42, and 0.47; 2-ingredient type concrete (50% OPC concrete and 50% ground granulated blast-furnace slag), and 3-ingredient type concrete (50% OPC concrete, 15% fly ash, and 35% ground granulated blast-furnace slag). As found in this study, the decrease of durability was much more noticeable in combined deterioration through both salt damage and frost damage than in a single deterioration through either ofthese; when using blast-furnace slag in freezing-thawing seawater, the frost durability and surface deterioration resistance was evaluated as higher than when using OPC concrete. BF 50% concrete, especially, rather than BFS35%+FA15%, had a notable effect on resistance to chloride penetration and freezing/expansion. It has been confirmed that surface deterioration can be evaluated through a quantitative analysis of scaling, calculated from concrete's underwater weight and surface-dry weight as affected by the freezing-thawing of seawater.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.708-717
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• 2002

Durability is a major concern in the design and construction of concrete structures which are located in the sea environments. In particular, the combined action of chlorides, sulfates, and carbonation nay influence greatly the deterioration behavior of concrete structures. The purpose of the present study is to explore the diffusion characteristics of chloride ions in concrete structures under combined deterioration conditions. The present test results indicate that the chloride penetration into concrete structures is more pronounced under combined attacks of chlorides, sulfates and carbonation. The diffusion coefficients and surface chloride contents were found to increase under combined multiple deterioration conditions. The present study provides quantitatively the penetration and diffusion characteristics of chloride ions in concrete structures under various deterioration conditions. The results of present study may be efficiently used for the realistic design of concrete structures under combined deterioration conditions.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.902-912
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• 2003

The most common deteriorating processes of concrete structures are carbonation and chloride ion ingress. Many concrete structures have been suffered from chloride ions diffusion or carbonation induced reinforcement corrosion damage and many studies have been done on it. However, those studies were confined mostly to the single deterioration of carbonation or chloride attack only, although actual environment is rather of combined conditions. In case of many in-situ concrete structures, deterioration happened more for the case of combined attack than the single case of carbonation or chloride attack. In this paper, chloride profiles of carbonated concrete is predicted by considering two layer composite model, which is based on Fick's 2nd law. From the experimental result on combined deterioration of chloride and carbonation, it was examined that high chloride concentration was built up to 3∼5 mm over depth from carbonation depth. The analytical modeling of chloride diffusion was suggested to depict the relative influence of the carbonation depth. The diffusion coefficients of carbonation concrete and uncarbonated concrete with elapsed time were considered in this modeling.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.297-306
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• 2017

The concrete median barrier used currently in South Korea was developed the impact level of SB5-B(270kJ). However, the impact level of SB6(420kJ) should be considered in many placed with the increased accident of heavy vehicles. In order to increase the impact resistance of newly developed concrete median barrier, the computer simulation was conducted before real field test. For the accurate behavior of concrete, the parameter, such as impact vehicle, concrete cover depth and deterioration, was important. In this paper, a parametric study was conducted depending on vehicle curb weight, concrete cover depth and level of deterioration. The impact resistance of concrete median barrier was severely changed depending on vehicle curb weight and concrete cover depth. Furthermore, the impact resistance of concrete median barrier was also decreased due to deterioration of concrete, therefore the repair and rehabilitation should be conducted for damaged concrete depending on deterioration level. Therefore, vehicle curb weight, cover depth of concrete structures and deterioration level of concrete should be carefully considered for conducting analysis of concrete structure to vehicle collision.