• Structural Engineering and Mechanics
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• v.9 no.6
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• pp.601-613
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• 2000

Existing models for the shear strength degradation of reinforced concrete members present varied conceptual approaches to interpreting test data. The relative superiority of one approach over the others is difficult to determine, particularly given the sparseness of ideal test data. Nevertheless, existing models are compared using a suite of test data that were used for the development of one such model, and significant differences emerge. Rather than relying purely on column test data, the body of knowledge concerning degradation of concrete as a material is considered. Confined concrete relations are examined to infer details of the degradation process, and to establish a framework for developing phenomenologically-based models for shear strength degradation in reinforced concrete members. The possibility of linking column shear strength degradation with material degradation phenomena is explored with a simple model. The model is applied to the results of 7 column tests, and it is found that such a link is sustainable. It is expected that models founded on material degradation phenomena will be more reliable and more broadly applicable than the current generation of empirical shear strength degradation models.

• Steel and Composite Structures
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• v.24 no.6
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• pp.753-765
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• 2017

This paper aims to investigate the strength degradation of reinforced concrete piers wrapped with steel plates which corrode at the pier base by employing a three dimensional elasto-plastic finite element formulation. The prediction accuracy of the employed finite element analysis method is firstly verified by comparing the analytical results with test results. Then, a series of parametric studies is carried out to investigate the effects of steel plate's corrosion position along width direction, corrosion depth along plate thickness, corrosion range along width direction, and steel plate-concrete bonding degradation on the strength of the piers. It is observed that the strength degradation of the piers is closely related to steel plate's corrosion position, corrosion depth and corrosion range in the case of local corrosion on the webs. In contrast, when the base of flanges corrodes, the strength degradation of the piers is only related to steel plate's corrosion depth and corrosion range, and the influence of corrosion position on the strength degradation is very gentle. Furthermore, the strength of the piers decreases with the degradation of steel plate-concrete bonding behavior. Finally, the maximum strength of the piers obtained from numerical analysis corresponding to different bonding behavior is compared with theoretical results within an accepted error.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.45-48
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• 2009

The performance of concrete mainly depend upon its water-cement ratio. If water percentage is excess in concrete, it may cause the degradation of performance. Because of these reasons, the change of water content is managed by using various evaluation method of unit water content. And criterion for the change of water content is regulated and used. However the criterion is set only considering production error and measurement error but criterion does not consider performance degradation of concrete. Therefore this study tries to investigate degradation of performance while adding extra water by artificial manipulation or management error in concrete, The contents of extra water for tests are set as 0, 20, 40, 60kg/m3, to examine the performance degradation of concrete, strength, shrinkage, cracks, carbonation are tested This study conclude that, when extra water content is excess than 20kg/m3 in concrete, then performance level of concrete declined rapidly. 80 it is very important to maintain quality of concrete for its better performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.122-123
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• 2016

Sulfate anion which cause concrete degradation is affected on marine structures. There are two of control method concrete degradation which is arisen by sulfate anion. Cementitious materials prevent permeation of sulfate anion and water-binder ratio increase to improve watertightness. But, those methods are passive. So, this study is developing new materials which prevent actively concrete degradation on sulfate anion.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.14 no.1
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• pp.11-19
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• 2016

This paper focuses on the estimation of durability and service-life of reinforced concrete structures in Wolsong Low- and intermediate-level wastes Disposal Center (WLDC) in Korea. There are six disposal silos located in the saturated environment. The silo concrete is degraded due to reactions with groundwater and chemical attacks, and finally it will lose its properties as a transport barrier. The infiltration of sulfate and magnesium, leaching of potassium hydroxide, and chlorine induced corrosion are the most significant factors for degradation of reinforced concrete structure in underground environment. From the result of evaluation of the degradation time for each factor, the degradation rate of the reinforced concrete due to sulfate and magnesium is $1.308{\times}10^{-3}cm/yr$, and it is estimated to take 48,000 years for full degradation while potassium hydroxide is leached in depth of less than 1.5 cm at 1,000 years after the initiation of degradation. In case of chlorine induced corrosion, it takes 1,648 years to initiate corrosion in the main reinforced bar and 2,288 years to reach the lifetime limit of the structural integrity, and thus it is evaluated as the most significant factor.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.1-4
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• 2005

This research is to present experimental materials model of high strength concrete for prediction of fire safety of structural members based on physical properties of materials during heating up to 800$^{circ}C$. The following conclusions are drawn from this study. First of all, between 100 to 200 $^{circ}C$, the physical models of concrete such as specific heat and thermal conductivity, show visible degradation, regardless of concrete strength. Second, between 300 to 600$^{circ}C$, the physical models of the 29MPa and 49MPa concrete show degradation continually at these temperatures. Finally, beyond 600$^{circ}C$, the physical models of 49MPa strength concrete show larger degradation than 29MPa strength concrete due to rise of pore pressure and melting of the interface between aggregate and cement paste.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.4
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• pp.391-398
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• 2011

After a concrete is poured, reinforced concrete structures were distressed by physical and chemical factor over time. It is in need to define important variables related to structural behavior for effectively conducting seismic analysis of structures with age-related degradation. In this study, a sensibility analysis using the first-order second moment method was performed to analyze an important variables for the reinforced concrete shear wall with age-related degradation. Because the seismic capacity of aging structures without a concrete hardening effect can be underestimated, the sensibility of analysis variables was analyzed according to the concrete hardening. Important variables for RC shear wall with age-related degradation was presented by using the tornado diagram.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.163-166
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• 2005

In this study, an unified algorithm for the degradation analysis which considers the cracks in concrete and steel corrosion is developed and implemented into finite element analysis program. Using the program, degradation analysis on reinforced concrete structures subjected to chloride attacks was carried out with time by considering the cracks and the steel corrosion and cracking due to expansion of corroded reinforcing bars. The analytical procedure proposal in this study can be used quantitative evaluation of degradation and service life prediction.

• Corrosion Science and Technology
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• v.3 no.3
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• pp.87-97
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• 2004

This paper presents a new approach with meso scale structure models to express mechanical property, such as stress - strain relationships, of concrete. This approach is successful to represent both uniaxial tension and uniaxial compression stress - strain relationship, which is in macro scale. The meso scale approach is also applied to predict degraded mechanical properties of frost-damaged concrete. The degradation of mechanical properties with frost-damaged concrete was carefully observed. Strength and stiffness in both tension and compression decrease with freezing and thawing cycles (FTC), while stress-free crack opening in tension softening increases. First attempt shows that the numerical simulation can express the experimentally observed degradation by introducing changes in the meso scale structure in concrete, which are assumed based on observed damages in the concrete subjected to FTC. At the end applicability of the meso scale approach to prediction of the degradation by combined effects of salt attack and FTC is discussed. It is shown that clarification of effects of frost damage in concrete on corrosion progress and on crack development in the damaged cover concrete due to corrosion is one of the issues for which the meso scale approach is useful.

• Computers and Concrete
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• v.23 no.5
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• pp.335-349
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• 2019

A low-cycle loading experiment of 16 transfer column specimens was conducted to study the influence of parameters, likes the extension length of shape steel, the ratio of shape steel, the axial compression ratio and the volumetric ratio of stirrups, on the shear distribution between steel and concrete, the concrete damage state and the degradation of lateral stiffness. Shear force of shape steel reacted at the core area of concrete section and led to tension effect which accelerated the damage of concrete. At the same time, the damage of concrete diminished its shear capacity and resulted in the shear enlargement of shape steel. The interplay between concrete damage and shear force of shape steel ultimately made for the failures of transfer columns. With the increase of extension length, the lateral stiffness first increases and then decreases, but the stiffness degradation gets faster; With the increase of steel ratio, the lateral stiffness remains the same, but the degradation gets faster; With the increase of the axial compression ratio, the lateral stiffness increases, and the degradation is more significant. Using more stirrups can effectively restrain the development of cracks and increase the lateral stiffness at the yielding point. Also, a formula for calculating the yielding lateral stiffness is obtained by a regression analysis of the test data.