• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.31-37
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• 2000

When a crack is produced in a concrete structure, a micro crack zone of fracture process zone (FPZ) appears at the crack tip. To investigate the behaviour of this the micro crack zone, nonlinear fracture mechanics (NLFM) must be applied. However, when a massive concrete structure such as a concrete gravity dam is considered, the micro crack zone can be neglected and the structure can be assumed to have linear elastic fracture mechanics (LEFM) behaviour. This study is divided into two main topics : (1) Calculating stress intensity factor (SIF) at the crack tip by surface integral method and (2) Investigating the propagation of the initial crack. If the initial crack propagates, the angle of the propagation is calculated by using maximum circumferential tensile strength theory. This study, also, contains the effects of body forces and water pressures on the crack face.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.1-6
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• 2006

Corrosion of reinforcing steel bars is a major concern for ocean engineers when reinforced concrete structures are exposed to marine environments. Evaluating the degree of corrosion and corrosion-induced defects is extremely necessary to pursue a proper retrofit or rehabilitation plan for reinforced concrete structures. A promising inspection should be carried out for the evaluation, otherwise the retrofit or rehabilitation process would be useless. Nowadays, ultrasonic guided wave-based inspection techniques become quite promising for the inspection, mainly because of their long-range propagation capability and their sensitivity to different types of defects or conditions. Evaluating haw the guided waves response to the different types of defects or conditions is quite challenging and important. This study shows how surface conditions of reinforcing bars and a corrosion-induced defect, separation, affect guided wave propagation in reinforced concrete. Experiments and associated signal analysis show the sensitivity of guided waves to the surface conditions, as well as the amounts of separation at the interface between. concrete and steel bar.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.53-56
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• 2000

The performance of high-strength concrete is controlled by the fact, affecting the quality management, especially by revision error in water content of the ratio of surface moisture in fine aggregate. The difference in water content results from the revision error of the ratio of surface moisture and errors in sampled aggregate in the processing ready-mixed concrete plant. This study is to investigate the properties of flowing and hardening by investionally varying the revision error of the ratio of surface moisture in fine aggregate to compare and analyze the variance in quality.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.235-240
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• 1997

The purpose of this experiment is to verify processing crack direction and state by the corrosion of electrifying re-bar in the salt water. The result of this experiment is the fact that the first crack appear on the surface of water-because of supplying of oxygen and water. The crack processing is on a surface to be contacted by air and to bottom as mainly the vertical direction from a surface of water. The crack by corrosion of steel reinforcing is emerged by the inside of concrete rather than surface concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.85-88
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• 2000

This paper is dealt with the ways of the improvement of the surface glossing of exposed concrete through the construction field test. The field applied in this test is located at Daechon, Chungnam province where the service training institute of Chongju university has been built. The flowing method is applied. According to the test results, as water to cement ratio, or slump increase after flowed, surface glossing tends to be improved. As for the effects of the forms typer, following orders, which is shown to be better surface glossing values, are given; Acryle > fancy wood forms > steel forms > plywood forms.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.59-60
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• 2022

When a metal sprayed film of several hundred ㎛ on the concrete surface is possible to 80 dB of shielding effect electromagnetic waves (ElectroMagnetic Pulse, EMP). Therefore, in this study, as a way to secure EMP shielding performance by applying a metal spray coating showing excellent EMP shielding performance to a concrete structure, the metal spray welding efficiency and thin film adhesion performance according to the concrete spray direction and surface treatment method were evaluated. Metal sprayed efficieny according to the metal spraying direction and method was confirmed that the difference was insignificant by applying the roughening agent. However, the method of strengthening the concrete surface and applying the sealing agent show maximum adhesion strength of 3.98 MPa compared to other methods, and it is judged that this method can be utilized for the metal spraying method for concrete EMP shielding.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.9-16
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• 2015

The goal of this research was evaluating and suggesting the solution of preventing carbonation of concrete replaced high-volume of slag. The concrete mixtures were prepared with high-volume slag and recycled aggregate, and the concrete samples were evaluated the carbonation depth with various surface treatment methods. For various surface treatment methods and surface protecting sheets, bonding strength and carbonation depth were measured. Basically, from the results, the carbonation of concrete was completely prevented with any type of surface treatment method and surface protecting sheet as far as the surface treatment materials were remained. Therefore, in this research, it was known and suggested that the easiness of handling and sufficient bonding performance was much important than the quality of surface protecting sheets.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.43-46
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• 2009

The purpose of this study is to enhance durability of concrete structures that uses this surface protecting material by carrying out the performance test of the surface protecting material of concrete, and as s result, we reached out the conclusion as follow. 1. As a result of the test measuring the stability and adhesive power of conductive film against ultraviolet, freezing & thawing, and damage from seawater that deteriorate the surface protecting material, it was turned out to meet the performance criteria specifying in the KS standard enough to gain a good evaluation to use as a surface protecting material. 2. As a result of the test identifying the neutralization-furtherance, it was assessed to be capable of protecting effectively concrete structures from carbonic acid gas by a very low depth of 0.1mm of neutralization. 3. As a result of the test identifying Penetrated Resistance Properties of chloride ion, as it was turned out to have a very low value of 819 Coulombs, it was assessed that even in the environment where the corrosion by chloride such sea environment is very affective, the film can effectively protect the concrete structure. 4. As a result of the test identifying freezing & thawing, as there was no change in reduction of mass after 400 cycle, it was assessed that the film has a good resistance against freezing & thawing. According to the results of study above, it is expected that this technology can extend its durability of concrete structure and be widely used for concrete structure through means (methods) to prevent the neutralization and damage from seawater as original purposes of the surface protecting material.

• Journal of the Korea Institute of Building Construction
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• v.12 no.3
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• pp.347-357
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• 2012

While it is generally possible to install curved panels manufactured in a factory within the permitted error range on an irregular surface frame of concrete or steel, it is difficult and expensive. Freeform architecture is thus designed and constructed differently from formal buildings. In order to more easily and inexpensively actualize freeform architecture, Building Information Modeling (hereinafter referred to as BIM) has recently been applied in the construction industry. However, the related research and case analyses are not sufficient to identify the implications and contributions of freeform buildings in future similar projects. Therefore, this research will study design and construction methods for freeform surfaces, particular the concrete surface frame of freeform buildings based on BIM, focused on the Tri-Bowl project. This study attempts to analyze the pros and cons of each method for the concrete surface frame of the Tri-Bowl, and then presents the lessons learned and implications related to the design and construction process of the freeform architecture. Several implications for design and construction of concrete surface frame of the freeform building, the Tri-Bowl, are found. The first is that manufacturing and installation of a curved concrete frame is precisely performed based on the exact numerical values of materials and installation made using BIM 3D technologies, such as CATIA and Rhino. The second is that close and continuous collaboration among the different participants in the construction of the Tri-Bowl allowed them to cope with virtual conditions. The third is that design and construction processes have changed, and high quality of the surface frame of a freeform building is required.

• Smart Structures and Systems
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• v.18 no.3
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• pp.601-623
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• 2016

Precast concrete elements are widely used in the construction of buildings and civil infrastructures as they provide higher construction quality and requires less construction time. However, any abnormalities in precast concrete surfaces such as non-flatness or distortion, can influence the erection of the elements as well as the functional performance of the connections between elements. Thus, it is important to undertake surface flatness and distortion inspection (SFDI) on precast concrete elements before their delivery to the construction sites. The traditional methods of SFDI which are conducted manually or by contact-type devices are, however, time-consuming, labor-intensive and error-prone. To tackle these problems, this study proposes techniques for SFDI of precast concrete elements using laser scanning technology. The proposed techniques estimate the $F_F$ number to evaluate the surface flatness, and estimate three different measurements, warping, bowing, and differential elevation between adjacent elements, to evaluate the surface distortion. The proposed techniques were validated by experiments on four small scale test specimens manufactured by a 3D printer. The measured surface flatness and distortion from the laser scanned data were compared to the actual ones, which were obtained from the designed surface geometries of the specimens. The validation experiments show that the proposed techniques can evaluate the surface flatness and distortion effectively and accurately. Furthermore, scanning experiments on two actual precast concrete bridge deck panels were conducted and the proposed techniques were successfully applied to the scanned data of the panels.