• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.425-428
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• 2006

The bigger of concrete strctures by a construct technique improvement, and the increase of the cement quantity which is caused by with use of the high-strength concrete for the load-carrying-capacity and a durability cause temperature cracks by a heat of hydration. The temperature crack due to the heat of hydration classified a nonstructural crack. but it has a bad effect on durability of concrete structures. especially, in case of a subway concrete box structure, when a water-proof facilities is beaked on an outer-wall, the water leakage occurs through a penetration crack generated from a wall of the concrete structure too. This paper, for the subway concrete box strucuture, the use of blended cement, the temperature of air and concrete, control joint, was considered and analysed by a three dimensional finite element method.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.821-824
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• 2008

This paper presents a systematic approach for estimating material performance of concrete mixture design based on satisfaction curves developed from statistical evaluation of existing or newly obtained material property related data. In performance based material design (PBMD) method, concrete material used for construction of a structure is designed considering a structure's specified performance requirements based on its usage and characteristics such as environmental conditions, structure types, expected design life, etc.Satisfaction curves express the probabilities that one component of substrates (i.e., aggregate size, cement content, etc) of concrete mixture will sustain different criterion value for a given concrete mixture design. This study presents a statistical analysis method for setting up concrete material parameter versus concrete criterion relationships in the form of satisfaction curves and for estimating confidence bounds on these satisfaction curves. This paper also presents an analysis method to combine multiple satisfaction curves to form one unique satisfaction curve that can relate the performance of concrete to a single evaluating value. Based on several evaluated mixture design examples for various material properties, the validity of the proposed method is discussed in detail.

• Land and Housing Review
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• v.11 no.3
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• pp.83-92
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• 2020

In South Korea, problems caused by material deterioration of time-worn concrete structures have been increased recently. Because severe material deterioration could damage the structure's safety, it's important to evaluate the old structure's condition and structural capacity regularly to keep its proper performance. The safety evaluation of concrete structures has been initiated and performed periodically since 1995 according to a guideline in accordance with a law in Korea. The guideline prescribes the evaluation types, intervals and methods of the target structure. A lot of cost and labor have been invested every year to carry out the regular safety evaluation. However, it's not clear that the current manual could inspect the old structure's condition and assess the structural capacity precisely. Thus, the verification study initiated to figure out the Korean safety evaluation manual's practicalness. First, the Korean manual was analyzed and then compared with that of other countries for concrete bridges which are representative concrete structure. After that, the previously written evaluation reports were collected and analyzed to find out how the safety evaluation has been carried out. Based on the study results, the parts requiring verification of the manual were drawn. A research program is in progress in order to verify the parts by performing tests with actual structural members from decommissioned concrete bridges.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.295-301
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• 2000

Various nondestructive prospecting method were applied to detect the flaws of concrete structure, but the satisfactory result could not be obtained, yet. Fracture and cavities existing concrete structure will have a bad effect on physical and mechanical characteristic of concrete. This study deal with detection of flaws using seismic first arrival and various inversion method in theoretical model. And ultrasonic seismic method is tried to experimental model to detect fracture and cavity.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.135-140
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• 2001

This study was developed high-quality a large size precast channel structure using polymer concrete to improve quality of the product as well as to enhance construction quality. Precast PC represent the fastest growing segment of the polymer concrete industry. The fast curing, high strength, and low impermeability permit thin section and rapid reuse of moulds. Developed precast channel structure will be structural experiment and analysis. Also, through an example to construct will be develop the most suitable section survey and make practicable.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.533-538
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• 1997

Topology optimization of a concrete structure is discussed using an Evolutionary Structural Optimization(ESO) method introduced by Xie and Steven. During the evolution process low stressed materials are progressively removed from the structure. This paper discussed a proper rejection criterion(RC) to get a more reasonable topology of concrete structure. Some examples are presented to illustrate the optimum topology achieved by such a procedure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.13-14
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• 2015

Carbonation is the results of the interaction of carbon dioxide gas in the atmosphere with the alkaline hydroxides in the concrete. in other words, of the hydrates in the cement pastes, the one which reacts with readily is Ca(OH)₂, the product of the reaction being CaCO₃ and which decreases the alkalinity of concrete. Consequently, RC structure is deteriorated due to steel corrosion in concrete. As the importance of maintenance of reinforced concrete structure recently has emerged, the attention of durability of structure has been increasing. There are many studies about durability decline especially due to the carbonation. In order to study carbonation progress after surface repair of carbonated concrete, each carbonation penetration velocity from different repair materials of concrete structure is compared through the experiment of carbonation accelerating CO₂ concentration to 100%. As carbonation infiltration progress is predicted through this study, the counterplan of service life evaluation will be prepared on selection of repair materials of concrete structure.

• Smart Structures and Systems
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• v.22 no.2
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• pp.201-207
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• 2018

This paper proposes a line laser thermography scanning (LLTS) system for multiple crack evaluation on a concrete structure, as the core technology for unmanned aerial vehicle-mounted crack inspection. The LLTS system consists of a line shape continuous-wave laser source, an infrared (IR) camera, a control computer and a scanning jig. The line laser generates thermal waves on a target concrete structure, and the IR camera simultaneously measures the corresponding thermal responses. By spatially scanning the LLTS system along a target concrete structure, multiple cracks even in a large scale concrete structure can be effectively visualized and evaluated. Since raw IR data obtained by scanning the LLTS system, however, includes timely- and spatially-varying IR images due to the limited field of view (FOV) of the LLTS system, a novel time-spatial-integrated (TSI) coordinate transform algorithm is developed for precise crack evaluation in a static condition. The proposed system has the following technical advantages: (1) the thermal wave propagation is effectively induced on a concrete structure with low thermal conductivity of approximately 0.8 W/m K; (2) the limited FOV issues can be solved by the TSI coordinate transform; and (3) multiple cracks are able to be visualized and evaluated by normalizing the responses based on phase mapping and spatial derivative processes. The proposed LLTS system is experimentally validated using a concrete specimen with various cracks. The experimental results reveal that the LLTS system successfully visualizes and evaluates multiple cracks without false alarms.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.77-81
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• 2004

The massive structures are not free to move with vibration, differential settlement, thermal stresses because, construction and expansion joint, crack etc., can be large enough to cause leakage as deformation of waterproofing. It has been depended on the test method of tensile/tear strength which is waterproofing performance as behavior of concrete structure crack. However, not to practically confirm the creep applied to concrete surface, even waterproofing membrane have more performance than definite strength and elasticity. Therefore, in this study will focus on the test method to consider a resistance performance about loose adhesion and deformation of waterproofing and behavior of concrete structure as construction/expansion joint, crack. Performance test method on the influence as behavior of concrete structure crack is to choose waterproofing materials and construction method which possible to confront with behavior of 50mm crack in the atmosphere and low temperature. Examine the deformation of waterproofing membrane and loose adhesion which can occur to structure in general job site, suggest standard testing method to analyze correlation waterproofing membrane and structure with 5-types of materials used in this study, such as Adhesion membrane and sheet complex, sheet and urethane complex, self-adhesive sheet, spray poly-urea, spray membrane of rubberized Asphalt.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.399-402
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• 2000

When concrete structures are built in marine environment, they may be deteriorated and have the poor durability and quality caused by steel corrosion or by chemical attack of magnesium or sulfate ions. Especially, Mg ions contained in seawater make concrete surface weaken by chemical reaction with $Ca(OH)_2$ In this study, a concrete structure built in 1947 was investigated to estimate the factors, especially chemical attack, which can cause concrete to deteriorate. Furthermore, the instrumental analysis methods such as XRD and ESEM were performed to find the reactants in concrete under marine environment.