• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.194-199
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• 1994

Frefab Construction known for durable construction skill prompting high productivity in developed country is not yet settled in Korea. This situation of prefab construction results from lack of skill, specialists and quality control. In introducing skill, all equipments are thoughtlessly imported without inside eudeavor for development. Regardless of production of goods, basic study for production of goods, construction and structure is not abailable. The object of this study is curing method in the production process of PC concrete product. From change of curing temperature and curing period which would be factors of product quality in PC concrete production, and research of optimized steam curing condition from relations between curing condition and strength development, basic data of concrete steam curing method will be presented.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.231-236
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• 1995

The object of this thesis is an analytical study on flexural deformation of high strength concrete structures using reliability theory. Using the established experimental data that have been presented in various documents the stress-strain relationship curves of high strength(500kgf/$\textrm{cm}^2$)models are proposed. Based on both methods of logarithm regression analysis and multiple regression analysis adopted in order to establish the relationships between design parameters, response random variables and flexural deformation analyzed using Monte Carlo simulation and Simpson composite formula. Additional random variables are introduced to incorporate both the confidence in the analytical accuracy of engineering mechanics associated with structural response quantities and the uncertainty in the construction quality control. The result is expected to accomodate other important design parameter of high strength concrete design in treating reliability theory that practicing engineers, structural engineering often face.

• Journal of the Korean Society of Safety
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• v.25 no.5
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• pp.39-43
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• 2010

The surfacing of bridge-decks are object to secure trafficability and to protect bridge face from impact load of traffic volume and other external conditions. But the deformation of pavements and cracks happen due to the damage of the bridge-decks surfacing from the increase of the traffic, short maintenance period and continuous vibration of bridge. This test is to make the 3-type high performance concrete that has different mixing ratio and is added the blast furnace slag, fly ash and silica respectively, and to compare 3-type high performance concrete of normal high strength concrete of $400kgf/cm^2$ strength through the static loading test and fatigue test. And test specimen is united floor slab and pavement for the durability of bridge.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.313-316
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• 2006

The most serious cause of deterioration in the concrete structures is reinforcing corrosion due to the chloride attack and carbonation. Therefore, it is needed to protect durability and performance according to the appropriate materials and methods in the concrete structures. In general, several types of polymer and silicate are used as protecting deterioration agents of concrete structures, but these agents have many problems because of low durability and properties. The object of this study is to develop a preventing aging technology. The work involves the development of silicate type penetration reinforcing agent.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.101-103
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• 2011

Various desired performances of concrete cannot be always obtained by current conventional mix proportion methods for recycled aggregate concrete (RAC). This paper suggests a new design method of mix proportion for RAC to reduce the number of trial mixes using genetic algorithm (GA) which has been an optimization technique to solve the multi-object problem. In mix design method by GA, several fitness functions for the required properties of concrete, i.e., slump, strength, price, and carbonation speed coefficient were considered based on conventional data or fitness function. As a result, various optimum mix proportions for RAC that meet required performances were obtained and the risk evaluation was also conducted for selected mixtures.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.59-67
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• 1998

The object of this study is to investigate the strength characteristics and the freeze-thaw resistance of high strength concrete incorporating fine blast furnace slag. Major experimental variables were the water/cement ratio, maximum size of coarse aggregate, and cement types such as ordinary portland and slag cement. The results were as follows ; The workability of fresh concrete incorporating fine blast furnace slag was better than that of OPC(ordinary Portland cement) in terms of slump. The freeze-thaw resistance showed better than that of OPC, keeping more than 90% of relative modules of elasticity after 506 cycles and showing only a hair crack at surface without serious damage. Thus, the fine blast furnace slag might be recycled at concrete to make high strength concrete at fields.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.297-306
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• 2016

This paper developed an analytical software, called Simulation of Concrete Structures (SCS), which is used for numerical analysis of shear-critical prestressed steel fiber concrete structures. Based on the previous research at the University of Houston (UH), SCS has been derived from an object-oriented software framework called Open System for Earthquake Engineering Simulation (OpenSees). OpenSees was originally developed at the University of California, Berkeley. New module has been created for steel fiber concrete under prestress based on the constitutive relationships of this material developed at UH. This new material module has been integrated with the existing material modules in OpenSees. SCS thus developed has been used for predicting the behavior of the prestressed steel fiber concrete I-beams and Box-beams tested earlier in this research. The analysis could well predict the entire behavior of the beams including the elastic stiffness, yield point, post-yield stiffness, and maximum load for both web shear and flexure shear failure modes.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2008.05a
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• pp.184-189
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• 2008

The change in a society have brought about other changes in the overall areas of culture and art. And have brought the advent of "object", which is a unique cultural aspect. The object became a trend of the world in a culture and art. This trend has satisfied the modern people who have look for new visual stimulation. The object appears well in the spaces restaurants and bars where are reflected in consumer's needs and change of life pattern. The reason is that the spaces restaurants and bars have expressed the differentiated and individualized image with the characteristic of the times. There are three types of the expressed characteristics of objects in interior design. These are visual, functional, and emotional characteristics. But in this study it could not be found that it characterized with one concrete vocabulary and concept. Therefore, it is need to understand the various tendency which expressed characteristics of objects in the spaces restaurants and bars.

• Journal of the Korean Society of Safety
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• v.34 no.6
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• pp.50-57
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• 2019

In this study, various types of deep learning models that have been proposed recently are classified according to data input / output types and analyzed to find the deep learning model suitable for constructing a crack detection model. First the deep learning models are classified into image classification model, object segmentation model, object detection model, and instance segmentation model. ResNet-101, DeepLab V2, Faster R-CNN, and Mask R-CNN were selected as representative deep learning model of each type. For the comparison, ResNet-101 was implemented for all the types of deep learning model as a backbone network which serves as a main feature extractor. The four types of deep learning models were trained with 500 crack images taken from real concrete structures and collected from the Internet. The four types of deep learning models showed high accuracy above 94% during the training. Comparative evaluation was conducted using 40 images taken from real concrete structures. The performance of each type of deep learning model was measured using precision and recall. In the experimental result, Mask R-CNN, an instance segmentation deep learning model showed the highest precision and recall on crack detection. Qualitative analysis also shows that Mask R-CNN could detect crack shapes most similarly to the real crack shapes.

• Advances in concrete construction
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• v.8 no.1
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• pp.55-64
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• 2019

Chloride corrosion has become the main factor of reducing the service life of reinforced concrete structures. The object of this paper is to propose a theoretical model that predicts the service life of chloride-corrosive concrete under fatigue load. In the process of modeling, the concrete is divided into two parts, microcrack and matrix. Taking the variation of mcirocrack area caused by fatigue load into account, an equation of chloride diffusion coefficient under fatigue load is established, and then the predictive model is developed based on Fick's second law. This model has an analytic solution and is reasonable in comparison to previous studies. Finally, some factors (chloride diffusion coefficient, surface chloride concentration and fatigue parameter) are analyzed to further investigate this model. The results indicate: the time to pit-to-crack transition and time to crack growth should not be neglected when predicting service life of concrete in strong corrosive condition; the type of fatigue loads also has a great impact on lifetime of concrete. In generally, this model is convenient to predict service life of chloride-corrosive concrete with different water to cement ratio, under different corrosive condition and under different types of fatigue load.