• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.342-348
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• 2018

The present study examined the various strength and deformation performances of molding materials recycled using film packaging wastes to ascertain the their applicability to secondary products in construction industries. The stress-strain relationships of molding materials were measured under compression, tension, and flexure in accordance with the ASTM procedure. The measured mechanical properties of recycled molding materials were comparable to typical ranges observed in low-density polyethylene and/or high-density polyethylene. However, to stabilize the properties of the molding materials, further management systems are required as follows: 1) evaluation of mechanical properties of materials with respect to various mixing proportions of waste ingredients; 2) estimation of the effect of foreign substance and moisture contents on the mechanical properties; and 3) establishment of comprehensive database including various sources such as manufacture process including applied pressure to produce the molding materials, and collection region and time of wastes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.69-77
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• 2019

In this study, we evaluated the mechanical properties and nitrogen oxides removal characteristics according to the type and incorporation rate of the photocatalyst and investigated the method of separated placement for the production of economical and efficient photocatalyst concrete. As a result, when the photocatalyst incorporation rate was 5%, the highest compressive strength and elastic modulus were measured. As a result of evaluating the nitrogen oxides removal performance by the photocatalytic reaction, as the photocatalyst incorporation rate increased, the nitrogen oxide removal rate increased. At this time, the nitrogen oxides removal performance of photocatalyst P-25 was better than the NP-A. In consideration of economic efficiency, we have provided a method of separated placement for casting a constant thickness of concrete surface with photocatalyst concrete and evaluated the integrated performance at this time. As a result, it appears to be equal to or higher than mechanical performance and durability performance as compared with Plain, and it is judged that the integrated behavior is satisfied.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.36-44
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• 2019

The purpose of this study is to evaluate the structural performance of press-formed type asymmetric column to beam connections of steel-PC composite module frames. Most of the column sections of the joints making up the modular frame use a closed square steel section. The column-beam connection using the closed column section has difficulty in reducing the workability and securing the fire resistance. In order to overcome this disadvantage, concrete is filled in the asymmetrical open type cross section of the steel plate by press forming. A total of four specimens were fabricated to investigate the structural performance of press formed type asymmetric column to beam connections. The experimental results show that the structural performance and behavior of the asymmetric columns are different depending on whether the asymmetric column cross section is composited or the column width thickness ratio. The structural performance of the press formed type asymmetric column to beam connection was evaluated by comparing the experimental results with the theoretical formulas.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.41-49
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• 2021

3D printing techniques have been recently adopted in the construction industry. It mainly utilizes additive manufacturing which is the fabrication process depositing successive layers of materials without any formworks. Conventional cementitious materials may not be directly applicable to 3D printing because 3D printable cementitious materials is required to satisfy such characteristics as pumpability, extrudability, and buildability in a fresh state. This study aimed to investigate rheological properties and required performances of 3D printable cementitious materials, by reviewing existing studies. Test methods and equipments, evaluation results and characteristics of mixture additives were compared. Based on reviews of existing studies, this study indicates that the viscosity is mainly relevant to the pumpability of 3D printable materials whereas the yield stress and thixotropy are important in securing buildability of the materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.506-513
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• 2022

In this paper, as part of a study for carbon neutrality, the quality properties of quaternary component high-fluidity concrete, which significantly replaced up to 80 % of the cement usage by using three industrial by-products, were evaluated. As a result of the evaluation, even if a large amount of industrial by-products were replaced by more than 80 % of the amount of cement used, it was possible to obtain quality that satisfies the target performance in all concrete mix. In the case of flow properties, mechanical properties, and durability, compared to the existing standard concrete mix, the performance tends to decrease, but it is judged that the performance above the required performance level can be satisfied. When considered comprehensively, the quaternary component High-Fluidity Concrete with a large mixing amount of fine powder of blast furnace slag showed relatively good performance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.386-394
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• 2022

In this study, the mechanical properties and frost resistance of concrete with steel and nylon fibers were experimentally investigated. Both of OPC concrete with 100 % ordinary portland cement and SGC concrete replaced with 50 % GGBFS were manufactured to evaluate effects of fibers to the performance of concrete. Compressive and split tensile strength, ultrasonic pulse velocity and surface electric resistivity measurements of concrete were carried out at a predetermined interval. In addition, the freezing & thawing resistance of concrete in accordance with ASTM C666 standard was also examined. As a result, it is seemed that the effect of fibers was remarkable to improve the mechanical properties and frost resistance of concrete, especially for the concrete incorporating steel fiber.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.2
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• pp.105-112
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• 2023

In this study, structural analyses were conducted to analyze the performance of a bridge to which friction pendulum systems (FPSs) were applied using different friction models. A Coulomb friction model and a rate dependent friction model were constructed using the friction coefficient of a PVDF/MgO friction material to analyze the effect of different friction analysis models. The Coulomb friction model uses a single friction coefficient regardless of friction velocity, while the rate dependent friction model can reflect the change in the friction coefficient with friction velocity. Nonlinear time history and seismic fragility analyses were conducted to confirm responses of the bridge. The seismic responses of a deck and a column were used to evaluate the performance of the base isolated bridge, and a friction model that can effectively evaluate the performance of isolated bridges was analyzed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.57-66
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• 2023

Asset valuation of social infrastructure is essential for rational decision-making for efficient management of assets. In addition, it can be an indicator for correctly recognizing assets. In general, Korea applies depreciated replacement cost based on the straight-line method to evaluate asset value, yet this is unsuitable for evaluating actual value because it is depreciated at a constant rate over the useful life period. In order to evaluate the asset value considering the performance of the bridge, the performance index of the bridge is estimated using the Weibull distribution. Using the estimated performance indicators and defect index, a new asset value evaluation method is proposed and compared and analyzed with the existing method. The proposed valuation method can take into account the performance of the bridge, so it is judged to be more objective and reasonable than existing method.

• Ecology and Resilient Infrastructure
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• v.5 no.4
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• pp.257-263
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• 2018

This study is to develop a GSTM (Green infrastructure Surface Temperature Measurment) equipment for reducing the surface temperature of GI by using LID Method. The tests were conducted including GI products such as Greening block, Pervious Block, Soil Block and so on. The GSTM equipment developed by considering the literature surveys are characterized as follows. The non-contact infrared temperature sensor was used to measure the surface temperature, and it was improved to measure the overall average temperature including the center and the corner temperature of the specimen. The developed GSTM equipment was used to compare performance of asphalt and GI products. As a result, the Greening Block show a high difference of $18.4^{\circ}C$ and it contributes to the decrease of surface temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.1-8
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• 2023

At construction sites, interest in the production of precast materials is increasing due to off-site conditions due to changes in construction site conditions due to increased labor costs and the Act on the Punishment of Serious Accidents. In particular, the precast prestressed hollow slab has a hollow shape in the cross section, so structural performance is secured by reducing weight and controlling deflection through stranded wires. With the application of structural standards, the urgency of securing fire resistance performance is emerging. In this study, a fire-resistance cross section was developed by reducing the concrete filling rate in the cross section and improving the upper and lower flange shapes by optimizing the hollow shape in the cross section of the slab to have the same or better structural performance and economic efficiency compared to the existing hollow slab. The PC hollow slab to which this was applied was subjected to a two-hour fire resistance test using the cross-sectional thickness as a variable, and as a result of the test, fire resistance performance (load bearing capacity, heat shielding property, flame retardance property) was secured. Based on the experimental results, it is determined that fire resistance modeling can be established through numerical analysis simulation, and prediction of fire resistance analysis is possible according to the change of the cross-sectional shape in the future.