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Ju M.,Kangwon National University | Park G.,Korea Institute of Civil Engineering | Lee S.,Korea Institute of Civil Engineering | Park C.,Kangwon National University
Journal of Reinforced Plastics and Composites | Year: 2017

In this study, we experimentally investigated the bond performance of a glass fiber-reinforced polymer hybrid bar with a core section comprising a deformed steel bar and a sand coating. The glass fiber-reinforced polymer and deformed steel hybrid bar (glass fiber-reinforced polymer hybrid bar) can contribute to longer durability and better serviceability of reinforced concrete members because of the increased modulus of elasticity provided by the deformed steel bar. Uniaxial tensile tests in compliance with ASTM D 3916 showed that the modulus of elasticity of the glass fiber-reinforced polymer hybrid bar was enhanced up to three times. For the bond test, a total of 30 specimens with various sand-coating and surface design parameters such as the size of the sand particles (0.6 mm and 0.3 mm), sand-coating type (partially or completely), number of strands of fiber ribs (6 and 10), and pitch space (11.4 mm to 29.1 mm) of the fiber ribs were tested. The completely sand-coated glass fiber-reinforced polymer hybrid bar exhibited a higher bond strength (90.5%) than the deformed steel bar and a reasonable mode of failure in concrete splitting. A modification parameter to the Eligehausen, Popov, and Bertero (BPE) model is suggested based on the representative experimental tests. The bond stress-slip behavior suggested by the modified BPE model in this study was in reasonable agreement with the experimental results. © 2017 SAGE Publications.

Choi H.J.,Korea Institute of Civil Engineering | Kim Y.M.,Korea Institute of Civil Engineering | Choi G.S.,Korea Institute of Civil Engineering | Kang J.S.,Korea Institute of Civil Engineering | Lee S.E.,Korea Institute of Civil Engineering
Materials Research Innovations | Year: 2015

Lately, constructions of large and high-rise buildings are steadily increasing, and various building envelope systems were developed in accordance with this trend. However, insulation methods applied to the building envelope may cause interior condensation, energy loss and discoloration of walls. In this study, ventilated insulation system was applied simultaneously considering conduction, convection and radiation of heat. This research performed a field experiment to evaluate insulating performance comparing ventilated insulation system with non-ventilated insulation system. © W. S. Maney & Son Ltd 2015.

Kim Y.M.,Korea Institute of Civil Engineering | Lee Y.J.,BEL Technology | Choi G.S.,Korea Institute of Civil Engineering | Kang J.S.,Korea Institute of Civil Engineering
Materials Research Innovations | Year: 2015

Highly insulated envelope or external insulation systems are being applied in recent energy saving buildings to reduce the heat loss through envelope. Internal insulation systems are applied to most apartments in Korea because they are inexpensive and convenient to construct. However, the internal insulation systems have poor performance because of the heat bridges through structures such as slabs. The external insulation systems have better thermal performance because the heat bridges through the structure are rarely formed. However, it has problems regarding the external insulator separation because of strong winds, spread of fire because of insulator combustion in case of fire, formation of heat bridges through the connectors between structure and external insulation. In this study, the thermal performance of the sandwich insulation system for apartment buildings was evaluated according to the shear connectors and insulation materials. © W. S. Maney & Son Ltd 2015.

Park E.,Korea Institute of Civil Engineering | Kwon S.J.,Dongguk University
Renewable and Sustainable Energy Reviews | Year: 2016

Due to significant social and environmental issues, public transportation is a very influential industry affecting our society and environment. From another perspective, because significant societal problems arise from the use of traditional energy sources such as fossil and nuclear fuels, employing optimized electricity generation systems powered by renewable energy resources is a potential pathway for sustainability while simultaneously minimizing any associated negative environmental effects. Consequently, Daejeon metropolitan city, South Korea, is attempting to introduce electric vehicles (EVs) for local taxis and establish renewable power generation systems. Therefore, the current study explores the use of potential renewable electricity generation systems by local taxi services in Daejeon. Using HOMER (Hybrid Renewable and Distributed Generation System Design) software, systems using solar energy, wind energy, batteries, converters, and the electrical grid are proposed for the third stage of the adoption of electric-powered taxis (EP taxis) in Daejeon. An economic assessment is conducted for renewable electricity generation systems, including the cost of energy (COE) and renewable fractions. Based on the simulations results, the potential system shows a renewable fraction of 0.82 and a COE of 0.425 $/kWh for the most reliable case (with grid connection), 0.79 and 0.180 $/kWh for the most optimal case (with grid connection), and 1.00 and 0.461 $/kWh for the most optimal independent case, respectively. Both the implications and limitations of such systems are discussed. © 2016 Elsevier Ltd. All rights reserved.

Kim J.-H.J.,Yonsei University | You Y.-J.,Yonsei University | You Y.-J.,Korea Institute of Civil Engineering | Jeong Y.-J.,Korea Institute of Civil Engineering | Choi J.-H.,Yonsei University
Polymers | Year: 2015

Many recent studies in the development of floating concrete structures focused on a connection system made of modules. In the connection system, the modules are designed to be attached by pre-stressing (PS) while floating on the water, which exposes them to loads on the surface of the water. Therefore, the development of a pre-connection material becomes critical to ensure successful bonding of floating concrete modules. Micro-silica mixed aqua-epoxy (MSAE) was developed for this task. To find the proper MSAE mix proportion, 0% to 4% micro-silica was mixed in a standard mixture of aqua-epoxy for material testing. Also, the effect of micro-silica on the viscosity of the aqua epoxy was evaluated by controlling the epoxy silane at proportions of 0%, ±5%, and ±10%. After completion of the performance tests of the MSAE, we evaluated the effect of MSAE in a connected structure. The plain unreinforced concrete module joint specimens applied with MSAE at thicknesses of 5, 10, and 20 mm were prepared to be tested. Finally, we evaluated the performance of MSAE-applied reinforced concrete (RC) module specimens connected by PS tendons, and these were compared with those of continuous RC and non-MSAE-applied beams. The results showed that the mix of micro-silica in the aqua-epoxy changed the performance of the aqua-epoxy and the mix ratio of 2% micro-silica gave a stable failure behavior. The flexural capacity of concrete blocks bonded with MSAE changed according to the bond thickness and was better than that of concrete blocks bonded with aqua-epoxy without micro-silica. Even though MSAE insignificantly increases the load-carrying capacity of the attached concrete module structure, the stress concentration reduction effect stabilized the failure of the structure. © 2015 by the authors.

Jung S.H.,Korea Institute of Civil Engineering | Jung S.H.,Yonsei University | Choi S.-U.,Yonsei University
Applied Soft Computing Journal | Year: 2015

A physical habitat simulation is a useful tool for assessing the impact of river development or restoration on river ecosystem. Conventional methods of physical habitat simulation use the habitat suitability index models and their success depends largely on how well the model reflects monitoring data. One of preferred habitat suitability index models is habitat suitability curves, which are normally constructed based on monitoring data. However, these curves can easily be affected by the subjective opinion of the expert. This study introduces the ANFIS method for predicting the composite suitability index for use in physical habitat simulations. The ANFIS method is a hybrid type of artificial intelligence technique that combines the artificial neural network and fuzzy logic. The method is known to be a powerful approach especially for developing nonlinear relationships between input and output datasets. In this study, the ANFIS method was used to predict the composite suitability index for the physical habitat simulation of a 2.5 km long reach of the Dal River in Korea. Zacco platypus was chosen as the target fish of the study area. A 2D hydraulic simulation was performed, and the hydraulic model was validated by comparing the measured and predicted water surface elevations. The distribution of the composite suitability index predicted by the ANFIS model was compared with that using the habitat suitability curves. The comparisons reveal that the two distributions are similar for various flows. In addition, the distribution of the composite suitability index of the Dal River is computed by the ANFIS method using monitoring data for the other watersheds, namely the Hongcheon River, the Geum River, and the Chogang Stream. The monitoring data for the Chogang Stream, correlation pattern of which was the most similar to that of the Dal River, yielded the distribution of the composite suitability index, which was very close to that obtained using data for the Dal River. This is also supported by the mean absolute percentage error for the difference in the weighted usable areas. © 2015 Elsevier B.V. All rights reserved.

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