• Structural Engineering and Mechanics
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• v.9 no.4
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• pp.349-364
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• 2000

This paper aims to make a contribution to understanding which methods apply for structural analysis of beams prestressed with FRP cables. A parametric non-linear numerical analysis of simply supported beams has been performed. In this analysis the shape of the cross-section, the strength of concrete, the material adopted for the cables (steel, GFRP, CFRP), the prestressing system (bonded or unbonded prestressing) and the degree of prestressing were changed to collect a broad range of data which, the author contends, should cover the most frequent types of common practice. The output data themselves and their comparison allow us to suggest some rules that could be adopted when dealing with beams prestressed with these innovatory materials that have an elastic-brittle behaviour.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.197-202
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• 2005

This study started to confirm and prove for the applicability of the dry-process waterproofing system to cover the defects of the wet-process waterproofing system according to weather circumstance, foundation condition and maintenance, etc. This process has triple combined waterproofing system using asphalt sheet, metal sheet, engineering plastic film. It is not influenced by the concrete's crack as the foundation of the roof according to the movement of the building because the waterproofing system is designed for maintaining good quality by absorbing the stress of contraction and expansion that is occurred by the variation of temperature. Ali components used in this process can be recycled environmentally. The superiority of this process proved and reconfirmed through with the investigation of about 130 fields, around 30,000nf for two years.

• Computers and Concrete
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• v.15 no.5
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• pp.759-770
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• 2015

In this study, a multi-layer perceptron neural network (MLPNN) prediction model for compressive strength of the cement mortars has been developed. For purpose of constructing this model, 8 different mixes with 240 specimens of the 2, 7, 28, 56 and 90 days compressive strength experimental results of cement mortars containing fly ash (FA), silica fume (SF) and FA+SF used in training and testing for MLPNN system was gathered from the standard cement tests. The data used in the MLPNN model are arranged in a format of four input parameters that cover the FA, SF, FA+SF and age of samples and an output parameter which is compressive strength of cement mortars. In the model, the training and testing results have shown that MLPNN system has strong potential as a feasible tool for predicting 2, 7, 28, 56 and 90 days compressive strength of cement mortars.

• Journal of the Korean Institute of Navigation
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• v.22 no.1
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• pp.55-62
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• 1998

In this paper, we have performed a numerical calculation of the scattered electromagnetic field around the building to evaluate electromagnetic interference caused by the building in the TV frequency band. The relations between the exposed concrete area of a building wall and the magnitude of the reflected wave have been examined in the case that the electroagnetic wave absorbers partially cover the building wall. From the obtained scattered electromagnetic field, we have calculated the DU radio and the required reflection loss of the electromagnetic wave absorbers which attached on the building wall to protect TV ghost.

• Korean Journal of Agricultural Science
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• v.37 no.1
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• pp.87-96
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• 2010

This study was performed to evaluate the planting properties of herbaceous plant and cool-season grass in porous polymer blocks that were manufactured by using recycled coarse aggregates and unsaturated polyester resin to develop environmentally friendly planting blocks. Unsaturated polyester resin, natural and recycled coarse aggregates and $CaCO_3$ were used. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate sizes(5-10 and 5-20mm). Tests for the void ratio and compressive strength of porous polymer concrete were performed at curing age 7 days. Also, porous polymer block using recycled coarse aggregates were applied to kinds of plants such as tall fescue, Perennial ryegrass, Lesedeza and Alfalfa. After seed, initial germination, germination ratio, cover view and growth length for planting blocks were estimated by various methods.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.274-280
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• 2008

To investigate the flexural behavior of real size RC beams strengthened with glass fiber sheets, 9 strengthened beams of real size are experimented and the results are compared with those of existing experimental studies. Experiments are considered glass fiber sheets, the number of fiber sheets, and the existence of U-wrap. By the results of experiments, the failure behavior and crack types of real size RC beams are almost equal to those of the small size RC beams, and the debonding and not the concrete cover delamination are occurred. It can be found from the load-deflection curves that as the number of fiber sheets is increased, the ductility of real size RC beam is more decreased than that of the small size RC beam. For the strengthening method with glass fiber sheets of the real size RC beams, it can be confirmed that the finding a solution to the bonding problem is required

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.3
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• pp.168-175
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• 1998

This study investigated the structural performance of the precast prestressed cylinder pipe having cracked under construction. The finite element formulation of PPC pipe incorporates Asoild elements using SAP90 program and the radial prestress force was transformed into the eqivalent external pressure. The analytical results were compared with the experimental results of full scale tests on PPC pipes subjected to static load. It is shown that the proposed modelling gives a realistic represention of the actual behavior. The analytical procedure is used to calculate the stresses in the PPC pipes and to check the crack opening under various situations such as bedding angle, earth pressure, and earth cover. Finally, the proposed modelling and analytical procedure should be especially usefull for the safety assessment of the PPC pipes under general loading conditions.

• Advances in concrete construction
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• v.3 no.1
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• pp.15-37
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• 2015

Ongoing efforts for improved fracture toughness of engineered cementitious materials address the inherent brittleness of the binding matrix at several different levels of the material's geometric scale through the addition of various types of reinforcing fibers. Crack control is required for crack widths that cover the entire range of the grain size spectrum of the material, and this dictates the requirement of hybrid mixes combining fibers of different size (nano, micro, macro). Use of Carbon Nano-Tubes (CNT) and Carbon Nano-Fibers (CNFs) as additives is meant to extend the crack-control function down to the nanoscale where cracking is believed to initiate. In this paper the implications of enhanced toughness thus attained at the material nanostructure are explored, with reference to the global smeared constitutive properties of the material, through consistent interpretation of the reported experimental evidence regarding the behavior of engineered cementitious products to direct and indirect tension.

• Journal of Environmental Impact Assessment
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• v.19 no.4
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• pp.397-407
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• 2010

The increase of the solar reradiation from urban areas relative to suburban due to urbanization heats up the air temperature in urban areas and this is called the urban heat island (UHI) effect. This UHI effect has a positive relationship with the degree of urbanization. Through the studies on UHI using the satellite imagery, the effect of the surface heat radiation was observed by verifying the relationship between the air temperature and the land cover types (surface materials such as urban, vegetation, etc.). In this study, however, the surface temperature distribution was studied in terms of land use types for Seoul. Using land use types, the surface temperature in urban areas such as residential, industrial, and commercial areas in Yeongdeungpo, highly packed with industrial and residential buildings, was maximum $6^{\circ}C$ higher than in the bare ground, which indicated that the surface temperature reflected the pattern of the human-consumed energy on the areas and showed that one of the important causes influencing the air temperature except the surface heat reradiation by the sun is the anthropogenic heat. Also, the effect due to the restoration of the Chunggae stream on UHI was investigated. The average surface temperature for the Chunggae stream was reduced about $0.4^{\circ}C$ after restoration. Considering that each satellite image pixel includes mixture of several materials such as concrete and asphalt, the average surface temperature might be much lower locally reducing UHI near the stream.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.3
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• pp.219-230
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• 2017

This study was conducted to predict and evaluate the uncertainty of safety after closure of the second phase surface disposal facility of the Gyeongju intermediate and low level repository in Korea. In this study, four scenarios are developed considering both intact and degraded states of multi-layered covers and disposal containers; also, the fluid flow by a rainfall into the disposal facility is simulated. The rainfall conditions are implemented based on the monthly average data of the past 30 years (1985~2014); the simulation period is 300 years, the management period regulated by institutional provisions. As a result of the evaluation of the basic scenario, in which the integrity of both of the containers and the covers is maintained, it was confirmed that penetration of rainfall does not completely saturate the inside of the disposal facility. It is revealed that the multiple cover layers and concrete containers effectively play the role of barrier against the permeation of rainfall.