• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.12
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• pp.984-991
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• 2006

The applications of multi air-conditioners into multiplex and high-rise buildings have been increased by replacing central air-conditioning systems. The pipe length and altitude difference between the indoor and outdoor units can be increased based on installation conditions, which may increase the possibility of flash gas generation at the expansion device inlet. The flash gas generation causes rapid reduction of refrigerant flow rate passing through the expansion device, yielding lower system efficiency. Accumulator heat exchangers have been widely used in multi air-conditioners in order to minimize flash gas generation and obtain system reliability. However, the studies on the heat transfer characteristics and pressure drops of accumulator heat exchangers are very limited in open literature. In this study, the heat transfer rates and pressure drops of accumulator heat exchangers were measured with refrigerant flow rate and operating conditions by using R-22. The heat transfer rate increased with the increase of refrigerant flow rate, while subcooling decreased. The heat transfer rate enhanced with the reduction of inlet superheat and subcooling due to the increased temperature difference between the accumulator and inner heat exchanger.

• Journal of the Korean housing association
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• v.21 no.4
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• pp.11-22
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• 2010

In the urban area where rapid suburbanization trend continues, the role of mixed use building is controversial. It is argued that the mixed use building is an effective tool to recover residential function of urban core(urban regeneration). It is also argued that the building is a cause of serious urban problems, such as congestion, public service shortages. The fundamental purpose of this study is to examine the role of mixed use building in terms of urban growth management in Seoul. For this purpose, data of mixed use building from 1981 to 2007 are collected and analysed. The results show that most of mixed use buildings are located in either sub-centers or population losing areas, rather than traditional urban core. Therefore, it is hard to accept that the two controversial arguments. The mixed use building noncore areas in most cases. However, it dose help to increase population inflow in non-core areas. it is difficult to accept the public service assertion which states that super-high rise mixed use building causes public service congestion, because the building is built in population losing or demand decreasing area. Based on these findings this study suggests some policy alternatives such as urban service boundary or concurrency program to management urban growth.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.181-182
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• 2015

The use of non-bearing light weight wall has increased recently due to the increase of high-rise buildings and supply of long-life housing. Light weight wall has advantages such as reducing the self-weight of the building, convenience in installation, and shortening construction period, however, must have a sufficient strength to external force. This study standardized the impact resistance test method for light weight walls by using the actual impact load obtained through load analysis test in previous studies. The impact resistance test method was divided into the test method that uses soft body and the one that uses hard body. The size of specimen was set up as height 2.4m and width 3.0m. The size and shape of the body followed those used in BS 5234-2 and so on for the compatibility with the test method used overseas. The judgment criteria for impact resistance based on test results were not defined uniformly as the assessment of functional damage can vary depending on the type of material, structural method, purpose of wall, and so on even when the same impact load was applied.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.185-186
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• 2015

The use of non-bearing lightweight wall has increased recently due to the increase of high-rise buildings and supply of long-life housing. Lightweight wall has advantages such as reducing the self-weight of the building, convenience in installation, and shortening construction period, however, must have a sufficient strength to external force. This study standardized the stiffness (static horizontal load resistance) test method for lightweight walls by using the actual impact load obtained through the load analysis test conducted in the previous studies. The size of specimen was set up as height 2.4m and width 3.0m. Test apparatus and test methods were referred to BS 5234-2:1992. However, the loading level applied to the specimen was divided into 3 steps (3000N, 1000N, 500N) that can be applied selectively depending on the purpose of the wall. The deformation characteristics according to the same loading level were vary depending on the specimen's type, and the evaluation criteria for functional damage may vary depending on the material, method of construction, and purpose of wall. Therefore, we did not suggest unified evaluation criteria of the stiffness to the test results.

• International Journal of High-Rise Buildings
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• v.3 no.4
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• pp.243-254
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• 2014

In this study, a demolition analysis code using the adaptively shifted integration (ASI)-Gauss technique, which describes structural member fracture by shifting the numerical integration point to an appropriate position and simultaneously releasing the sectional forces in the element, is developed. The code was verified and validated by comparing the predicted results with those of several experiments. A demolition planning tool utilizing the concept of a key element index, which explicitly indicates the contribution of each structural column to the vertical load capacity of the structure, is also develped. Two methods of selecting specific columns to efficiently demolish the whole structure are demonstrated: selecting the columns from the largest index value and from the smallest index value. The demolition results are confirmed numerically by conducting collapse analyses using the ASI-Gauss technique. The numerical results suggest that to achieve a successful demolition, a group of columns with the largest key element index values should be selected when explosives are ignited in a simultaneous blast, whereas those with the smallest should be selected when explosives are ignited in a sequence, with a final blast set on a column with large index value.

• International Journal of High-Rise Buildings
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• v.3 no.4
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• pp.297-304
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• 2014

Recently, there have been some reported examples of structural collapse due to gravity, subsequent to damage from accident or an excitation that was not prepared for in the design process. A close view of new concepts, such as a redundancy and key elements, has been taken with the aim of ensuring the robustness of a structure, even in the event of an unexpected disturbance. The author previously proposed a sensitivity index of the vertical load carrying capacity to member disappearance for framed structures. The index is defined as the ratio of the load carrying capacity after a member or a set of an adjacent member disappears, to the original load carrying capacity. The member with the highest index may be regarded as a key element. The concept of bio-mimicry is being applied to various fields of engineering, and tree-shaped structures are sometimes used for the design of building structures. In this study a sensitivity analysis is applied to the irregular-framed structures such as tree-shaped structures.

• Journal of the Korea Safety Management & Science
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• v.4 no.4
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• pp.1-14
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• 2002

As domestic buildings have been large-scaled, diversified and high-rise, there have been a consistent demand for design, development of construction technology and accident prevention activity as well as quality enhancement. In spite of governmental and related institutions' efforts for reducing national losses which come from numerous accidents, there have been endless small and large accidents on the construction site and thus, it is urgent to conduct empirical researches in this area. Currently safety supervision system in construction industry has enforced harm and danger prevention planning system, however it merely stick to other existing materials. In addition, it is difficult to put it into practice in that it requires bearing too much burden to draw out the planning itself in a case of large construction work. Consequently in this paper we select evaluation criteria by construction progress, classify into several categories, and regard potential danger which often occurs, as a evaluation criterion. Further step is to allow workers or collaborated companies to express their expert opinions or experiences and to encourage quality and process control and autonomous safety control by applying PSM method. The reason why PSM method should be quantitative and substantial progress is because it contributes Korean constructing companies to enhancing their safety control ability and to taking an equal stance just like developed countries,' thereby strengthening there competitive edges. Boost of safety control system by PSM method will make an enormous contribution to preventing construction accidents on the site by establishing and securing an autonomous safety control system.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.103-111
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• 2007

Since the 1980's the school of Busan metropolitan city has been converted into the other land-use such as high-rise apartment houses, commercial and office buildings. School facilities are available to locate in green area due to not restricted by land use zone. And the location of school facilities were closely related with the school district, distribution of neighborhood unit, safety of students, and so on. The purpose of this study is to understand the location characteristic of school - moved sites in Busan metropolitan city.

• International Journal of High-Rise Buildings
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• v.2 no.2
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• pp.131-139
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• 2013

The field of structural fire engineering has evolved within the construction industry, driven largely by the acceptance of performance-based or goal-based design. This evolution has brought two disciplines very close together - that of structural engineering and fire engineering. This paper presents an overview of structural systems that are frequently adopted in tall building design; typical beams and columns, concrete filled steel tube columns and long span beams with web openings. It is shown that these structural members require a structural analysis in relation to their temperature evolution and failure modes to determine adequate thermal protection for a given fire resistance period. When this is accounted for, a more explicit understanding of the behaviour of the structure and significant cost savings can be achieved. This paper demonstrates the importance of structural fire assessments in the context of tall building design. It is shown that structural engineers are more than capable of assessing structural capacity in the event of fire using published methodologies. Rather than assumed performance, this approach can result in a safe and quantified design in the event of a fire.

• Steel and Composite Structures
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• v.20 no.3
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• pp.599-621
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• 2016

In order to study the working mechanism of rectangular steel-concrete composite columns subjected to compression-bending load and further determine the seismic performance index, a bottom strengthened rectangular steel reinforced concrete (SRC) column with concealed steel plates and a bottom strengthened rectangular concrete filled steel tube (CFST) columns were proposed. Six column models with different configurations were tested under horizontal low cyclic loading. Based on the experiments, the load-bearing capacity, stiffness and degradation process, ductility, hysteretic energy dissipation capacity, and failure characteristics of the models were analyzed. The load-bearing capacity calculation formulas for a normal section and an oblique section of bottom strengthened rectangular steel-concrete composite columns were pesented and a finite element (FE) numerical simulation of the classical specimens was performed. The study shows that the load-bearing capacity, ductility, and seismic energy dissipation capacity of the bottom strengthened rectangular steel-concrete composite columns are significantly improved compared to the conventional rectangular steel-concrete composite columns and the results obtained from the calculation and the FE numerical simulation are in good agreement with those from the experiments. The rectangular steel-concrete composite column with bottom strengthened shows better seismic behavior and higher energy dissipation capacity under suitable constructional requirements and it can be applied to the structure design of high-rise buildings.