• International conference on construction engineering and project management
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• 2024.07a
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• pp.1264-1271
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• 2024

Tatami serves as a multi-functional flooring and furniture material in traditional Japanese houses, and Westerners use it with suitable arrangements. Some choose to sleep on tatami for health reasons, while others adopt the lifestyle of 'floor living' to solve the spatial problems in cities. In any case, people use tatami for practical reasons rather than due to a cultural preference. I surveyed 750 respondents, including 463 non-Japanese people, and conducted both quantitative and qualitative analysis. I also interviewed European vendors and users of tatami during 2022-2023. The results showed that non-Japanese customers, especially Europeans, wanted authentic tatami mats made of natural materials such as igusa and rice straw to ensure health and sustainability. On the other hand, Japan's tatami industry is shifting towards artificial, or alternative, tatami-like mats. Few authentic tatami rooms exist in Japanese homes nowadays, and producers of tatami materials are almost extinct in Japan. Chinese farmers who supply almost 80% of igusa to the Japanese market may also discontinue their trade because the production is time-consuming and yields low profit. This paper discusses the possibilities of continuously producing and selling tatami in and outside Japan.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.4
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• pp.1-12
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• 2020

In this study, the effect of the social distance maintenance and pedestrian route system was analyzed for Seoul Station, one of the multi use facilities according to the COVID-19 pandemic. For analysis, the Seoul Station pedestrian network was established through the survey of the number of passengers and CAD floor plan. A pedestrian that maintaining Social Distance was implemented using the Social Force Model. Based on this, scenario analysis was proceed. As a result, when the walking line system was installed the average walking speed decreased compared to the current situation. but the average density was analyzed that maintain the walking level of service (LOS)'C', this mean walking line system is effective, and the effect of the walking line system was proved. It can be used as a pedestrian simulation model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.227-231
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• 2014

Underwater radiated noise is one of the vital factors in underwater weapon systems like submarine. A passive elastic mount is an effective reduction method for the vibration from a ship-board machinery transmitted to the hull which is radiated as noise outside the hull. A passive elastic mount shows the limitation on the vibration reduction and needs multi stage mounting system including double stage one to meet the required underwater radiated noise criteria. It is necessary for the multi stage mounting system to consider the large displacement in the underwater shock explosion. So it is difficult to apply the multi stage mounting system in submarine because of space limitation. Also recent navy sonar system are trying to have the capability to detect the ship-borne acoustic signals in the low frequency range. An alternative to the passive mount is an active mount with moving-coil type electromagnetic actuator based on a conventional rubber mount in the low frequency range. In the previous paper, 4 active mounts with moving-coil type electromagnetic actuator based on the rubber mount were installed on the hard floor of the facility, which means no consideration on the elastic foundation effect for the control of the active mounts was taken into account. In this study, an experimental performance analysis on the active mount was carried out using 4 active mounts installed on the cylindrical structure to investigate the elastic foundation effect.

• Korean Journal of Construction Engineering and Management
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• v.16 no.2
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• pp.29-37
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• 2015

Multi-household buildings are efficiently maintained from the mid- and long-term viewpoint according to the long-term repair coverage system etc. On the other hand, public buildings are not systematically maintained due to a lack of past maintenance cost data and inefficient budget plans, among other problems. Targeting public buildings in Incheon, this study analyzed operation costs variables. To verify the analysis results, they underwent a correlation analysis and a multi-regression analysis. With regard to public buildings electricity, gas and tap water cost, the influence power of the served life, floor area, and workforce were analyzed, revealing that electricity cost was highly correlated with workforce, while gas and tap water cost were correlated with tap water cost. Also, the correlation analysis results were verified through a multi-regression analysis, and a maintenance cost estimation model was presented using a regression equation.

• Wind and Structures
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• v.32 no.4
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• pp.355-369
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• 2021

Shape optimization of tall buildings is an efficient approach to mitigate wind-induced effects. Several studies have demonstrated the potential of shape modifications to improve the building's aerodynamic properties. On the other hand, it is well-known that the cross-section geometry has a direct impact in the floor area availability and subsequently in the building's profitability. Hence, it is of interest for the designers to find the balance between these two design criteria that may require contradictory design strategies. This study proposes a surrogate-based multi-objective optimization framework to tackle this design problem. Closed-form equations provided by the Eurocode are used to obtain the wind-induced responses for several wind directions, seeking to develop an industry-oriented approach. CFD-based surrogates emulate the aerodynamic response of the building cross-section, using as input parameters the cross-section geometry and the wind angle of attack. The definition of the building's modified plan shapes is done adopting the reduced basis approach, advancing the current strategies currently adopted in aerodynamic optimization of civil engineering structures. The multi-objective optimization problem is solved with both the classical weighted Sum Method and the Weighted Min-Max approach, which enables obtaining the complete Pareto front in both convex and non-convex regions. Two application examples are presented in this study to demonstrate the feasibility of the proposed strategy, which permits the identification of Pareto optima from which the designer can choose the most adequate design balancing profitability and occupant comfort.

• Journal of Korean Society of Forest Science
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• v.97 no.2
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• pp.156-164
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• 2008

Recognizing the importance of the multi-purpose management of natural deciduous forest, this study was carried out to implement the partial cutting for stand regulation to examine agroforestry practice as well as other concurrent forest resource production, and to investigate the changes in stand characteristics and understory vegetation in a silvopasture practiced natural deciduous stand in the Research Forest of Kangwon National University, Korea. Three different partial cutting intensities (68.1%, 48.6%, and control) were performed in the unmanaged natural deciduous stand in order to improve the growing condition, especially light condition, for introducing some commercial herbaceous plants on the forest floor to establish agroforestry and/or silvopastoral system. Dominated by Quercus varibilis Blume (50.5%) and Quercus dentata Thum. ex Murray (42.6%), eight tree species were composed of the study forest, including poles of Pinus desiflora Siebold & Zucc and sapling of Pinus Koraiensis Siebold & Zucc. The total of 87 (13 tree species, 12 shrub species, 58 herbaceous species, and 4 woody climbers) vascular plant species were observed in study site after partial cutting treatments, while that of before partial cutting was 53 species (14 tree species, 8 shrubs species, 30 herbaceous species, and 1 woody climbers). The proportion of life form spectra in plot B was Mi (28.4%)-Na (23.0%)-Ge (17.5%)-Ch (10.8%)-He (9.5%)-MM (6.7%)-Th (4.1%). No statistically significant differences were observed in changes of life form spectra from before to after partial cutting treatment and among partial cutting gradients in this study. Partial cutting and scratching for forage sowing made plants invade easily on the forest floor, and light partial cutting (LPC) plot (500 stems/ha) had much higher number of undersory species than those of heavy partial cutting (HPC) plot (310 stems/ha) and control plot (1,270 stems/ha).

• Steel and Composite Structures
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• v.29 no.1
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• pp.1-22
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• 2018

Multi-storey precast concrete skeletal structures are assembled from individual prefabricated components which are erected on-site using various types of connections. In the current design of these structures, beam-to-column connections are assumed to be pin jointed. Welded plate beam to-column connections have been used in the precast concrete industry for many years. They have many advantages over other jointing methods in component production, quality control, transportation and assembly. However, there is at present limited information concerning their detailed structural behaviour under bending and shear loadings. The experimental work has involved the determination of moment-rotation relationships for semi-rigid precast concrete connections in full scale connection tests. The study reported in this paper was undertaken to clarify the behaviour of such connections under symmetrical vertical loadings. A series of full-scale tests was performed on sample column for which the column geometry and weld arrangements conformed with successful commercial practice. Proprietary hollow core slabs were tied to the beams by tensile reinforcing bars, which also provide the in-plane continuity across the connections. The strength of the connections in the double sided tests was at least 0.84 times the predicted moment of resistance of the composite beam and slab. The secant stiffness of the connections ranged from 0.7 to 3.9 times the flexural stiffness of the attached beam. When the connections were tested without the floor slabs and tie steel, the reduced strength and stiffness were approximately a third and half respectively. This remarkable contribution of the floor strength and stiffness to the flexural capacity of the joint is currently neglected in the design process for precast concrete frames. In general, the double sided connections were found to be more suited to a semi-rigid design approach than the single sided ones. The behaviour of double sided welded plate connection test results are presented in this paper. The behaviour of single sided welded plate connection test results is the subject of another paper.

• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.527-537
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• 2004

Consequence-Based Engineering (CBE) is a new paradigm proposed by the Mid-America Earthquake Center (MAE) to guide evaluation and rehabilitation of building structures and networks in areas of low probability - high consequence earthquakes such as the central region of the U.S. The principal objective of CBE is to minimize consequences by prescribing appropriate intervention procedures for a broad range of structures and systems, in consultation with key decision makers. One possible intervention option for rehabilitating unreinforced masonry (URM) buildings, widely used for essential facilities in Mid-America, is passive energy dissipation (PED). After the CBE process is described, its application in the rehabilitation of vulnerable URM building construction in Mid-America is illustrated through the use of PED devices attached to flexible timber floor diaphragms. It is shown that PED's can be applied to URM buildings in situations where floor diaphragm flexibility can be controlled to reduce both out-of-plane and in-plane wall responses and damage. Reductions as high as 48% in roof displacement and acceleration can be achieved as demonstrated in studies reported below.

• Journal of the Korean Society of Safety
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• v.35 no.4
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• pp.32-39
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• 2020

The fire compartments with fire-resistant construction are installed in the principal structural parts of a building in order to reduce damage in the event of a building fire. As a fire may spread through a crack in the fire compartment, the firestop with secured performance is used according to the procedure, methods, and standards specified in the detailed operation guideline. According to the current detailed operation guideline, vertical members (wall penetration) and horizontal members (floor penetration) are classified into different categories respective to each other for the classification of the firestop. Therefore, an accreditation applicant must apply for the performance test for each structure even if the wall and the floor have the same structure. Also, Grade T is used for the firestop that penetrates the fire compartment. However, in the case of foreign countries, the use of Grade F for the firestop is allowed even if it penetrates the fire compartment. The result of the precedent studies also showed that there was a significantly low possibility of fire to spread even if Grade F was applied for a metallic duct that penetrated the fire compartment. In this study, the improved scheme for the classification and performance standard of firestops was presented by analyzing the results of precedent studies regarding the firestop and domestic and overseas firestop qualification systems.

• Journal of the Korean housing association
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• v.20 no.3
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• pp.11-18
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• 2009

The purpose of this study is to propose a method of developing an improved Hanok. To achieve this, an investigation was carried out on the factors of the main floor plan in the improved Hanok development and an interview was conducted with residents who live in the improved Hanok development. The conclusions obtained through this study are as follows: First, The shape of 一 was marked at the highest in the Korean traditional plan types such as 一, ㄱ and 田. It is considered that this reduces the cost of construction by simplifying the structure of the roof. Second, the size was consisted of $5{\times}3$ Kan, the Korean traditional module that determines the number of columns and expresses the position of the inner wall. However, the Kan measure ments for the bathroom and multi-purpose room differed. Third, 57.6% of the 2 bedroom units were investigated. However, 60% of the residents preferred 3 bedroom units. Fourth, the results of the relationship between the living room and the kitchen showed that the residents preferred L+DK type to LDK type by 54.2% and 45.8% respectively. Fifth, the residents preferred a bathroom constructed next to the bedroom because they considered that the improved Hanok development would be used as an Inn during holiday periods. Moreover, they desired a plan where the bathroom could be directly entered from the outside. Sixth, the design for the improved Hanok development should have a suitable multipurpose-room because 72.5% of the residents have extended their house to accommodate such a room. Seventh, 61% of the improved Hanok units had an entrance space, which does not exist in Korean traditional houses. For this reason, the Korean traditional floor (: the Maru) was avoided due to its inconvenience.