• Smart Structures and Systems
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• v.32 no.1
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• pp.9-21
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• 2023

The parameters of civil engineering structures have time-variant characteristics during their service. When extremely large external excitations, such as earthquake excitation to buildings or overweight vehicles to bridges, apply to structures, sudden or gradual damage may be caused. It is crucially necessary to detect the occurrence time and severity of the damage. The unscented Kalman filter (UKF), as one efficient estimator, is usually used to conduct the recursive identification of parameters. However, the conventional UKF algorithm has a weak tracking ability for time-variant structural parameters. To improve the identification ability of time-variant parameters, an adaptive UKF with forgetting factor (AUKF-FF) algorithm, in which the state covariance, innovation covariance and cross covariance are updated simultaneously with the help of the forgetting factor, is proposed. To verify the effectiveness of the method, this paper conducted two case studies as follows: the identification of time-variant parameters of a simply supported bridge when the vehicle passing, and the model updating of a six-story concrete frame structure with field test during the Yangbi earthquake excitation in Yunnan Province, China. The comparison results of the numerical studies show that the proposed method is superior to the conventional UKF algorithm for the time-variant parameter identification in convergence speed, accuracy and adaptability to the sampling frequency. The field test studies demonstrate that the proposed method can provide suggestions for solving practical problems.

• Journal of Korean Association for Spatial Structures
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• v.22 no.4
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• pp.15-22
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• 2022

Micro-climate measurements and computational fluid analysis were conducted to use it as basic data for the preservation and management of the old house of Kim Myung-kwan, a traditional building that is National Folk Cultural Property No. 26. As a result of the actual measurement, the temperature and humidity are relatively evenly distributed indoors unlike outdoors, but the temperature and humidity vary depending on the time change and the installation location in the outdoors. It was found that the temperature increases after dawn and the temperature varies depending on the installation position around 14:00-15:00, when the temperature becomes the highest. In particular, the temperature was high at the outdoor measurement point adjacent to the building and the fence. As a result of the computational fluid analysis, the temperature was high in the buildings and fences in the old house or in the area adjacent to the building, and it was about 1℃ higher than the surrounding area. In this area, it is judged that the thickening of wood will occur more severely than in other locations, and special preservation management is required.

• Earthquakes and Structures
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• v.26 no.1
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• pp.17-30
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• 2024

Earthquakes can lead to substantial damage to buildings, with long-period ground motion being particularly destructive. The design of high-performance building structures has become a prominent focus of research. The double-story isolated structure is a novel type of isolated structure developed from base isolated structure. To delve deeper into the building performance of double-story isolated structures, the double-story isolated structure was constructed with the upper isolated layer located in different layers, alongside a base isolated structure for comparative analysis. Nonlinear elastoplastic analyses were conducted on these structures using different ground motion inputs, including ordinary ground motion, near-field impulsive ground motion, and far-field harmonic ground motion. The results demonstrate that the double-story isolated structure can extend the structural period further than the base isolated structure under three types of ground motions. The double-story isolated structure exhibits lower base shear, inter-story displacement, base isolated layer displacement, story shear, and maximum acceleration of the top layer, compared to the base isolated structure. In addition, the double-story isolated structure generates fewer plastic hinges in the frame, causes less damage to the core tube, and experiences smaller overturning moments, demonstrating excellent resistance to overturning and a shock-absorbing effect. As the upper isolated layer is positioned higher, the compressive stress on the isolated bearings of the upper isolated layer in the double-story isolated structure gradually decreases. Moreover, the compressive stress on the isolated bearings of the base isolated layer is lower compared to that of the base isolated structure. However, the shock-absorbing capacity of the double-story isolated structure is significantly increased when the upper isolated layer is located in the middle and lower section. Notably, in regions exposed to long-period ground motion, a double-story isolated structure can experience greater seismic response and reduced shock-absorbing capacity, which may be detrimental to the structure.

• Korean Journal of Heritage: History & Science
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• v.48 no.3
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• pp.96-119
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• 2015

This research has studied the changes of Gwi-po(轉角包) by taking the cases of China's medieval wooden buildings as objects. The purpose of the study is to examine the time-periodic transition process of Gwi-po through the cases of 71 wooden buildings which were built from Tang(唐) dynasty(AD 618~690 & 705~907) until Jin(金) dynasty(AD 1115~1234) and also designated as 'Major Historical and Cultural Sites Protected at the National Level'. This research has taken note of various frame types of Jwau-dae(左右隊), which are architectural components of Gwi-po, to study the changes and development process of Gwi-po. The results are as follows. An important factor in the transformations of Gwi-po format is the changes in perception of the craftsmen about Jwau-dae, who took charge in the building process. In the early periods, the principles of Yidou sanshen dougong(一斗三升) in constructing ancons of Gwi-po had been well-maintained, while there appeared many different types of Gwi-po in later periods, due to the usage of Jwau-dae and $Shu{\check{a}}$ $t{\acute{o}}u$(?頭) in each Chulmok of Gwi-po. Transitional types of Gwi-po, which were evolved from the earlier ones, are divided into 3 categories by different forms of Jwau-dae, placed on odd number stages. The first one is 'none-$f{\bar{a}}ng$ $t{\acute{o}}u$(無枋頭) type' of Song(AD 960~1127, 1127~1279) and Liao dynasty(AD 907~1125) buildings, which doesn't have $f{\bar{a}}ng$ $t{\acute{o}}u$(枋頭)s, for the reason that Jwau-dae(左右隊) is in direct contact with Gwihan-dae(耳限大). The second one is '$Shu{\check{a}}$ $t{\acute{o}}u$ $f{\bar{a}}ng$ $t{\acute{o}}u$(?頭枋頭) type' of Song(AD 960~1127, 1127~1279) and Jin dynasty(AD 1115~1234), that has $f{\bar{a}}ng$ $t{\acute{o}}u$(枋頭)s of Jwau-dae(左右隊) identical to $Shu{\check{a}}$ $t{\acute{o}}u$(?頭) in form. The last one is '$Xi{\check{a}}o$ $g{\check{o}}ng$ $t{\acute{o}}u$(小?頭) type' of Jin(AD 1115~1234) and Yuan dynasty(AD 1271~1368), which has $f{\bar{a}}ng$ $t{\acute{o}}u$(枋頭)s of Jwau-dae identical to $Xi{\check{a}}o$ $g{\check{o}}ng$ $t{\acute{o}}u$(小?頭) in form. The earlier forms of Gwi-po, which appeared between Tang dynasty(AD 618~690 & 705~907) and Five Dynasties periods(907~960) went through transitional forms of 'non-$f{\bar{a}}ng$ $t{\acute{o}}u$(無枋頭) type', '$Shu{\check{a}}$ $t{\acute{o}}u$ $f{\bar{a}}ng$ $t{\acute{o}}u$(?頭枋頭) type' and '$Xi{\check{a}}o$ $g{\check{o}}ng$ $t{\acute{o}}u$(小?頭) type' and finally had its form settled between Yuan(元, AD 1271~1368) and Ming(明. AD 1368~1644) dynasty periods. In Liao(遼) dynasty period(AD 907~1125), as the buildings got bigger and the tendency of longer eave-exposure was implemented, there grew a certain need to structurally reinforce Gwi-po, on which load of the whole roof is concentrated. Especially, the transition from Tōuxīn $z{\grave{a}}o$(偸心造) style to Jì xīn $z{\grave{a}}o$(計心造) style in this period had a great influence on standardization of Gwi-po, along with None-${\acute{A}}ng$(無仰) style. Furthermore, Wing-type Gong(翼型?), which developed in Liao dynasty(AD 907~1125), is also thought to have had a great influence on the transition from Tōuxīn $z{\grave{a}}o$(偸心造) style to Jì xīn $z{\grave{a}}o$(計心造) style by changing the forms of Gongs(?), such as Gwi-po. However, unlike None-${\acute{A}}ng$(無仰) style, there occurred a gradual change from '$Shu{\check{a}}$ $t{\acute{o}}u$ $f{\bar{a}}ng$ $t{\acute{o}}u$(?頭枋頭) type' to '$Xi{\check{a}}o$ $g{\check{o}}ng$ $t{\acute{o}}u$(小?頭) type' of Gwi-po in $Xi{\grave{a}}$ ${\acute{a}}ng$ style.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.43-51
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• 2015

At present, in the case of small and medium window manufacturers in South Korea, glazing and window frame manufacturers are divided into separate businesses. However, in the fenestration energy consumption efficiency rating system and the energy-saving design criteria for buildings, the coefficient of overall heat transmission standard for windows is defined by window sets, which integrate glazing and window frames. At most construction sites, windows are constructed by installing separately supplied glass and frames. Research that can integrate the reality and the system is therefore necessary. The present study first investigated and analyzed the on-site situation of the fenestration energy consumption efficiency rating system. According to the results, while overall understanding of the fenestration energy consumption efficiency rating system was high, satisfaction with it was low, and the general practice at construction sites was to use windows assembled on site rather than integrated window systems manufactured at factories, thus making it difficult to confirm that the current rating system was well applied on site. Consequently, the reality of industrial sites must be reviewed and a realistic alternative to the fenestration energy consumption efficiency rating system must be presented instead of focusing on theory.

• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.519-530
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• 2013

Cyclic tests on modular building units for low-rise buildings composed of stud panels and a light-weight steel perimeter frame, were performed to evaluate the earthquake resistance such as stiffness, load-carrying capacity, ductility, and energy dissipation per load cycle. The strap-braced and sheeted stud panels were used as the primary lateral load-resistant element of the modular building units. Test results showed that the modular building units using the strap-braced and sheeted stud panels exhibited excellent post-yield ductile behaviors. The maximum drift ratios were greater than 5.37% and the displacement ductility ratios were greater than 5.76. However, the energy dissipation per load cycle was poor due to severe pinching during cyclic loading. Nominal strength, stiffness, and yield displacement of the modular building units were predicted based on plastic mechanisms. The predictions reasonably and conservatively correlated with the test results. However, the elastic stiffness of the strap-braced stud panel was significantly overestimated. For conservative design, the elastic stiffness of the strap-braced stud panel needs be decreased to 50% of the nominal value.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.1-8
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• 2020

Air ducts installed for ventilation inside buildings accumulate contaminants during their service life. Robots are installed to clean the air duct at low cost, but they are still not fully automated and depend on manpower. In this study, an intersection detection algorithm for autonomous driving was applied to an air duct cleaning robot. Autonomous driving of the robot was achieved by calculating the distance and angle between the extracted point and the center point through the intersection detection algorithm from the camera image mounted on the robot. The training data consisted of CAD images of the duct interior as well as the cross-point coordinates and angles between the two boundary lines. The deep learning-based CNN model was applied as a detection algorithm. For training, the cross-point coordinates were obtained from CAD images. The accuracy was determined based on the differences in the actual and predicted areas and distances. A cleaning robot prototype was designed, consisting of a frame, a Raspberry Pi computer, a control unit and a drive unit. The algorithm was validated by video imagery of the robot in operation. The algorithm can be applied to vehicles operating in similar environments.

• Korean Journal of Construction Engineering and Management
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• v.19 no.6
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• pp.3-13
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• 2018

The formwork cost amounts for a significant proportion of project construction costs. It costs 10-15% of the total construction cost and 30-40% of the frame structure construction cost. In addition, the formwork collapse accidents are frequently causing deaths in the construction industry, and thus, is known to be of relatively high degree of risk. As so, the accuracy of structural calculation and quantity take-off when planning the formwork in a construction project are a very important matter. Accordingly, this study develops a BIM based formwork design prototype, that enables the construction manager to optimize the design through applying the proposed new IFC entities associated with the formwork design. The approach proposed in this study is expected to support the construction manager with accurate quantity calculation and rapid planning and construction. Since this study considered specific small-scale buildings using Euro-form and show the possibility of utilizing BIM entities in the formwork design process, further research is recommended towards the limitations in applying the system to other types of formworks.

• Journal of Environmental Policy
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• v.14 no.4
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• pp.3-21
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• 2015

This paper attempts to determine the most reasonable and agreeable option for new MRV framework in Post-2020 Climate Regime as well as to develop South Korea strategies to reflect our national circumstances and capacities appropriately. The options for MRV framework considered here are 1) Dual MRV and 2) Unified MRV. We reached the conclusion that the Unified MRV framework may be the most reasonable option in the 2015 agreement in line with the objectives of MRV. To this end, it is essential to develop effective stepwise strategies consisted of: 1) reaching a consensus internally on the Unified MRV framework, 2) developing detailed procedures and methodologies to make the major elements of the Unified MRV framework understandable and predictable, 3) delivering an overview and blueprint to make sure of the flexibility of the Unified MRV framework to reflect the Parties' capacities and national circumstances, 4) ensuring the financial and technical support schemes for developing countries to improve the capacity-buildings of MRV, and 5) developing a realistic road map to successfully implement the Unified MRV scheme within the required time frame. Korea, as a rational mediator between developed and developing countries, should play a leading role in reaching post-2020 agreement.

• Journal of architectural history
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• v.13 no.2 s.38
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• pp.57-70
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• 2004

Since Korea disclaimed to open the ports, Korean architecture has met the impetuous transformation. Although there would be various factors of this transformation, the new-coming architecture by missionary seemed to be a significant one, and many researches have been carried out on this theme in diverse viewpoints. However, because these researches have preponderated on the Catholic tradition, it is deficient for clarify the whole history of mission architecture. Therefore, this research has the meaning to enrich the history of Korean modern architecture by making balance. First of all, this paper is focused on the activities of one missionary, Graham Lee. He is a practical missionary at the beginning, his architecture made a critical influence in Korean traditional architecture. Graham Lee was born in Rock Island, Illinois, 1861, and he determined to become a missionary through grown up. He spent his boyhood by working as a plumber for his purpose and studied in a university afterward. Graduating of McComick Theological Seminary, he was nominated as a pioneer of Pyeng Yang Mission Station and set foot in Korea, September of 1892. Since then he started to erect missionary facilities in Pyeng Yang, such as Well House(1898), Pyeng Yang Central Church(1900-1901), Pyeng Yang Academy(1902). These all his works are designed with eclectic style which shows western and Korean traditional style intermingled. This unique characteristic made a profound influence to the Korean mission architecture afterwards. Especially, the L-type plan of Pyeng Yang Central Church, which is first shown by him, is recognized very unique, and this plan type had been spread all over the country. Therefore the L-type plan became the peculiar feature of the early Korean churches. Furthermore, working with Korean carpenters, he taught them new skills of modem buildings. After that, they were expanded out northern part of Korea and took the roles of master builders. According to this expansion, his particular style had got spread and had been settled as a unique eclectic style in Korean modern architecture. In the conclusion, he is evaluated to be a critical pioneer missionary, who left a big influence on the frame work of Korean modern architecture in the transitional times.