• Smart Structures and Systems
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• v.18 no.1
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• pp.75-92
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• 2016

The design of a semi-active (SA) control system addressed to mitigate wind induced structural demand to high wind turbine towers is discussed herein. Actually, the remarkable growth in height of wind turbines in the last decades, for a higher production of electricity, makes this issue pressing than ever. The main objective is limiting bending moment demand by relaxing the base restraint, without increasing the top displacement, so reducing the incidence of harmful "p-delta" effects. A variable restraint at the base, able to modify in real time its mechanical properties according to the instantaneous response of the tower, is proposed. It is made of a smooth hinge with additional elastic stiffness and variable damping respectively given by springs and SA magnetorheological (MR) dampers installed in parallel. The idea has been physically realized at the Denmark Technical University where a 1/20 scale model of a real, one hundred meters tall wind turbine has been assumed as case study for shaking table tests. A special control algorithm has been purposely designed to drive MR dampers. Starting from the results of preliminary laboratory tests, a finite element model of such structure has been calibrated so as to develop several numerical simulations addressed to calibrate the controller, i.e., to achieve as much as possible different, even conflicting, structural goals. The results are definitely encouraging, since the best configuration of the controller leaded to about 80% of reduction of base stress, as well as to about 30% of reduction of top displacement in respect to the fixed base case.

• The International Journal of Costume Culture
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• v.2 no.1
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• pp.31-42
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• 1999

The category killer that has been rapidly growing mainly in advanced countries since early 1990's, is a mew distribution model which aims for obtaining market controlling power by surpassing competing businesses in a specific area of products. The domestic situation of category killers is very different from that of advanced ones abroad since it has just been introduced into the Korean market. At the moment, there are only 10 or so companies operating in the market : Geopyung's , Taeheng's , Midopa's , of Sinsegye Department store, adn of Yerim International. The purpose of this study is to examine problems of domestic companies in the present market by analysing the operation status of category killers in domestic markets as well as foreign ones, and to suggest a counter-strategy of category killers for the distribution environment of the 21st century to improve the competitiveness of Korean distribution industry. The competitiveness of category killers lies above all in products lines. Category killers are equipped with the greatest number of products lines among those of competing businesses due to maximized product selections in an limited range. Another source of competitiveness may be found in balanced strategy positioning. That is to say, category killers are in a position where they can adjust policies towards any of the three purposes while aiming at them altogether : prices of discount stores, products range of specialty stores, and customer service level of department stores. It is also necessary for efficient store operation to use information technology such as electronic data interchange (EDI), electronic pose system(EPOS) and electronic funds transfer (EFTPOS). As for the cost structure, category killers can gain an advantage over other business since operating cost of various sections can be saved. There are, however, certain risks that category killers with strong competitiveness may influence on other businesses a great deal and even facilitate their decline. Yet it seems that the growth of category killers will be more viciously restrained by continuous challenges from other businesses. The distribution industry is supposed to develop through such competition and restraint.

• Journal of architectural history
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• v.18 no.5
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• pp.81-100
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• 2009

The study on Buddhism architecture in early Joseon dynasty was inactive. The period of King Sejo is important for studying the trend of Buddhism architecture in early Joseon, that was transmitted from the end of Goryeo dynasty, but it was difficult to know its exact situation due to lack of related records. The records were all written by Kim Su-ohn, which are Wongaksabi' 'Sangwonsajungchanggi' 'Bongseonsagi 'Geonginsajungchanggi'. The main hall was mainly second floor and there were necessarily annexed buildings at the right and left of the main hall. So the plane figure of $\Box\Box\Box$ was shown. It was a main stream for main hall. This layout may be referred to search for the origin of the layout in courtyard based structure(中庭形) in the late Joseon dynasty. Most of temples had 3 gates. Some part of horizontal corridor was used as 2 gates and the outer gate, far from main hall, was without corridor. The gate leading to front yard of main hall was called front gate, the next middle gate and the outer gate was Oisamun(外沙門) or Samun(沙門). Im most of the temples, people could enter into the front yard through pavilion which had the function of bell tower. The pavilions were located between front gate and first corridor. It is thought that this layout of the place for making bean curd outside the temple area will contribute to different studies on temples making bean cure in the future. The records about temples's foundation studied above are a little different between temples, but have more similarities. There common denominators represent the architecture tendency of Buddhist temples in the related period. It is thought that such a tendency was also shown on architecture of other temples during the reign of King Sejo as well as Buddhist temples.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.335-341
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• 2015

Various display devices has been increasing also using waste LCD glass in accordance with the used developed, because circumstances that are most landfill or incineration, are needed research on recycling measure of the using waste LCD glass. Therefore, in this study, to try to assess the basic mechanical properties of concrete mixed with using waste LCD glass micropowder through the room mixed test. According to the study results, the more replacement rate increases, the characteristics of the concrete showed a tendency to decrease slightly. However, according to the small value, it is expected to improve the advanced experimental values by refining the grain size of the materials used to be processed into spheres.

• Wind and Structures
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• v.17 no.1
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• pp.43-68
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• 2013

The fluctuating wind induced vibration is one of the most important factors which has been taken into account in the design of long-span bridge due to the low stiffness and low natural frequency. Field measurement characteristics of sustained wind on structure site can provide accurate wind load parameters for wind field simulation and structural wind resistance design. As a suspension bridge with 1490 m main span, the Runyang Suspension Bridge (RSB) has high sensitivity to fluctuating wind. The simultaneous and continuously wind environment field measurement both in mid-span and on tower top is executed from 2005 up to now by the structural health monitoring system installed on this bridge. Based on the recorded data, the wind characteristic parameters, including mean wind speed, wind direction, the turbulence intensity, the gust factors, the turbulence integral length, power spectrum and spatial correlation, are analyzed in detail and the coherence functions of those parameters are evaluated using statistical method in this paper. The results indicate that, the turbulence component of sustain wind is larger than extremely strong winds although its mean wind speed is smaller; the correlation between turbulence parameters is obvious; the power spectrum is special and not accord with the Simiu spectrum and von Karman spectrum. Results obtained in this study can be used to evaluate the long term reliability of the Runyang Suspension Bridge and provide reference values for wind resistant design of other structures in this region.

• Earthquakes and Structures
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• v.8 no.4
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• pp.859-887
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• 2015

Structural health monitoring (SHM) has gained in popularity in recent years since it can assess the performance and condition of instrumented structures in real time and provide valuable information to the asset's manager and owner. Operational modal analysis plays an important role in SHM and it involves the determination of natural frequencies, damping ratios and mode shapes of a constructed structure based on measured dynamic data. This paper presents the operational modal analysis and seismic response characterization of the Tsing Ma Suspension Bridge of 2,160 m long subjected to different earthquake events. Three kinds of events, i.e., short-distance, middle-distance and long-distance earthquakes are taken into account. A fast Bayesian modal identification method is used to carry out the operational modal analysis. The modal properties of the bridge are identified and compared by use of the field monitoring data acquired before and after the earthquake for each type of the events. Research emphasis is given on identifying the predominant modes of the seismic responses in the deck during short-distance, middle-distance and long-distance earthquakes, respectively, and characterizing the response pattern of various structural portions (deck, towers, main cables, etc.) under different types of earthquakes. Since the bridge is over 2,000 m long, the seismic wave would arrive at the tower/anchorage basements of the two side spans at different time instants. The behaviors of structural dynamic responses on the Tsing Yi side span and on the Ma Wan side span under each type of the earthquake events are compared. The results obtained from this study would be beneficial to the seismic design of future long-span bridges to be built around Hong Kong (e.g., the Hong Kong-Zhuhai-Macau Bridge).

• Computers and Concrete
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• v.16 no.4
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• pp.503-529
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• 2015

Traditionally, multi-story buildings are designed to provide stiffer structural support to withstand lateral earthquake loading. Introducing flexible elements at the base of a structure and providing sufficient damping is an alternative way to mitigate seismic hazards. These features can be achieved with a device known as an isolator. This paper covers the design of base isolators for multi-story buildings in medium-risk seismicity regions and evaluates the structural responses of such isolators. The well-known tower building for police personnel built in Dhaka, Bangladesh by the Public Works Department (PWD) has been used as a case study to justify the viability of incorporating base isolators. The objective of this research was to establish a simplified model of the building that can be effectively used for dynamic analysis, to evaluate the structural status, and to suggest an alternative option to handle the lateral seismic load. A finite element model was incorporated to understand the structural responses. Rubber-steel bearing (RSB) isolators such as Lead rubber bearing (LRB) and high damping rubber bearing (HDRB) were used in the model to insert an isolator link element in the structural base. The nonlinearities of rubber-steel bearings were considered in detail. Linear static, linear dynamic, and nonlinear dynamic analyses were performed for both fixed-based (FB) and base isolated (BI) buildings considering the earthquake accelerograms, histories, and response spectra of the geological sites. Both the time-domain and frequency-domain approaches were used for dynamic solutions. The results indicated that for existing multi-story buildings, RSB diminishes the muscular amount of structural response compared to conventional non-isolated structures. The device also allows for higher horizontal displacement and greater structural flexibility. The suggested isolation technique is able to mitigate the structural hazard under even strong earthquake vulnerability.

• Journal of the Korean Geophysical Society
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• v.9 no.2
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• pp.77-86
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• 2006

Aplications of the real-time kinematic GPS surveying and inertial measurement unit have been beingRTK GPS allows the use of a static base station and remote rover unit to allow for data collectionwithin several seconds and in real time. It is useful for monitoring the behaviors of massive structureslike bridges. And this study purposed to implement a method of deciding the acurate dynaimc attitudeof structures by IMU. In this study, among GPS methods, we used RTK GPS to analyze the precisionof monitoring and then on the basis of it, we developed a monitoring system using RTK GPS anda deviation betwen observation values, X axis was 1mm, Y axis was 1mm and Z axis 2.2mm. I tturned out that it was possible to monitor and measure structures by RTK GPS and IMU.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.48-59
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• 2019

In recent years, the type of bridge where cables such as suspension bridge and cable-stayed bridge are the main factors in the construction of long-range bridges has been soaring. The effects of cables on these structures are very large, and for structural analysis, it is necessary to study the cable and the structural changes according to the mode characteristics of the cables. In particular, cables are directly connected to camber adjustment, which conveys load effects on girders to tower, and are important components in the overall structure, and since the initial tension on the construction is compared with the tension over time, this study was conducted to help identify the condition of the bridge's aging and abnormalities. Therefore, in this study, the characteristics of the mode from the mode analysis through the impact hammer to the mass of the cable and the change in the length of the cable are analyzed.

• International journal of steel structures
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• v.18 no.4
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• pp.1191-1199
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• 2018

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS-AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.