• Title/Summary/Keyword: dynamic characteristics of concrete

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The use of SMA wire dampers to enhance the seismic performance of two historical Islamic minarets

  • El-Attar, Adel;Saleh, Ahmed;El-Habbal, Islam;Zaghw, Abdel Hamid;Osman, Ashraf
    • Smart Structures and Systems
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    • v.4 no.2
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    • pp.221-232
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    • 2008
  • This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

A Case Study on Student's Perspective on Java Applets in Web-based Online Courseware (자바 애플릿(Java Applets)의 교육적 활용에 대한 학습자의 인식 및 태도 : 웹기반수업 사례연구)

  • Park, HaeOck;Choi, WonSik
    • 대한공업교육학회지
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    • v.31 no.1
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    • pp.170-184
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    • 2006
  • The purpose of this paper is to examine student's perspective on java applets used in web-based online courseware. undergraduate The subject of study was 94 undergraduates and web-based online courseware for the study was made. A suvey was conducted using a questionnaire form right after the semester was over. The results of this study were as follows; 1. 61.7% of the students answered that java applets used in the web-based courseware was very interesting. 2. For the reason why the students had the feeling of liking on the java applets, 33% of the students checked the item "due to the java applets' characteristics of repetition", and 30.9% of the students checked the item "due to the concrete and dynamic explanation on the contents". 3. The majority of the students answered that the java applets helped their learning(71.3%), induced their academic motivation(67%), and felt interactivity while learning(73.4%). 4. 81.9% of the students felt that java applets was necessary and essential contents in the industrial education web-based online courseware.

A Study on the Vibration Characteristics of Subway Structure by Train Load (열차 하중에 의한 지하철 구조물의 진동 특성에 관한 연구)

  • Park, Sung Woo;Park, Seung Su;Hwang, In Baek
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.4
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    • pp.107-115
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    • 2011
  • In this study, the vibration analysis of the underground box structures induced train movement is studied. In order to perform these analysis, dynamic data, which was measured when subway is in service, are gained by attaching accelerometers on the structure such as lower beam, lateral wall and upper slab. Also, accelerometers are attached on the lower beams and side walls of the gravel ballast and concrete ballast sections in order to compare vibration due to ballast materials. The vibration results of upper slabs and lower beams reveal that the vibration on the upper slabs is greater than the lower beams. Also, the results of the crack gauge on the upper slab show that crack width dose not change due to vibration, These means that the effect of the vibration on the structure is very limited. In order to evaluate the vibration of the structure, acceleration unit is converted to velocity unit comparing with the existing velocity data gained from the platforms.

Time Adverb 'Cengjing (曾經)' and 'Yijing (已經) Tense and Aspect of the Comparative Analysis of the Characteristics of China and South Korea (시간부사 '증경(曾經)', '이경(已經)' 시상(時相) 자질 중한 대조분석)

  • Han, Keung-Shuk
    • Cross-Cultural Studies
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    • v.42
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    • pp.451-474
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    • 2016
  • Analysis of the syntactic structure of the modern Chinese adverbs for time 'Cengjing (曾經)' and 'Yijing (已經)' was performed to examine the tenses and aspects of the terms. The corresponding Korean words were examined and the terms in both languages were compared. The syntactic structures used in China and South Korea were found to be different. We hope the study of the Chinese language will help Korean students. 'Cengjing (曾經)' specific projects with 'aspect' of, 'Past experience aspect', 'Past continuous aspect', 'Past continuous aspect' in the past tense. [ED: unclear, please reword] These correspond to '_었 (았)_', '_었었_' in the Korean language. 'Yijing (已經)' has 'finished phase' of concrete projects, 'Past experience aspect', 'Past continuous aspect', also has a specific project tense, the 'past tense', 'present tense', 'future tense', and so tense. [ED: unclear, please reword] Adjectives can also be modified with a 'change of status'. These correspond to '_었 (았)_', '_고_', '_었었_', '곧' etc. in Korean. 'Cengjing (曾經)' and the dynamic auxiliary 'Guo (過)' were compared to determine whether they have the aspect and tense features. However, 'Guo (過)' can only modify the predicate verb, so it possesses only aspect characteristics. 'Cengjing (曾經)' modifies the range more widely. 'Yijing (已經)' may be modified by the adverb 'Zai (在)' whereas 'Cengjing (曾經)' may not. Additionally, 'Yijing (已經)' can be modified by predicate adjectives and noun predicates, while 'Cengjing (曾經)' cannot.

Practical Strategies for Urban Regeneration through an Application of Landscape Urbanism (랜드스케이프 어바니즘 관점에서 본 도시재생 전략 연구)

  • Cho, Se-Hwan
    • Journal of the Korean Institute of Landscape Architecture
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    • v.38 no.2
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    • pp.109-118
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    • 2010
  • This study aims to propose practical strategies for the new urban ideal of regeneration. A book review highlights the emergence of new trends of urbanization in knowledge-information industrial society beyond the new town Ideal of the industrial society. The meaning of ‘landscape’ in landscape urbanism represents not the visual and decorative pictures, but the dynamic process in the context of changes and evolutions. Also, knowledge-information industrial society and landscape have a meaning in the same context of flow and process with changes of velocity. Finally, these key words convey a meaning with the new urban trends of urbanization in knowledge-information industrial society in the context of value-oriented characteristics of dynamics and process. Urban regeneration is emerging as the new urban ideal in the knowledge-information industrial society, beyond the new town ideal of industrial society. It is in the same context as landscape urbanism with respect to green infrastructure buildings and designs for the transformation of urban surfaces covered with concrete and asphalt into the ecological surface, and of the ecological surfaces into the cultural surface that could be communicated with human beings. This research revealed the six strategies for urban regeneration as follows. The First, the strategies for the transformation of urban surfaces into ecological surfaces, the second, the strategies for the transformation of ecological surfaces into cultural surfaces, the third, the introduction of mixed and convergence land use, the forth, the transformation of former sites(e.g. military and factory) into urban parks, the fifth, the introduction of waterfront park zones that have the function of ecological and park-oriented mixed land use and, the sixth, the building and design of green infrastructure in the residential and commercial complex in CBD. These strategies call for the reforms of development laws and regulations to restrict building coverage ratio, building heights, and the introduction of park-oriented mixed zoning regulations. Another method for implementating the above listed strategies was the introduction of a strategic planning system instead of the traditional master plan system. This system uses a value planning approach and brand making by imagery. It is able to construct the meaning of an image and its creativeness directly.