• Title/Summary/Keyword: natural mode shapes

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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.

Measurement System of Dynamic Liquid Motion using a Laser Doppler Vibrometer and Galvanometer Scanner (액체거동의 비접촉 다점측정을 위한 레이저진동계와 갈바노미터스캐너 계측시스템)

  • Kim, Junhee;Shin, Yoon-Soo;Min, Kyung-Won
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.5
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    • pp.227-234
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    • 2018
  • Researches regarding measurement and control of the dynamic behavior of liquid such as sloshing have been actively on undertaken in various engineering fields. Liquid vibration is being measured in the study of tuned liquid dampers(TLDs), which attenuates wind motion of buildings even in building structures. To overcome the limitations of existing wave height measurement sensors, a method of measuring liquid vibration in a TLD using a laser Doppler vibrometer(LDV) and galvanometer scanner is proposed in this paper: the principle of measuring speed and displacement is discussed; a system of multi-point measurement with a single point of LDV according to the operating principles of the galvanometer scanner is established. 4-point liquid vibration on the TLD is measured, and the time domain data of each point is compared with the conventional video sensing data. It was confirmed that the waveform is transformed into the traveling wave and the standing wave. In addition, the data with measurement delay are cross-correlated to perform singular value decomposition. The natural frequencies and mode shapes are compared using theoretical and video sensing results.

A Study on the Problem of Organic Image in the 20th Post-paintings (20세기 후기회화에 있어서 유기 이미지의 문제)

  • Park Ji-Sook
    • Journal of Science of Art and Design
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    • v.3
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    • pp.145-177
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    • 2001
  • The artist's interest has been captivated by ecological phenomena in Nature. Her keen captivation has then been focused into plastic art depicting the image of primitive life. The wide sweep of her work encompasses the totality of nature which consists of the human's subconscious power and imagination which she then portrays by organic images. These organic images are in contrast to scientific, mathematical and logical inference and consciousness. This research examines the character of the organic images in modern art by her analysis of some representative works by others. The image is an essential concept in the art which appeared in very different ways and in different perspectives. The image in the artwork appears to be the realistic expression until the early part of the 20th Century. Well into the 20th Century, it began being expressed in various ways such as combined images by imagination which is combined or rejected in the story of artwork. It also began being expressed by transferred images by changed original conditions. It is the main purpose of this research is to study of various expressions of organic images in the artwork of the Post-Modernism era. The character and meaning of organic image painting helps people to approach the human instinct more easily to find out the natural essence. It is also an objective of the organic image to tenderise our human sensibilities, thus helping us to regain vitality and recover our poor humanity in the barren wilderness of modern society. 'Life communion with nature' is a meeting point and common ground for Oriental Philosophy and organic image painting. Through this research, organic image painting is characterised in the four following ways : 1st) Organic image painting seeks regularity and perfection of outer shapes, in contrast to disordered and deformed nature, resulting in organic and biotic formalistic mode of plastic art. 2nd) Organic image painting seeks the formative. 3rd) Organic image painting pursues the priceless dignity of life by researching the formatted arrangement and figure, which contains primitive power of life. 4th) Organic image painting makes crystal clear the power of human and nature, which is a historic and biological phenomenon. This, in turn, exposes the humanistic view of the world from modern society best characterised in lost self-understanding, isolation and materialism. The representative organic image painting artists are Elizabeth Murray, Kusama Yayoi, and Niki do Saint Phalle. Elizabeth Murray used shaped canvas and a round construction of relief works. Kusama Yayoi used Automatistic expressionism originating from the realms of unconsciousness and which is represented by the mass and shape of a water drop. Niki do Saint Phalle shows the transcendence of universal life and anti-life to respect the dignity of life and the eco-friendliness relationship of human and nature in the post-modernism in art history. This is accomplished by surrealistic, symbolic, fantastic and humoristic expression. These three artists' works express the spirit of the organic image in contemporary art. It contains the stream of nature and life to seek not only the state of materialism in the reality, but also the harmonized world of nature and human which has almost lost the important meaning in modern times. Finally, this organic image is the plastic language of the majestic life. It is the romantic idea that the intimacy of nature and the universe and Surrealism, which emphasizes the unconsciousness , is the source of truth and spirit. Also it is influenced by primitive art and abstract art. According to this research, the subject 'Research About Organic Images' is not only an important element in the plastic arts from primitive society to the present, but is also fundamental to an true understanding of Post-Modernism.

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