• Title/Summary/Keyword: collapse characteristics

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Bifurcation Criterion in Eccentrically Compressed Rectangular Tubes (편심압축하중을 받는 사각튜브의 분기세장비)

  • 김천욱;한병기;정창현;김치균
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.6
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    • pp.270-278
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    • 1999
  • This paper describes the collapse characteristics of the rectangular tube under eccentric compressive load. Overall buckling stress and bifurcation criterion (slenderness ration)are investigated. modified secant formula(MSF) is proposed to decide overall buckling stress. The bifurcation criterion which can distinguish between the local and overall buckling mode shapes is suggest by equating the local and overall buckling stresses. Additionally the effect of initial imperfection on bifurcation criterion is investigated.

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Mechanical Design of Deepwater Pipeline Wall Thickness Using the Recent Rules

  • Choi, Han-Suk
    • International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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    • v.5 no.1
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    • pp.58-63
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    • 2002
  • This paper presents a mechanical design of the deepwater pipeline wall thickness using the recent design rules. Characteristics and limitations of the new codes were identified through a case study design in the Gulf of Mexico. In addition to the ASME, API, and DVD codes, the code of federal regulations (CFR) was also utilized in the design. It was found that conservatism still exists within the collapse prediction for water depth greater than 1500 m. Comparision of the results from DNV and API codes were presented.

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The Energy Absorption of Combined Structure Subjected to Axial Compression

  • J.W.,Lee
    • Bulletin of the Society of Naval Architects of Korea
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    • v.19 no.4
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    • pp.1-10
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    • 1982
  • An experimental investigation on the energy absorption of two staged combined structures is presented, which deals with the plastic collapse test as a series of research on soft bow structure involved in a ship collision. The principle of arithmetic superposition of energy absorption is derived upon experimental analysis and based upon the characteristics of the energy absorptions of component structures. This relationship is related to the further approach toward the design of soft bow.

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The Structual Restoration on Gyeongju-Style Piled Stone-Type Wooden Chamber Tombs (경주식 적석목곽묘의 구조복원 재고)

  • Gweon, Yong Dae
    • Korean Journal of Heritage: History & Science
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    • v.42 no.3
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    • pp.66-87
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    • 2009
  • The definition of the structure of wooden chamber tomb(piled stone-type) is as follows. It is a tomb with wooden chamber, and stones were piled on top of the wooden chamber, and then a wooden structure was placed on top of the piled stones, and more stones were piled on top of the wooden structure, and sealed with clay. Of course this definition can vary according to periods, the buried, etc. Gyeongju-style piled stone type wooden chamber tombs have some distinguished characteristics compared to general definition of piled stone type wooden chamber tombs. Outside the wooden chamber, either stone embankments or filled-in stones were layed out, and pilet-in stones are positioned right above the wooden chamber, and almost every class used this type, and finally, it is exclusively found in Gyeongju area. First generations of this Gyeongju-style piled stone type wooden chamber tombs appeared in first half of 5th century. These tombs inherited characteristics like ground plan, wooden chamber, double chamber(inner chamber and outer chamber), piled stones, burial of the living with the dead, piled stones, from precedent wooden chamber tombs. However these tombs have explicit new characteristics which are not found in the precedent wooden chamber tombs such as stone embankments, wooden pillars, piled stones(above ground level), soil tumuluses. stone embankments and wooden pillars are exclusively found on great piled stone type above-ground level wooden chamber tombs such as the Hwangnamdaechong(皇南大塚). Stone embankments, wooden pillars, piled stones(above ground level) are all elements of building process of soil tumuluses. stone embankments support outer wall of above-ground level wooden chambers and disperse the weight of tumuluses. Wooden pillars functioned as auxiliary supports with wooden structures to prevent the collapse of stone embankments. Piled stones are consists of stones of regular size, placed on the wooden structure. And after the piled stones were sealed with clay, tumulus was built with soil. Piled stones are unique characteristics which reflects the environment of Gyeongju area. Piled stone type wooden chamber tombs are located on the vast and plain river basin of Hyeongsan river(兄山江). Which makes vast source of sands and pebbles. Therefore, tumulus of these tombs contains large amount of sands and are prone to collapse if soil tumulus was built directly on the wooden structure. Consequently, to maintain external shape of the tumulus and to prevent collapse of inner structure, piled stones and clay-sealing was made. In this way, they can prevent total collapse of the tombs even if the tumulus was washed away. The soil tumulus is a characteristic which emerges when a nation or political entity reaches certain growing stage. It can be said that after birth of a nation, growing stage follows and social structure will change, and a newly emerged ruling class starts building new tombs, instead of precedent wooden chamber tombs. In this process, soil tumulus was built and the size and structure of the tombs differ according to the ruling class. Ground plan, stone embankments, number of the persons buried alive with the dead, quantity and quality of artifacts reflect social status of the ruling class. In conclusion, Gyeongju-style piled stone type wooden chamber tombs emerged with different characteristics from the precedent wooden chamber tombs when Shilla reached growing stage.

A Study on Characteristics of Shear Strength in Rock-soil Contacts (암석과 토층 경계면의 전단강도 특성연구)

  • Lee, Su Gon
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.4 no.3
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    • pp.49-54
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    • 2001
  • It is common that the soil layer is a few meters below the earth's surface and the rock mass is below the soil layer in the view of geological characteristics in Korea. And the boundary between rock and soil is clearly divided. When dealing with the stability of rock masses, as in the case of rock slopes or dam foundations, the majority of the collapses is not within the soil layer, but within the soil-rock boundary. Therefore it is important to identify the shear strength characteristics between soil-rock boundary. And then in the method of reinforcement on landslide this chose a cut slope near Daemo elementary school in Seoul, surveyed shear strength between soil-rock contacts and considered a large scale collapse using a limit equilibrium method.

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Cavitation Characteristics on Impeller Materials of Centrifugal Pump for Ship in Sea Water and Fresh Water (해수와 청수환경에서 선박용 원심펌프 임펠러 재료의 캐비테이션 특성)

  • Im, Myeong-Hwan
    • Corrosion Science and Technology
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    • v.10 no.6
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    • pp.218-224
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    • 2011
  • The fresh water and sea water in present ships is used as cooling water for marine engine. Therefore, corrosion damage in seawater system is frequently occurred. In particular, in the impeller of pump, the performance and material span due to the corrosion and cavitation erosion has adverse effects. Most of the pump impellers in vessels are used Cu-Al alloy. Cu-Al alloy which having the excellent mechanical properties and corrosion resistance is widely used in marine environments. However, despite the excellent characteristics, the periodic replacement parts due to the cavitation damage in seawater is vulnerable to economic viewpoint. In this study, Cu-Al alloy used with impeller for centrifugal pump were conducted various experiments to evaluate its characteristics in seawater and fresh water solutions. As an electrochemical result, the dynamic conditions that exposed to the cavitation environment presented high corrosion current density with collapse of the cavity compared with the static conditions. Cavitation test results, the weightloss and weightloss rate in fresh water are observed more than those of seawater.

Pharmacognostical Study on the Panax ginseng C. A. Meyer (인삼의 생약학적 연구)

  • Do, Won-Im;Lee, Yu-Jin;Park, Jong-Hee
    • Korean Journal of Pharmacognosy
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    • v.35 no.1 s.136
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    • pp.45-51
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    • 2004
  • Panax ginseng C. A. Meyer (Araliaceae) is listed in Shen Nung Pentsao Ching(神農本草經) as the remedy for replenishing the primodial qi(氣), restoring pulse, treating collapse, tonifing the spleen and lag, promoting the production of body fluid to quench thirst, tranquilizing the mind, and improving the function of brain. The prescriptions of In Sam Tang(人參揚) are also recorded in many other Chinese medical books. The identification of the age of Panax ginseng is very important in commercial market as well as in research field. However, any reports about it have not been clearly established yet. To clarify the criterion, the morphological and anatomical characteristics of the roots of various age Panax ginseng cultivated in Korea were studied. The characteristics of cork layer, secretory canal, and vessel were shown to bε useful keys to confirm the age of Panax ginseng.

Seismic Performance Assessment of Unreinforced Masonry Wall Buildings Using Incremental Dynamic Analysis (증분동적해석을 통한 비보강 조적벽식 건물의 내진성능 평가)

  • Kwon, Ki Hyuk;Kim, Man Hoe;Kim, Hyung Joon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.3
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    • pp.28-39
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    • 2013
  • The most common housing type in Korea is low-rise buildings with unreinforced masonry walls (UMWs) that have been known as a vulnerable seismic-force-resisting system (SFRS) due to the lack of ductility capacities compared to high lateral stiffness of an UMW. However, there are still a little experimental investigation on the shear strength and stiffness of UMWs and on the seismic performance of buildings using UMWs as a SFRS. In Korea, the shear strength and stiffness of UMWs have been evaluated with the equations suggested in FEMA 356 which can not reflect the structural and material characteristics, and workmanship of domestic UMW construction. First of all, this study demonstrates the differences in shear strength and stiffness of UMWs obtained from between FEMA 356 and test results. The influence of these differences on the seismic performance of UMW buildings is then discussed with incremental dynamic analyses results of a prototype UMW building that were selected by the site survey of more than 200 UMW buildings and existing test results of UMWs. The seismic performance assessment of the prototype UMW building are analyzed based on collapse margin ratios and beta values repesenting uncertainty of seismic capacity. Analysis results show that the seismic performance of the UMW building estimated using the equations in FEMA 356 underestimates both a collapse margin ratio and a beta value compared to that estimated by test results. Whatever the estimation is carried out two cases, the seismic performance of the prototype building does not meet the criteria prescribed in a current Korean seismic code and about 90% collapse probability presents for more than 30-year-old UMW buildings under earthquakes with 2400 return years.

Suitability Examination of Flex sensor and FBG Sensor for Levee Safety Management (제방 안전관리를 위한 Flex센서와 FBG센서의 적용성 검토)

  • Lee, In-Je;Lee, Eun-Tae;Kang, Jeong-Hoon;Kim, Dong-Min;Chang, Ki-Tae
    • Journal of Korea Water Resources Association
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    • v.41 no.11
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    • pp.1135-1142
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    • 2008
  • Collapse of the levee surrounding structure(culvert) accounts for l0 % of collapse factors of the river levees. In particular, in 2002, the levee collapse that happened at "Nakdong River" at flood usually happened around culverts. This levee collapse has mechanism that the cavity expands with internal erosion at flood after the pore and cavity are formed between culvert and levee copula which are heterogeneity material. The study regarding the cavity or flowing detection around a culvert for safety management of a river levee is in the proceeding. In this study, the characteristic of two sensors could be figured out through an experiment about displacement measure of Flex sensor and FBG sensor and the decision of more suitable sensor was possible for safety supervision of river levee. According to an experiment result, several characteristics of FBG sensor could be known in consistency of the measure data and minute displacement measure part regarding displacement measure and this characteristic may supplement a shortcoming of Flex sensor at this time.

Mesh Simplification for Preservation of Characteristic Features using Surface Orientation (표면의 방향정보를 고려한 메쉬의 특성정보의 보존)

  • 고명철;최윤철
    • Journal of Korea Multimedia Society
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    • v.5 no.4
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    • pp.458-467
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    • 2002
  • There has been proposed many simplification algorithms for effectively decreasing large-volumed polygonal surface data. These algorithms apply their own cost function for collapse to one of fundamental simplification unit, such as vertex, edge and triangle, and minimize the simplification error occurred in each simplification steps. Most of cost functions adopted in existing works use the error estimation method based on distance optimization. Unfortunately, it is hard to define the local characteristics of surface data using distance factor alone, which is basically scalar component. Therefore, the algorithms cannot preserve the characteristic features in surface areas with high curvature and, consequently, loss the detailed shape of original mesh in high simplification ratio. In this paper, we consider the vector component, such as surface orientation, as one of factors for cost function. The surface orientation is independent upon scalar component, distance value. This means that we can reconsider whether or not to preserve them as the amount of vector component, although they are elements with low scalar values. In addition, we develop a simplification algorithm based on half-edge collapse manner, which use the proposed cost function as the criterion for removing elements. In half-edge collapse, using one of endpoints in the edge represents a new vertex after collapse operation. The approach is memory efficient and effectively applicable to the rendering system requiring real-time transmission of large-volumed surface data.

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