• Title/Summary/Keyword: Plastic Work

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Equivalent frame model and shell element for modeling of in-plane behavior of Unreinforced Brick Masonry buildings

  • Kheirollahi, Mohammad
    • Structural Engineering and Mechanics
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    • v.46 no.2
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    • pp.213-229
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    • 2013
  • Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM (Unreinforced Masonry) buildings occupy significant portion of buildings in earthquake prone areas of the world as well as in IRAN. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of masonry walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented. The work presented in this study is about performance assessment of unreinforced brick masonry buildings through nonlinear equivalent frame modeling technique. Reliability of the proposed models is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia. The pushover curves were found to provide good agreement with the experimental backbone curves. Furthermore, the results of analysis show that EFM (Equivalent Frame Model) with Dolce RO (rigid offset zone) and shell element have good agreement with finite element software and experimental results.

Energy absorption of the ring stiffened tubes and the application in blast wall design

  • Liao, JinJing;Ma, Guowei
    • Structural Engineering and Mechanics
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    • v.66 no.6
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    • pp.713-727
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    • 2018
  • Thin-walled mental tubes under lateral crushing are desirable and reliable energy absorbers against impact or blast loads. However, the early formations of plastic hinges in the thin cylindrical wall limit the energy absorption performance. This study investigates the energy absorption performance of a simple, light and efficient energy absorber called the ring stiffened tube. Due to the increase of section modulus of tube wall and the restraining effect of the T-stiffener flange, key energy absorption parameters (peak crushing force, energy absorption and specific energy absorption) have been significantly improved against the empty tube. Its potential application in the offshore blast wall design has also been investigated. It is proposed to replace the blast wall endplates at the supports with the energy absorption devices that are made up of the ring stiffened tubes and springs. An analytical model based on beam vibration theory and virtual work theory, in which the boundary conditions at each support are simplified as a translational spring and a rotational spring, has been developed to evaluate the blast mitigation effect of the proposed design scheme. Finite element method has been applied to validate the analytical model. Comparisons of key design criterions such as panel deflection and energy absorption against the traditional design demonstrate the effectiveness of the proposed design in blast alleviation.

Influence of Initial Water Content, Specific Surface, Air Drying and Freezing-thawing Action on the Liquid Limit of Soils (초기함수비, 비표면적, 풍건 및 동결.융해작용이 흙의 액성한계에 미치는 영향)

  • 류능환
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.38 no.5
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    • pp.116-124
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    • 1996
  • The purpose of The work described in this paper is to clear up the initial moisture content, specific surface, air drying and freezing-thawing process on liquid limit of clayey soils distributed widely at estuary of three main rivers in the west coast. To this end, a series of tests were conducted on clayey soils samples with natural state and treated state. From the test results, the liquid limit was decreased with decrement of initial moisture content, air drying process, and freezing-thawing cycles and increased with increment of specific surface. The specific surface which influenced on the liquid limit is over $25 m^2$m$^2$/g, and their relationships are well formulated. Air drying process is expected to improve the engineering properties of the soils such the pro-water properties were changed to anti-water proper-ties through lowering of water holding as resulted to incline from A-7-5 to A-5 on the soil classificaction plastic chart. The freezing-thawing process decreased 20% of liquid limit, especially under the first cycle of the behavious, as a result of above mentioned reasons, phase change of soil-water system brought the decrement of specific surface and affected to the liquid limit.

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A Study on Ex-Formal Expression Observed in Space.Form of Korean Modern Architecture (한국 현대건축의 공간.형태에서 나타난 탈정형적 표현에 관한 연구)

  • Jang, Hoon-Ick
    • Journal of The Korean Digital Architecture Interior Association
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    • v.9 no.3
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    • pp.85-93
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    • 2009
  • In this study, the ex-formal expressions observed in space form of Korean modern architecture are distributed for characteristic analysis based on the period and type. The result of the study is certified by the work analysis and the result is as follows. Initially, due to the limited materials and influence of western brutalism, the works developed during 1960~70 tend to be plastic and contain expressionism. Around 1980's, the works tend to show forms of amusement and popularity. In 1990's the works show significance in deconstructive expression. From after 2000, ecological concept of architecture was introduced and organic expression started increasing Secondly, the ex-formal expressions are found to be in four different types. The organic expression is shown regardless of the period. In modern days, not only the physical properties of materials, but also the ecological concept is combined with the organic expression and is in increase. The plural expression started appearing after the 1980's and the sculptural diversity is enhancing with the addition of decorative factors or modification of geometrical form. The ex-construction and deconstructive expression show significance in some characteristics such as folding, inclination, and geometrical explosion. The free form and nonlinear expression tend to increase dramatically based on the development of structure technology as well as execution and introduce of the digital design technique.

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Study of 3D Simulator for Human Hand Writing (3차원 방식의 수기 모사 연구)

  • Kang, Tae-Won;Lee, Kee Sung;Choi, WonSik;Kim, Tae-Woo
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.22 no.2
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    • pp.192-198
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    • 2013
  • A light-weight enough to be portable yet functionally complete hand-writing machine was designed with hardware assembled and software implemented. The machine simulating human hand-writing not only allows identical massive scriptings on papers in human's proxy, but also offers emotional appearance as if the script was directly hand-written in ink. The features of human writing were independently put together to complete the action of scripting. The writing style could be altered in order to mimic a person's own specific writing style. The present work demonstrates that the assembled hand-writing machine was able to duplicate writing of scripts in almost parallel lines in consistent manner. The machine can be used in the emotional marketing area where seasonal greetings or thank-you cards are to be sent in massive manner. The pen-holding machine can also find an emotional application such as writing a short greeting note on a plastic lid on a disposable coffee cup in coffee-selling stores.

An Automated Process Planning and Die design System for Bolt Products (볼트류 제품에 관한 공정설계 및 금형설계 자동화 시스템)

  • Song, S.W.;Choi, Y.;Jung, S.Y.;Kim, C.;Choi, J.C.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.774-777
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    • 2001
  • This paper describes a research work of developing a computer-aided design system of cold forging products. An approach to the system is based on the knowledge-based rules. Knowledge for the system is formulated from plastic theories, experimental results and the empirical knowledge of field experts. The system has been written in AutoCAD with a personal computer and is composed of six modules, which are selection of billet material, input of final product, process planning design, preform modification, insert design, shrink rings design module. Based on knowledge-based rules, the system is designed by considering several factors such as volume constancy, limite of formability by material, preform shape and so on.

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Study on the thickness precision of rolled sheets (압연판의 두께 정밀도에 관한 연구)

  • 김동원;윤상건
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.11 no.5
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    • pp.837-845
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    • 1987
  • In the research of the rolling of strip, producing the strip with a close tolerance of thickness over the rolling direction was a principal object. But it was solved by the contribution of two-dimensional theory of rolling and the development of automatic gauge control system. And new requirements for the study of flatness, crown of rolled strip and edge drop grow up recently. These phenomena are closely related with the thickness distribution along the lateral direction of rolled strip. To analyse the thickness distribution of rolled strip along the lateral direction, elastic deformation of rolls and plastic deformation of work material must be discussed simultaneously. In this report, an approximate three-dimensional analysis based on Tozawa's three dimensional approach was applied to 12 cases of different rolling conditions and the numerical results were investigated. Especially stresses were laid upon the investigation of optimal boundary position between the three-dimensional analysis region and the plane strain analysis region.

The Influence of Temperature on Low Cycle Fatigue Behavior of Prior Cold Worked 316L Stainless Steel (II) - Life Prediction and Failure Mechanism - (냉간 가공된 316L 스테인리스 강의 저주기 피로 거동에 미치는 온도의 영향 (II) - 수명예측 및 파손 기구 -)

  • Hong, Seong-Gu;Yoon, Sam-Son;Lee, Soon-Bok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.10
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    • pp.1676-1685
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    • 2003
  • Tensile and low cycle fatigue tests on prior cold worked 3l6L stainless steel were carried out at various temperatures ftom room temperature to 650$^{\circ}C$. Fatigue resistance was decreased with increasing temperature and decreasing strain rate. Cyclic plastic deformation, creep, oxidation and interactions with each other are thought to be responsible for the reduction in fatigue resistance. Currently favored life prediction models were examined and it was found that it is important to select a proper life prediction parameter since stress-strain relation strongly depends on temperature. A phenomenological life prediction model was proposed to account for the influence of temperature on fatigue life and assessed by comparing with experimental result. LCF failure mechanism was investigated by observing fracture surfaces of LCF failed specimens with SEM.

Failure Assessment Diagrams of Semi-Elliptical Surface Crack with Constraint Effect (구속상태를 고려한 반타원 표면균열의 파손평가선도)

  • Seo, Heon;Han, Tae-Su;Lee, Hyeong-Il
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.11 s.170
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    • pp.2022-2032
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    • 1999
  • In recent years, the subject of remaining life assessment has drawn considerable attention in the power generation industry. In power generation systems a variety of structural components, such as steam pipes, turbine rotors, and superheater headers, typically operate at high temperatures and high pressures. Thus a life prediction methodology accounting for fracture and rupture is increasingly needed for these components. For accurate failure assessment, in addition to the single parameter such as K or J-integral used in traditional fracture mechanics, the second parameter like T-stress describing the constraint is needed. The most critical defects in such structures are generally found in the form of semi-elliptical surface cracks in the welded piping-joints. In this work, selecting the structures of surface-cracked plate and straight pipe, we first perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework for including constraint effects (T-stress effects) in the R6 failure assessment diagram approach for fracture assessment.

Study for improvement of grounds subjected to cyclic loads

  • Mittal, Satyendra;Meyase, Kenisevi
    • Geomechanics and Engineering
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    • v.4 no.3
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    • pp.191-208
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    • 2012
  • Due to rapid industrialisation, large scale infrastructure development is taking place worldwide. This includes railways, high speed highways, elevated roads etc. To meet the demands of society and industry, many innovative techniques and materials are being developed. In developed nations like USA, Japan etc. for railways applications, new material like geocells, geogrids are being used successfully to enable fast movement of vehicles. The present research work was aimed to develop design methodologies for improvement of grounds subjected to cyclic loads caused by moving vehicles on roads, rail tracks etc. Deformation behavior of ballast under static and cyclic load tests was studied based on square footing test. The paper presents a study of the effect of geo-synthetic reinforcement on the (cumulative) plastic settlement, of point loaded square footing on a thick layer of granular base overlying different compressible bases. The research findings showed that inclusion of geo-synthetics significantly improves the performance of ballasted tracks and reduces the foundation area. If the area is kept same, higher speed trains can be allowed to pass through the same track with insertion of geosynthetics. Similarly, area of machine foundation may also be reduced where geosynthetics is provided in foundation. The model tests results have been validated by numerical modeling, using $FLAC^{3D}$.