• 제목/요약/키워드: composite factors

검색결과 1,092건 처리시간 0.034초

A Study on the fire-resistance of concrete-filled steel square tube columns without fire protection under constant central axial loads

  • Park, Su-Hee;Choi, Sung-Mo;Chung, Kyung-Soo
    • Steel and Composite Structures
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    • 제8권6호
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    • pp.491-510
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    • 2008
  • This paper presents a plan and guidelines that were drawn for Korean based research carried out on the fire-resistance of CFT columns. This research was carried out by reviewing the Korean regulations related to the fire-resistance of CFT columns and examining studies which had been made in Korea as well as overseas. The first phase of the study plan was to compare the fire-resistance of square CFT columns without fire protection (obtained through fire-resistance tests and numerical analyses) with estimated values (obtained through fire-resistance design formulas proposed in Korea and overseas). This comparison provided conclusions as outlined below. Fire-resistance tests conducted in this study proved that, when the actual design load is taken into consideration, square CFT columns without fire protection are able to resist a fire for more than one hour. A comparison was made of test and analysis results with the fire-resistance time based on the AIJ code, the AISC design formula and the estimation formula suggested for Korea. The results of this comparison showed that the test and analysis results for specimens SAH1, SAH2-1, SAH2-2 and SAH3 were almost identical with the AIJ code, the AISC design formula and estimation formula. For specimens SAH4 and SAH5, the estimation formula was more conservative than the AIJ code and the AISC design formula. It was necessary to identify the factors that have an influence on the fire-resistance of CFT columns without fire protection and to draw fire-resistance design formulas for these columns. To achieve this, it is proposed that numerical analyses and tests be conducted in order to evaluate the fire-resistance of circular CFT columns, the influence of eccentricity existing as an additional factor and the influence of the slenderness ratio of the columns. It is also suggested that the overall behavior of CFT structures without fire protection within a fire be evaluated through analysis simulation.

Damping and vibration response of viscoelastic smart sandwich plate reinforced with non-uniform Graphene platelet with magnetorheological fluid core

  • Eyvazian, Arameh;Hamouda, Abdel Magid;Tarlochan, Faris;Mohsenizadeh, Saeid;Dastjerdi, Ali Ahmadi
    • Steel and Composite Structures
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    • 제33권6호
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    • pp.891-906
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    • 2019
  • This study considers the instability behavior of sandwich plates considering magnetorheological (MR) fluid core and piezoelectric reinforced facesheets. As facesheets at the top and bottom of structure have piezoelectric properties they are subjected to 3D electric field therefore they can be used as actuator and sensor, respectively and in order to control the vibration responses and loss factor of the structure a proportional-derivative (PD) controller is applied. Furthermore, Halpin-Tsai model is used to determine the material properties of facesheets which are reinforced by graphene platelets (GPLs). Moreover, because the core has magnetic property, it is exposed to magnetic field. In addition, Kelvin-Voigt theory is applied to calculate the structural damping of the piezoelectric layers. In order to consider environmental forces applied to structure, the visco-Pasternak model is assumed. In order to consider the mechanical behavior of structure, sinusoidal shear deformation theory (SSDT) is assumed and Hamilton's principle according to piezoelasticity theory is employed to calculate motion equations and these equations are solved based on differential cubature method (DCM) to obtain the vibration and modal loss factor of the structure subsequently. The effect of different factors such as GPLs distribution, dimensions of structure, electro-magnetic field, damping of structure, viscoelastic environment and boundary conditions of the structure on the vibration and loss factor of the system are considered. In order to indicate the accuracy of the obtained results, the results are validated with other published work. It is concluded from results that exposing magnetic field to the MR fluid core has positive effect on the behavior of the system.

A four-unknown refined plate theory for dynamic analysis of FG-sandwich plates under various boundary conditions

  • Menasria, Abderrahmane;Kaci, Abdelhakim;Bousahla, Abdelmoumen Anis;Bourada, Fouad;Tounsi, Abdeldjebbar;Benrahou, Kouider Halim;Tounsi, Abdelouahed;Adda Bedia, E.A.;Mahmoud, S.R.
    • Steel and Composite Structures
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    • 제36권3호
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    • pp.355-367
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    • 2020
  • The current work, present dynamic analysis of the FG-sandwich plate seated on elastic foundation with various kinds of support using refined shear deformation theory. The present analytical model is simplified which the unknowns number are reduced. The zero-shear stresses at the free surfaces of the FG-sandwich plate are ensured without introducing any correction factors. The four equations of motion are determined via Hamilton's principle and solved by Galerkin's approach for FG-sandwich plate with three kinds of the support. The proposed analytical model is verified by comparing the results with those obtained by other theories existing in the literature. The parametric studies are presented to detect the various parameters influencing the fundamental frequencies of the symmetric and non-symmetric FG-sandwich plate with various boundary conditions.

Analysis of Porcine $\beta$-casein Gene Promoter by Site-directed Mutagenesis

  • Chung, Hee-Kyoung;Seong, Hwan-Hoo;Im, Seok-Ki;Lee, Hyun-Gi;Kim, Soon-Jeung;Lee, Poongyeong;Lee, Yun-Keun;Chang, Won-Kyong;Moosik Kwon
    • 한국수정란이식학회:학술대회논문집
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    • 한국수정란이식학회 2002년도 국제심포지엄
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    • pp.71-71
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    • 2002
  • Promoters for milk proteins have been used far producing transgenic animals due to their temporal and spatial expression patterns. ${\beta}$-casein, a calcium-sensitive casein, is a major milk protein that corresponds ca. 30 per cent of total milk protein. Expression of ${\beta}$-casein is controlled by lactogenic hormones such as prolactin (PRL), composite response elements (CoREs) and transcription factors. CoREs are clusters of transcription factor binding sites containing both positive and negative regulatory elements. ${\beta}$-casein gene promoter contains various regions (CoREs) for gene transcription. We analyzed the promoter region by mutagenesis using exonuclease III and linker-scanning. Transcription control elements usually are positioned in 5'-flanking region of the gene. However, in some cases, these elements are located in other regions such as intron 1. The nucleotide sequences of ${\beta}$-casein promote. region has been reported (E12614). However, the properties of the promoter is not yet clear. In this study, we plan to investigate the properties of cis-regulating elements of porcine ${\beta}$-casein by mutation analysis and expression analysis using dual-luciferase repoter assay system.

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An Analytical Study of Mammalian Bite Wounds Requiring Inpatient Management

  • Lee, Young-Geun;Jeong, Seong-Ho;Kim, Woo-Kyung
    • Archives of Plastic Surgery
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    • 제40권6호
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    • pp.705-710
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    • 2013
  • Background Mammalian bite injuries create a public health problem because of their frequency, potential severity, and increasing number. Some researchers have performed fragmentary analyses of bite wounds caused by certain mammalian species. However, little practical information is available concerning serious mammalian bite wounds that require hospitalization and intensive wound management. Therefore, the purpose of this study was to perform a general review of serious mammalian bite wounds. Methods We performed a retrospective review of the medical charts of 68 patients who were referred to our plastic surgery department for the treatment of bite wounds between January 2003 and October 2012. The cases were analyzed according to the species, patient demographics, environmental factors, injury characteristics, and clinical course. Results Among the 68 cases of mammalian bite injury, 58 (85%) were caused by dogs, 8 by humans, and 2 by cats. Most of those bitten by a human and both of those bitten by cats were male. Only one-third of all the patients were children or adolescents. The most frequent site of injury was the face, with 40 cases, followed by the hand, with 16 cases. Of the 68 patients, 7 were treated with secondary intention healing. Sixty-one patients underwent delayed procedures, including delayed direct closure, skin graft, composite graft, and local flap. Conclusions Based on overall findings from our review of the 68 cases of mammalian bites, we suggest practical guidelines for the management of mammalian bite injuries, which could be useful in the treatment of serious mammalian bite wounds.

고체상미량분석법(SPME-GC/FID)에서 실험계획법을 이용한 디젤첨가제 미량분석의 최적화 연구 (Optimization Study of Trace Analysis of Potential Diesel Oxygenate Using the Design Of Experiment (DOE) in Solid-Phase Microextraction with GC/FID)

  • 박재상;장순웅
    • 한국지하수토양환경학회지:지하수토양환경
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    • 제12권5호
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    • pp.73-85
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    • 2007
  • 본 연구에서는 액상에서 EGBE, DGBE, DBM, TGME의 효율적인 분석을 위해 이용되던 액상추출법을 대신할 수 있는 방법으로 GC/FID를 이용한 SPME법 실험 연구를 진행하였다. 그리고 실험계획법(DOE)을 사용하여 EGBE를 포함한 디젤첨가제 미량분석의 최적조건을 설명하였다. 실험은 통계분석결과 뿐만 아니라 요인 수의 최적화에 따른 중심합성설계에 의한 완전요인 설계법을 사용하였다. 반응표면분석은 추출 효율이 주 영향인 염농도, 흡착 온도, 흡착 시간과 sonication 시간에 따른 2차 다항식에 의해 설명될 수 있음을 보여주었다. 실험계획법(DOE)을 사용하는 것은 액상 시료에서 디젤첨가제의 정량분석을 개선하는 자료분석법이 될 것이다.

알코올 사용장애 환자의 음주심각도, 일주기리듬과 수면의 질이 수면장애에 미치는 영향 (Influence of Severity of Problem Drinking, Circadian Rhythm and Sleep Quality on Sleep Disorder in Alcohol Use Disorder Patients)

  • 고상진;박영신;강민재;홍해숙
    • Journal of Korean Biological Nursing Science
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    • 제19권1호
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    • pp.48-54
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    • 2017
  • Purpose: This study was done to identify the influence of severity of drinking problem, circadian rhythm and sleep quality in patients with alcohol use. Methods: A descriptive study design was utilized. Data were collected using self-report questionnaires from 139 patients with alcohol use disorder who were admitted to a psychiatric hospital in D city, Korea. The questionnaires included Alcohol Use Disorders Identification Test (AUDIT), Composite Scale of Morningness (CMS), Pittsburgh Sleep Quality Index (PSQI), and Korea sleep scale A. Data were analyzed using descriptive statistics, Pearson's correlation coefficients, and multiple regressions using the SPSS 20.0 program. Results: There was significant correlations among severity of problem drinking, circadian rhythm, sleep quality and sleep disorder. The significant factors influencing sleep disorder were severity of problem drinking(${\beta}=.12$, p= .042), circadian rhythm(${\beta}=-.14$, p= .039) and sleep quality(${\beta}=.63$, p= < .001). This model explained 56% of variance in sleep disorder(F = 57.34, p= < .001). Conclusion: The results of this study suggest that the development of sleep intervention programs for alcohol use disorder patients needs to consider severity of alcohol use, circadian rhythm and sleep quality, and sleep assessment and intervention are needed the early stage of the treatment and recovery process.

사면보강 뿌리말뚝공법의 준3차원적 안정해석기법 (Method of Quasi-Three Dimensional Stability Analysis of the Root Pile System on Slope Reinforcement)

  • 김홍택;강인규;박사원
    • 한국지반공학회지:지반
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    • 제13권5호
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    • pp.101-124
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    • 1997
  • The root pile system is insitu soil reinforcement technique that uses a series of reticulately installed micropiles. In terms of mechanical improvement by means of grouted reinform ming elements, the root pile system is similar to the soil nailing system. The main difference between root piles and soil nailing are due to the fact that the reinforcing bars in root piles are normally grouted under high pressure and that the alignments of the reinforcing members differ. Recently, the root pile system has been broadly used to stabilize slopes and retain excavations. The accurate design of the root pile system is, however, a very difficult tass owing to geometric variety and statical indetermination, and to the difficulty in the soilfiles interaction analysis. As a result, moat of the current design methods have been heavily dependent on the experiences and approximate approach. This paper proposes a quasi-three dimensional method of analysis for the root pile system applied to the stabilization of slopes. The proposed methods of analysis include i) a technique to estimate the change in borehole radium as a function of the grout pressure as well as a function of the time when the grout pressure is applied, ii) a technique to evaluate quasi -three dimensional limit-equilibrium stability for sliding, iii) a technique to predict the stability with respect to plastic deformation of the soil between adjacent root piles, and iv) a quasi -three dimensional finite element technique to compute stresses and dis placements of the root pile structure barred on the generalized plane strain condition and composite unit cell concept talon형 with considerations of the group effect and knot effect. By using the proposed technique to estimate the change in borehole radius as a function of the grout pressure as well as a function of the time, the estimations are made and compar ed with the Kleyner 8l Krizek's experimental test results. Also by using the proposed quasi-three dimensional analytical method, analyses have been performed with the aim of pointing out the effects of various factors on the interaction behaviors of the root pile system.

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도심지 붕괴사고에 따른 매몰지역 생명선 시공기술 평가 (Assessment of Lifeline Construction Technology for Buried Alive in Building Collapse)

  • 유병현;강재모;이장근;김영삼;주낙봉
    • 한국지반환경공학회 논문집
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    • 제17권9호
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    • pp.47-52
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    • 2016
  • 최근 사회기반시설의 안전설계 용량을 초과하는 잦은 위험기상 등으로 자연재난의 빈도가 증가하고 피해규모도 대형화되고 있으며, 도시화 진전에 따른 시설의 고층화 노후건축물 증가와 세계화에 따른 유동인구 및 물류 증가 등이 신종 복합 재난을 가중시키는 요인으로 작용하고 있다. 첨단 과학기술을 활용하여 재난위험 사전 감지, 실시간 정보분석, 재난현장에 대한 신속한 대응이 가능하지만, 매몰자 긴급구호에 필요한 시공에서는 반드시 검증된 기술을 활용해야 함에도 불구하고 현장 시험시공을 통한 검증은 미흡하다. 본 연구에서는 도심지 시설물 붕괴 재난 사고 발생 시 매몰지점에 고립된 피구호자를 대상으로 골든타임인 72시간 이내에 식수 및 구호품을 신속하게 공급하기 위한 1차 생명선 설치와 철근 콘크리트 구조체 굴착 성능을 평가하는 데 목적이 있다.

Analysis of restrained steel beams subjected to heating and cooling Part I: Theory

  • Li, Guo-Qiang;Guo, Shi-Xiong
    • Steel and Composite Structures
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    • 제8권1호
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    • pp.1-18
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    • 2008
  • Observations from experiments and real fire indicate that restrained steel beams have better fire-resistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. In addition, axial forces will be induced with temperature increasing and play an important role on the behaviour of the restrained beam. The factors influencing the behavior of a restrained beam subjected to fire include the stiffness of axial and rotational restraints, the load type on the beam and the distribution of temperature in the cross-section of the beam, etc. In this paper, a simplified model is proposed to analyze the performance of restrained steel beams in fire condition. Based on an assumption of the deflection curve of the beam, the axial force, together with the strain and stress distributions in the beam, can be determined. By integrating the stress, the combined moment and force in the cross-section of the beam can be obtained. Then, through substituting the moment and axial force into the equilibrium equation, the behavior of the restrained beam in fire condition can be worked out. Furthermore, for the safety evaluation and repair after a fire, the behaviour of restrained beams during cooling should be understood. For a restrained beam experiencing very high temperatures, the strength of the steel will recover when temperature decreases, but the contraction force, which is produced by thermal contraction, will aggravate the tensile stresses in the beam. In this paper, the behaviour of the restrained beam in cooling phase is analyzed, and the effect of the contraction force is discussed.