• Title, Summary, Keyword: critical load

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Study on critical buckling load calculation method of piles considering passive and active earth pressure

  • Chen, Yong-Hui;Chen, Long;Xu, Kai;Liu, Lin;Ng, Charles W.W.
    • Structural Engineering and Mechanics
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    • v.48 no.3
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    • pp.367-382
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    • 2013
  • Different types of long slender pile shall buckle with weak soil and liquefied stratum surrounded. Different from considering single side earth pressure, it was suggested that the lateral earth pressure can be divided into two categories while buckling: the earth pressure that prevent and promotes the lateral movement. Active and passive earth pressure calculation model was proposed supposing earth pressure changed linearly with displacement considering overlying load, shaft resistance, earth pressure at both sides of the pile. Critical buckling load calculation method was proposed based on the principle of minimum potential energy quoting the earth pressure calculation model. The calculation result was contrasted with the field test result of small diameter TC pile (Plastic Tube Cast-in-place pile). The fix form could be fixed-hinged in the actual calculation assuring the accuracy and certain safety factor. The contributions of pile fix form depend on the pile length for the same geological conditions. There exists critical friction value in specific geological conditions that the side friction has larger impact on the critical buckling load while it is less than the value and has less impact with larger value. The buckling load was not simply changed linearly with friction. The buckling load decreases with increased limit active displacement and the load tend to be constant with larger active displacement value; the critical buckling load will be the same for different fix form for the small values.

Influence of Elastic Restraint and Tip Mass at Free End on Stability of Leipholz's Column (Leipholz 기둥의 안정성에 미치는 자유단의 탄성구속과 말단질량의 영향)

  • 윤한익;박일주;김영수
    • Journal of KSNVE
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    • v.7 no.1
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    • pp.91-97
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    • 1997
  • An analysis is presented on the stability of an elastic cantilever column having the elastic restraints at its free end, carrying an added tip mass, and subjected to uniformly distributed follower forces. The elastic restraints are formed by both a translational spring and a rotatory spring. For this purpose, the governing equations and boundary conditions are derived by using Hamilton's principle, and the critical flutter loads and frequencies are obtained from the numerical evaluation of the eigenvalue functions of this elastic system. The added tip mass increases as a whole the critical flutter load of the elastic cantilever column, but the presence of its moment of inertia of mass has a destabilizing effect. The existence of the translational and rotatory springs at the free end increases the critical flutter load of the elastic cantilever column. Nevertheless, their effects on the critical flutter load are not uniform because of their coupling. The translational spring restraining the free end of the cantilever column decreases the critical flutter load by coupling with a large value of tip mass, while by coupling with the moment of inertia of tip pass its effect on the critical flutter load is contrary. The rotatory spring restraining the free end of the cantilever column increases the critical flutter load by coupling with the tip mass, but decreases it by coupling with the moment of inertia of the tip mass.

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Decision of Critical Area Due to NPS Pollutant Loadings from Kyongan Stream Watershed using BASINS-SWAT (BASINS-SWAT 모델을 이용한 경안천 유역의 비점원 오염배출 중점관리 대상지역 결정)

  • Jang, Jae-Ho;Yoon, Chung-Gyeong;Jung, Kwang-Wook;Son, Yeung-Kwon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.51 no.5
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    • pp.69-78
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    • 2009
  • In order to improve water quality of upper watershed of Paldang reservoir, it is necessary to evaluate non-point source pollution loads and identify critical watershed pollution sources. A GIS based Soil and Water Assessment Tool was applied to evaluate model application and reliability, estimate NPS pollution load, identify critical watershed by NPS pollution sources, and suggest various best management practices for Kyongan Stream watershed. Yearly NPS pollution loads were estimated 30.0% SS, 60.1% TN and 35.4% TP, respectably. The watershed pollution load is mainly decided by precipitation condition and SS and nutrients load have a significant regression relationship. Based on 10-year average yearly NPS pollution load, critical sub-watersheds were identified. The No. 5 and 17 which have lots of relatively intensive agricultural fields and scattered industrial area were vary critical sub-watersheds and under more intensive pollution load. In order to control critical watershed, watershed best management practices such as scientific fertilizer, contour farming and parallel terrace, transferring the sloppy farmland to grass or forest and constructing a buffer zone, and constructing wetlands and retention ponds will be applied. Overall the SWAT model can be efficiently used for identification of critical sub-watersheds in order to develop a priority watershed management plan to reduce water pollutions.

An Analysis of Dynamic Critical Loads for Low Parabolic Arches with Different End Conditions (지지조건을 고려한 낮은 포물선 아치의 동적 임계하중의 해석)

  • 박승범
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.28 no.2
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    • pp.87-92
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    • 1986
  • The differential equation, which can determine the dynamic critical loads for low parabcoic arches, is derived in this study. The dynamic critical loads of the parabolic arches subjected to a concentrated step load are nummerically analyzed for the changes of load positions. In cases of arches with different end conditions (both hinged, fixed hinged, both fixed), the effect of end conditions and that of the rises are investigated in detail. The summary of the results are the following: 1)The snapthrough does not occur when the rise of arch is very low, and the bifurcation appears clearly as the rise of arch increases. 2)The regions in which the dynamic critical loads are not defined for the both ends fixed are broader than that for the both ends hinged. 3)For all case, the load positions of minimum dynamic critical loads exsit at the near position from the end hinged. Thus, the results obtained in present study show that the magnitude of dynamic critical loads, the load positions of minimum dynamic critical loads and the regions in which the dynamic critical loads are not defined depend on end conditions of arches.

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Influence of Elastic Restraints and Tip Mass at Free End on stability of Leipholz Column (Leipholz 기둥의 안정성에 미치는 자유단의 탄성구속과 말단질량의 영향)

  • 윤한익;박일주;진종태;김영수
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.309-315
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    • 1996
  • An analysis is presented on the stability of elastic cantilever column subjected to uniformly distributed follower forces as to the influence of the elastic restraints and a tip mass at the free end. The elastic restraints are formed by both the translational and the rotatory springs. For this purpose, the governing equations and boundary conditions are derived by using Hamilton's principle, and the critical flutter loads and frequencies are obtained from the numerical evaluation of the eigenvalue functions of this elastic system. The added tip mass increases as a whole the critical flutter load in this system, but the presence of its moment of inertia of mass has a destabilizing effect. The existence of the translational and rotatory spring at the free end increases the critical flutter load of the elastic cantilever column. Nevertheless their effects on the critical flutter load are not uniform because of their coupling. The translational spring restraining the end of cantilever column decreases the critical flutter load by coupling with a large value of tip mass, while by coupling with the moment of inertia of tip mass its effect on the critical flutter load is contrary. The rotatory spring restraining the free end of cantilever column increases the critical flutter load by coupling with the tip mass, but decreases it by coupling with the moment of inertia of tip mass.

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Evaluation of the characteristics of plasma sprayed ceramic coatings by Indentation test (압입 시험에 의한 플라즈마 세라믹 용사코팅의 특성 평가)

  • Choi, Se-Young;Chae, Young-Hun;Kim, Seock-Sam
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.248-254
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    • 2002
  • The most controversial topics in plasma sprayed ceramic coating system are recently mechanical properties such as bond strength, cohesive strength, toughness and so on. Determination of bond strength of coatings is one of the most important problems. In the industry, the bond strength of coating system has been estimated by Pull-off test(ASTM standard C633-79). But, without a fixed jig and specimen, it is impossible to obtain the bond strength. Therefore, it is necessary to study the critical fracture load on interface of the coating by indentation test. Because the critical fracture load plays an important role in evaluating the bond strength for plasma sprayed ceramic coating system. So, we have estimated critical fracture load in plasma sprayed ceramic coating system, and it was shown that inverse relationship between the cross-section hardness of coating and the critical fracture load(Pc). In case of the high load(1kgf, 2kgf) in $Al_{2}O_{3}+13%TiO_{2}$, it was found that the critical point(Pco), which the coating was broken on.

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Design load-carrying capacity estimates and an improved wooden shore setup

  • Huang, Y.L.;Lin, Y.C.;Lee, C.F.;Chen, H.J.;Yen, T.
    • Structural Engineering and Mechanics
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    • v.17 no.2
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    • pp.167-186
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    • 2004
  • The design load-carrying capacities of wooden shores depend on factors, such as the wood species and properties, and construction methods. This paper focuses on the construction methods, including an upright single shore, group of upright shores, group of inclined shores, butt connections and lap connections. This paper reports experiments to obtain critical loads and then developed an empirical equation based on Euler' formula for the critical loads and design load-carrying capacities. The test results show that the critical loads for an upright single wooden shore are greater than the average values for a group of upright shores, and the latter are greater than the average values for a group of inclined shores. Test results also show that the critical loads become smaller when butt or lap connections are used, butt connections possessing greater critical loads than lap connections. Groups of inclined shores are very popular at work sites because they have some practical advantages even though they actually possess inferior critical loads. This paper presents an improved setup for constructing groups of inclined shores. With this method, the inclined shores have larger critical loads than upright shores. The design load-carrying capacities were obtained by multiplying the average critical loads by a resistance factor (or strength reduction factor, ${\phi}$) that were all smaller than 1. This article preliminarily suggests ${\phi}$ factors based on the test results for the reference of engineers or specification committees.

Buckling behavior of composite cylindrical shells with cutout considering geometric imperfection

  • Heidari-Rarani, M.;Kharratzadeh, M.
    • Steel and Composite Structures
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    • v.30 no.4
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    • pp.305-313
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    • 2019
  • Creating different cutout shapes in order to make doors and windows, reduce the structural weight or implement various mechanisms increases the likelihood of buckling in thin-walled structures. In this study, the effect of cutout shape and geometric imperfection (GI) is simultaneously investigated on the critical buckling load and knock-down factor (KDF) of composite cylindrical shells. The GI is modeled using single perturbation load approach (SPLA). First, in order to assess the finite element model, the critical buckling load of a composite shell without cutout obtained by SPLA is compared with the experimental results available in the literature. Then, the effect of different shapes of cutout such as circular, elliptic and square, and perturbation load imperfection (PLI) is investigated on the buckling behavior of cylindrical shells. Results show that the critical buckling load of a shell without cutout decreases by increasing the PLI, whereas increasing the PLI does not have a great impact on the critical buckling load in the presence of cutout imperfection. Increasing the cutout area reduces the effect of the PLI, which results in an increase in the KDF.

Design and Control Method for Critical Load Supply Equipment using MCFC Electricity Generation Systems (대용량 MCFC 발전시스템을 이용한 비상부하 전력 공급 장치 설계 및 제어방법)

  • Kim, Dong-Hee;Kim, Jong-Soo;Choe, Gyu-Yeong;Lee, Byoung-Kuk;Kawk, Cheol-Hoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.16 no.1
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    • pp.20-29
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    • 2011
  • This paper proposes critical load following back-up system using MCFC stack. This system enables MCFC generation system to supply power to critical load without UPS and to generate rated power under grid fault state. This back-up system includes 'Load Leveler' that is connected with 3-phase inverter and is controlled by additional algorithm that includes critical load following. The proposed system and algorithm are verified by computer simulation based on 5kW system.

A study on critical load due to external force influencing on flight characteristics of a small slender body rocket. (가늘고 긴 소형로켓의 비행특성에 영향을 주는 외력에 기인한 임계하중에 관한 연구)

  • Go, Tae-Sig;Na, Seon-Hwa
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.393-397
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    • 2007
  • The aim of this study is to investigate critical load, which can influence on flight path of a small slender body rocket, due to external forces such as thrust, drag and weight. The critical load was firstly obtained from Euler column equation, and compared with analysis results using Finite Element Method to evaluate the theoretical critical load.

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