• 제목/요약/키워드: Response curve

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외부변형이 섬유보강콘크리트의 인성에 미치는 영향 (Influence of Extraneous Deformation on the Toughness of Fiber Reinforced Concrete)

  • 김경수;고영주;임정환;배주성
    • 한국구조물진단유지관리공학회 논문집
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    • 제4권1호
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    • pp.111-120
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    • 2000
  • This study discusses the issues related to the accuracy of deflection measurement in the testing of FRC. Some deflection methods may include large extraneous deformations. such as local crushing at the loading points, elastic and inelastic deformations of the loading fixture, etc. A faulty load-deflection curve will be obtained if an unstable deflection measuring system is used, and incorrect toughness evaluation can be reached on the basis of this faulty curve. In this paper, the discussion will focus on the effects of the deflection measuring system on both the measurement of the load-deflection response of FRC and the evaluation of FRC toughness. It is observed that ASTM toughness indices which is based on measuring deflection at first cracking is influenced significantly by extraneous deformation in deflection measurement. But extraneous deformation in deflection measurement result in negligible errors in toughness evaluation using JSCE and JCI definition. However, in order to evaluate toughness accuracy, it is desirable to use net load-deflection curve eliminated extraneous deformation.

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Analysis of the Phillips Curve: An Assessment of Turkey

  • NAR, Mehmet
    • The Journal of Asian Finance, Economics and Business
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    • 제8권2호
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    • pp.65-75
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    • 2021
  • This study analyzes the validity of the Phillips curve with regards to Turkey. The existence and direction of the causality relationship (reason-outcome relationship) between unemployment and inflation is investigated using inflation and unemployment data for the period 1980-2019. Unit root tests were utilized to evaluate the stationarity of the series. In line with the Zivot-Andrews unit root test, which was developed in response to the criticism of the failure of studies that presented macro-variables like inflation to consider traditional unit root tests, in this research, the Engle-Granger cointegration test was implemented to check whether the series could perform a joint action, and, finally, the Granger causality relationship was explored. According to the results of the analysis, over the relevant period there was a single directional causality relationship from inflation toward unemployment in Turkey. The importance of this relationship at the 10% significance level indicates the existence of many different factors that affect inflation and unemployment. Given the existence of a cointegration and causality relationship between inflation and unemployment, it can be said that, in Turkey, the Phillips curve is valid for the period 1980-2019 and that an increase of 1% in inflation will reduce the unemployment rate by 0.028%.

이중골조에 대한 비선형 약산법들의 응답특성 (The Response Characteristics of Approximate Nonlinear Methods with RC Dual System)

  • 남영우;강병두;전대한;김재웅
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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    • pp.71-78
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    • 2005
  • In performance-based design methods, it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear tim history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. The nonlinear time analysis is the most accurate method in computing the nonlinear response of structures, but it is time-consuming and necessitate more efforts. Some codes proposed the capacity spectrum method based on the nonlinear static analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. The nonlinear direct spectrum method is proposed and studied to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from the pushover analysis. The purpose of this paper is to compare the accuracy and the reliability of approximate nonlinear methods with respect to RC dual system and various earthquakes.

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방향성 주파수 응답 함수를 이용한 일반 회전체의 비대칭성 규명 (Identification of Asymmetry in General Rotors from Directional Frequency Response Functions)

  • 서윤호;강성우;이종원
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 춘계학술대회논문집
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    • pp.941-944
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    • 2005
  • Asymmetry of rotor systems is an important factor for identification of dynamic characteristics including the stability and response of rotors and for condition monitoring. In this work, asymmetry of rotors is identified by applying curve-fitting method to the directional frequency response functions (dFRFs), which are known as a powerful tool for detecting the presence and degree of asymmetry. This method minimizes least square error between analytical and measured dFRFs by iteratively updating physical parameters associated with rotor asymmetry. The effectiveness of the identification method is demonstrated by experiments with a laboratory test rotor.

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Beam-Column의 동적(動的) 역성(逆性) 응답(應答)에 관한 이산화(離散化) 해석(解析) (A Discrete Analysis of Dynamic Plastic Response of Beam-Columns)

  • 박성환;장창두
    • 대한조선학회지
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    • 제24권3호
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    • pp.43-51
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    • 1987
  • In this paper, dynamic elastic, plastic response of beam-columns is analysed using discrete models. composed of rigid bars and springs. The equation of motion is formulated including the shear deformation effect, and the stress change of yielding points is calculated with various yielding criteria. The effect of initial axial force is considered by two ways: (1) including the effect in interaction curve only. (2) including the effect directly in the equation of motion in terms of initial stiffness method is also used in nonlinear interaction procedure. It is found that this model is very effective in analysing not only the plastic response but the elastic response, and present method is more efficient than Finite Element Method from the viewpoint of calculation time and accuracy.

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초기결함을 갖는 철근 콘크리트 축대칭 쉘의 동적 특성;벽체 결함의 영향을 중심으로 (Dynamic Characteristics of Reinforced Concrete Axisymmetric Shell with Initial Imperfection -effect of wall imperfection on the dynamic response-)

  • 조진구
    • 한국농공학회지
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    • 제42권3호
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    • pp.114-120
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    • 2000
  • In this study a computer program considering initial imperfection of wall of axisymmetric reinforced concrete shell which show plastic deformation by large external loading is developed. initial imperfection of wall of axisymmetric reinforced concrete shell is assumed as sinusoidal curve expressed as {{{{ {W }_{i } }}}}={{{{ {W}_{0 } }}}}sin (n$\pi$y/$\ell$)y. The developed program is applied to the analysis of the dynamic response of axisymmetric reinforced concrete shell when the wall has initial imperfection. The initial imperfection of 0.0 -5.0, and 5cm and steel ratio 0.3, and 5% are tested for numerical examples. The effects of the wall initial imperfection and steel ratio on the dynamic response of the axisymmetric reinforced concrete shell are analysed, It is shown that the direction of the initial imperfection is very important factors for determining the dynamic response.

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2주탑 콘크리트 사장교의 주요 부재 지진 취약도 분석 (Seismic Fragility Analysis by Key Components of a Two-pylon Concrete Cable-stayed Bridge)

  • 신연우;홍기남;권용민;연영모
    • 한국구조물진단유지관리공학회 논문집
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    • 제24권4호
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    • pp.26-37
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    • 2020
  • 본 연구에서는 2주탑 콘크리트 사장교를 모델링하고 취약부재에 대한 비탄성 시간이력해석 결과들로부터 설계기준과 재료특성을 반영한 취약도 분석을 수행하여 콘크리트 사장교에 적합한 취약도 분석을 제시하고자 한다. 사장교의 지진 취약도 곡선을 작성하기 위해 사장교의 주요 취약부재에 대한 한계상태를 결정하고 비탄성 시간이력해석에 의한 응답값과 비교하여 손상상태를 구분한다. 입력지반운동에 대한 취약부위들의 동적응답이 각 구조부재의 한계상태를 초과할 손상확률을 최대지반가속도(PGA)에 대해 구함으로써 사장교의 지진 취약도 곡선을 작성하였다. 주탑의 취약도 곡선에 의하면 0.5g에서 보통손상상태의 확률이 교축방향의 경우 32%인데 반해 교축직각방향의 경우 7%로 나타나 동일 PGA에서 교축직각방향에 비해 교축방향의 손상확률이 더 높은 것으로 나타났다. 연결부의 지진 취약도 곡선을 보면 심한 손상상태의 손상확률이 다른 부재에 비해 매우 높은 수준을 보였는데 이는 지진에 의한 연결부의 손상이 주탑과 케이블의 손상에 비해 매우 민감하다는 것을 의미한다. 케이블의 지진 취약도 곡선에서는 보통손상상태 등급 이후의 손상확률이 점차 낮아져 완전손상상태에 이를 확률은 2.0g의 큰 지진에서도 30%미만의 확률을 가지는 것으로 나타났다.

${\gamma}$-Fe$_2$O$_3$센서의 위험성 가스 감지 특성에 $K_2$CO$_3$가 미치는 영향 (Effect of $K_2$CO$_3$ on Dangerous Gas Sensing Characteristics of ${\gamma}$-Fe$_2$O$_3$ Sensor.)

  • 임병오;박영구
    • 한국안전학회지
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    • 제5권2호
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    • pp.32-39
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    • 1990
  • The ${\gamma}$-Fe$_2$O$_3$ compounds were oxidized in the furance after gas detecting sensor made molding as the Fe$_3$O$_4$ the synthesized Fe$_3$O$_4$, by ferrous sulfate and sodium hydroxide. Their sensities on carbon monoxide, ethyl alcohol and L. P. G. were measured at various temperatures, respectively. And then their electrical resistivities, thermal properties (D.T.A. & T.G.A.), were examined about their having an effet on the gas-sensing in company with the effect of pure ${\gamma}$-Fe$_2$O$_3$ and the detecting sensor ${\gamma}$-Fe$_2$O$_3$, which reacts with $K_2$CO$_3$ in the hydrothermal coundition, and the electrical conductive mechanism was reflected simultaneously. It was observed that the electrical conductivities and response ratios showed highest value at the endothermic temperature part, 300~35$0^{\circ}C$ of D.T.A.―curve. Consequently, the response ratios and response times of the hydrothermal detecting sensor were higher than that of pure detecting sensor, the specific surface areas were the highest at the endothermic range of D.T.A.-curve. These response ratios of detecting sensor for $K_2$CO$_3$, process at hydrothermal condition on carbon monoxide appeared higher than that on ethyl alcohol and in case of L.P.G. last.

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피로시험 데이터의 산포를 고려한 스프링의 신뢰성 최적설계 (Reliability based optimization of spring fatigue design problems accounting for scatter of fatigue test data)

  • 안다운;원준호;최주호
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회A
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    • pp.1314-1319
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    • 2008
  • Fatigue reliability problems are nowadays actively considered in the design of mechanical components. Recently, Dimension Reduction Method using Kriging approximation (KDRM) was proposed by the authors to efficiently calculate statistical moments of the response function. This method, which is more tractable for its sensitivity-free nature and providing the response PDF in a few number of analyses, is adopted in this study for the reliability analysis. Before applying this method to the practical fatigue problems, accuracies are studied in terms of parameters of the KDRM through a number of numerical examples, from which best set of parameters are suggested. In the fatigue reliability problems, good number of experimental data are necessary to get the statistical distribution of the S-N parameters. The information, however, are not always available due to the limited expense and time. In this case, a family of curves with prediction interval, called P-S-N curve, is constructed from regression analysis. Using the KDRM, once a set of responses are available at the sample points at the mean, all the reliability analyses for each P-S-N curve can be efficiently studied without additional response evaluations. The method is applied to a spring design problem as an illustration of practical applications, in which reliability-based design optimization (RBDO) is conducted by employing stochastic response surface method which includes probabilistic constraints in itself. Resulting information is of great practical value and will be very helpful for making trade-off decision during the fatigue design.

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Earthquake risk assessment of concrete gravity dam by cumulative absolute velocity and response surface methodology

  • Cao, Anh-Tuan;Nahar, Tahmina Tasnim;Kim, Dookie;Choi, Byounghan
    • Earthquakes and Structures
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    • 제17권5호
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    • pp.511-519
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    • 2019
  • The concrete gravity dam is one of the most important parts of the nation's infrastructure. Besides the benefits, the dam also has some potentially catastrophic disasters related to the life of citizens directly. During the lifetime of service, some degradations in a dam may occur as consequences of operating conditions, environmental aspects and deterioration in materials from natural causes, especially from dynamic loads. Cumulative Absolute Velocity (CAV) plays a key role to assess the operational condition of a structure under seismic hazard. In previous researches, CAV is normally used in Nuclear Power Plant (NPP) fields, but there are no particular criteria or studies that have been made on dam structure. This paper presents a method to calculate the limitation of CAV for the Bohyeonsan Dam in Korea, where the critical Peak Ground Acceleration (PGA) is estimated from twelve sets of selected earthquakes based on High Confidence of Low Probability of Failure (HCLPF). HCLPF point denotes 5% damage probability with 95% confidence level in the fragility curve, and the corresponding PGA expresses the crucial acceleration of this dam. For determining the status of the dam, a 2D finite element model is simulated by ABAQUS. At first, the dam's parameters are optimized by the Minitab tool using the method of Central Composite Design (CCD) for increasing model reliability. Then the Response Surface Methodology (RSM) is used for updating the model and the optimization is implemented from the selected model parameters. Finally, the recorded response of the concrete gravity dam is compared against the results obtained from solving the numerical model for identifying the physical condition of the structure.