• Title, Summary, Keyword: moment method

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A new statistical moment-based structural damage detection method

  • Zhang, J.;Xu, Y.L.;Xia, Y.;Li, J.
    • Structural Engineering and Mechanics
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    • v.30 no.4
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    • pp.445-466
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    • 2008
  • This paper presents a novel structural damage detection method with a new damage index based on the statistical moments of dynamic responses of a structure under a random excitation. After a brief introduction to statistical moment theory, the principle of the new method is put forward in terms of a single-degree-of-freedom (SDOF) system. The sensitivity of statistical moment to structural damage is discussed for various types of structural responses and different orders of statistical moment. The formulae for statistical moment-based damage detection are derived. The effect of measurement noise on damage detection is ascertained. The new damage index and the proposed statistical moment-based damage detection method are then extended to multi-degree-of-freedom (MDOF) systems with resort to the leastsquares method. As numerical studies, the proposed method is applied to both single and multi-story shear buildings. Numerical results show that the fourth-order statistical moment of story drifts is a more sensitive indicator to structural stiffness reduction than the natural frequencies, the second order moment of story drift, and the fourth-order moments of velocity and acceleration responses of the shear building. The fourth-order statistical moment of story drifts can be used to accurately identify both location and severity of structural stiffness reduction of the shear building. Furthermore, a significant advantage of the proposed damage detection method lies in that it is insensitive to measurement noise.

FREE SURFACE FLOW COMPUTATION USING MOMENT-OF-FLUID AND STABILIZED FINITE ELEMENT METHOD (Moment-Of-Fluid (MOF) 방법과 Stabilized Finite Element 방법을 이용한 자유표면유동계산)

  • Ahn, H.T.
    • 한국전산유체공학회:학술대회논문집
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    • pp.228-230
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    • 2009
  • The moment-of-fluid (MOF) method is a new volume-tracking method that accurately treats evolving material interfaces. Based on the moment data (volume and centroid) for each material, the material interfaces are reconstructed with second-order spatial accuracy in a strictly conservative manner. The MOF method is coupled with a stabilized finite element incompressible Navier-Stokes solver for two fluids, namely water and air. The effectiveness of the MOF method is demonstrated with a free-surface dam-break problem.

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Sidesway가 생기는 강구조의 Moment분배법 완전해법

  • Kim, Taek-Sin
    • Korean Architects
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    • no.11
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    • pp.26-35
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    • 1975
  • The present Structuralists have usually calculated the end Moment of Rigid-frame members by using the Moment Distribution Method, presented by Hardy Cross in 1930, on the Basis of Elastic Law. But this method is considered to be an unfinished solution in case of the moment condition, which the Non-Equilibrium distributed loads or the Horizontal Force acted upon it result in deflection. Hence, after finishing the calculation of stress by means of the Moment Distribution Method, the stress condition due to Horizontal Forces had to be corrected approximatly. However we can directly get the solution of Rigid-frame having sidesway not by above method but by the Moment Distribution computation. Consequently this method is regarded as a Perfect Moment Distribution Method. Here 1 present.

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Probabilistic models for curvature ductility and moment redistribution of RC beams

  • Baji, Hassan;Ronagh, Hamid Reza
    • Computers and Concrete
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    • v.16 no.2
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    • pp.191-207
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    • 2015
  • It is generally accepted that, in the interest of safety, it is essential to provide a minimum level of flexural ductility, which will allow energy dissipation and moment redistribution as required. If one wishes to be uniformly conservative across all of the design variables, curvature ductility and moment redistribution factor should be calculated using a probabilistic method, as is the case for other design parameters in reinforced concrete mechanics. In this study, simple expressions are derived for the evaluation of curvature ductility and moment redistribution factor, based on the concept of demand and capacity rotation. Probabilistic models are then derived for both the curvature ductility and the moment redistribution factor, by means of central limit theorem and through taking advantage of the specific behaviour of moment redistribution factor as a function of curvature ductility and plastic hinge length. The Monte Carlo Simulation (MCS) method is used to check and verify the results of the proposed method. Although some minor simplifications are made in the proposed method, there is a very good agreement between the MCS and the proposed method. The proposed method could be used in any future probabilistic evaluation of curvature ductility and moment redistribution factors.

MOMENT-OF-FLUID METHOD FOR FREE SURFACE FLOW SIMULATION USING UNSTRUCTURED MESHES (비정렬 격자상에서 Moment-of-Fluid 방법을 이용한 자유표면유동계산)

  • Ahn, H.T.
    • 한국전산유체공학회:학술대회논문집
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    • pp.65-67
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    • 2011
  • The moment-of-fluid (MOF) method is a new volume-tracking method that accurately treats evolving material interfaces. The MOF method uses moment data, namely the material volume fraction, as well as the centroid, for a more accurate representation of the material configuration, interfaces and concomitant volume advection. In this paper, unstructured mesh extension of the MOF method is to be presented. The MOF method is coupled with a stabilized finite element incompressible Navier-Stokes solver for two materials. The effectiveness of the MOF method is demonstrated with a free-surface dam-break problem.

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ESTIMATING THE DOMAIN OF ATTRACTION OF HIV-1 SYSTEM BASED ON MOMENT METHOD

  • LI, CHUNJI;YAO, HAN
    • Journal of applied mathematics & informatics
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    • v.36 no.5_6
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    • pp.349-358
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    • 2018
  • In this article, we discuss the domain of attraction of HIV-1 system by using the moment theory. First, the asymptotic stabilities of the equilibrium point of the system are given, and then we introduce how to use the moment method to estimate domain of attraction. Finally, one simulation shows the effectiveness of moment method.

Service load response prediction of reinforced concrete flexural members

  • Ning, Feng;Mickleborough, Neil C.;Chan, Chun-Man
    • Structural Engineering and Mechanics
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    • v.12 no.1
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    • pp.1-16
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    • 2001
  • A reliable and accurate method has been developed to predict the flexural deformation response of structural concrete members subject to service load. The method that has been developed relates the extent of concrete cracking, measured as a function of the magnitude of applied moment in a member, to the reduction in the effective moment of inertia of cracked reinforced concrete members under service load conditions. The ratio of the area of the moment diagram where the moment exceeds the cracking moment, to the total area of the moment diagram for any loading, provides the basis for the calculation of the effective moment of inertia. This ratio also represents mathematically a probability of crack occurrence. Verification of this method for the determination of the effective moment of inertia has been achieved from an experimental test program, and has included beam tests with different loading configurations, and shear wall tests subjected to a range of vertical and lateral load levels. Further verification of this method has been made with reference to the experimental investigation of other recently published work.

Estimation of Plastic Bending Moment of Offshore Pipelines (해저관로의 대변형 굽힘에 의한 소성 모멘트 추정)

  • 이종현;최한석;이승건
    • Journal of Ocean Engineering and Technology
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    • v.17 no.2
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    • pp.21-26
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    • 2003
  • The reel-lay method of submarine pipelines a continuous string of pipe coiled onto a reel. Assembly of this pipe that is string is accomplished onshore by welding, and nondestructive testing is carried out prior to coiling the pipe. The total length of pipes on the reel depends on the reel and pipe diameters. Pipeline installation is accomplished by uncoiling, straightening the pipe, and laying out the pipe string onto the seabed as the barge moves forward. Installation associated with coiling and uncoiling is related to the bending moment and strain relationship of the pipeline, A highgrade pipe material is required when the reel-lay method is used. This paper is concerned with the highly plastic bending moment of the pipeline, including the effect of ovality. Moment calculation in the pipe is accomplished by the numerical method, including the variable ovalities during the plastic bending of the pipe string. The new calculation method of the high plastic bending moment was applied to the reel-lay method.

A Study on the Analysis of Stochastic Nonlinear Dynamic System (확률적 비선형 동적계의 해석에 관한 연구)

  • 남성현;김호룡
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.3
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    • pp.697-704
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    • 1995
  • The dynamic characteristics of a system can be critically influenced by system uncertainty, so the dynamic system must be analyzed stochastically in consideration of system uncertainty. This study presents the stochastic model of a nonlinear dynamic system with uncertain parameters under nonstationary stochastic inputs. And this stochastic system is analyzed by a new stochastic process closure method and moment equation method. The first moment equation is numerically evaluated by Runge-Kutta method and the second moment equation is numerically evaluated by stochastic process closure method, 4th cumulant neglect closure method and Runge-Kutta method. But the first and the second moment equations are coupled each other, so this equations are approximately evaluated by a iterative method. Finally the accuracy of the present method is verified by Monte Carlo simulation.

Application of the Method of Spatial Moment for Analysis the Multi-Region Model (다영역 모델의 해석을 위한 공간모멘트법의 적용)

  • 이덕주
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.42 no.2
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    • pp.78-85
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    • 2000
  • The moment equations of the concentration distribution for the multi-region model are derived using the method of moment. The method originally devised by Aris is to obtain the concentration moments satisfying a given PDE (Partial Differential Equation. The method of moment is used to obtain the first five moments (0th to 4to) that satisfy the model PDE. Each moment of the concentration distribution for the model equation is plotted for the dimensionless time and gave similar results except the skewness and the kurtosis. The results of the analysis show the physical meaning of each moment. The comparisons with the number of regions or the global interaction coefficient give a possibility to determine the parameters of the multi-region model with the analytical concepts.

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