AN IMPROVED M-C METHOD AND ITS APPLICATION TO STRUCTURAL RELIABILITY

An improved Monte-Carlo method for the failure calculation of structureis proposed.The present method can determine whether some sample points are in thesafe region without doing structural analysis,so the calculation work is greatly reducedcompared with the ordinary M-C method.Finally,the new M-C method is applied toreliability analysis of frame and the torsional buckling reliability analysis of cylindricalshells.     

A NEW TWO-POINT ADAPTIVENONLINEAR APPROXIMATION METHOD FOR RELIABILITY ANALYSIS

I. INTRODUCTION Reliability analysis is becoming increasingly important in structural design. Over the years, manyresearchers have been involved in the evaluation of failure probability and many methods have beenpresented for structural reliability anal…     

SUPPORT VECTOR MACHINE FOR STRUCTURAL RELIABILITY ANALYSIS

Support vector machine (SVM) was introduced to analyze the reliability of the implicit performance function, which is difficult to implement by the classical methods such as the first order reliability method (FORM) and the Monte Carlo simulation (MCS). As a classification method where the underlying structural risk minimization inference rule is employed, SVM possesses excellent learning capacity with a small amount of information and good capability of generalization over the complete data. Hence, two approaches, i.e., SVM-based FORM and SVM-based MCS, were presented for the structural reliability analysis of the implicit limit state function. Compared to the conventional response surface method (RSM) and the artificial neural network (ANN), which are widely used to replace the implicit state function for alleviating the computation cost, the more important advantages of SVM are that it can approximate the implicit function with higher precision and better generalization under the small amount of information and avoid the "curse of dimensionality". The SVM-based reliability approaches can approximate the actual performance function over the complete sampling data with the decreased number of the implicit performance function analysis (usually finite element analysis), and the computational precision can satisfy the engineering requirement, which are demonstrated by illustrations.     

A NEW METHOD FOR THE UNCERTAIN RESPONSE ANALYSIS OF STRUCTURES WITH UNCERTAIN PARAMETERS

A computing method for estimating the upper and lower bounds of the response ofstructures with uncertainties is presented.The uncertain parameters are described by the convexmodel.A numerical example of the frame structure is given to illustrate the effectiveness of thismethod.     

MIXED HYBRID PENALTY FINITE ELEMENT METHOD AND ITS APPLICATION

The penalty and hybrid methods are being much used in dealing with the general incompatible element. With the penalty method convergence can always be assured, but comparatively speaking its accuracy is lower; and the condition number and sparsity are not so good. With the hybrid method, convergence can be assured only when the rank condition is satisfied. So the construction of the element isextremely limited. This paper presents the mixed hybrid penalty element method, which combines the two methods together.And it is proved theoretically that this new method is convergent, and it has the same accuracy, condition number and sparsity as the compatible element.That is to say, they are optimal to each other. Finally, a new triangle element for plate bending with nine freedom degrees is constructed with this method (three degrees of freedom are given on each corner——one displacement and two rotations), the calculating formula of the element stiffness matrix is almost the same as that of the old triangle     

APPLICATION OF PENALTY FUNCTION METHOD IN ISOPARANIETRIC HYBRID FINITE ELEMENT ANALYSIS

IntroductionSince T.H.H.Pain firstly puts forward hybrid element method[1]in1964, the researchand application of hybrid element have got great development. T.H.H.Painet al.havemade important pioneer works in the domain of the research on incompatible displacementstructure hybrid elementstress pattern[2,3]in recentdecades. Reference [4] had provided theoptimizing design concept of hybrid element further and established standardization methodof incompatible displacement structure hybrid eleme…     

MESHLESS ANALYSIS FOR THREE-DIMENSIONAL ELASTICITY WITH SINGULAR HYBRID BOUNDARY NODE METHOD

The singular hybrid boundary node method (SHBNM) is proposed for solving three-dimensional problems in linear elasticity. The SHBNM represents a coupling between the hybrid displacement variational formulations and moving least squares (MLS) approximation. The main idea is to reduce the dimensionality of the former and keep the meshless advantage of the later. The rigid movement method was employed to solve the hyper-singular integrations. The 'boundary layer effect', which is the main drawback of the original Hybrid BNM, was overcome by an adaptive integration scheme. The source points of the fundamental solution were arranged directly on the boundary. Thus the uncertain scale factor taken in the regular hybrid boundary node method (RHBNM) can be avoided. Numerical examples for some 3D elastic problems were given to show the characteristics. The computation results obtained by the present method are in excellent agreement with the analytical solution. The parameters that influence the performance of this method were studied through the numerical examples.     

SEMI-ANALYTICAL AND SEMI-NUMERICAL METHOD FOR DYNAMIC ANALYSIS OF FOUNDATION

A semi-analytical and semi-numerical method is proposed for the dynamic analysis of foundations. The Lamb's solution and the approximate formulae were used to establish the relation of the contact force and deflection between the foundation and soil. Therefore, the foundation can be separated from soil and analyzed by FEM as for the static cases. The plate can be treated as that the known forces are acting on the upper surface, and the contact pressure from soil can be represented as the deflection. So that only the plate needs to be divided into elements in the analysis. By this method, a series of vibration problems, including various shapes and rigidities of foundations, different excitation frequencies, were analyzed. Furthermore, it can be used for the embedded foundation. The numerical examples show that this method has simplicity, highly accurate and versatile. It is an effective method for the dynamic analysis of foundations.     

GENERALIZED VARIATIONAL PRINCIPLES WITH SEVERAL ARBITRARY PARAMETERS AND THE VARIABLE SUBSTITUTION AND MULTIPLIER METHOD

The functional transformations of variational principles in elasticity are classified asthree patterns:Ⅰ relaxation pattern,Ⅱ augmented pattern and Ⅲ equivalent pattern.On the basis of pattern Ⅲ,the generalized variational principles with several arbitraryparameters are formulated and their functionals are defined They are:the generalizedprinciple of single variable u with several parameters,the generalized principle of twovariables u,σ with several parameters,the generalized principle of two variables u,εwith several parameters,and the generalized principle of three veriables u,ε.σ withseveral parameters.From these principles,a series of new forms of equivalent functionalscan be obtained.When the values of these parameters are properly chosen.a series of finiteelement models can be formulated.In this paper,the question of losing effectiveness for Lagrange multiplier method isalso discussed.In order to“recover”effectiveness for multiplier method,a modifiedmethod,namely,the variable substitutio     

A NEW METHOD OF STRESS ANALYSIS IN PHOTOELASTICITY

A new method of stress analysis in photoelasticity has been developed in this paper. Only the orders of isochromatic fringes and boundary conditions in three sections are adopted to analyse the stress components in these sections. The method requires minimum known data and can quickly analyse stress components. It reduces computational programs.     

A HYBRID GRANULARITY PARALLEL ALGORITHM FOR PRECISE INTEGRATION OF STRUCTURAL DYNAMIC RESPONSES

Precise integration methods to solve structural dynamic responses and the corre- sponding time integration formula are composed of two parts:the multiplication of an exponential matrix with a vector and the integration term.The second term can be solved by the series solu- tion.Two hybrid granularity parallel algorithms are designed,that is,the exponential matrix and the first term are computed by the fine-grained parallel algorithm and the second term is com- puted by the coarse-grained parallel algorithm.Numerical examples show that these two hybrid granularity parallel algorithms obtain higher speedup and parallel efficiency than two existing parallel algorithms.     

THEORY AND METHOD OF OPTIMAL CONTROL SOLUTION TODYNAMIC SYSTEM PARAMETERS IDENTIFICATION (Ⅰ)──FUNDAMENTAL CONCEPT AND DETERMINISTIC SYSTEM PARAMETERS IDENTIFICATION

IntroductionDynamicsystemidentificationistheinverseproblemofdynamics.Throughtheuseofexperimentaloroperahonalinput-outputdata,modelofdynaITilcsystemcanbeestablishedbysystemidentificationtechnique,andundetCndnedparametersofmodelcanalsobeidenhfied.Ingeneral,dynamicequahonsofsystemareknownPrior,whilesystemidentificahonisjustanundetendnedparametersidentificationproblem.TheseparametersaremodalparameterssuchasfrequenciesandmodeshapesorstrUctUralparameterssuchasdampingandstiffness.T'hisisatypical"g…     

BOUNDARY ELEMENT METHOD FOR BUCKLING EIGENVALUE PROBLEM AND ITS CONVERGENCE ANALYSIS

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THEORY AND METHOD OF OPTIMAL CONTROL SOLUTION TO DYNAMIC SYSTEM PARAMETERS IDENTIFICATION (I)──FUNDAMENTAL CONCEPT AND DETERMINISTIC SYSTEM PARAMETERS IDENTIFICATION

Based on the concept of optimal control solution to dynamic system parameters identification and the optimal control theory of deterministic system, dynamics system parameters identification problem is brought into correspondence with optimal control problem. Then the theory and algorithm of optimal control are introduced into the study of dynamic system parameters identification. According to the theory of Hamilton-Jacobi-Bellman (HJB) equations' solution, the existence and uniqueness of optimal control solution to dynamic system parameters identification are resolved in this paper. At last the parameters identification algorithm of determi-nistic dynamic system is presented also based on above mentioned theory and concept. Project supported by the National, Defence Science and Technology Foundation (A966000-50) and the Across Century Scientist Foundation from the State Education Commission of China     

MODEL AND METHOD OF WELL TEST ANALYSIS FOR WELLS WITH VERTICAL FRACTURE

NomenclatureB———volumecoefficientofformationfluid,dimensionless;C———wellborestoragecoefficient,m3 MPa;Cft ———comprehensivecompressioncoefficientoffluidinfracture ,1 MPa;Ct ———comprehensivecompressioncoefficientofformationfluid,1 MPa ;h———heightofformation ,m ;K———formationpermeability ,μm2 ;Kf ———fracturepermeability ,μm2 ;KfWf ———fractureconductivity ,μm2 ·cm ;Lf ———halfoffracturelength,m ;N———thetotalnumberofselectedtimepoint,dimensionless;P———for…     

THE RATIONALISM THEORY AND ITS FINITE ELEMENT ANALYSIS METHOD OF SHELL STRUCTURES

In this paper,a kind of rationalism theory of shell is established which is of differentmechanic characters in tension and in compression,and the finite element numericalanalysis method is also described.     

DYNAMIC CHARACTERISTIC ANALYSIS OF FUZZY- STOCHASTIC TRUSS STRUCTURES BASED ON FUZZY FACTOR METHOD AND RANDOM FACTOR METHOD

A new fuzzy stochastic finite element method based on the fuzzy factor method and random factor method is given and the analysis of structural dynamic characteristic for fuzzy stochastic truss structures is presented. Considering the fuzzy randomness of the structural physical parameters and geometric dimensions simultaneously, the structural stiffness and mass matrices are constructed based on the fuzzy factor method and random factor method; from the Rayleigh's quotient of structural vibration, the structural fuzzy random dynamic characteristic is obtained by means of the interval arithmetic; the fuzzy numeric characteristics of dynamic characteristic are then derived by using the random variable's moment function method and algebra synthesis method. Two examples are used to illustrate the validity and rationality of the method given. The advantage of this method is that the effect of the fuzzy randomness of one of the structural parameters on the fuzzy randomness of the dynamic characteristic can be reflected expediently and objectively.     

A TIME DOMAIN BOUNDARY ELEMENT METHOD FOR WATER-SOLID IMPACT ANALYSIS

A reciprocal theorem of dynamics for potential flow problems is first derived by meansof the Laplace transform in which the compressibility of water is taken into account.Based on this the-orem,the corresponding time-space boundary integral equation is obtained.Then,a set of time do-main boundary element equations with recurrence form is immediately formulated through discretiza-tion in both time and boundary.After having carried out the numerical calculation two solutions arefound in which a rigid semicircular cylinder and a rigid wedge with infinite length suffer normal impacton the surface of a half-space fluid.The results show that the present method is more efficient than theprevious ones.     

A FINITE ELEMENT METHOD ON THE PLANE ELASTIC MATERIAL ANALYSIS

Based on the finite element displacement method, a finite element method on the analysis of mechanical behaviour of plane elastic materials is proposed in this paper. By using this method and the corresponding computational program, the material behaviour of any unknown plane elastic material can be determined and all the elastic constants can be calculated.