Effect of Shear Lag on Structural Behaviours in Indeterminate Box Girders

A finite element method considering interaction betwee bending and shear lag deformation was proposed and the finite element formulations including the effect of shear lag was deduced. The effect of shear lag on structural behaviours in indeterminate box girders was studied in detail based on the proposed method. Firstly, the shear lag effects on deflection and the shear lag coefficients were analyzed for both determinate and indeterminate beams. The results obtained by using the proposed method were compared with those by using the analytical method. Finally, the effect of shear lag on redistribution of internal forces including shear force, bending moment, and additional bending moment due to shear lag in indeterminate box girder bridges was studied. It is found that the effects of shear lag on deflection and stresses at a cross section are obvious for both determinate and indeterminate beams, while the effect of shear lag on internal forces in indeterminate box girder bridges is small and may be neglected.     

Deformation equations of thin-walled open-profile members considering distortion and its application

In order to simplify the analysis of thin-walled open-profile bars, a method is presented in which the analysis is split into two parts, dominated by in-plane and out-plane loading effects respectively. This article focuses on the out-plane loading effects. Based on bending theory of thin plate with small deflection, each slab or strip is analyzed separately and the results are integrated into vectors, in which, the deformation shapes and equilibrium conditions are simplified appropriately, thus leading to the slabs' out-plane bending resistance system of thin-walled bars, which reflects the properties of the bar's distortion and torsion. By composing the slabs in-plane tension-bending resistance system and the slabs' out-plane bending resistance system, deformation equations of thin-walled open-profile bars considering distortion are deduced. In order to set up the finite bar element method, stiffness equation and equivalent nodal forces of internode loadings are deduced. Comparative analysis with finite shell element method indicates the high efficiency and accuracy of this method.     

Boundary Element Methods with Overlapping Domain Decomposition for Parabolic Problem

Boundary element method is a numerical method for solving partial differential equations. There are several formulations of boundary element method (BEM) applied to solve a parabolic differential equation.The approach,which employs time- dependent fundamental solution,allows longer time steps in time integration than other approaches,and this can cut down on time for computer implementation with high precision.Domain decomposition method,which decompose the domain that a given problem is to be solved into subdomains,has the advantages of reducing the large problem into smaller ones and reducing the complex problem into simpler ones,and allows parallel computing.An overlapping domain decomposition method is applied combining a boundary element formulation with time-dependent fundamental solution to solve a diffusion equation. Firstly, by domain decomposition, the problem divided into two problems on subdomains, and then the initial-Boundary problems are solved by boundry element method on each subdomain.Some numerical examples are presented to illustrate feasibility and efficiency of the method. The numerical experiments show that the convergence rate of the method is dependent with the overlapping degree of the subdomains.     

Finite Element Analysis and Experimental Research on Pedestal of PC Beam for Light Railcar

In design of light railcar used freely supported beam, the cast steel pedestals will bear complex loads, which include weight, acceleration and wind, etc. Because of pedestals' peculiarity and complexity, the strength of the pedestals play an important role in safety of light railcar. So it's necessary to analyze their stress and deformation in order to insure safety of light railcar. Up to now, finite element analysis is still the most effective means. By studying cast steel pedestal with finite element method, 3-D finite element models of fixed and kinetic pedestals were built, and the loads and boundary condition of pedestals were analyzed. By means of finite element analysis software, the contact and von mises stresses were obtained and deformation were resolved. As a result of analysis, the tow of pedestal can fulfill requirement of use in light railcar, the contact stress and von mises stress are not exceeded limit stress strength of materials. There is enough static strength for the structures of pedestals. For verifying theoretical analysis result, the fatigue test was carried out, with examining the testing points locating on the pedestals, the stress and deformation data were measured. By comparing between theoretical analysis and test data, the experimental results show calculated and testing results can meet the case well which assure the reliability of finite element analysis. But in the result, there are differences in deformations of them. The reason may be that boundary conditions and loads are not same between analysis and experiment.     

Finite Element Reliability Analysis of the Stability of a Slope

The whole reliability index of a slope is derived through using the strength reduction method in the finite element analysis, which can make use of the former finite element program and can be used to both linear and nonlinear finite element analysis. The affection of the evaluation of derivative and the selection of reliability analysis methods is discussed, which shows that it is very important to select the type of limit state function of the slope stability. A new iterafive formula, which can consider the correlation of fundamental parameters, is proposed for FORM, and the convergence is very well.     

Finite Element Simulate Analysis of Small Span-to Depth Ratio Coupling Beams with Special Reiforcement

Test investigations show that the reinforcement scheme with adding diagonal and rhombic bars to traditional reinforcement in the foundation is an ideal way, for the seismic performance of small span-to depth ratio coupling beams with this scheme is better than that of traditional reinforcement. Because the regions in the small aspect ratio coupling beam belong to D-regions, in which the Bernoulli hypothesis of plane strain distribution is invalid, the traditional bending theory can not be used. This paper simulates the coupling beam through non-linear finite element analysis program, and contrasts the analysis result of the bar's stress distribution with test result. The contrast results confirm that it is a valid way to analyse the bar's stress distribution in this coupling beam through non-linear finite element analysis program.     

Study and Application of High Precision Nonlinear Plane Stress Element

A tangent stiffness matrix for quadrilateral plane stress element under large rotation with small strain is proposed in this paper,The corresponding program based on this theory has been worked out;The computation of examples with analytic values has verified that the element's formulation, its program given in this paper have strong nonlinear computation ability;A nonlinear whole-course analysis of stone arch bridge has been done in this paper.The computations presented preferably a comprehensive understanding of nonlinear characteristics of stone arch bridge with small span and could be beneficial for the engineer designers.     

The Element Flexibility Matrix of Thin-walled Beam and Its Application

In this paper, the calculation of the space deformation of thin-walled element by "dynamic coordinate method" is explained in detail through an example. The thin-walled element with different shear-centers on one section is analyzed and calculated by this method as well, then, the element flexibility matrix is presented. Some difficulties in calculation of thin-walled structures with "plane bending theory" and "constrict twist theory" are overcome, showing the advantages of this method.     

Finite Element Programming Based on Template Chain Structure

Traditional Finite Element Method is the structuralization programming method and the structuralization language (such as FORTRAN). Its data store uses fixed array structure, which makes the expanding ability of program limited, code's reuse ratio low, debugging complex. The template is an opposite new important characteristic of the object-oriented programming language C++. The template can quickly establish class library so as to increase greatly the development speed of the large software. The object-oriented programming concept is applied to finite element method. According to the nature of the finite element analysis, the classes and their methods, which describe virtual element, node, material etc., have been developed and implemented using the object-oriented programming language C++. The elements, nodes and materials are stored by chain. Many type's elements are stored mixedly by polymorphism characteristic. The program is implemented and a instance is given to show the programming of finite element method. The results show that the period of programming and debugging is obviously shorter than that of traditional method; the code's utilization ratio is also increased obviously.     

Analysis of Numerical Simulation of Seepage Failure and Seepage Feature of Seawall

In order to analyze seepage feature and seepage failure mechanisms of seawall under flood infiltration, a numerical model for saturated-unsaturated and unsteady seepage flow analysis considering soil permeability variation with seepage failure process was established. And the corresponding finite element computation program was made. Numerical simulation of flood seepage for typical section of real seawall was carried out by use of the program. The computed results were compared with the measured results of field test, which shows good agreement. Based on the numerical simulation results, it can be seen that flood seepage of seawall is a saturated-unsaturated and unsteady seepage flow process and seepage failure of seawall is caused by long time flood infiltration under large seepage gradient. Therefore, upon the flood infiltration, seepage failure of the seawall is a very complicated process, which involves soil permeability variation with seepage failure process and saturated-unsaturated/unsteady seepage flow. It is questionable to use the steady seepage analysis method to simulate seepage failure process of seawall.     

Face Stability Analysis of Shield Tunneling in Sandy Cobble Stratum

When shield crossed the sandy cobble stratum in Chengdu metro line 1, ground subsidence reached as high as dozens of times. The losing stability of excavation face caused excessive ground loss. Conditions of engineering geology and hydrogeology about sandy cobble stratum in Chengdu were analyzed. Mechanical characteristics of sandy cobble were obtained via large-scale triaxial test. According to the low cohesion and heavily discrete characteristics of sandy cobble, numerical computation was conducted by discrete element method. Based on numerical simulation of the large scale triaxial test, the micro parameters of the sandy cobble were calibrated. The influence of support pressure on shield excavation face deformation, surface settlement, max horizontal displacement and stress of soil was analyzed. The results show that: 1) Collapse pattern of excavation face by numerical simulation coincides with result of centrifuge model test in sand. 2) When supporting pressure is small, contact forces of particle in front of excavation face is low. The tendency of particle flow is apparent. Since over-excavation is easily brought out, cavity in the ground is caused after shield tunneling. 3)Soil arching effect in shield construction is obvious. Shield excavation forms cavity in deep ground and obvious earth surface collapse is not observed. This is main reason for lagged settlement phenomena of shield tunneling in Chengdu.     

The Taylor series multipole boundary element method (TSM BEM)and its applications in rolling engineering

Rainfall is the main input for probabilistic analysis and prediction of rainfall-triggered landslide. The joint probabilistic structure of daily rainfall (DR) and cumulative rainfall (CR), which are dominant parameters of rainfall related on landslide in Chongqing region, was analyzed. Following the traditional technology, daily rainfall was translated into discrete variable by rainfall grade and cumulative rainfall became continuous variable if records with very small cumulative rainfall were ignored. Then joint probabilistic model of discrete variable and continuous one was derived, and transiting solution of conditional density function was put forward, together with its approximation via a family of Dirac δ sequences. Naturally, the proposed method was used to analyze conditional density function of cumulative rainfall in Chongqing region, and the numerical results were verified by comparison. However, most of the conditional density functions were irregular and not modeled by simple probability density function, thus the finite mixture distribution was introduced, which is of uncomplicated format and relatively high precision. At last, the joint probabilistic model of daily rainfall and cumulative rainfall was built up by combining frequency function of grade of daily rainfall with conditional density model of cumulative rainfall.     

Finite Element Analysis of Masonry RVE Homogenization Procedure

Homogenization is one of the most important steps in the numerical analysis of masonry structure, where the continuum is used. A masonry representative volume element (RVE) is formed as the equivalent element of masonry components and it is the most important step in homogenization procedure. The RVE is molded with consideration of the material properties of mortar and brick as well as their interaction separately. In this paper the masonry RVE is simulated with the finite element software ANSYS. The stress-strain relationships of RVE subjected to different types of loading conditions are presented. The equivalent elastic modulus and Poisson's ratio are calculated and the feasibility of finite element method used in the procedure of masonry homogenization is demonstrated.     

Generalized conforming quadrilateral membrane element with vertex rotational freedom

A new generalized conforming quadrilateral membrane element is developed by introducing additional rigid vertex rotational freedoms to the normal 4 node quadrilateral membrane element. The rotational stiffness of the present element is not zero so that the singularity of the stiffness matrix is avoided. Numerical analysis of the Cook problem cantilever beam shows that the EAE/Mem element passes the patch test and possesses good convergence, reliability, and precision without a zero energy mode. It provides a lock free solution to the MacNeal beam problem. Numerical results also show that the EAE/Mem element is insensitive to mesh distortion. The results demonstrate that the generalized conforming technique is an efficient tool for developing high performance finite element models.     

Finite Element Method of 3D Stable Heat Conduction of Steel Fluid in Continuous Casting Moulds

The heat transfer of steel fluid in continuous casting mould is a stable process and can be depicted with three-dimensional stable heat conduction equation depending on tension speed. The corresponding finite element equation, including the first, second and third boundary conditions, is deduced out with Galerkin residual method. The coded FEM program is used to analyze the temperature distribution of Q235 steel in continuous billet casting mould. The method proposed is a foundation of thermo-mechanical coupled analysis for the formation of solidified shells and stress in the shells in continuous casting.     

Analysis of Leaf Suspension of Vehicle Using Non-linear Finite Element

This paper introduced basic concept and resolvent of nonlinear FEA, the analysis of intensity and stiffness of the rear leaf spring on SC1020 vehicle was carried out with contact nonlinear function of FEA program ANSYS, and the pre-stress distribution and pre-deformation after assembled were introduced , the stress distribution and deformation under different loads had also been presented. Thus we can calculate the mechanical and dynamic performance of leaf spring at the design stage. The result showed a great agreement with the test. It is convinced that the CAE (Computer Aided Engineering) technology can improve the design of vehicle suspension and the cost and time can be saved.     

Coupled Thermo-Elastic Contact Finite Element Method and It''s Application in Gearing

A new finite element method is presented in this paper to analyze the thermo- elastic contact problem with heat input on meshing tooth faces. The computational model of meshing gear has been established and the frictional heat input on meshing tooth faces is estimated. In addition, 2-D finite element analysis program for this kind of problem is listed. The test and practical examples are given to show the validity and versatility of this method.     

AN EXTENDED TRANSFER MATRIX AND BOUNDARY ELEMENT METHOD

A combination of extended transfer matrix and boundary element method is proposed for solving two dimentional statics problems of complicated nonhomogeneous structure. It is explained with the theory and the example. The method can get greater numerical accuray and shorten computation time in small amount of computer storage without getting involved with large matrices.     

Non-linear finite element analysis based on the spatial catenary cables

According to the elastic catenary theory,this paper derives the spatial catenary cable element from the exact analytical expression,which is used for finite element analysis of the structure.It deduces the precise expression of two-node cable element tangent stiffness matrix and the tension of cable end.The equivalent node load of cable element is expressed by the total load algorithm,and the non-linear equation is solved by double Newdon-rapson method.The proposed non-linear semi-analytical finite element method based on spatial catenary cable element can take full account of the impact of non-linear geometry.The initial configuration and the internal forces on any directional spatial loads can be solved.The example shows that the calculation method is accurate and effective.