Analysis on Seismic Capacity for RC Specially Shaped Columns in Different Horizontal Direction

With fiber beam-column element based on flexibility method of finite element, the RC specially shaped columns of different axial compression ratio under cyclic loading have been simulated and the analysis results have been compared in aspects of strength, stiffness and ductility in order to provide some suggestions for seismic-resistant design of specially shaped columns. The strength, stiffness and ductility of L,T-shaped columns are apparently different in different horizontal direction, but those of t-shaped column are close.     

Modeling and Its Application of Reinforced Concrete Columns Considering Nonlinear Shear Effects

A fiber beam-column element in conjunction with zero-length elements attached to its ends was proposed to simulate the flexural and shear mechanism respectively. Based on the Limit State Material model and the Shear Limit Curve model provided by OpenSees, the nonlinear shear effect of reinforced concrete column and its coupling with the flexural effect were defined. The reliability of the proposed model was validated by means of comparisons with existing test results. Finally, a plane frame from in-situ pushover test was simulated. It is shown that the proposed method, by taking the nonlinear shear effect into account, produces satisfactory results for frame columns with shear strength and stiffness degradation, while the conventional fiber beam-column element can hardly simulate actual flexure-shear failure mechanism for columns characterized by insufficient transverse reinforcement. The proposed method is applicable for nonlinear analysis of reinforced concrete frame structures with shear deficiencies.     

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.     

Nonlinear Stiffness Matrices of Plane Beam Element Including Initial Stress and Strain Item

There were often happened cases for beam elements with initial stress or initial strain while the geometrically nonlinear analysis was performed for the plane structure. The deduction of stiffness matrices was awfully difficult because the nonlinear stiffness matrices included node displacement vectors and extensive matrix operations. Based on the nonlinear geometric equation of plane beam element and general elastic relationship of stress-strain including initial stress and initial strain,the tangent stiffness matrix was derived. All explicit formula of stiffness matrices including initial stress and strain item have been developed by use of the MATLAB Mathematical Tools. The results are of great significance to the nonlinear finite element programming for plane beam elements.     

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.     

Experimental Analysis of Rotational Behavior of Timber Beam-column Connection of Ancient Tibetan Architecture

Static experiment was carried out to study rotation behavior of timber beam-column connection. The influence of length of Gongmu and position of dowel on the initial rotational stiffness of the joint was analyzed. Rules of stiffness degradation under cyclic loading were studied as well. The results show that: the moment-rotation curve of typical timber beam-column connection can be simplified as bilinear model; the initial rotational stiffness of the joint is enhanced with the increase of the length of Gongmu, and it is decreased with the inward movement of dowel; under the same conditions, the influence of the inward movement of Gongmu-beam dowel on the initial rotational stiffness of the joint is smaller than that of Dianmu-Gongmu dowel; and stiffness degrades under cyclic loading and there exists obvious transition phenomenon.     

The Critical Load of Varied-Axial-Force Beam-Column Calculated by CDC Method

The varied-axial force beam-column is widely used in practice. Unlike the academic method, the numerical method is usually used only to solve its stability problem, but not to give the general answer a series of problems for beam-column. In this paper, firstly, a new conception of dimensionless beam column is presented. Secondly, based on the column deflection curve (CDC) method, the calculation formula for critical load of variable-axial force beam-column is derived. Thirdly, the numerical results under axial symmetric load are derived. Finally, the interaction formula on the critical load of beam-column under concentrated axial load, even distributed axial load and triangular distributed axial load and under these loads acted simultaneously are proposed respectively. The method given in this paper expands the application of CDC.     

Nonlinear Finite Element Analysis for Seismic Performance of High - Strength Concrete Beam -Column Joints with New Reinforcement Details

Because the factors that affect the behavior of the beam-column joints are complicated,an experimental study alone is not sufficient.Therefore,a nonlinear finite element analysis was conducted to provide better understanding of the performance of the beam-column joints.The authors intend to do the parameter study with nonlinear finite element method after a lot of high-strength concrete beam-column joints have been experimented.In this paper,the analytical model firstly was applied to simulate the experimental joint behavior and the comparison results were very well.Based on this,the parametric analysis of concrete strength on seismic performance of beam-column joints has been conducted.     

Primary Study of Applicability of Plane-section Assumption of Shaped RC Columns

Adopting the element SOLID65 and LINK8 in the general finite element analysis software ANSYS and fiber model beam-column element based on finite element flexibility method respectively, the comparative analysis of the cross, L and T-shaped RC columns under compression, bending, shear and torsion with flange width-thickness ratio of 4:1 is carried out. The applicability of plane section assumption in the nonlinear analysis is discussed primarily, which shows that it is feasible on the whole for shaped RC columns with flange width-thickness ratio equal to or smaller than 4:1.     

A Comparative Study of Confined Concrete Models under Cyclic Loading

In this paper,four models are selected as the representatives and applied to nonlinear dynamic analysis program for space frames which is based on the beam-column elements using the finite element flexibility method and the fiber model.Park's test on combined axial and bending columns under cyclic loading are taken as the calibrations,comparisons to material and structural member level are drawn and the analytical results of various models are discussed.     

Effects of cover displacement functions for the stiffness matrixof the numerical manifold method

Based on basic theory of numerical manifold method, effects of cover displacement functions for the stiffness matrix is analyzed with the relationship between the cover displacement function and the formation of the stiffness matrix. The increasing speed of matrix element value has relation to the values of absolute coordinates in cover displacement function. An improved function is adopted for better solution to solve partial oversize problem of stiffness values in the stiffness matrix with the high order cover displacement function. The validity of the proposed approach is approved with case study.     

THE SPLINE BOUNDARY ELEMENT METHOD FOR CALCULATION OF ELECTROMAGNETIC FIELD PROBLEMS

The spline boundary element method is presented for electromagnetic field problems. Based on B-spline function interpolation, the formulation of calculation of two dimensional statical electromagnetic field problems is obtained. Boundary corner and singular integration problems are efficiently handled. Furthermore,the Method is used for solving two calculation examples.     

Sensitivity analysis and lightweight design for the frame of all-terrain vehicles

In order to decrease the manufacture cost of all-terrain vehicles rapidly and effectively,a finite element model for the frame structure of all-terrain vehicles is built by using pre-processing software HyperMesh. The correctness of the model is verified by computing the freedom mode of all-terrain vehicles with Optisturct solver and contrasting it with existing test results. Through applying Optistruct solver and Fatigue to analyze stress distribution,deform and fatigue life of the frame under multi-conditions,and combining with sensitivity analysis results,the lightweight project of the frame is put forward. The validity of this lightweight project is identified after analyzing the optimized frame structure intensity and the fatigue life. The lightweight result show that the frame structure is lightened 6.6063 kg. At the same time,it shows that the structure optimization efficiency and the lightweight effect are enhanced by sensitivity analysis.     

Mechanical Model of Steel Plate Composite Shear Walls

Based on concepts of mechanics, a mechanical model of novel type of steel plate composite shear wall is presented. The novel type of structure is formed by steel plate shear wall and T-shaped solid-web composite columns. Flexural stiffness of steel beams, lateral stiffness of the T-shaped solid-web composite columns, shear stiffness of steel plate composite shear wall and shear stiffness of beam-column connection are taken into account in the mechanical model. And the equivalent damping between steel plate and boundary is considered. Based on the deformation features of structures and the calculation hypothesis, the lateral stiffness model and the energy dissipation model of structures are developed. Meanwhile, the calculation equations of elastic ultimate and plastic ultimate of shear strength of structures are set up. The theoretical analysis results inosculate better with the results of experiment. The comparison between the result calculated from the formula and the experimental result shows that the calculation precision is high enough to meet the demand of theoretical analysis. The difference, including equivalent model, stress states, manufacturing defect and installation error, between the formula and the experiment has been further discussed.     

Mixed Finite Element Method for Dynamic Problems of Fluid Saturated Biphasic Porous Media

Based on the fluid saturated biphasic porous media model deduced from mixture theory,a finite element formulation with u S u F p variables for dynamic response analysis is given out.This method overcomes the difficulty of choosing suitable penalty parameter in penalty finite element method,and the accuracy of pressure distribution obtained with the mixed finite element method is higher than the penalty finile element method.An iterative solution method is suggested to solve the system of equations whose coefficient matrices are non positive definite.It is concluded from patch test that the order of interpolation function for pressure variables must be higher than that of displacement variables of solid phase.     

渐变刚度钢板弹簧建模方法对比

为更好地分析钢板弹簧刚度特性,对钢板弹簧建模方法进行了对比研究。依据钢板弹簧国家标准GB/T 19844-2005,针对某型渐变刚度钢板弹簧分别在有限元软件Hypermesh和多体动力学软件Adams中建立其有限元模型和离散梁模型,并进行了仿真,得到刚度特性。将仿真结果与试验值进行了比较。结果表明,在针对该钢板弹簧的刚度分析中,运用离散梁法得到的刚度特性更加接近试验值。     

软母线刚度对特高压电气设备地震响应影响分析

为研究软母线刚度对特高压电气设备地震响应的影响,建立考虑刚度的软母线位形函数、最大弧垂及软母线最大应力的计算公式。通过软母线连接的特高压设备振动台模型试验与有限元计算的对比分析,验证了笔者给出的考虑刚度的软母线位形函数、最大弧垂计算公式的正确性。有限元分析结果表明:当软母线的刚度增大时,软母线的垂跨比减少,软母线与特高压设备之间的地震耦合作用增强,增强了软母线对设备的拉伸作用,从而使设备的地震反应随着导线刚度的增加而增加。软母线刚度对频率较高的设备其地震反应的影响要大于对设备频率较低设备地震反应的影响。     

NONLINEAR RESPONSE STUDIES OF TALL STEEL FRAMES

Considerable eftects of geometric nonlinearity upon tallsteel frames and flexibly jointed steel frames are recognized.Systematicanalysis philosophy of geometric nonlinearity under various coordinatesystems and its corresponding explicit expression of tangent stiffness matrices are comprehensively embodied.The entries in tangent stiffnessmatrices with its nonlinear behavior and its abstrusely implied physicmeanings are expounded and a straight forward derivation technique ofnonlinear matrices is given.A computer algorithm which can performwhole range studies of steel frames by considering geometric and materialnonlinearities up to the ultimate load carrying capacity is implemented.     

Three Dimensional Eddy-current Field computation by Edge Finite Element Method of Mixed Elements

The edge finite element interpolation function of 1-forms for prism is derived.The electrical field intensity is used as the unknown variable.If the tangential component of electrical field intensity is an enforcing condition on the interface of eddy-current region and non-eddycurrent region,the tangential component of magnetic field intensity is a natural continuous condition.At last,the mixed elements of prism and hexahedron are used to compute a three dimensional eddy-current problem.