基于有限元法的水电站厂房结构建模及其静动力行为研究

在水电站厂房结构中,板壳是最基本的构件。为了更好地运用ANSYS软件模拟水电站厂房结构,首先应研究如何准确地模拟板壳结构。探究了实体单元与板壳单元在模拟板梁结构时的相同和区别之处,并对薄板结构进行了研究。结论表明由于"剪切闭锁"的现象存在,实体单元并不能准确模拟薄板结构的静动力行为,而板壳单元也只能在模拟特定的某种结构时能够保证准确度。对如何运用ANSYS更加准确地模拟水电站厂房构件静动力行为进行了初步的探索。     

板锥网壳结构的形态分析

板锥网壳结构是一种受力性能合理 ,技术经济效益良好的新型空间结构形式。本文提出板锥网壳结构的合理结构形式和分类 ,对其锥体单元进行形体分析 ,并对板锥网壳结构的选型原则进行了探讨     

160t铁路起重机转台结构研究及有限元分析

利用有限元方法,采用板壳单元和实体单元建立有限元模型,运用有限元分析软件ANSYS对新设计的160t铁路起重机转台结构进行应力、应变计算,得到应力、应变分布情况,从而验证了新型转台结构的可靠性。     

球面组合网壳的有限元法分析及受力特性的研究

组合网壳是一种新型空间结构形式,本文首次采用板壳元、空间偏心梁单元的组合结构有限元法对这种结构的受力特性作了探讨分析,研制了组合网壳受力分析专用计算软件ＣＧＡＳ。文中给出了某一代表性球面组合网壳工程实例,通过分析,阐述了这种结构位移、内力分布规律,讨论了几种与组合网壳相似结构的受力比较,以及肋、钢杆的偏心对受力的影响,总结出的规律对组合网壳结构设计应用有一定参考意义。     

板锥网壳结构的抗风分析

板锥网壳结构是由薄板及钢管组合而成的一种轻质高强、技术经济效益良好的新型空间结构.本文应用谐波法模拟板锥网壳结构所受风荷载,并研究其风致响应特性.根据板锥网壳结构特点,基于CFD方法,采用数值风洞技术模拟结构周围风压变化,得到了板锥网壳结构的风荷载体型系数,并和荷载规范推荐的常规网壳结构的风荷载体型系数进行了比较.采用结构通用分析软件,通过模拟结构周围风压变化,对板锥网壳结构进行了风振响应时程分析,并对不同材料的板锥网壳结构风振响应分析结果进行了对比.为板锥网壳结构的抗风设计提供理论依据,得到了一些可应用于工程实际的重要结论.     

论空间结构的形式和分类

当前空间结构的发展方兴未艾、极具活力,新的空间结构形式不断涌现。传统的空间结构分类方法有时难以适应新的发展要求。本文提出一种以空间结构组成的基本单元进行分类的新的空间结构分类方法。组成空间结构的基本单元可归纳为板壳单元、梁单元、杆单元、索单元和膜单元等五种。根据国内外已建的空间结构工程,总结了33种具体的空间结构形式,它们均可由某一种单元或某两种、三种单元构成。文中还结合近年来空间结构发展中出现的一些新结构,对新的分类方法作了说明与讨论。     

板锥网壳结构的形体和受力特性分析

板锥网壳结构是一种新型的空间结构，它是在板锥单元系和常规的双层网壳结构的基础上组合形成的一种新型结构的形式，具有良好的技术经济效益和建筑视觉效果，本文首先对这类结构的形式和构成进行了分析，然后用有限元法编制了相应的程序对其进行了受力性能分析。     

工字型钢梁双重非线性分析

利用通用分析软件ANSYS分别建立＂工＂字型梁的梁单元和壳单元模型,对比分析了静力作用下,两种模型的应力和位移,发现采用壳单元模型的计算结果低于梁单元模型的分析结果,壳单元模型能更好地模拟结构的失稳破坏。     

几何非线性有限元分析中一种广义协调平板型四边形壳元

本文在文献[1][2]的基础上构造了一种广义协调的任意四边形平板型壳元，在Total－Lagrange坐标下，推导了该单元在板壳结构几何非线性有限元分析中全部有限元列式。算例表明，该单元具有自由度少、精度高、收敛快、适应性强等优点，适用于一些复杂形状板壳结构的几何非线性有限元分析。     

板锥网壳结构的广义协调元分析

板锥网壳结构是一种新型的空间结构,它是在板锥单元和常规的双层网壳结构的基础上,组合形成的一种新型半连续化、半格构化的结构形式。本在对这类结构有限元法分析的基础上,应用广义协调元法的基本思想,对这类结构进行了分析,给出了这类结构广义协调元分析的基本公式。分析表明,广义协调元法适宜于板锥网壳结构的受力性能分析,广义协调元固有的简便、高效和可靠的特性,将会使结构分析得到更为可信和可靠的结论。     

Postbuckling analysis of cross-ply laminated cylindrical shell panels under parabolic mechanical edge loading

Postbuckling equilibrium paths of simply supported cross-ply laminated cylindrical shell panels subjected to non-uniform (parabolic) inplane loads are traced in this paper. Love's shell theory with higher order shear deformation theory and von Kármán nonlinear strain–displacement relations are used in the mathematical formulation of the problem. In the first step, the plate membrane problem is solved to evaluate the stress distribution within the prebuckling range as the applied inplane edge load is non-uniform. The governing shell panel postbuckling equations are derived from the principle of minimum total potential energy using the above stress distributions. Adopting multi-term Galerkin's approximation, the governing equations are reduced into a set of non-linear algebraic equations. Newton–Raphson method in conjunction with Riks approach is employed to plot the postbuckling paths through limit points. Numerical results are presented for symmetric (0/90/0) crossply laminated cylindrical shell panels under parabolic inplane load, lateral distributed load and initial imperfections. Limit loads and snap-through behavior of shell panels are studied.     

Numerical investigation on ultimate shear strength of steel plate shear walls

Ultimate shear strength of steel plate shear walls, SPSW, was conventionally computed as the sum of base shear supported by in-fill plate and boundary frame elements. The base shear supported by the in-fill plate was computed assuming that it was fully yielded after buckling whereas the base shear supported by the boundary frame elements was computed by plastic analysis assuming uniform yielding mechanism. In this paper the ultimate shear strength of SPSW was investigated by the finite element method. A detailed three-dimensional finite element model was established using ANSYS software at which the in-fill plate and the boundary frame elements were modeled using finite strain iso-parametric shell elements. The analysis included material and geometric non-linearities. Numerical results obtained from cyclic and pushover loading of SPSWs were verified by comparison to test results published in the literature. A comprehensive parametric analysis was conducted to assess the effect of geometric and material parameters of the wall on its ultimate shear strength. Discrepancies between numerical results and conventional theory were attributed to interaction of in-fill plate and boundary frame elements at ultimate load. When the flexural rigidity of boundary frame elements decreased, the in-fill plate did not achieve full yield strength. On the other hand, the base shear supported by boundary frame elements increased when thicker in-fill plates were utilized. Numerical results were used to update the theoretical expression of ultimate shear strength of SPSWs. The proposed expression was assessed by comparison to test results published in the literature.     

国际期刊导读

受压或受弯开孔薄板的弹性屈曲性能 摘要：开发、论证并总结了一组闭合公式,可以估算在弯矩或压力作用下,板的单个或多个开孔对其临界弹性屈曲应力的影响。公式适用于四边简支和三边简支的板（这在设计中又称为加劲板和非加劲板）。由于有限壳单元特征值屈曲分析需要运用商业有限元程序,而这些程序又不是专为结构分析而开发的,不能很方便地用于工程设计,所以可以采用这些公式作为这种屈曲分析方法的简化替代。     

Triangular higher-order element for better prediction of stress resultants and stresses in plated and shell structures

Although they furnish accurate displacements, conventional displacement-based lower order finite elements fail to predict accurate stress resultants and stresses in certain classes of plate and shell problems that involve free edges, steep stress gradients and singularities. In order to tackle such problems, a triangular higher-order shell element based on the nodal basis approach has been developed. The nodes of the element are located at optimal points and its more superior shape functions derived from orthogonal Proriol polynomials. To illustrate the improved performance of the higher-order element as compared to commonly used lower order shell elements in predicting the variations of stress resultants and stresses, three example problems involving a simply supported skew plate, a corner supported square plate, and a clamped cylindrical shell are solved. The stress resultants and the stresses furnished by the higher-order element for the problems considered are found to be accurate with the satisfaction of the natural boundary conditions and devoid of any oscillations. When compared to lower order elements, the higher-order element requires a simple mesh design and lesser degrees of freedom resulting in a considerable reduction in the computational effort, especially for large scale nonlinear analysis.     

The transition from thin plates to moderately thick plates by using finite element analysis and the shear locking problem

Two simple plate bending elements, based on Mindlin theory for analysis of both moderately thick and thin plates, are presented in this paper. These elements have either four nodes or eight nodes with 12 and 24 DOF, respectively. To illustrate the accuracy of these finite elements named as TURE12 and TURE24, several numerical examples of displacements and stresses for both thin and moderately thick plate bending problems are presented and discussed with a range of finite element meshes and thickness-to-plate length ratios. In addition, the bending and shearing behaviours of a Mindlin plate are analyzed with respect to shear locking. In order to test the shear locking, the results obtained from the Mindlin plate analysis using 4- or 8-noded elements with full, reduced, and selective reduced integration are compared with the exact classical thin plate solution.     

Interaction between laser-welded web-core sandwich deck plate and girder under bending loads

Present paper investigates the interaction between laser-welded web-core sandwich deck plate and supporting girder under bending loads. The study is based on two linear-elastic Finite Element (FE) approaches, i.e. one using beam elements to model the girder and shell elements to model the homogenized web-core sandwich plate. With this approach the obtained FE model is considerably smaller than in the case of modeling the full, periodic, 3D geometry with shell elements. The FE solution results in stress resultants for beam and shell elements. These stress resultants do not describe accurately the periodic stress response of the sandwich plate or shear stress distribution at girder web. Therefore, the paper utilizes analytical methods to calculate these stress components from the obtained Finite Element solution. The second computational approach is based on modeling the actual 3D topology with shell elements. The two approaches are shown to be in very good agreement. The investigation shows that the effective flange width of the sandwich is different for the top and bottom face plates indicating that the interaction is different for these face plates. The present study also shows that this difference between the two faces depends strongly on the orientation of the web plates of the sandwich with respect to girder axis and the stiffness of the girder. The investigation also shows that the normal stress response in bending is dominated by the interaction between the sandwich plate and the girder, but also by the shear-induced normal stresses at the outer surface of the plate.     

Vibration and elastic instability of thin-walled domes under uniform external pressure

Two thin-walled varying meridional curvature axisymmetric shell elements are presented for the vibration and elastic instability of thin-walled hemi-ellipsoidal domes under uniform external pressure. The theoretical analysis is an extension of previous work carried out by the author, where for the two elements presented in the present report, a cubic and a quadratic variation was assumed for the meridional and the circumferential displacements along the meridian of these elements. In the previous study, only linear variations were assumed for the meridional and circumferential displacements along the meridian of these elements. Comparisons were made between experiment and theory for both buckling and vibration of hemi-ellipsoidal shell domes, which varied from very flat oblate vessels to very long prolate vessels. In general, agreement between experiment and theory was good for the hemi-spherical dome and the prolate vessels, but not very good for the fat oblate vessels. Additionally, the two new elements gave poorer results than the original simpler element for the cantilever mode of vibration, but better results for the lobar modes of vibration.     

Numerical solution of curved pipes submitted to in-plane loading conditions

An alternative formulation to current meshes dealing with finite shell elements is presented to solve the problem of stress analysis of curved pipes subjected to in-plane bending forces. The solution is based on finite curved elements, where displacements are defined from a total set of trigonometric functions or a fifth-order polynomial, combined with Fourier series. Global shell displacements are achieved through the one associated with curved arch bending and the other referred to the toroidal thin-walled shell distortion. Beam-type displacement and in-plane rotation are uncoupled and separately formulated, using trigonometric shape functions, as in Timoshenko or Mindlin beam theory. To build up the solution, a simple deformation model was adopted, based on the semi-membrane concept of the doubly curved shells behaviour. Several studies are presented and compared with experimental and numerical analyses reported by other authors.     

基于扁壳理论的半解析有限条法用于冷弯构件的屈曲分析

提出了一种基于Marguerre的扁壳理论的有限条法。现有的大多数半解析有限条法都是基于基尔霍夫和Mindlin的板理论。在本文中,该板理论可以被视为扁壳理论的特殊情况。数值分析结果证实了基于扁壳理论的有限条法的有效性。     

Strength analysis of concrete-filled thin-walled steel box columns

An elasto-plastic finite displacement analysis of concrete-filled thin-walled steel stub-columns of box shape is presented. In the analysis, a hardening-softening model is used to describe rationally the elasto-plastic behavior of concrete. A contact element for the interface combined with a bilinear constrained shell element for the plate and a cubic element for the concrete is employed. Both initial geometrical imperfections and residual stresses are also considered in the plate elements. Analytical results are then compared with previous experimental results. In addition, a parmetric study is conducted to investigate the effects of various parameters such as the plate aspect ratio, the plate width-thickness ratio and the concrete strength on the column strength. Finally, a design formula for concrete-filled stub-columns in compression is proposed.