Shallow shell finite element for the large deflection geometrically nonlinear analysis of shells and plates

An investigation into the large deflection, geometrically nonlinear behaviour of shells is carried out in the present paper. The finite element method is used in conjunction with linearised incrementation and the Newton-Raphson iterative technique.The finite element used is based on independent strain assumptions insofar as it is allowed by the compatibility equations. Strain-displacement relationships based on shallow shell formulation are used and applied to an element having three principal curvatures. The resulting element has the only essential external degrees of freedom, satisfies the exact requirement of strain free rigid body modes of displacements and can be used for the representation of cylindrical, spherical and hyperbolic paraboloid shells.Complex load-deflection curves are obtained for cylindrical and spherical shells by incrementing loads as well as deflections. The relative behaviour of cylindrical and spherical panels having the same overall dimensions are also discussed in terms of stiffness, instability and snap-through phenomena.     

拱结构空间几何非线性分析的曲梁单元

利用势能原理和插值函数推导了一种供结构空间几何非线性分析的曲梁单元。采用固定Lagrange坐标系和Newton-Raphson求解法。使用本文的方法与其他方法相比，该方法将轴向应变的非线性部分取平均值，提高了结果的精确性，而且单元数量大大减少。     

箱梁桥自振分析的非协调实体退化壳元法

桥梁结构的自振特性对研究其在风荷载和地震荷载作用下的动力响应具有重要意义,其分析精度取决于结构质量和刚度分布特性的准确计算。根据质量等效原理推导了非协调实体退化板壳元的一致质量矩阵,并采用逆迭代法求解了箱梁桥的固有频率和振型。实体退化板壳元可精确描述箱梁桥质量分布,便于同实体单元连接,对不同板厚的箱梁桥均适用。非协调位移的引入使其更适合描述箱梁桥各构件的变形特性。算例表明:单元可显著提高箱梁桥动力特性分析的效率,可获得满意的计算精度。     

Buckling and geometrically nonlinear analysis of frames using one element/member

The commonly used Hermite cubic element represents the solution for the linear differential equilibrium equation of a straight beam under the Bernoulli hypothesis. However, this element grossly over-estimates the buckling load of a strut when only a single element is used to model a member. This paper presents a simple higher-order element capable of predicting the buckling load of a strut with various boundary conditions by using only a single element for each member. It is found that a direct introduction of a displacement degree of freedom to the mid-length of the cubic element will improve significantly its performance in a nonlinear analysis. The computational efficiency and formulation of this new element are very similar to those for the cubic element in spite of their discrepancies in accuracy.     

将弧长法应用于结构的几何非线性有限元分析

首先介绍了弧长法的发展及基本理论，随后根据笔者的研究，对其中的几个问题提出了相应的参考意见，最后给出了几个算例。     

组合肋壳几何非线性分析

提出了一种球面组合肋壳截面形式,基于非线性有限元理论,采用空间梁单元和等厚曲边壳单元,考虑空间结构的几何非线性影响,推导了T．L坐标系下组合肋壳非线性单元刚度矩阵。分别讨论了在不同矢跨比、不同荷载作用、不同边界条件下组合肋壳的极限承载力和失稳形态。由大量算例得到了非线性极限承载力与线性极限承载力的比值为0．66及不同情况下结构承载力变化趋势,组合肋壳的极限承载力比混凝土壳承载力提高20％。     

An improved treatment of mixed interpolation functions in eight-node assumed natural strain shell element for vibration analysis

In this article, we investigate the vibration analysis of plates and shells, using an eight-node shell element that allows for the effects of transverse shear deformation and rotary inertia. The natural frequencies of plates and shells are presented, and the forced vibration analysis of plates and shells subjected to arbitrary loading is carried out. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. To improve the eight-node shell element for free and forced vibration analysis, a new combination of sampling points for assumed natural strain method was applied. The refined first-order shear deformation theory based on Reissner–Mindlin theory, which directly addresses the transverse shear deformation without a shear correction factor, is adopted for the development of a new eight-node assumed strain shell element with rotary inertia effect. In order to validate the finite element numerical solutions, the reference solutions of plates based on the first-order shear deformation theory are presented. Results of the present theory show good agreement with the reference solutions. In addition, the effect of damping is investigated on the forced vibration analysis of plates and shells.     

Quadrilateral shell element for rotational shells

A doubly curved shell element of quadrilateral shape which is suitable for the analyses of rotational shells is derived. Geometry is defined in a polar coordinate system while displacements are specified in cartesian coordinates. The element is a C° element which includes transverse shear deformations and is intended for modelling shells which follow a circular curve form in one direction.     

Beam and shell element model for advanced analysis of steel structural members

Plastic zone method of advanced analysis, which uses shell elements to model the entire structure, is the most accurate method available to predict the ultimate strength and behavior of steel frames. The disadvantage of such full shell plastic zone models is that it is computationally expensive and hence its use is limited to small structures. Beam elements in commercial finite element packages can model residual stress and capture spread of plasticity, but cannot model local buckling of plates that the member is made up of, which leads to unloading and failure in steel frames. A hybrid model using shell elements only in the regions vulnerable to elastic or inelastic local buckling and beam elements in other locations could overcome this limitation of full beam element model. The issues in using this hybrid model are, knowing a priori the location and length of the shell element region and connecting the beam and shell regions without any artificial stress concentrations or incompatible displacements. In this study, in addition to addressing these issues, the hybrid model is systematically evaluated by studying its performance in structural elements. It is seen that the hybrid model strength predictions has an average error of only 0.91% but requires on an average 83% less computational time when compared to the full shell plastic zone models.     

有限元节点自由度自动编号的简捷算法

阐述了单元定位向量是一种重要的数据结构，而节点自由度编号是形成单元定位向量的基础，介绍了一种简单高效的节点自由度编号算法，并用C语言正确地实现了该算法，以供参考借鉴。     

Thermal analysis of FRP chimneys using consistent laminated shell element

Due to their high corrosion and chemical resistance, fiber reinforced plastic (FRP) materials are increasingly being used in the construction of industrial chimneys. The design of a chimney is governed by wind loads as well as thermal loads resulting from the differences among the ambient, the operating and the curing temperatures. This study involves an investigation for the thermal stresses induced in angle-ply laminated FRP chimneys, using an in-house developed laminated shell element model. The finite element model is verified by performing thermal analysis of a number of plate and shell problems and comparing the results to those available in the literature. An extensive parametric study is then conducted using the shell element model to identify the parameters which significantly affect thermal stresses induced in FRP chimneys.The study indicates that the thermal stresses are only affected by the inclination of the lamina plies, the percentage of fibers content and the through thickness temperature distribution. Analyses also show that localized cracks in the direction perpendicular to the fibers are expected to occur due to the thermal loads. Finally, thermal stress values that can be used in the design of FRP chimneys, when cracking is considered, are presented as function of the through thickness temperature distributions.     

An oriented finite element model for shearwall analysis

Generally, loadbearing wall structures exhibit some regularity along the height. This regularity is exploited by cutting the building into typical slices. Each slice is obtained from the assemblage of basic structural units. The finite element method supports the calculation of the boundary stiffness matrices of these components which are stored in a user-defined structural library. Evaluation of structural response is based on a frontal process. The resulting program is runable on a minicomputer at low cost. Torsion of a model core illustrates the application of the method.     

导流隧洞进水口结构非线性有限元分析

对龙滩导流隧洞进水结构进行三维有限元分析,求得整体结构的应力、位移,并确定结构中的薄弱环节.针对薄弱环节进行二维有限元分析,确定钢筋应力,裂缝开展情况.在此基础上对现有的设计做出评价,并提出相应的建议.     

Evaluating rating factor for prestressed concrete girder bridges by nonlinear finite element analysis

This study provides a new approach to evaluate the load carrying capacity in rating factor (RF) of prestressed concrete I type girder bridges utilising nonlinear finite element (FE) analysis. RF has been conventionally calculated either by ultimate strength design (USD) or allowable stress design methods in terms of live load effects. This study introduces nonlinear FE analysis as a new approach to estimate the RF. In general, nonlinear FE analysis is considered as one of the most efficient methods to simulate structural behaviour. This method can also simulate a live load effect, which is very important for the load carrying capacity of structures. To apply nonlinear FE analysis, an FE live load constant was conceptually suggested to estimate the RF. On comparing the RF obtained via the conventional method of USD, it was found that the RF estimated by nonlinear FE analysis approach has almost the same value. Hence, the nonlinear finite element method-based RF methodology can be efficiently used to estimate the load carrying capacity of bridges.     

Geometric nonlinear analysis of thin plates by a refined nonlinear non-conforming triangular plate element

Based on the refined non-conforming element method for geometric nonlinear analysis, a refined nonlinear non-conforming triangular plate element is constructed using the Total Lagrangian (T.L.) and the Updated Lagrangian (U.L.) approach. The refined nonlinear non-conforming triangular plate element is based on the Allman’s triangular plane element with drilling degrees of freedom [1] and the refined non-conforming triangular plate element RT9 [2]. The element is used to analyze the geometric nonlinear behavior of plates and the numerical examples show that the refined non-conforming triangular plate element by the T.L. and U.L. approach can give satisfactory results. The computed results obtained from the T.L. and U.L. approach for the same numerical examples are somewhat different and the reasons for the difference of the computed results are given in detail in this paper.     

基于ANSYS的袋式除尘器壳体有限元分析

以某电厂袋式除尘器壳体为研究对象,利用ANSYS有限元分析软件进行了优化分析。对设计方案进行了详细计算分析,优化后的结构重量下降了15%以上,为袋式除尘器壳体设计和工程实践提供了可靠依据。     

半刚性端板连接节点有限元模拟分析

运用通用有限元软件ANSYS对试验进行非线性有限元分析,通过与试验结果进行对比,验证了有限元方法能够很好地分析计算端板半刚性连接钢框架的受力特性,可给试验研究和工程应用带来极大的方便。     

某土石坝静力非线性有限元分析

利用土石坝分析程序对某土石坝进行了静力非线性有限元分析,研究了在无水荷载的情况下,水平位移、竖向位移在坝体的分布情况,得出在只考虑重力作用下坝体及坝基的水平位移、竖向位移分布规律.     

混凝土非线性有限元分析中的网格尺寸效应

对混凝土结构进行非线性有限元分析时,存在网格尺寸效应.通过对简支梁划分不同网格尺寸进行分析,讨论了单元尺寸大小对荷载-位移关系及极限荷载等计算结果的影响,提出了把极限拉应变作为网格尺寸的函数,以保证混凝土开裂单位面积吸收的能量唯一,从而有效地消除混凝土非线性有限元分析中的网格尺寸效应.     

外包FRP壳钢筋混凝土梁的有限元分析

对外包FRP壳钢筋混凝土梁进行了有限元分析,并与试验结果进行对比分析,结果表明,有限元方法可较好的预测外包FRP壳钢筋混凝土梁的整体力学性能,但在荷载较大时,计算值与试验值偏差较大。