A direct stiffness analysis of a composite beam with partial interaction

The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd.     

Application of piece‐wise linear weight functions for 2D 8‐node quadrilateral element in contact problems

The present study is a continuation of our previous work with the aim to reduce problems caused by standard higher order elements in contact problems. The difficulties can be attributed to the inherent property of the Galerkin method which gives uneven distributions of nodal forces resulting in oscillating contact pressures. The proposed remedy is use of piece‐wise linear weight functions. The methods to establish stiffness and/or mass matrix for 8‐node quadrilateral element in 2D are presented, i.e. the condensing and direct procedures. The energy and nodal displacement error norms are also checked to establish the convergence ratio. Interpretation of calculated contact pressures is discussed. Two new 2D 8‐node quadrilateral elements, QUAD8C and QUAD8D, are derived and tested in many examples, which show their good performance in contact problems. Copyright © 2004 John Wiley & Sons, Ltd.     

筒体结构连续化模型的弹性动力时程分析

本文用连续化模型对高层筒体结构在地震作用下的动力时程反应进行分析．     

聚四氢呋喃及其下游产品的开发应用

本文论述了聚四氢呋喃技术进展、氨纶弹性纤维发展现状和国内外聚四氢呋喃产能和需求。     

高速微粒携基因侵入植物细胞的速度条件

本文围绕基因枪技术中用高速微粒向植物细胞中导入外源基因的速度条件，分析了其中的三个动力学过程：发射宏弹、加速微弹、侵入细胞．提出了气动撞击发射式基因枪中弹簧刚度应满足的条件；得到了一种用理论分析与试验测试相结合确定微弹出射速度的方法；找到了微弹侵入植物细胞的最小速度条件。从而为基因枪的设计提供了理论依据。     

Laminated beams subjected to transverse load

A simple elastic solution has been developed for predicting the shear stress distribution in a laminated beam subjected to a variety of transverse loading conditions. Photoelastic tests on composite models involving a single bonding layer have been used to validate the theory, and also to comment upon the significance of these results in interpreting the interlaminar shear strength and bending modulus of the simplest form of laminated strip.     

特低渗透油藏驱替及开采特征的影响因素

应用非达西渗流理论和非线性弹性渗流理论，分析了影响特低渗透油藏驱替及开采特征的主要因素。研究结果表明，启动压力梯度和毛细管压力是影响特低渗透油藏驱替特征的主要因素；而影响特低渗透油藏开采特征的主要因素是储层的弹塑性，即储层的压力敏感性。在特低渗透油藏的开发中应适当缩小注采井距提高驱替压力梯度，采取整体压裂措施减小启动压力梯度，通过气驱或活性水驱油减小毛细管压力，及时补充地层能量以减少压力敏感性对储层的伤害。     

A note on stress-constrained truss topology optimization

The purpose of this brief note is to demonstrate that general-purpose optimization methods and codes should not be discarded when dealing with stress-constrained truss topology optimization. By using a disaggregated formulation of the considered problem, such methods may find also “singular optima”, without using perturbation techniques like the ε-relaxed approach. Received February 19, 2002     

CZF90测井中子发生器使用寿命浅谈

Ｃ／Ｏ测井中采用同步测量技术来分析非弹性γ与俘获γ，但在一些ＭＳＩ Ｃ／Ｏ测井中发现非弹性γ的一小部分或一大部分超前于非弹性门而进入俘获门，我们把这一问题叫做“错位”。“错位”使得Ｃ／Ｏ的ＣＩ值不正常，测井曲线不合格。这样的仪器不能用来测井。吉林油田测井公司碳氧比维修班成功地解决了Ｃ／Ｏ仪器“错位”等技术难题，在该油田所使用的ＣＺＦ９０－９４－０９发生器已测井８８口，累计打靶时间２３０ｈ，并且至今     

非对称复合材料层板在面内载荷作用下的非线性横向变形或屈曲

本文利用广义富里叶级数法对非对称复合材料层板在面内载荷作用下的非线性横向变形或屈曲问题进行了分析。文中主要研究了四边简支边界条件下,非对称层板的铺层方式和面内载荷形式对横向变形的影响。通过求解非线性控制方程得到了层板的载荷—挠度曲线或特殊情况下的后屈曲平衡曲线。计算结果表明,对于大多数非对称复合材料层板在面内载荷作用下所产生的是横向变形问题,而不是分叉屈曲问题。