多自应力模态索穹顶结构的几何构造分析

索穹顶结构是发展和推广Fuller张拉整体结构思想后唯一实现的一种新型大跨空间结构,它的几何构造分析是一项非常重要的工作。本文在对一般空间杆件体系的分类、自应力模态和机构位移模态研究的基础上,从索穹顶结构特有的杆件拓扑关系入手,提出了单位整体可行预应力这一新概念,并最终解决了多自应力模态下该体系稳定性判定问题;通过对若干类型索穹顶结构的几何构造分析,得出了一些对结构设计有用的结论。     

横向流激励下绳索的扩张和回转运动

基于横向流激励下绳索的微段受力分析,建立了横向流体对绳索作用力的解析表达.借助坐标变换,将绳索的运动表示为扩张和回转两部分.在此基础上,分析了小垂跨比绳索的流激振动问题,对无伸张态临界流速、平衡解稳定性、重力对绳索运动的影响等问题进行了讨论.     

Nonlinear vibration analysis of viscoelastic cable with small sag

Both the inplane and out-of-plane transverse vibrations of a viscoelastic cable subjected to an initial stress distributing uniform on the cross section are studied. The constitution of the cable material is assumed to be of the hereditary integral type. The partial differential-integral equations of motion are derived first. Then by applying Galerkin's method, the governing equations are reduced to a set of second-order nonlinear differential-integral equations which are solved by finite difference numerical integration procedures. Finally, the effects of the viscosity parameter and the elastic parameter on the transient amplitudes of the first mode are investigated by numerical simulation. Project supported by the National Natural Science Foundation of China (No. 59635140) and the National Postdoctoral Foundation of China.     

小垂度粘弹性索非线性响应及振动主动控制

研究具有初始应力的小垂度粘弹性索的非线性动态响应及振动主动控制。在假定索材料的本构关系为一般微分本构类型的基础上,建立小垂度粘弹性索的运动微分方程;应用Galerkin方法将其转化为可用Runge-Kutta数值积分方法求解的一系列三阶非线性常微分方程。在仅考虑面内的横向振动及忽略非线性的情况下得到了连续状态空间中的状态方程,将状态方程离散为差分方程形式,并用矩阵指数来逐步近似状态转移矩阵;基于二次性能指标的最小化得到了最优的控制力与状态向量。最后通过数值仿真研究说明了粘性参数对索动态响应的影响。     

Dynamic analysis of beam-cable coupled systems using Chebyshev spectral element method

The dynamic characteristics of a beam–cable coupled system are investigated using an improved Chebyshev spectral element method in order to observe the effects of adding cables on the beam. The system is modeled as a double Timoshenko beam system interconnected by discrete springs. Utilizing Chebyshev series expansion and meshing the system according to the locations of its connections,numerical results of the natural frequencies and mode shapes are obtained using only a few elements, and the results are validated by comparing them with the results of a finiteelement method. Then the effects of the cable parameters and layout of connections on the natural frequencies and mode shapes of a fixed-pinned beam are studied. The results show that the modes of a beam–cable coupled system can be classified into two types, beam mode and cable mode, according to the dominant deformation. To avoid undesirable vibrations of the cable, its parameters should be controlled in a reasonable range, or the layout of the connections should be optimized.     

Establishment of several differential equations for the case of variable solid thermal conductivity

In this paper we propose that the solid thermal conductivity varies first with the space coordinate according to a linear law and then with an exponential one. In this way we have set up six differential equations successfully; and for variable density, variable specific heat as well as variable conductivity, another six differential equations have also been deduced.     

Pansystems research on a type of fixed subsets

The present paper continues the pansystems research on fixed studies. Under the pansystems framework it gives the existence critertion of I-type fixed and the theorems about the relations between the classes of reflexive and equation one and fixed subsets: introdaces the concept of fixpoints of binary relations extstence theorems about fixpoints for a kind of panweighted netwest.     

Morphological study of aging phenomena in XLPE by TEM technique

The long-term dielectric performance of underground power cable XLPE (cross-linked polyethylene) insulation suffers from poorly understood aging phenomena. A study of the morphological modifications of XLPE due to electrical aging may provide insight for a better understanding of aging mechanisms. The TEM technique has been used to study the XLPE morphology of unaged, laboratory-aged, and field-aged cable samples. A suitable image contrast enhancing and a stabilization of radiation damage were both successfully achieved by staining the sections with ruthenium tetroxide (RuO₄), as individual XLPE lamellae were neatly and reproducibly resolved. Image analysis was used to help in the determination of any aging-induced morphological changes. XLPE samples from an unaged cable (D1) has been exposed to a low-energy electron beam, in an attempt to simulate certain conditions thought to occur in electric field-stressed dielectrics. © 1996 John Wiley & Sons, Inc.     

在中支座可滑动的两跨连续索的静力分析

基于非线性弹性理论,从单索的平衡出发,在索元的无应力长度已知情况下,提出了两跨连续索在中间节点滑移的初始平衡位置确定及均布荷载作用下的静力响应分析方法,建立了其非缄性计算的基本理论、公式和求解方法,并进行了实例计算。     

悬索结构非线性分析的滑移索单元法

本文提出了一种悬索结构存在在滑移单元时的非线性计算方法,利用文献（１）提出的五节点曲线索单元有限元基本方程,建立了滑移单元非线性分析的计算理论、方法及公式,并进行了实例计算,结果表明,本文方法是行之有效的,可供悬索结构设计、施工时参考。