嵌在倾斜半空间的轴向受力刚性桩的线载荷积分方程法的分析

嵌在表面水平的弹性半空间的桩或杆他人已做了许多工作。但嵌在表面倾斜的半空间的桩或杆与半空间表面夹角非直角情形的分析则未见到。在基楚工程中常遇见这类情形,如斜坡的桩,或码头,桥墩,海洋结构等的斜桩等。这类轴向受力的三维非轴对称问题宜用作者提出的线载荷积分方程法来分析。本短文分析嵌在小斜度弹性半空间轴向受力刚性桩的铅垂位移(沉陷)。所用的假设是:半空间是均匀各向同性的;轴向受力后桩仍保持铅垂状态;桩为中等长度(20≤L/D≤80,见图1)。为计算简便,只考虑桩一土表面上x_1=0线上的点的铅垂方向位移的相容性。据文献[7],忽略桩的径向位移的相容性对于计算的沉陷值的影响是不大的。图1表示本问题及其座标;图2为本文所用的基本虚载荷。     

Analysis of ellipsoid compressed by two axial concentrated forces at two ends

Integral equation method and photoelastic experiment are used for the stress analysis of an axial compressive ellipsoid. Let the concentrated forces and the centers of compression, with symmetrical unknown intensive functions X₁(c)=X₁(–c) and X₂(c)=X₂(–c) respectively, be distributed symmetrically to =0 plane along the axis z(=–c) in [a,) and [–a,–) of the elastic space, in addition to a pair of equal and opposite axial forces acting on z=a and z=–a. We can reduce the problem of an axial compressive ellipsoid to two coupled Fredholm integral equations of the first kind. Furthermore, numerical calculation is then made. Two photo-elastic models of ellipsoid were analysed by Freezing and Cutting method, and the results, in which ₂ is quite nearly to those obtained by integral equation method, had been used in the analysis of the data of compressive rock specimens.     

一类带约束的二维弱奇异积分方程的解*

本文找出二维弱奇异第一类积分方程作用着约束方程的解p.p=p(r,θ)={2/[π2k(φ₀]}√F(r,θ)-c_*(0≤r≤r_*)其中是(s,φ)原点在M(r,θ)的局部极坐标,(r,θ)是原点在O(0,0)的总体极坐标:k和F是给出的连续函数;φ₀是一常数;F(_*,θ)=c_*(常数)是研究域Q的边界围线。所用方法可推广到三维情形。     

Properties of a half space including a twisted shaft of revolution

The properties of an elastic half space including a partly embedded twisting shaft of revolution are studied. Without knowing the exact solution of the torsion problem of a given embedded shaft, these properties can indicate some features of the displacement or stress field of the half space and can sometimes be used for checking a numerical solution. An example for checking the correct stress distribution on surfaces of twisted rigid cylindrical shaft embedded in a half space is given. This Work was Supported by the National Science Foundation of China.     

Asymmetric dynamic instability of axisymmetric polar dimpling of thin shallow spherical shells

If the parameter ², which measures the thickness-to-rise of the shell, is small, the axisymmetric polar dimpling of shallow spherical shell due to quadratic pressure distribution is dynamic instability, i.e., a small perturbation can change it to an asymmetric polar dimple mode. In two cases, the problem can be reduced to an eigenvalue problem Tw_n=c_n w_n, where T can approximately be reduced to a Sturm-Liouville operator if ²1. The existence of at least one real eigenvalue of T, which means that the axisymmetric polar dimpling is dynamically unstable, is proved by spectral theorem or Hilbert theorem. Furthermore, an eigenfunction, which represents one of the asymmetric modes of the unstable dimple shell, belonging to an eigenvalue of T is found.The Project Supported by National Natural Science Foundation of China. This paper was accepted to present at ICTAM 88(Grenoble).