动力刚度计算方法-"盐溶”法-的改进

本文首先讨论了采用盐溶法（damping-solvent extraction method)争动力刚度时，在某些频率点（奇点）产生误差的原因；提出一种多次逼近的改进办法，提高了计算精度。在一般情况下，动力刚度的奇点是未知的。本文建议的逼近技术可用于校核这一方法所获得的结果。     

基础动力刚度的精确数值解及集中参数模型

土－结构相互作用分析的关键是建立以土－结构界面定义的无限半空间的动力刚度矩阵。本文介绍了一种求解半无限地基动力刚度的新方法，通过两个算例验证了该方法的精度，并给出了一种利用频域刚性基础动力刚度计算基础时域荷载响应的实用方法，该研究为刚性基础设计提供了一种新的，可靠的理论方法。     

沉箱与地基相互作用在浪冲击力下的动力分析

提出了6节点映射无限元，4节点双向映射无限元与有限元耦合，分析了一海岸防波堤在浪冲击力的动力特性。结果表明，用这一模型来离散无限域的远场，特别是研究动力问题，具有较好的经济性和可靠性。     

结构-地基相互作用体系动力特性参数的简化计算方法

本文首先介绍了几种计算结构－地基相互作用体系动力特性的简化方法，并用振动台模型试验的数据资料进行计算分析，讨论了各方法的局限性；在此基础上，提出了一种改进的简化计算方法。在该方法中，主要改进是合理考虑了桩基对体系刚度的贡献。     

土—结构动力相互作用几个实际应用问题

对上－结构动力相互作用的效应和分析方法作了简要的回顾,对土－结构动力相互作用几个实际应用问题进行了分析讨论。     

机器基础动力相互作用的研究

本文分别对单台、双台、联合基础与地基土相互作用体系在扰力作用下的振动特性进行了研究。在计算中考虑了外围土体的影响。通过算例,得到了单台、双台、联合基础的一些振动规律。     

高耸塔体结构抗震设计的动力相互作用模型研究

基于高耸塔体结构多质点简化力学模型,以动力方程附加项的形式提出一种简便的地基边界统一处理模式,用于对比刚性地基、伏格特弹性地基及集总参数无限地基的影响。结合工程实例,以时程法探讨结构的抗震性能,结果显示伏格特地基条件给出了结构动力响应的上界,无限地基条件则给出了下界,可明确为结构的响应区间,保证必要的安全储备。而在简便材料力学模型的基础上,探讨复杂的结构-地基-水体动力相互作用,利于工程人员接受,也是传统简便设计方法向已考虑复杂因素为特征的新设计方法过渡的体现。     

结构刚度矩阵的一种反演方法

本文在总结线弹性结构则度矩阵识别方法的基础上，提出了一种新的反演刚度矩阵的方法，即利用实测的结构各阶固有频率和各阶振型数据，以刚度矩阵中的各元素作为未矩数，代入特征值方程，逐一解出刚度矩阵内各元素。     

三维层状场地的精确动力刚度矩阵及格林函数

本文对Wolf二维层状场地精确动力刚度矩阵进行推广,给出了三维层状场地的精确动力刚度矩阵。刚度矩阵具有对称的特点,且因刚度矩阵是精确的,计算结果不受土层单元厚度的影响,可以大大提高计算效率。文中对刚度矩阵进行了数值验证。利用三维层状场地动力刚度矩阵,计算分析了基岩上单一土层场地的动力响应。最后作为动力刚度矩阵的另一重要应用,给出了表面或埋置矩形均布荷载或集中荷载的动力格林函数计算方法。     

Dynamic stiffness of unbounded medium based on damping-solvent extraction

In the damping-solvent extraction method, to calculate the dynamic-stiffness matrix of an unbounded medium, a finite region of the medium, adjacent to the structure is analysed in the first step, whereby hysteretic material damping is introduced artificially as a solvent. This leads to the dynamic-stiffness matrix of the damped bounded medium, which is assumed in the second step to be equal to that of the damped unbounded medium. In the third step, the effect of the material damping on the dynamic-stiffness matrix is eliminated, i.e. the damping solvent is extracted, resulting in the dynamic-stiffness matrix of the unbounded medium. The damping-solvent extraction method permits an efficient calculation of the dynamic-stiffness matrix of an unbounded medium by analysing the adjacent bounded medium only, which exhibits the same dynamic characteristics as the (bounded) structure. The familiar standard finite-element method is sufficient for the analysis and the hysteretic damping is introduced by multiplying the elastic moduli by 1 + 2i£. The introduced hysteretic material damping, the solvent, is extracted at the end of the analysis for each coefficient of the dynamic-stiffness matrix and for each frequency independently of the others by a very concise equation based on a Taylor expansion. The method is evaluated thoroughly for dynamic soil-structure interaction and for seismic reservoir-dam interaction using stringent simple cases with analytical solutions available and is also applied to practical examples, by calculating the dynamic-stiffness matrix of a semi-infinite wedge and an embedded foundation.     

Dynamic stiffness of foundation embedded in layered halfspace based on wave propagation in cones

An Erratum has been published for this article in Earthquake Engineering & Structural Dynamics 33(6) 2004, 793. The dynamic stiffness of a foundation embedded in a multiple‐layered halfspace is calculated postulating one‐dimensional wave propagation in cone segments. In this strength‐of‐materials approach the sectional property of the cone segment increases in the direction of wave propagation. Reflections and refractions with waves propagating in corresponding cone segments occur at layer interfaces. Compared to rigorous procedures the novel method based on cone segments is easy to apply, provides conceptual clarity and physical insight in the wave propagation mechanisms. This method postulating one‐dimensional wave propagation in cone segments with reflections and refractions at layer interfaces is evaluated, calculating the dynamic stiffness of a foundation embedded in a multiple‐layered halfspace. For sites resting on a flexible halfspace and fixed at the base, engineering accuracy (deviation of ±20%) is achieved for all degrees of freedom with a vast parameter variation. The behaviour below the cut‐off frequency in an undamped site fixed at its base is also reliably predicted. The accuracy is, in general, better than for the method based on cone frustums, which can lead to negative damping. Copyright © 2003 John Wiley & Sons, Ltd.     

Dynamic stiffness of parabolic cables

A closed-form expression for the in-plane horizontal stiffness of a viscously damped, uniform, inclined cable in harmonic motion is presented. The cable is presumed to be deflected in a parabolic profile at its position of static equilibrium, and all dynamic displacements are assumed to be small. The stiffness expression is valid for an arbitrary angle of inclination of the cable chord in the range between zero and 90 degrees. In addition, a simpler solution, valid over a narrower range of the parameters, is included and its accuracy examined. Comprehensive numerical data are presented and discussed, with particular emphasis on explaining the physical significance of the results and providing insight into the action of the cable and into the parameters that control it. Finally, a simple, single-degree-of-freedom model is proposed which reproduces with good accuracy the salient features of the response of the prototype cable over a wide range of conditions.     

Dynamic similarity in erosional processes

Summary A study is made of the dynamic similarity conditions obtaining in a variety of erosional processes. The pertinent equations for each type of process are written in dimensionless form; the similarity conditions can then easily be deduced. The processes treated are: raindrop action, slope evolution and river erosion.     

Dynamic stiffness of rigid rectangular foundations on the half-space

The dynamic soil–structure interaction of a rigid rectangular foundation with the subsoil represents a mixed-boundary value problem. This problem is formulated in terms of a system of coupled Fredholm integral equations of the first kind. The subsoil is modelled by a homogeneous, linear-elastic and isotropic half-space which is perfectly bonded to the rigid, rectangular foundation. An approximate solution for the resultant loads between the foundation and the half-space due to a unit forced displacement or rotation is obtained using the Bubnov–Galerkin method. Using this method the displacement boundary value conditions are exactly satisfied and the contact stress distributions between the foundation and the half-space are approximated by series expansions of Chebyshev polynomials. This method provides a simple means of studying the soil-structure interaction of rectangular foundations with different inertia properties.     

Dynamic stiffness matrices for two circular foundations

A systematic procedure is presented for generating dynamic stiffness matrices for two independent circular foundations on an elastic half-space medium. With the technique reported in References 1–3, the analytic solution of three-dimensional (3D) wave equations satisfying the prescribed traction due to the vibration of one circular foundation can be found. Since there are two analytic solutions for two prescribed tractions due to the vibrations of two circular foundations, the principle of superposition must be used to obtain the total solution. The interaction stresses (prescribed tractions) are assumed to be piecewise linear in the r-directions of both cylindrical co-ordinates for the two circular foundations. Then, the variational principle and the reciprocal theorem are employed to generate the dynamic stiffness matrices for the two foundations. In the process of employing the variational principle, a co-ordinate transformation matrix between two cylindrical co-ordinate systems is introduced. Some numerical results of dynamic stiffness matrices for the interaction of two identical rigid circular foundations are presented in order to show the effectiveness and efficiency of the present method, and some elaborations for its future extensions are also discussed.     

基于相似系统理论的地震危险性分析

不同地区地震危险性的产生机制具有相似性，地震危险性可由若干地震活动指标（要素）加以描述，因此，这些指标特性的相似性反映了地震危险性大小的差异。为此，给出了一种计算相似度的新方法，并用这一方面对若干地区的地震危险性进行了评价，结果令人满意。     

Dynamic stiffness of deep foundations with inclined piles

The influence of inclined piles on the dynamic response of deep foundations and superstructures is still not well understood and needs further research. For this reason, impedance functions of deep foundations with inclined piles, obtained numerically from a boundary element–finite element coupling model, are provided in this paper. More precisely, vertical, horizontal, rocking and horizontal–rocking crossed dynamic stiffness and damping functions of single inclined piles and 2 × 2 and 3 × 3 pile groups with battered elements are presented in a set of plots. The soil is assumed to be a homogeneous viscoelastic isotropic half‐space and the piles are modeled as elastic compressible Euler–Bernoulli beams. The results for different pile group configurations, pile–soil stiffness ratios and rake angles are presented. Copyright © 2010 John Wiley & Sons, Ltd.