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31.
32.
主动隔振下固支薄板基础振动抑制的参数多目标优化 总被引:1,自引:0,他引:1
考虑动力设备-隔振器-薄板基础为复合主动隔振体系,并将薄板视为固支形式;以传递力作用在薄板基础上某点导纳为中间变量,在传递力、导纳、薄板振动峰值位移及峰值点距离影响因素分析的基础上,进行了系统耦联参数的多目标优化研究。优化算法采用较新的强度Pareto进化算法(SPEA2),该算法具有参数设置少、收敛速度快、寻优能力强及Pareto最优解分布均匀等优点。目标函数考虑为薄板振动的位移峰值及峰值点间的距离,目的是在有效控制薄板振动的同时,尽可能地使薄板趋于单峰值点振动,这对于板上附属操作设备及工作人员是有利的;最后,在最优参数的基础上对隔振器的安装位置进行讨论研究。数值计算结果表明,本文方法可有效地计算出隔振系统的最优参数,并为工业建筑及其他工程振动的最优隔振设计提供新思路。 相似文献
33.
海上箱筒型基础结构下沉到位后,舱内土体的受力变形可以看作是侧限压缩模型问题,上部荷载引起的侧壁摩擦力与土体应力之间的关系较为复杂。本文通过简化模型,列出了侧限压缩模型的平衡微分方程,分析了方程解析计算时存在的难点,结合摩擦应力边界条件的特点,构造函数迭代法对该方程进行数值求解,展示了计算的收敛过程,得到接触侧面上水平应力和土体表面位移的非线性分布规律,并将其结果与ABAQUS数值模拟结果进行了对比。结果表明,函数迭代法收敛速度较快,计算过程稳定,对其他存在变量耦合边界条件的微分方程数值求解有一定的参考价值。 相似文献
34.
A higher-order nonlocal strain-gradient model is presented for the damped vibration analysis of single-layer graphene sheets (SLGSs) in hygrothermal environment. Based on Kirchhoff plate theory in conjunction with a higher-order (bi-Helmholtz) nonlocal strain gradient theory, the equations of motion are obtained using Hamilton's principle. The higher-order nonlocal strain gradient theory has lower- and higher-order nonlocal parameters and a material characteristic parameter. The presented model can reasonably interpret the softening effects of the SLGS, and indicates a reasonably good match with the experimental flexural frequencies. Finally, the roles of viscous and structural damping coefficients, small-scale parameters, hygrothermal environment and elastic foundation on the vibrational responses of SLGSs are studied in detail. 相似文献
35.
This paper deals with the free vibration analysis of circular alumina (Al2O3) nanobeams in the presence of surface and thermal effects resting on a Pasternak foun- dation. The system of motion equations is derived using Hamilton's principle under the assumptions of the classical Timoshenko beam theory. The effects of the transverse shear deformation and rotary inertia are also considered within the framework of the mentioned theory. The separation of variables approach is employed to discretize the governing equa- tions which are then solved by an analytical method to obtain the natural frequencies of the alumina nanobeams. The results show that the surface effects lead to an increase in the natural frequency of nanobeams as compared with the classical Timoshenko beam model. In addition, for nanobeams with large diameters, the surface effects may increase the natural frequencies by increasing the thermal effects. Moreover, with regard to the Pasternak elastic foundation, the natural frequencies are increased slightly. The results of the present model are compared with the literature, showing that the present model can capture correctly the surface effects in thermal vibration of nanobeams. 相似文献
36.
基坑内撑式支护具有经济、快捷和效率高等特点. 通过郑州市某雨水管道工程基坑支护的实践,介绍了内撑式支护结构在深基坑支护中的受力特点,结构分析与方案选择,为内撑式支护设计和施工提供了参考. 相似文献
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G. B. Muravskii 《Archive of Applied Mechanics (Ingenieur Archiv)》2008,78(2):149-162
In the paper, a method of averaging displacements in a circular area lying in a linearly elastic transversally isotropic foundation
is developed for the four modes of motion: vertical, horizontal, rocking and torsional. The corresponding formulae are constructed
in a general form which does not depend on the kind of Green functions. For vertical and horizontal modes, uniform load distribution
are applied and the simple integral mean is considered, whereas for rotational modes the load proportional to the distance
from an axis of rotation is used, and angles of rotation for individual points are averaged with weight of the distance squared.
Along with the case of equal radii of circles of loading and averaging, the case of different radii is studied, which allows
one to consider contact problems for embedded axisymmetric foundations having the radius varying with depth. As examples the
following contact problems are studied: static stiffness for a cone embedded in a homogeneous isotropic half-space in vertical
motion, and dynamic stiffness for a disk on a layer resting on a homogeneous half-space for four modes of motion. Comparisons
with the corresponding exact solutions are carried out. 相似文献
40.