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71.
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
72.
The classical problem of a beam on a tensionless Winkler elastic foundation is reconsidered for the derivation of the conditions of complete contact between the beam and the foundation. This is achieved through the application of modern quantifier elimination software included in the computer algebra system Mathematica together with Taylor–Maclaurin series approximations to the deflection of the beam. Four particular beam problems have been considered in detail and the related QFFs (quantifier-free formulae) have been obtained for several values of the order in the series approximations. Additional approximation possibilities have also been investigated with an emphasis put on the use of the Galerkin method based on weighted residuals. The present results seem to constitute one more interesting application of modern quantifier elimination algorithms and the related software (here in Mathematica) to applied and engineering mechanics. 相似文献
73.
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
74.
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
75.
76.
考虑桩体内径向渗流的复合地基固结解 总被引:4,自引:0,他引:4
考虑了桩体内径竖向组合渗流和涂抹区土体水平渗透系数的两种变化模式,得到了此类固结问题的控制方程.采用新的初始条件,得到了控制方程的解答,给出了桩周土体和桩体内的平均孔压.在此基础上,把桩体的固结压缩引人对复合地基总平均固结度的定义中,分别给出了复合地基按应力和按应变定义的总平均固结度.结果表明:按应力和按应变定义的复合地基的总平均固结度相等;考虑桩体内径向渗流比不考虑桩体内径向渗流的复合地基固结度要小,而且随着桩间距的增大,两者之间的差值逐渐减小;考虑涂抹区水平渗透系数逐渐变化比假定涂抹区水平渗透系数保持不变的复合地基的总平均固结度大. 相似文献
77.
78.
In this study, a slightly curved Euler Bernoulli beam carrying a concentrated mass was handled. The beam was resting on an elastic foundation and simply supported at both ends. Effects of the concentrated mass on nonlin- ear vibrations were investigated. Sinusoidal and parabolic type functions were used as curvature functions. Equations of motion have cubic nonlinearities because of elongations during vibrations. Damping and harmonic excitation terms were added to the equations of motion. Method of mul- tiple scales, a perturbation technique, was used for solving integro-differential equation analytically. Natural frequen- cies were calculated exactly for different mass ratios, mass locations, curvature functions, and linear elastic foundation coefficients. Amplitude-phase modulation equations were found by considering primary resonance case. Effects of nonlinear terms on natural frequencies were calculated. Frequency-amplitude and frequency-response graphs were plotted. Finally effects of concentrated mass and chosen curvature function on nonlinear vibrations were investigated. 相似文献
79.
通过室内模型试验,对黄土地基中大直径超长群桩基础的承载-沉降关系、承台下土体附加应力的分布及发展、桩土承载情况以及不同位置桩的受力特性分别进行了研究。结果表明:黄土地基中大直径超长群桩基础荷载-沉降曲线呈缓变型且没有明显拐点,故群桩基础的极限承载力应综合沉降-时间对数s-lgt曲线和荷载-沉降Q-s曲线来确定。承台下土体附加应力分布为边缘大中心小。不同位置的桩承载性能不同,总体上是角桩(6#桩)最大,边桩(5#桩)次之,中心桩(1#桩)最小;同时各桩的桩侧摩阻力及桩身轴力沿桩长的变化也有所不同。 相似文献
80.