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为改善使用板式橡胶支座连续梁桥的抗震性能,通过附加黏滞阻尼器进行组合减隔震设计,采用复模态、近似实模态分析方法,研究结构地震响应及阻尼特性。结果表明:黏滞阻尼器提供的附加阻尼能有效降低梁体位移,但同时也导致桥梁具有非经典阻尼特性,主梁位移受非经典阻尼影响较小;黏滞阻尼器能明显提升结构阻尼水平,为有效控制梁体位移,应考虑黏滞阻尼器的合理布设位置,多墩布置优于单墩布置。 相似文献
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有阻尼结构线性振动系统的模态综合 总被引:2,自引:0,他引:2
研究了线性阻尼结构振动系统的模态综合技术.在线性阻尼结构振动系统实变换进行方程解耦的还原变换的基础上,构造了线性阻尼结构振动系统的固定界面模态综合方法。这一方法克服了以往的模态综合法中无法同时给出子结构刚度、阻尼和质量矩阵,以及只能给出复系数时域方程等不足,可直接给出子结构经模态降阶后的刚度、阻尼和质量矩阵。综合得到的整体方程仍是时域中的实系数二阶振动方程。数值算例表明了本文方法的正确和可行。 相似文献
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本文设计了一个用速度反馈实现粘性阻尼的结构振动系统并进行了实验和模态参数识别,实验模态分析结果表明,具有非比例阻尼的结构振动系统,在欠阻尼范围内,系统是可以成为亏损的;对于亏损系统,其频响特性只有用广义模态理论才能正确地描述。 相似文献
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非比例阻尼线性结构体系动力分析的拟力实模态叠加法 总被引:2,自引:0,他引:2
对于非比例阻尼线性结构体系,利用体系无阻尼实模态来形成模态响应方程时,得到的模态方程组是关于模态阻尼矩阵耦合的。非比例阻尼可以分成两部分:耗散能量的比例阻尼和转换能量的非比例阻尼。基于这种概念,本文采用了一种拟力实模态叠加法来求解非比例阻尼体系的动力分析,即把前述耦合模态方程中代表非比例阻尼的耦合项作为虚力,放到方程的右端,再运用迭代法进行求解。这种方法综合了经典模态叠加法和拟力法的优点。数值算例表明,此方法具有很好的收敛特性,所得结果精度高。我们认为,这种方法可应用于实际工程分析。 相似文献
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求解有阻尼多自由度结构系统的振动微分方程,实模态分析法是得到广泛应用的一种有效方法。但随着对阻尼的深入研究,发现广泛采用的 Rayleigh 比例阻尼假设,往往不符合实际情况。但若采用非比例型的阻尼,用实模态矩阵变换结构振动微分方程时,往往不能使之完全解耦而进行求解。通常的处理方法,可将阻尼耦合项忽略,但这样有时会使计算结果的精度很差。或者转而用复模态求解,这又使方程自由度数增加一倍,计算量大增,且占用计算机内存过多,使计算难以在容量有限的小型机上进行。本文针对这一问题,提出一种新的求解方法。在实模态分析法的基础上,计入模态阻尼耦合项,对计算结果进行反复迭代修正,使其逐渐逼近精确解。本文方法经数学证明,在一定条件下收敛,且收敛条件易获满足,因而具有一定实用价值。 相似文献
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阻尼控制下高层建筑模态分析及试验研究 总被引:1,自引:0,他引:1
本文对具有阻尼控制系统的高层建筑的模态特性进行了深入的理论分析和试验研究。文中对于具有非经典阻尼分布的建筑结构体系的模态分析,应用并发展了Veselic的整体Jacobi法,具有显著的优越性。研究表明,对高层建筑施加阻尼控制、随着阻尼控制系统的阻尼参数及其在建筑上的安装位置的变化,将显著地改变建筑的模态特性。最后通过对一三层框架建筑模型进行试验研究,从而验证了所取得的研究成果。 相似文献
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为提高非比例阻尼体系强迫振动时复模态叠加法的计算效率,基于模态摄动法基本原理,提出一种利用无阻尼体系实模态的复模态叠加法.该方法由模态摄动法将非比例阻尼体系的复模态表示为实模态线性组合,在此基础上,建立了强迫振动复模态叠加法的实模态的线性组合解.以一个带附加阻尼的强非比例阻尼三层框架结构为例进行地震反应分析,计算结果表... 相似文献
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S. T. Mau H. C. Dan 《International journal for numerical methods in engineering》1986,23(8):1495-1508
A direct method, which uses stress and displacement modes obtained from the governing equations of a problem, is adopted for finite element formulation. It is shown that this method actually leads to a restricted hybrid stress formulation if the displacement modes are changed to ensure symmetry of the stiffness matrix. Through this direct method, however, the problem of selecting the appropriate number of stress modes in the regular hybrid stress model is bypassed. Only the minimum number of modes that are compatible with the number of nodal degrees-of-freedom of an element is needed in the formulation. Using more modes only leads to a combination of stress modes, and will not improve the order of performance of the element. It is shown through numerical examples that the restricted hybrid stress formulation leads to well-balanced elements. 相似文献
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单层网壳结构风振响应的主要贡献模态识别 总被引:2,自引:0,他引:2
网壳结构具有频谱分布密集、振型复杂的动力特性,在对该类结构进行风振响应分析时,通常存在着一些对响应贡献较大的高阶振型,但由于其频率较高而容易被忽略。因此,研究网壳结构风振响应的主要贡献模态分布规律有利于提高结构风振响应计算的精度和效率。本文利用Ritz-POD法,分析了单层球面网壳和单层柱面网壳结构风振响应的主要贡献模态,着重考察了主要贡献模态的自身参振能力。及其与脉动风压空间分布模式之间的关系。在此基础上,初步给出了网壳结构风振响应的主要贡献模态识别准则。 相似文献
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爆炸荷载作用下钢筋混凝土结构的动态响应与破坏模式的数值分析 总被引:2,自引:0,他引:2
在爆炸荷载(尤其是脉冲荷载)作用下,除了常见的弯曲破坏形态之外,钢筋混凝土结构还可能发生直剪破坏和弯剪破坏。如何准确地预测爆炸荷载作用下的钢筋混凝土结构动态响应和破坏特征是当前抗爆结构领域十分关注的课题之一。该文介绍作者近年来在这方面的一些研究成果,主要有:将三参数形式的应变速率型材料模型推广应用于二维状态下的混凝土本构关系,建立了弹粘塑性混凝土结构有限元分析方法;基于Timoshenko梁理论和弹粘塑性理论,分别采用有限差分法和有限元法,建立了土中浅埋钢筋混凝土结构动力响应和破坏模式的有限差分和有限元分析方法。对爆炸荷载作用下的典型钢筋混凝土结构计算结果表明:基于Timoshenko梁理论的有限差分分析方法和有限元分析方法能较好地模拟梁的动态响应和弯曲、弯剪以及直剪的破坏模式,而二维弹粘塑性混凝土结构有限元分析方法只能较好地模拟梁的弯曲破坏模式。 相似文献
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Snyder JJ 《Applied optics》2007,46(22):5056-5061
In the mode-expansion method for modeling propagation of a diffracted beam, the beam at the aperture can be expanded as a weighted set of orthogonal modes. The parameters of the expansion modes are chosen to maximize the weighting coefficient of the lowest-order mode. As the beam propagates, its field distribution can be reconstructed from the set of weighting coefficients and the Gouy phase of the lowest-order mode. We have developed a simple procedure to implement the mode-expansion method for propagation through an arbitrary ABCD matrix, and we have demonstrated that it is accurate in comparison with direct calculations of diffraction integrals and much faster. 相似文献
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Charbel Farhat Francois-Xavier Roux 《International journal for numerical methods in engineering》1991,32(6):1205-1227
A novel domain decomposition approach for the parallel finite element solution of equilibrium equations is presented. The spatial domain is partitioned into a set of totally disconnected subdomains, each assigned to an individual processor. Lagrange multipliers are introduced to enforce compatibility at the interface nodes. In the static case, each floating subdomain induces a local singularity that is resolved in two phases. First, the rigid body modes are eliminated in parallel from each local problem and a direct scheme is applied concurrently to all subdomains in order to recover each partial local solution. Next, the contributions of these modes are related to the Lagrange multipliers through an orthogonality condition. A parallel conjugate projected gradient algorithm is developed for the solution of the coupled system of local rigid modes components and Lagrange multipliers, which completes the solution of the problem. When implemented on local memory multiprocessors, this proposed method of tearing and interconnecting requires less interprocessor communications than the classical method of substructuring. It is also suitable for parallel/vector computers with shared memory. Moreover, unlike parallel direct solvers, it exhibits a degree of parallelism that is not limited by the bandwidth of the finite element system of equations. 相似文献
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Abstract The dispersion characteristics are needed to evaluate the performance of optical fibres. In general, these will have to be obtained numerically. For this, a computationally fast method is required which will give accurate values of the propagation constants (eigenvalues). In this work, the variation method is used with the propagation equation imposed as a constraint. This method is computationally fast and gives accurate results. In an earlier work, the LP01 mode had been dealt with for the parabolic-profile fibre and it was speculated that the same method could be extended to the higher-order modes. In the present work, the LP11 and LP12 modes have been dealt with by the same method for the parabolic-profile fibre, thus confirming the speculation. 相似文献
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大跨圆拱屋盖结构的风致响应分析 总被引:10,自引:2,他引:10
大跨屋盖特征值问题的求解是结构动力响应分析中最繁琐的一个环节,而且一些对结构响应贡献较大的高阶模态容易在传统的模态叠加法中被忽略。本文以典型的大跨圆拱屋盖为例,将里兹向量直接叠加法应用于屋盖系统特征值问题计算和风致响应分析,其特点是在误差逼近的基础上自动生成一组正交的里兹向量并用于缩减系统自由度数。与传统模态叠加法算得的结果相比,里兹向量直接叠加法只用很少数目的向量就可以得到较精确的结果,而且高阶模态的贡献不会被忽略。该方法不仅大幅度地减少了机时,而且提供了动力分析的误差估计。 相似文献
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In this work a quantum mechanical derivation of the Spin operator in integrated isotropic and anisotropic photonic waveguides is obtained from both first principles of the electromagnetic theory and conservation laws, and moreover, within a phenomenological quantization approach. The Spin operator will be derived by starting from the spin conservation law to obtain the spin flux density and by means of a quantization based on the vector structure and orthonormality property of guided modes; likewise, since anisotropic guides produce polarization changes, and consequently changes of the expected values of spin, we will also present the Momentum operator for anisotropic guides. The expression for the Spin angular momentum operator shows that both the presence of modal longitudinal components and the modal mismatching reduces the spin values, but it comes into the standard expression when it is used in homogeneous media and in particular with uniform and infinite plane modes. Likewise these results have a direct influence on the Stokes's operators which allow one to analyze quantum polarization in integrated photonics. 相似文献