共查询到20条相似文献,搜索用时 15 毫秒
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Pushover分析方法近年来引起了地震工程界的广泛兴趣,我国新的抗震设计规范已将其作为大震下结构弹塑性变形分析的一种方法。结构不规则性是影响Pushover分析应用的一个主要因素,而加载模式的选取则是Pushover分析的一个关键问题。本文采用FEMA273建议的3种加载模式对两个典型的三维偏心结构(刚度偏心和质量偏心)进行了Pushover分析,并与非线性动力时程分析的结果进行了比较,给出了三维偏心结构Pushover分析加载模式选取的建议。 相似文献
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A segregated algorithm for the solution of laminar incompressible, two- and three-dimensional flow problems is presented. This algorithm employs the successive solution of the momentum and continuity equations by means of a decoupled implicit solution method. The inversion of the coefficient matrix which is common for all momentum equations is carried out through an approximate factorization in upper and lower triangular matrices. The divergence-free velocity constraint is satisfied by formulating and solving a pressure correction equation. For the latter a combined application of a preconditioning technique and a Krylov subspace method is employed and proved more effecient than the approximate factorization method. The method exhibits a monotonic convergence, it is not costly in CPU time per iteration and provides accurate solutions which are independent of the underrelaxation parameter used in the momentum equations. Results are presented in two- and three-dimensional flow problems. 相似文献
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弹塑性结构优化的并行算法 总被引:1,自引:0,他引:1
本文给出了弹塑性结构优化设计的序列二次规划算法,分别考虑了弹塑性结构分析,灵敏度分析和二次规划的Lemke算法的并行计算。针对弹塑性结构灵敏度的不连续性,比较了连续模型和间断模型的计算结果,结果是接近的。算例表明此算法有很好的并行性。 相似文献
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Topology optimization of continuum structures with design-dependent loads has long been a challenge. In this paper, the topology optimization of 3D structures subjected to design-dependent loads is investigated. A boundary search scheme is proposed for 3D problems, by means of which the load surface can be identified effectively and efficiently, and the difficulties arising in other approaches can be overcome. The load surfaces are made up of the boundaries of finite elements and the loads can be directly applied to corresponding element nodes, which leads to great convenience in the application of this method. Finally, the effectiveness and efficiency of the proposed method is validated by several numerical examples. 相似文献
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Mamoru Tanahashi Shohei Inoue Masayasu Shimura Shohei Taka Gyung-Min Choi Toshio Miyauchi 《Experiments in fluids》2008,45(3):447-460
Flame structures of turbulent premixed flames in a noise-controlled, swirl-stabilized combustor are investigated to clarify
the mechanism of combustion noise reduction by the secondary fuel injection. Planar laser-induced fluorescence (PLIF) is conducted
for several cases with different secondary fuel injection, and 3D flame structure is reconstructed from PLIF results on multiple
planes. The secondary fuel injection suppresses the fluctuation of high-temperature gas in the recirculation zone and reduces
Reynolds stress and entropy terms in the acoustic sound source. In the flame zone, effects of the injection frequency are
discussed by introducing mean progress variable. The flame brush is very wide for the no control case, whereas it becomes
thin and is confined to a narrow space for the secondary fuel injection cases. The investigated combustor gives minimum sound
level at a relevant fuel injection frequency, which is very low compared with the natural acoustic mode of the combustor.
The flame brush becomes very thin, and self-induced oscillations of the flame brush disappear at this relevant frequency.
The oscillation of the flame brush represents large-scale fluctuation of the mean heat release rate. The relations between
characteristics of flame brush and combustion noise are discussed by introducing instantaneous and dynamical effects of flame
front on the entropy term of the sound source. The secondary fuel injection works for the control of the entropy term in the
sound source because the thin flame brush represents suppression of the instantaneous and dynamical effects. 相似文献
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This paper presents a 3D topology optimization approach for designing shell structures with a porous or void interior. It is shown that the resulting structures are significantly more robust towards load perturbations than completely solid structures optimized under the same condi-tions. The study indicates that the potential benefit of using porous structures is higher for lower total volume fractions. Compared to earlier work dealing with 2D topology opti-mization, we found several new effects in 3D problems. Most notably, the opportunity for designing closed shells signifi-cantly improves the performance of porous structures due to the sandwich effect. Furthermore, the paper introduces improved filter boundary conditions to ensure a completely uniform coating thickness at the design domain boundary. 相似文献
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We have proved that any 3-dimensional dynamical system of ordinary differential equations (in short, 3D ODE) with time-independent
invariants can be rewritten as Hamiltonian systems with respect to generalized Poisson brackets and the Hamiltonians are these
invariants. As an example, we discuss the Kermack-Mckendrick model for epidemics in detail. The results we obtained are generalization
of those obtained by Y. Nutku.
First Received Nov. 22, 1993 相似文献
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This paper presents a novel form-finding algorithm for tensegrity structures that is based on the finite element method. The required data for the form-finding is the topology of the structure, undeformed bar lengths, total cable length, prestress of cables and stiffness of bars. The form-finding is done by modifying the single cable lengths such that the total cable length is preserved and the potential energy of the system is minimized. Two- and three-dimensional examples are presented that demonstrate the excellent performance of the proposed algorithm. 相似文献
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提出了一种改进的遗传算法,用于优化具有离散尺寸、连续形状和0-1拓扑变量的桁架问题。考虑到离散和连续变量的本质,文中提出了混合编码方法,其中包括二进制和实数编码,整数和实数编码。本文采用了凝聚选择法-基于约束和适应度值双重标准,完全适应约束问题的本质。在优化过程中,初始种群和算子具有不确定性,因此有必要检验结构拓扑的合理性。为了增强算法的可靠性,采用了改进的重新开始算子,引入新基因并且探索新空间。求解了典型的算例,证明改进的遗传算法是可行且有效的。 相似文献
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The definition of local optimum solution of the discrete optimization is first given, and then a comprehensive combinatorial algorithm is proposed in this paper. Two-level optimum method is used in the algorithm. In the first level optimization, an approximate local optimum solution is found by using the heuristic algorithm, relative difference quotient algorithm, with high computational efficiency and high performance demonstrated by the performance test of random samples. In the second level, a mathematical model of (-1, 0, 1) programming is established first, and then it is changed into (0, 1) programming model. The local optimum solution X* will be from the (0, 1) programming by using the delimitative and combinatorial algorithm or the relative difference quotient algorithm. By this algorithm, the local optimum solution can be obtained certainly, and a method is provided to judge whether or not the approximate optimum solution obtained by heuristic algorithm is an optimum solution. The above comprehensive combinatorial algorithm has higher computational efficiency.Project supported by Natural Science Foundation of Shandong Province 相似文献
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滞变智能隔震结构的序列最优控制算法 总被引:3,自引:1,他引:2
将地震波简化为一系列脉冲,在每个时间步长上重新构造控制目标函数,建立了一种新的时域内的结构振动最优控制算法,并在滞变模型的智能隔震结构中用状态转移法加以实现.文中采用Bouc-Wen模型描述结构恢复力,并利用等效线性化方法处理非线性运动方程,分别导出了状态反馈和输出加权的两种表达式.文末选用作者承担设计过的实际隔震建筑中的一个单体工程作为算例,比较了输入三种不同地震波时各种算法的控制效果.结果表明,在相同控制能量下,本文算法对滞变结构能有效地削减响应峰值,综合性能优于现有的两种时域内的结构最优控制算法. 相似文献
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桁架结构大都具有较强的几何非线;浊,受荷载后易出现较大的脯变形。提出一种基于力密度的针对桁架结构几何大变形问题的解法;引入杆件单元的力密度矩阵,推导出相应非线性方程的Jacobi矩阵;与有限单元法集成求解的思想相同,采用力密度矩阵建立结构变形后整体的精确非线性平衡方程。研究结果表明:应用Newton-Raphson迭代法求解,采用适当的迭代收敛精度可得到较精确的桁架结构位移解。 相似文献
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Nonlinear Dynamics - A large group of real mechanical problems can be modeled and analyzed using the approaches of flexible multibody dynamics. The computational models in the form of... 相似文献
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An unstructured dynamic mesh adaptation and load balancing algorithm has been developed for the efficient simulation of three‐dimensional unsteady inviscid flows on parallel machines. The numerical scheme was based on a cell‐centred finite‐volume method and the Roe's flux‐difference splitting. Second‐order accuracy was achieved in time by using an implicit Jacobi/Gauss–Seidel iteration. The resolution of time‐dependent solutions was enhanced by adopting an h‐refinement/coarsening algorithm. Parallelization and load balancing were concurrently achieved on the adaptive dynamic meshes for computational speed‐up and efficient memory redistribution. A new tree data structure for boundary faces was developed for the continuous transfer of the communication data across the parallel subdomain boundary. The parallel efficiency was validated by applying the present method to an unsteady shock‐tube problem. The flows around oscillating NACA0012 wing and F‐5 wing were also calculated for the numerical verification of the present dynamic mesh adaptation and load balancing algorithm. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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An advanced incremental crack growth algorithm for the three-dimensional (3D) simulation of fatigue crack growth in complex 3D structures with linear elastic material behavior is presented. To perform the crack growth simulation as effectively as possible an accurate stress analysis is done by the boundary-element method (BEM) in terms of the 3D dual BEM. The question concerning a reliable 3D crack growth criterion is answered based on experimental observations. All criteria under consideration are numerically realized by a predictor–corrector procedure. The agreement between numerically determined and experimentally observed crack fronts will be shown on both fracture specimens and an industrial application. 相似文献