共查询到17条相似文献,搜索用时 468 毫秒
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膜结构找形方法——改进力密度法 总被引:2,自引:0,他引:2
在膜结构找形中,力密度法引入了"力密度"的概念,使问题简化.但力密度法需要多次试算后才能确定合适的力密度取值,很大程度上依赖个人经验,给找形过程带来一定困难.本文针对力密度法的找形过程进行改进,避开其中"力密度"的概念,直接引入膜面应力和索拉力作为初始条件,以节点不平衡力作为控制误差,避免了传统力密度法需要反复试算力密度取值的弊端,使找形计算过程简洁高效.据此编制找形程序,通过复杂算例验证了该算法的正确性和普适性. 相似文献
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SHANG Renjie 《力学与实践》2019,41(6):718
力学和几何学是密不可分的,本文给出了一种几何作图法进行端面平行时张拉整体三棱柱的找形方法和作图确定自平衡内力大小的找力方法,并推导出找形后张拉整体三棱柱自平衡内力的力密度计算公式,通过算例验证了几何作图法找形与找力的正确性。几何作图法找形和找力方法操作简单,直观可控,可以在CAD软件中实现,甚至可以纸上手绘实现;自平衡力密度公式简单,表达直观,是力密度法的一种几何实现。 相似文献
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为了扩大结构弹性动力分析的规模和提高分析速度,在微机机群环境下给出了两种基于边界元法的瞬态问题并行求解算法,即并行拉普拉斯变换求解算法和并行时域求解算法.并行拉氏变换法通过拉氏变换隐去时间变量,由各结点机独立求解各自负责的变换边界元问题.并行时域法采用与时间有关的基本解,使得边界元系统矩阵可以实现时间域上的并行形成.系数矩阵采用卷帘存储,以保持负载平衡.通过矩阵向量运算的并行化实现时间步进算法的并行化.理论分析和数值试验结果表明:两种算法都具有较好的并行性能.可以用于大型问题的高效求解. 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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在结构计算中,根据算法中所采用的基本未知量的不同.结构分析方法可以分为力法、位移法和混合法。其中位移法由于适宜计算机处理而在结构计算领域得到了广泛的应用.经典力法相比之下应用就远不如位移法普遍,虽然力法本身在力学上有其独特的优势。广义逆矩阵做为一种较新的数学工具,自二十世纪五十年代诞生以来正日益表现出越来越旺盛的生命力。广义逆力法就是一种基于力法和广义逆矩阵理论的新的迭代算法。这种算法是一种完全适合计算机处理的力法方法。该算法的思路以及对于求解线弹性空间刚架结构问题的具体公式均在文中给出并给出了算例。从算例计算结果可以看到广义逆力法有着较好的计算效率和计算精度。该算法的提出为力法在计算机计算领域的应用开拓了新的发展空间。该算法在材料非线性问题和结构并行计算方面也有着较好的应用前景。 相似文献
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A new computational framework is proposed for the form-finding and design of tensegrity structures with or without super-stability. The form-finding of tensegrities is formulated as two unconstrained minimisation problems where their objective functions are defined based on eigenvalues of a modified force density matrix. The Nelder–Mead simplex method is then used to solve the minimisation problems. Furthermore, another efficient method is suggested for the interactive form-finding and design of tensegrities with geometrical and force constraints. Examples of the form-finding of tensegrities are presented and the results obtained are compared and contrasted with those analytical results documented in the literature, to verify the accuracy and efficiency of the developed methods. 相似文献
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《International Journal of Solids and Structures》2006,43(22-23):6855-6868
A novel and versatile numerical form-finding procedure that requires only a minimal knowledge of the structure is presented. The procedure only needs the type of each member, i.e. either compression or tension, and the connectivity of the nodes to be known. Both equilibrium geometry and force densities are iteratively calculated. A condition of a maximal rank of the force density matrix and minimal member length, were included in the form-finding procedure to guide the search of a state of self-stress with minimal elastic potential energy. It is indeed able to calculate novel configurations, with no assumptions on cable lengths or cable-to-strut ratios. Moreover, the proposed approach compares favourably with all the leading techniques in the field. This is clearly exemplified through a series of examples. 相似文献
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A numerical method is presented for form-finding of cable-strut structures. The topology and the types of members are the only information that is required in this form-finding process. Dummy members are used to transform the cable-strut structure with supports into self-stressed system without supports. The requirement on rank deficiencies of the force density and equilibrium matrices for the purpose of obtaining a non-degenerate d-dimensional self-stressed structure has been explicitly discussed. The spectral decomposition of the force density matrix and the singular value decomposition of the equilibrium matrix are performed iteratively to find the feasible sets of nodal coordinates and force densities which satisfy the minimum required rank deficiencies of the force density and equilibrium matrices, respectively. Based on numerical examples it is found that the proposed method is very efficient, robust and versatile in searching self-equilibrium configurations of cable-strut structures. 相似文献
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A novel analysis method is presented for form-finding of tensegrity structures. The spectral decomposition of the force density matrix and the singular value decomposition of the equilibrium matrix are performed iteratively to find the feasible sets of nodal coordinates and force densities. An algorithm of determining the sole configuration of free-form tensegrities is provided by specifying an independent set of nodal coordinates, which indicates the geometrical and mechanical properties of the structures can be at least partly controlled by the proposed method. Several illustrative examples are presented to demonstrate the efficiency and robustness in finding self-equilibrium configurations of tensegrity structures. 相似文献
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含可动机构的杆系结构非线性力法分析 总被引:6,自引:0,他引:6
推导了基于矩阵奇异值分解的小变形条件下杆系结构的力法分析(LFM)过程,并采用杆件内力修正的方法,提出了考虑大位移的几何非线性力法分析(NFM)方法思想和步骤。该方法有效地解决了结构中同时存在刚体位移、弹性位移的结构分析问题,适合计算机编程,结构的强度计算、机构分析和形态分析,讨论了力法与位移法的优缺点,给出的算例表明所提出的方法是正确的、有效的。 相似文献
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《International Journal of Solids and Structures》2014,51(7-8):1521-1533
The paper proposes an unitary strategy for the static analysis of general cable nets under conservative loads. A form-finding is first performed in order to initialize the successive non linear analysis. The numerical procedures carried on in both steps, form finding and structural analysis of the net, employ a three dimensional elastic catenary element. Equilibrium conditions at internal nodes and kinematic compatibility at the end nodes of each cable are used to derive the global equations of the net. When the pre-stresses are high and the topology of the net is involved, an accurate initializing solution is essential for the convergence of the successive numeric non linear structural analysis (performed by Newton method). The numerical applications highlight the capability of the proposed procedure to solve three dimensional problems with taut and slack cables, out of plane distributed forces (modeling wind loads), point loads along the cables. The contemporary presence of cables and compression truss elements is also considered testing the effectiveness of the method in the analysis of tensegrity structures. 相似文献
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本文提出了基于高频动态测力天平试验的风振响应的频域分析方法,采用该方法可以用来求解复杂高耸结构的三维耦联风振响应,并给出了利用高频动态测力天平试验来确定广义模态力谱的计算方法.该方法利用高频动态测力天平试验得到的基底剪力自谱、基底弯矩自谱以及基底剪力与弯矩的互谱与脉动风荷载的自谱密度的相互关系并通过引入振型修正系数来求得广义模态力谱,求解结构的三维耦联风振响应.然后,采用本文方法对在建的河南省广播电视发射塔的风振响应进行了研究,结果表明横风向的位移和加速度响应的均方根值要大于顺风向,因此在计算中必须考虑横风向风振的影响.最后本文对计算振型数目和模态耦联项对结构风振响应的影响进行了分析.本文的方法对于求解复杂高耸结构的风振响应具有重要的借鉴意义. 相似文献