拉索预应力巨型网格结构参激振动及动力稳定性研究

针对拉索预应力巨型网格结构的参激振动及动力稳定性问题进行了研究。首先建立索-拱简化模型,分析了桁架拱拉索参激振动的诱发机制与特征,并利用ANSYS软件进一步探究了参激振动的影响因素,然后对简谐荷载作用下拉索预应力桁架拱及整体结构的动力稳定性进行了分析。研究表明：当结构振动频率为索基频的2倍左右时,拉索会发生参激振动,振动响应特征与激励幅值、阻尼、拉索初张力、支承方式等相关;拉索预应力桁架拱在水平简谐荷载作用下一般会发生动力失稳破坏,在竖向简谐荷载作用下发生动力强度破坏,拉索预应力巨型网格整体结构在简谐荷载作用下通常发生动力失稳破坏。     

随机拉索刚度预应力空间钢桁架随机内力摄动分析

基于已建立的拉索式平面预应力钢桁架基本理论 ,考虑到拉索刚度的随机性 ,得到了拉索式空间预应力钢桁架随机内力摄动分析的一般公式及敏度分析式 ,给出了空间预应力钢桁架随机内力统计特性计算表达式。为进一步进行空间预应力钢桁架可靠性分析奠定了一定的理论基础。最后针对工程中常见的三角形立体钢桁架 ,给出了算例     

空间网格结构损伤探测的研究进展

空间网格结构损伤探测技术是目前结构工程领域研究的热点和难点．根据国内外的最新文献信息，讨论了损伤探测技术在空间网格结构中的应用及最新的研究进展，对现有文献中的方法进行了分类和评述．重点介绍了目前比较适用的柔度法和模型修正方法，对该领域中尚存在的问题进行了讨论，对今后的发展方向及趋势进行了展望．     

巨型钢框架——拉索吊挂结构拉索参数确定方法

如何确定拉索参数是巨型钢框架——拉索吊挂结构的关键问题. 基于简化模型推导了竖向载荷下结构内力及变形的求解方程;依据牛顿定律分析了水平载荷作用下, 不同的滑移状态拉索对框架受力变形的影响, 得到了拉索索力增量最大值的关系式;最终, 根据"正常使用状态下, 巨型梁的挠度满足规范要求"的拉索参数确定准则, 建立了首先确定拉索截面积、再确定拉索预拉力的确定方法. 为巨型钢框架-拉索吊挂结构的性能评判和初步设计奠定理论基础.     

巨型钢框架-拉索支撑结构中拉索的抗侧机理

研究巨型钢框架-拉索支撑结构中预应力拉索的抗侧机理,为确定拉索参数提供理论依据. 基于预应力的作用形态及力学原理分析得到预应力拉索的抗侧机理,推导了预应力拉索抗侧刚度理论公式. 从模型试验的角度进一步研究,将模型试验的结果与理论推导及数值分析的结果进行对比分析,最终验证了预应力拉索的抗侧机理：预应力为柔性拉索建立轴向刚度和稳定性,使预紧过的拉索既可承受拉力,也可承受压力,从而为结构提供弹性约束支撑.     

结构拓扑优化设计的三角网格进化法

针对进化或拓扑优化方法的不足，提出了一种基于遗传算法的新型进化式拓扑优化方法－－三角网格进化法，该方法不仅能够同时进行拓扑，形状与截面变量优化设计，而且在优化过程中实现了退化和进化的统一，提高了优化效率。另外本文还首次对结构类型变量进行了优化计算，取得了有益的结果。最后几个数值算例证明了本方法的可行性和有效性。     

基于虚拟激励法的空间网格结构风致抖振响应分析

基于虚拟激励法理论,推导了空间网格结构的抖振响应计算公式,公式中自动包含了激励之间的非完全相关性、振型之间耦合项的贡献。根据虚拟激励法直接求解出位移均方根的特点,推导了适用于多振型参振的脉动风等效静力荷载及相应的荷载风振系数计算公式。在此基础上,利用Matlab编制了相应的计算程序,并进行了算例验证与分析。算例分析验证了本文理论及程序的正确性,也表明本文方法具有很高的计算效率。本文工作为进一步系统研究大跨网格结构的风振随机响应打下了良好的基础。     

具有随机拉索刚度的预应力钢桁架随机内力摄动分析

本文在建立拉索式预应力钢桁架基本计算理论的基础上，考虑到拉索刚度的随机性，推导了拉索式平面预应力钢桁架随机内力摄动分析的一般公式及敏度分析式，并给出了算例。为进一步进行预应力钢桁架可靠性分析奠定了基础。     

空间网格结构动力分析的非线性模态方法

空间网格结构因自由度数多且无简化的力学模型,非线性动力分析通常要耗费大量时间．传统的非线性模态方法用于求解多高层结构的局部非线性问题已获得良好的效果,但对系统非线性问题的应用尚缺少研究．对比分析多高层结构和空间网格结构动力性能差异,指出网格结构动力非线性分析存在的问题．以主振型理论和切线刚度分离法为基础,将非线性模态方法用于几何非线性效应显著的空间网格结构动力分析．通过对运动方程的非线性恢复力进行拆分,形成线性表达形式,然后解耦到主振型所在的广义坐标系,以达到缩减自由度数量的目的．并通过实例验证非线性模态方法的高效性与适用性．     

多点输入下大跨空间网格结构的可靠度分析

在虚拟激励反应谱法的基础上进行了多点输入下大跨空间网格结构的可靠度分析,并且将之与一致输入下结构抗震可靠度的分析结果进行了对比,考查了两种输入方法下杆件内力可靠指标之间的变化,进而分析了危险杆件在结构分布、数量等方面的差异以及危险杆件随结构跨度、视波速的变化关系。通过工程实例可以看出本文的分析方法对于分析大跨度网架、网壳这样复杂结构在多点输入下的抗震性能非常合适,为理论研究向实际应用搭建了桥梁。     

Deformation mode and energy absorption of polycrystal-inspired square-cell lattice structures

Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption (SEA) capacity. In this paper, square-cell lattice structures with different lattice orientations are investigated in terms of the deformation modes and the energy absorption (EA) performance. Finite element (FE) simulations of in-plane compression are carried out, and the theoretical models from the energy balance principle are developed for calculating the EA of these lattice structures. Satisfactory agreement is achieved between the FE simulation results and the theoretical results. It indicates that the 30° oriented lattice has the largest EA capacity. Furthermore, inspired by the polycrystal microstructure of metals, novel structures of bi-crystal lattices and quad-crystal lattices are developed through combining multiple singly oriented lattices together. The results of FE simulations of compression indicate that the EA performances of symmetric lattice bi-crystals and quad-crystals are better than those of the identical lattice polycrystal counterparts. This work confirms the feasibility of designing superior energy absorbers with architected meso-structures from the inspiration of metallurgical concepts and microstructures.     

变体分比功能梯度点阵结构两尺度拓扑优化设计

功能梯度点阵结构以其轻质、高比强度/比刚度及高抗断裂韧性等诸多优越的性能受到广泛关注,由于其跨尺度及空间渐变的几何结构特点,目前功能梯度点阵结构的设计仍然是一项具有挑战性的任务。本文采用两步优化策略进行多分区功能梯度点阵结构刚度优化设计。（1）结合离散材料优化方法进行多分区离散材料优化,获得宏观均匀结构拓扑及合理的微结构分区。（2）进行空间梯度变化点阵结构参数优化,进一步扩大设计空间,获得变体分比的结构设计。相较于单一点阵微结构设计,两步优化策略可以更为有效地实现材料利用,显著提高结构刚度,且该方法适用于不同微结构构型,数值算例验证了该方法的有效性。     

求解一类网格结构模型的代数多重网格法

针对网格结构离散模型的特点,设计了一类适用于求解大规模二维网格结构数值计算的代数多重网格方法,详细描述了代数多重网格方法中粗化策略与插值算子的构造,并在此基础上得到了一类以该代数多重网格为预条件子的预处理方法。数值试验表明,本文建立的代数多重网格方法及相应的预处理方法是健壮的,具有较好的数值效率,非常适合于大规模网格结构材料的数值计算。近似连续模型的建立为代数多重网格方法的可靠性和计算的准确性提供了有效的理论基础。     

Optimal prestress of structures with frictional unilateral contact interfaces

Summary The problem of optimal prestress stabilization of elastic structures with frictional contact interfaces subject to static loads is studied in this paper. A linear elastic structure with given unilateral contact at frictional interfaces is considered. The prestressing control is modelled by the pin-load method. The static problem is formulated as a nonsymmetric variational inequality. The goal of the optimal control design is closing of the unilateral contact joints as well as minimization of the friction induced slips with a minimum effort. The resulting optimal control problem is nonsmooth and nonconvex, as it concerns the control of structures governed by variational inequalities. Appropriate techniques of nonsmooth analysis are used for its numerical solution. Effective computer realization and integration into existing finite element software is facilitated by appropriate static condensation techniques, which are outlined in the paper. Numerical examples illustrate the theory.     

Optimal semiactive control of structures with isolated base

The paper investigates the benefits of implementing the semiactive control systems in relation to passive viscous damping in the context of seismically isolated structures. Frequency response functions are compiled from the computed time history response to pulse-like seismic excitation. A simple semiactive control policy is evaluated in regard to passive linear viscous damping and an optimal non-causal semiactive control strategy. The optimal control strategy minimizes the integral of the squared absolute accelerations subject to the constraint that the nonlinear equations of motion are satisfied. The optimization procedure involves a numerical solution to the Euler-Lagrange equations Published in Prikladnaya Mekhanika, Vol. 42, No. 2, pp. 129–135, February 2006.     

两类网格结构模型的预处理方法

针对参考节点分别为q=3和q=4的网格结构模型,设计了两种预处理方法:以块对角逆为预条件子的共轭梯度法(BPCG)及以块下三角逆为预条件子的PGMRES法。数值结果表明,BPCG法对q=3具有很好的求解效率和鲁棒性,但对q=4的情形,特别是当α很小时,其求解效率将变得很差。当α很小时,以块下三角逆为预条件子的PGMRES法对求解q=4的蜂窝状结构在计算CPU和算法稳定性等方面均全面占优。在这两种预处理方法中,利用了基于标量椭圆问题的GAMG法求各个子块矩阵的逆,以提高内迭代运算效率。近似连续方程的建立为内迭代方法的合理性提供了有效的理论支撑。     

Effects of high order deformations on the strength of planar lattice materials

Lattice materials have been attractive over the last decade for use as load-carrying structures, energy absorbing elements and heat exchanging structures because of their excellent mechanical properties and multifunctional characters. However, the quantitative analysis accounting for high order deformations upon the collapse of lattice materials, which is important for their applications, has not been reported. An analytical investigation of yield surfaces with respect to the high order deformations was carried out for two typical planar lattice materials： triangular and Kagome lattices separately. The analytical results were validated by the finite element method （FEM） simulations. It was found that the effect of high order deformation on the yield strength increases with the relative density. The bending effect of the Kagome lattice is more obvious than that of the triangular one with the same relative density and stress state. The yield strength of the Kagome lattice calculated by neglecting the bending effect overestimates the result by more than 10% when the relative density is higher than about 11.1%, which may not be ignored in engineering applications. The yielding surfaces of the two lattice materials demonstrated in the paper also confirm the analytical results.     

DYNAMIC RESPONSE OPTIMIZATION DESIGN FOR ENGINEERING STRUCTURES BASED ON RELIABILITY

IntroductionTheoptimumdesignofstructuraldynamicresponseisoneoftheimportantcontentsinthestructuraloptimizationdesign ,inwhichtherespondedphysicalquantityofstructuresunderdynamicexcitationaretakenasobjectorconstraintfunctions.Fortheproblemcomesdownsimultaneouslytothedynamiccharacteristicanalysisandthedynamicresponseanalysisaswellastheoptimumdesign ,itismoredifficultandcomplicatedthantheproblemofstructuralstaticoptimumdesign[1].However,therestillcomeoutsomeresearchproductionsinpastyears.Forexampl…     

三轴转台框架的形状优化设计

本文叙述了三轴转台四种不同的布局型式。提出了用Ｂｅｚｉｅｒ曲线和Ｆｏｕｒｉｅｒ级数描述三轴转台框架的形状，将形状优化设计问题转换为可用参数优化设计方法求解的形式。建立了ＯＵＴ型三轴转台外框架结构的形状优化设计数学模型，然后给出了用增广乘子法对问题进行求解的步骤