地震作用下基于ADMF和系统参数组合的最优MTMD

多重调谐质量阻尼器 ( MTMD)是由许多频率成线性分布的调谐质量阻尼器组成。可能的系统参数组合形成 5种 MTMD,即 MTMD-1～MTMD-5。基于在基底加速度作用下具有一般 MTMD时结构的加速度传递函数 ,建立了 MTMD-1～ MTMD-5加速度动力放大系数 ( ADMF)的统一模式。利用 ADMF和数值寻优技术进行了详细的最优参数研究。最优参数包括 :最优频率间隔、最优阻尼比、最优调谐频率比。大量的数值比较表明 :在MTMD地震反应控制工程中 ,应优先选择 MTMD-1。     

地震作用下高层钢结构MTMD控制参数取值及优化设计研究

本文对地震作用下结构－MTMD系统的动力特性及优化设计进行了探讨,通过数值分析研究了MTMD系统各设计参数间的关系,给出了MTMD系统最优参数取建设,提出了MTMD系统优化设计及结构－MTMD系统优化设计方法,最后,算例说明了本文方法的应用及MTMD对结构地震反应控制的有效性。     

地震作用下结构的AMTMD主动控制策略

提出了一种新的控制策略--主动多重调谐质量阻尼器(AMTMD).AMTMD控制系统频率呈线性分布.AMTMD保持相同的刚度和阻尼但质量变化.AMTMD的主动控制力采用Roorda(1975)提出的生成模式.基于结构的广义振型模型,导出了设置AMTMD时结构的动力放大系数(DMF).于是AMTMD优化准则选择为结构最大动力放大系数的最小值的最小化.分别使用位移、速度和加速度传感器,通过最优搜寻,研究了反映AMTMD有效性和鲁棒性的参数.这些参数包括:频率间隔、平均阻尼比、调谐频率比、Min.Min.Max.DMF、标准化反馈增益系数和环增益系数.为比较,同时考虑了多重调谐质量阻尼器和主动调谐质量阻尼器.而且,数值结果表明:AMTMD比MTMD具有更高的有效性和鲁棒性且比ATMD也有更高的有效性.     

多维地震作用下高层结构振动混合控制研究

针对水平和竖向地震作用下高层建筑结构的混合振动控制问题,研究调谐质量阻尼器(tuned mass damper, TMD)体系、隔震结构体系、隔震与TMD混合控制体系3种策略对水平与竖向地震共同作用下结构振动响应的减振效果。选取典型的20层钢结构Benchmark结构模型,利用ANSYS软件建立带有TMD和隔震层结构的有限元模型,比较了结构在水平地震单独作用下与水平和竖向地震共同作用下的振动响应。结果表明,水平方向上的振动响应无明显变化;竖直方向上,有控状态下的减振指标相对于无控状态出现了增大现象,尤其是层间隔震结构增大较为明显。研究成果可为高烈度区高层隔震结构设计提供参考。     

地震作用下结构的基于阻尼柔性连接MTMD控制

研究了基于阻尼柔性连接多重高谐质量阻尼器(MTMD)在减小结构地震反应方面的动力特性。利用导出的设置MTMD结构的传递函数，建立了设置MTMD结构的动力放大系数(DMF)设计公式，于是MTMD的优化准则可定义为结构最大动力放大系数的最小值的最小化(Min．Min．Max．DMF)。根据优化准则，得不同刚度比MTMD的最优参数和相应的Min.Min.Max．DMF值。为比较，同时给出了基于阻尼刚性连接(R＝0)MTMD的结果，广泛的数值分析表明，传统的阻尼刚性连接MTMD的性能可以扩展至一定刚度比范围的阻尼柔性连接MTMD。     

强震时高层钢结构中外挂板减震作用的下限值

文中利用常遇地震下的结构分析模型,对在罕遇地震（强震）作用下设置外挂板的实际高层钢结构分别输入多条地震波进行了时程反应近似分析．计算结果表明,在罕遇地震作用下与在常遇地震作用下一样,外挂板有不可忽视的减震作用．通过分析,找到了外挂板减震作用的下限值     

大射电望远镜馈源舱的风激振动及其MTMD减振设计研究

采用修正的Davenport风谱来模拟风荷 ,分析了FAST (Five -hundred -meterApertureSphericalTelescope)大射电望远镜馈源舱在该风荷作用下的振动 ,并根据分析和计算的结果设计了多频调谐质量阻尼器 (MultipleTunedMassDampers) ,计算结果表明 ,这种动力吸振阻尼器可以有效地减少馈源舱的振动     

钢结构电视塔的MTMD风振控制研究及设计

在风荷载作用下，ＭＴＭＤ（ＭｕｔｉｐｌｅＴｕｎｅｄＭａｓＤａｍｐｅｒｓ）能有效地控制结构的风振反应，本文考察了ＭＴＭＤ的基本动力特性及其主要参数变化对风振控制效果的影响。数值分析表明，ＭＴＭＤ在控制结构反应有效性和稳定性方面均好于经优化设计的ＳＴＭＤ（ＳｉｎｇｅＴｕｎｅｄＭａｓｓＤａｍｐｅｒ）。最后，以洛阳电视塔为工程背景，阐述了ＭＴＭＤ的设计方法。     

正交约束下的D-最优试验设计

针对一类因素间具有正交约束的回归模型的试验设计问题,以D-最优为准则,以加速度计试验设计为背景,从试验点的均衡分布原则出发,以不同试验环境下合加速度大小为依据,给出了不同环境下球内接正多面体的试验方法,通过进一步计算和深入分析表明,单球面时为避免信息矩阵降秩应采用不同安装方式,降低模型维数以达到试验目的;两球面下试验设计的优劣与两个半径的大小有关,半径越大计划越优,而且信息矩阵的秩最大时两个球半径之间呈近似线性关系.试验结果的优劣还受到初始安装位置的影响,为了达到最优化,应使合加速度方向与加速度计的某个轴同向.     

分布振子复合板的模态阻尼及多点激励下阻尼减振相关性

分布阻尼振子可拓宽结构减振频带,因此可将振子分布于板中以形成复合板（简称“分布振子复合板”）,进而实现较宽的减振频带．对于多点支撑处受到宽频非一致激励（例如在不同激励点处的激励频率、幅值与相位有差异）的分布振子复合板,目前还缺乏有效简便的优化控制指标．在作者之前的研究中,针对含分布振子的梁推导了基于模态应变能的模态阻尼计算理论,讨论了模态阻尼与单点激励下梁的减振效果的相关性,并应用于宽频减振设计优化．本文进一步将模态阻尼计算理论推广到分布振子复合板,并将研究从梁的单点激励扩展到板的多点非一致激励下的阻尼减振相关性．首先,在利用模态应变能法推导得到分布振子复合板的模态阻尼计算公式后,从理论上讨论了不同边界条件与模态阶次对计算结果的影响,以及计算理论的适用性．而后,进一步通过有限元参数分析了边界条件、频率比、模态阶次与质量比的影响．最后,通过算例分析了无振子板或分布振子复合板在四个激励点具有多种幅值与相位组合情况下的稳态响应．结果表明,推导的模态阻尼计算公式可正确预测不同边界条件下的模态阻尼,且理论预测的模态阻尼与基板的稳态平均加速度减小率、稳态峰值应变能减小率均有较高的相关性．     

高层建筑TMD风振控制优化设计

本文探讨了高层建筑TMD风振控制优化设计方法,研究了高层建筑TMD风振控制最优参数取值问题,给出了高层建筑TMD风振控制设计步骤,最后给出了算例说明及其应用。     

Optimal design of structures subjected to follower forces

Summary The optimal design of columns, consisting of segments with arbitrary thickness and length, subjected to follower forces is considered in this paper. The solution is presented for the case of cross modal interaction of a vibrating system. Since the resulting boundary value problem is nonselfadjoint only approximate solutions are generally possible. Herein, for the solution the method of the generalised functional and the transfer matrix technique have been used. As typical examples, the solutions of Beck's, Reut's, Leipholz's and Hanger's column are investigated.

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Übersicht Behandelt wird die optimale Auslegung von Stäben, die aus Abschnitten beliebiger Querschnittsfläche und Länge bestehen und durch Folgelasten beansprucht sind. Eine Lösung wird angegeben unter Berücksichtigung des Zusammenwirkens der Eigenformen des Systems. Da das zugehörige Randwertproblem nicht selbstadjungiert ist, sind im allgemeinen nur Näherungslösungen angebbar. Hier werden das Verfahren eines generalisierten Funktionais sowie das Übertragungsmatrizenverfahren verwendet. Als typisches Beispiel werden die Lösungen zu den Stäben von Beck, Reut, Leipholz und Hauger betrachtet.

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Fellow of the Alexander von Humboldt Foundation 1978/1979, visiting the University of Hannover     

Efficient design sensitivities of structures subjected to dynamic loading

Calculation of design sensitivities often involves much computational effort, particularly in large structural systems with many design variables. Approximation concepts, which are often used to reduce the computational cost involved in repeated analysis, are usually not sufficiently accurate for sensitivity analysis. In this study, approximate reanalysis is used to improve the efficiency of dynamic sensitivity analysis. Using modal analysis, the response derivatives with respect to design variables are presented as a combination of sensitivities of the eigenvectors and the generalized displacements. A procedure intended to reduce the number of differential equations that must be solved during the solution process is proposed. Efficient evaluation of the derivatives, using finite difference and the recently developed combined approximations approach, is presented. Numerical examples show that high accuracy of design sensitivities can be achieved efficiently.     

高层建筑桩箱（筏）基础的优化设计

基于桩箱基础的工作特征，建立桩箱基础最小造价的优化设计数学模型。算例表明，优化设计具有主动改进设计的优势和明显的经济效益。     

Optimum design of band-gap beam structures

The design of band-gap structures receives increasing attention for many applications in mitigation of undesirable vibration and noise emission levels. A band-gap structure usually consists of a periodic distribution of elastic materials or segments, where the propagation of waves is impeded or significantly suppressed for a range of external excitation frequencies. Maximization of the band-gap is therefore an obvious objective for optimum design. This problem is sometimes formulated by optimizing a parameterized design model which assumes multiple periodicity in the design. However, it is shown in the present paper that such an a priori assumption is not necessary since, in general, just the maximization of the gap between two consecutive natural frequencies leads to significant design periodicity.The aim of this paper is to maximize frequency gaps by shape optimization of transversely vibrating Bernoulli–Euler beams subjected to free, standing wave vibration or forced, time-harmonic wave propagation, and to study the associated creation of periodicity of the optimized beam designs. The beams are assumed to have variable cross-sectional area, given total volume and length, and to be made of a single, linearly elastic material without damping. Numerical results are presented for different combinations of classical boundary conditions, prescribed orders of the upper and lower natural frequencies of maximized natural frequency gaps, and a given minimum constraint value for the beam cross-sectional area.To study the band-gap for travelling waves, a repeated inner segment of the optimized beams is analyzed using Floquet theory and the waveguide finite element (WFE) method. Finally, the frequency response is computed for the optimized beams when these are subjected to an external time-harmonic loading with different excitation frequencies, in order to investigate the attenuation levels in prescribed frequency band-gaps. The results demonstrate that there is almost perfect correlation between the band-gap size/location of the emerging band structure and the size/location of the corresponding natural frequency gap in the finite structure.     

Design and identification of high performance steel alloys for structures subjected to underwater impulsive loading

Martensitic and austenitic steel alloys were designed to optimize the performance of structures subjected to impulsive loads. The deformation and fracture characteristics of the designed steel alloys were investigated experimentally and computationally. The experiments were based on an instrumented fluid–structure interaction apparatus, in which deflection profiles are recorded using a shadow Moiré technique combined with high speed imaging. Fractographic analysis and post-mortem thickness reduction measurements were also conducted in order to identify deformation and fracture modes. The computational study was based on a modified Gurson damage model able to accurately describe ductile failure under various loading paths. The model was calibrated for two high performance martensitic steels (HSLA-100 and BA-160) and an austenitic steel (TRIP-120). The martensitic steel (BA-160) was designed to maximize strength and fracture toughness while the austenitic steel (TRIP-120) was designed to maximize uniform ductility, in other words, to delay necking instability. The combined experimental–computational approach provided insight into the relationships between material properties (strength, uniform ductility, and post-necking ductility) and blast resistance of structures. In particular, the approach allowed identification of material/structure performances by identifying impulse-center deflection behavior and the impulse leading to panel fracture.     

Optimum design of laminated composite foam-filled sandwich plates subjected to strength constraint

Optimum design of laminated composite sandwich plates with both continuous (core thickness) and discrete (layer group fiber angles and thicknesses) design variables subjected to strength constraint is studied via a two-level optimization technique. The strength of a sandwich plate is determined in a failure analysis using the Tsai–Wu failure criterion and the finite element method which is formulated on the basis of the layerwise linear displacement theory. In the first level optimization of the design process, the discrete design variables are temporarily treated as continuous variables and the corresponding minimum weight of the sandwich plate is evaluated subject to the strength constraint using a constrained multi-start global optimization method. In the second level optimization, the optimal solution obtained in the first level optimization is used in the branch and bound method for solving a discrete optimization problem to determine the optimal design parameters and the final weight of the plate. Failure test of laminated composite foam-filled sandwich plates with different lamination arrangements are performed to validate the proposed optimal design method. A number of examples of the design of laminated composite foam-filled sandwich plates are given to demonstrate the feasibility and applications of the proposed method.