框架结构平扭耦联弹塑性地震反应分析的力学模型

本文分别用理想弹塑性和运动强化模型来描述结构材料的力学行为,考虑柱中双向弯矩的相互作用,采用广义应力空间的屈服条件及与其相关联的流动法则,对剪切型框架结构平扭耦联弹塑性地震反应分析提供了一个力学模型。分析中用一个线性的附加项来计入“P-△”效应的影响。     

基于Takagi—Sugeno模型的半主动TLCD对偏心结构的减震控制

采用在结构水平双向设置TLCD半主动控制装置的方法，对偏心结构在多维地震作用下的振动控制问题进行了研究。首先论述了基于Takagi—Sugeno模型的模糊神经网络的基本理论。然后介绍结构-TLCD扭转耦联控制系统微分方程及其状态空间求解方法，最后在建立起半主动控制策略的基础上。利用基于Takagi—Sugeno模型的模糊神经网络，根据控制准则调整TLCD的开孔率，实现对结构的半主动控制。数值结果表明，这种方法能对结构的平动反应和扭转反应都能起到较好的减震效果。     

半主动TLCD对偏心结构的离散模糊变结构控制

采用在结构水平双向设置TLCD半主动控制装置的方法,对偏心结构在多维地震作用下的离散模糊变结构控制问题进行了研究.首先建立了结构-TLCD扭转耦联控制系统微分方程及其离散化状态空间表达,然后阐述了基于模糊逻辑的变结构控制的基本策略,最后应用该模糊变结构控制策略对一个五层偏心结构的TLCD半主动控制问题进行了仿真分析.仿真分析的结果表明,该方法在对结构的平动反应和扭转反应都能起到较好的减震效果的同时,还具有对结构固有参数不确定性的较强的鲁棒性.     

基于概率地震需求分析的750 kV-SF6罐式断路器耦联体系地震易损性模型

变电站作为电力系统的枢纽,其抗震性能评估尤为重要,其中罐式断路器耦联体系是变电站中的重要设备之一。为研究750 kV-SF₆罐式断路器耦联体系的抗震性能,采用增量动力分析(IDA)以及概率地震需求分析(PSDM)相结合的方法评估了其地震易损性。首先分析了750 kV-SF₆罐式断路器耦联体系的结构特性和震损特征,构建了有限元模型。通过增量动力分析(IDA),以地面峰值加速度(PGA)为地震动输入参数,得到关键易损部位的地震响应。在此基础上,通过概率地震需求模型(PSDM)生成了每个易损部位在不同震损状态下的地震易损性曲线。最后,基于可靠度理论计算得到了750 kV-SF₆罐式断路器耦联体系的地震易损性模型。结果表明,可以确定该结构在不同PGA下发生完全、严重、中度和轻微损坏的概率,反映了结构的抗震性能水平,例如当PGA达到0.6g时,750 kV-SF₆罐式断路器耦联体系4种破坏状态的概率分别分0%,1%～5%,88%～93%和100%。     

考虑双向地震动作用的非对称结构多维Pushover分析

目前的Pushover分析多集中于平面单向分析,考虑到非对称结构反应的多维性,在单向地震动作用振型Pushover分析研究基础上,提出了考虑双向地震动作用的结构多维Pushover分析程序。采用弹性振型分解的思路,将非线性结构反应近似为结构多振型弹塑性反应的叠加,进而将结构按振型等效为多个等效方程,将每一等效方程转化为以双向实际地震记录的组合为地震输入的等效单自由度体系。在此基础上给出了考虑双向地震作用的非对称结构多维Pushover分析程序,并阐述了该方法与传统Pushover分析方法的区别,最后通过算例将该方法结果与非线性时程分析结果进行比较,证明了该方法具有一定的准确性。     

考虑扭转耦联效应的附属结构最优位置分析

实际建筑物大多为偏心结构,扭转耦联效应使同层楼板上不同位置处附属结构的动力响应也不相同,通常存在一个平面最优位置.本文建立了主附结构体系的扭转耦联模型,利用复模态理论和模式搜索方法研究了影响附属结构最优位置的几个重要因素,包括地震输入方向、场地类别、主体结构偏心、附属结构质量、频率及阻尼比等,通过数值分析得出了一些有益的结论.     

两向地震波的输入方向对平—扭耦联系统动力反应的影响

本文按有限输入方向计算并采用线性予测的方法讨论了两向地震对平-扭耦联系统动力反应的影响.通过实例计算说明:弹塑性结构受地震波输入方向的影响显著大于相应弹性结构.对弹塑性结构而言,在本质上不存在确定不变的最不利地震波输入方向.     

调液阻尼器对结构扭转耦联振动控制的优化设计

提出了利用调液柱型阻尼器(Tuned Liquid Column Dampers,简称TLCD)和环形调液阻尼器(Circular Tuned Liquid Column Dampers,简称CTLCD)来控制偏心结构在多维地震作用下扭转耦联振动的方法。采用遗传算法,在双向地震作用下,对调液阻尼器的相关参数进行优化。选取了两种目标函数,一种只考虑最大的楼层反应,另一种考虑结构所有自由度的反应。用一个12层的偏心结构作为算例,进行优化计算,结果表明,采用第二种目标函数得到的阻尼器的参数,能有效降低结构的平动反应和扭转反应。     

基于修正的Clough-Penzien地震动模型时MTMD的动力特性

研究了由许多刚度和阻尼保持常量而频率呈线性分布的TMD形成的MTMD的地震特性，基于虚拟激励法和本文提出的平稳过滤有色噪声地震动模型（修正的Clough-Penzien地震动模型），建立了结构－MTMD系统的传递函数，进而导出了设置MTMD时结构的动力放大系数（DMF）明确表达式。MTMD的优化准则可选为最大动力放大系数的最小值的最小化（Min.Min.Max.DMF)。通过最优搜寻可得MTMD的最优频率间隔、平均阻尼比、调谐频率比和相应的无量纲控制有效性指标。考虑结构受控频率与场地土卓越频率比的不同取值和不同场地类型，研究了场地土卓越频率和场地类型对MTMD最优参数及有效性的影响。而且，为比较，基于Clogh-Penzien地震动模型和不考虑地震动模型的结果也被考虑。     

考虑竖向地震作用的振动控制及其优化研究

目前,MRD结构的分析通常只考虑水平地震动而不考虑竖向地震动的影响,地面的水平运动和竖向运动具有相关性,从而影响控制效果．因此对双向地震耦合作用下MRD结构的理论进行研究,建立动力分析模型并得出运动微分方程．以8层MRD结构为例进行地震反应分析,研究表明,考虑和不考虑竖向地震作用,MRD对结构均有良好的控制作用,但是竖向地震作用的存在,使结构各层的层间位移峰值有不同程度的增加,其增量随着竖向地震作用的增加而增加,因此建议在高烈度地区的建筑物考虑竖向地震作用对结构的影响．建立MRD结构优化设计模型,采用IHGA程序对结构进行优化设计．结果表明, MRD结构在各种工况下的各项地震反应均得到更好的控制．     

The Description of Localized Normal Modes in a Chain of Nonlinear Coupled Oscillators Using Complex Variables

We present an asymptotic approach to the analysis of coupled nonlinearoscillators with asymmetric nonlinearity based on the complexrepresentation of the dynamic equations. The ideas of the approach arefirst developed for the case of the system with two degrees of freedom.Special attention is paid to the study of localized normal modes in achain of weakly coupled nonlinear oscillators. We discuss also certainpeculiarities of the localization of excitations in the case of strongcoupling between the oscillators.     

基于对称性的三维车辆轨道耦合系统随机振动虚拟激励方法

基于结构的对称性提出了用于三维车辆轨道耦合系统高效随机动力响应分析的虚拟激励方法.车辆采用刚体动力学模型,轨道结构利用三维轨道广义单元建模,车辆与轨道通过线性轮轨关系耦合.采用虚拟激励法将高低、方向和水平三类轨道不平顺转化为一系列筒谐的虚拟不平顺;考虑车辆及轨道结构的对称性,分别推导了耦合系统的对称和反对称凝聚矩阵,提出了用于车辆轨道耦合系统动力响应计算的自由度凝聚方法,将耦合系统的自由度缩减至原来的一半以下,并在此基础上实现了耦合系统随机振动的高效分析.数值算例将本文方法与传统有限元方法进行对比,验证了本文方法的正确性和有效性.     

Inelastic seismic demand of low-rise buildings with soil-flexibility

Relying on the ductile behaviour of structures during earthquake, building codes introduce response reduction factors (R) to reduce design forces in earthquake resistant design. However, applicability of such factors has not been systematically explored for low-rise buildings with stiff periods. Present study is an attempt to address this issue. Both elasto-plastic and degrading hysteresis behaviour for lateral load-resisting structural elements are considered herein, while sub-soil is idealized as linear and elasto-plastic in parallel. The study recognizes that inelastic response for short period systems is very sensitive to R and may be phenomenally amplified even for small R due to soil-structure interaction implying restrictive applicability of dual-design philosophy. Limited study on the plan-asymmetric low-rise buildings depicts that inelastic response of the asymmetric structure relative to its symmetric counterpart is not appreciably influenced due to soil-structure interaction (SSI). The study also confirms that equivalent single story model characterized by the lowest period rather than the fundamental one of the real system tends to yield conservative estimation of inelastic demand at least for the short-period systems.     

Optimization of characteristics of porous materials based on a modal synthesis method

Complex structures used in the automotive industry often include porous materials, in order to reduce the noise in acoustic cavities. The method proposed in this paper aims at optimizing the characteristics of these porous materials using modal criteria based on the modal analysis of the structure. The use of a generalize modal synthesis method allow to describe the structure and the cavities with sets of modes; the size of the resulting system is smaller, for only generalized degrees of freedom are used for each part of the coupled fluid–structure system. First, a modelization of the porous media is proposed, and the generalized modal analysis method is explained. An optimization is then processed on the thickness of the porous materials.     

非饱和土-结构动力响应的多耦合周期性有限元法

真实的地基土体-隧道系统中土体及结构性质往往沿线路纵向变化.为考虑土体与结构沿纵向的变化特性,提出了一种非饱和土-结构系统动力响应分析的多耦合周期性有限元法.首先基于非饱和土的实用波动方程,采用Galerkin法推导了单节点5个自由度的非饱和土ub-pl-pg格式有限元表达式,相比于单节点9个自由度的ub-v-w格式有...     

COUPLED VIBRATION OF STRUCTURAL THIN-WALLED CORES

This paper presents an analysis of the coupled vibration of asymmetric core structures in tall buildings. The governing equation of free vibration and its corresponding eigenvalue problem, which is a set of equations for laterally flexural vibrations in two different directions coupled by a warping-St. Venant torsional vibration, are derived. Based on the Calerkin method, a generalized approximate method is developed for the analysis of coupled vibration and thus proposed for determining the natural frequencies and mode shapes of the structure in triply-coupled vibration. The results of the proposed method for the example structure show good agreement with those of the FEM analysis. The proposed method has been shown to provide a simple and rapid, yet accurate, means for coupled vibration analysis of core structures.     

Reduced order nonlinear aeroelasticity of swept composite wings using compressible indicial unsteady aerodynamics

Nonlinear dynamic aeroelasticity of composite wings in compressible flows is investigated. To provide a reasonable model for the problem, the composite wing is modeled as a thin walled beam (TWB) with circumferentially asymmetric stiffness layup configuration. The structural model considers nonlinear strain displacement relations and a number of non-classical effects, such as transverse shear and warping inhibition. Geometrically nonlinear terms of up to third order are retained in the formulation. Unsteady aerodynamic loads are calculated according to a compressible model, described by indicial function approximations in the time domain. The aeroelastic system of equations is augmented by the differential equations governing the aerodynamics lag states to derive the final explicit form of the coupled fluid-structure equations of motion. The final nonlinear governing aeroelastic system of equations is solved using the eigenvectors of the linear structural equations of motion to approximate the spatial variation of the corresponding degrees of freedom in the Ritz solution method. Direct time integrations of the nonlinear equations of motion representing the full aeroelastic system are conducted using the well-known Runge–Kutta method. A comprehensive insight is provided over the effect of parameters such as the lamination fiber angle and the sweep angle on the stability margins and the limit cycle oscillation behavior of the system. Integration of the interpolation method employed for the evaluation of compressible indicial functions at any Mach number in the subsonic compressible range to the derivation process of the third order nonlinear aeroelastic system of equations based on TWB theory is done for the first time. Results show that flutter speeds obtained by the incompressible unsteady aerodynamics are not conservative and as the backward sweep angle of the wing is increased, post-flutter aeroelastic response of the wing becomes more well-behaved.     

Bifurcation and chaos analysis of torsional vibration in a PMSM-based driven system considering electromechanically coupled effect

The rotor of PMSM-based electromechanically driven system is a typical electromechanically coupled system. In this paper, we analyzed the nonlinear magnetic interaction torque of permanent magnet synchronous motor (PMSM) and deduced the nonlinear electromechanically coupled equation of PMSM-based electromechanical driven system using Lagrange–Maxwell theory. We determined the equation of the movement of the dynamic system from his asymmetric double well potential. The unperturbed system was classified to several categories based on the shapes of potential functions and phase portraits. An analytical criterion for homoclinic chaos is written in terms of the system parameters by means of Melnikov’s method. Detailed numerical studies including phase portrait, Poincare map, and bifurcation diagram confirm the analytical prediction and reveal the effect of excitation amplitude and damp on the system transition to chaos. The conclusion can provide reference for deeply research the dynamic behaviors of mechanical drive system.     

Resonance response of fluid-conveying pipe with asymmetric elastic supports coupled to lever-type nonlinear energy sink

This paper studies the vibration absorber for a fluid-conveying pipe, where the lever-type nonlinear energy sink (LNES) and spring supports are coupled to the asymmetric ends of the system. The pseudo-arc-length method integrated with the harmonic balance method is used to investigate the steady-state responses analytically. Meanwhile, the numerical solution of the fluid-conveying pipe is calculated with the Runge-Kutta method. Moreover, a special response, called the collapsible closed detached response (CCDR), is first observed when the vibration response of mechanical structures is studied. Then, the relationship between the CCDR and the main structure primary response (PR) is obtained. In addition, the closed detached response (CDR) is also observed to research the resonance response of the fluid-conveying pipe. The appearance of either the CCDR or the CDR does affect the resonance attenuation. Furthermore, the mentioned two phenomena underline that the trend of vibration responses under external excitation goes continuous and gradual. Besides, the main advantage of the LNES is presented by contrasting the LNES with the nonlinear energy sink (NES) coupled to the same pipe system. It is found that the LNES can reduce the resonance response amplitude by 91.33%.     

Dynamic Model of a Periodic Medium with Double Porosity

The paper presents a unified mathematical approach for describing the dynamic stressstrain state of mechanical structures from heterogeneous materials possessing a double coupled system of pore channels filled with fluid. New dynamic equations describing the oscillations of poroelastic systems based on the developed model of a continuous medium with additional degrees of freedom in the form of various pressures of the components constituting the liquid phase of the material are obtained. The equations and the method of obtaining them have a greater degree of generalization than those encountered in the literature. Theoretical results can be used to study the propagation of vibrations in fractured geological rocks saturated with liquid, to develop technical systems of new structural materials with a porous structure, for the analysis of micro streams of fluid in the hierarchical system of microporous bone tissue.