Semiactive Control of Building Structures with Semiactive Tuned Mass Damper

Abstract:   This study proposed a new semiactive control device for building control. Semiactive tuned mass damper (STMD) combine a tradition tuned mass damper (TMD) and a semiactive damper. The property of semiactive damper can be adjusted online to produce the desired control force. In the present year, many types of semiactive dampers are proposed. In this study, the variable damping device and MR damper are used to illustrate the control effect of STMD. In addition, the control effect of the TMD and active tuned mass damper are also compared. The numerical simulation results show that the STMD can greatly improve the control efficiency of TMD.     

Numerical Investigation of a Variable Damping Semiactive Device for the Mitigation of the Seismic Response of Adjacent Structures

Abstract:   When two structures in close proximity and with different properties (heights, structural systems, materials) are subjected to a strong seismic ground motion there is the possibility that pounding between them may occur. The large impact loads induced by this phenomenon usually lead to catastrophic results. One way to overcome this effect is to couple the structures through elastic or damping elements. This article examines the use of a new variable damping device as a coupling element. The system, which is termed a variable damping semiactive (VDSA) device, consists of two dampers with constant parameters whose lower ends are attached to a common vertical rod whereas the upper ends are attached to the two structures. As the structures vibrate due to the ground motion, the lower end is moved up and down by means of an actuator. By changing the orientation of the dampers, the effective damping in the two structures can be changed in time in an appropriate manner to minimize the response. A new control law is used to calculate the optimal position of the dampers. The algorithm, referred to as Q v , is a variation of the Instantaneous Optimal Control and it is based on the minimization of a performance index J quadratic in the state vector, the control force vector, and a vector of absolute velocities measured at selected points. The algorithm includes a generalized LQR scheme where penalties are imposed on the state vector, on the control vector, and on the absolute velocity vector through three predefined matrices. A numerical simulation is used to verify the performance of the proposed protective system in reducing the seismic response to a series of historic earthquakes. The results show that the proposed device is able not only to eliminate the pounding effects but also to significantly reduce the response of the individual adjacent structures .     

Neuro-Fuzzy Control of Railcar Vibrations Using Semiactive Dampers

Abstract:   This article describes a new approach to reducing vertical vibrations in a 70-ton railcar using a neuro-fuzzy controller and a magnetorheological (MR) damper. A semiactive control technique is developed for a two-degree-of-freedom quarter car model of the railcar that has an installed MR damper. A fuzzy controller in real time continuously updates damping properties of the device. The controller uses feedback acceleration of the freight mass to specify a voltage signal to the MR damper. Correlations between acceleration (controller input) and voltage applied to the MR damper (controller output) are developed using Neuro Fuzzy Controller (NEFCON). To assess effectiveness of the semiactive control scheme, responses of the railcar to various haul conditions are compared with those for uncontrolled and for passive operating conditions of the MR damper. Results indicate that semiactively controlled MR dampers can reduce vibrations to acceptable levels provided that sufficient force capacity can be supplied by the damper .     

结构半主动变阻尼控制的研究

作为经典范例之一,半主动变阻尼系统得到了广泛的应用,然而近来的研究显示仍需要对其控制性能重新认识。本文以谐波作用下支座激励的理论为出发点,讨论了粘性变阻尼控制系统可能成立的基本条件和适用范围。算例以一个设置在基础层的半主动变阻尼器控制系统为例,采用离复位控制策略进行了数值模拟,并得出了两个重要结论:(1)变阻尼控制系统只有在结构动力反应远离共振的情况下,才有可能同时取得位移峰值和加速度峰值的减小;(2)结构动力反应与控制效果的改善依赖地面运动特性,在一般情况下相比被动阻尼控制并不能明显提高控制效果,甚至有所不及。     

间隔阻尼层式支重轮减振效果分析

针对传统刚性支重轮减振效果较差的现状，将减振性能良好的间隔阻尼层结构（管状）引入支重轮，以提高支重轮结构的损耗因子，改良其减振性能。通过建立支重轮减振模型，推导出其幅频特性函数，结合实际工作状况和支重轮的结构设计出实体模型。以某型号推土机为研究对象，利用Matlab软件编写仿真程序，并将推土机的各项参数带入，仿真结果表明，经过改良的支重轮可对履带式工程车辆的振动进行有效的缓冲，并能避免整机在低频工作状态下发生共振。     

State-Derivative Feedback Control of Cable Vibration Using Semiactive Magnetorheological Dampers

Abstract:   This article presents the theoretical and in situ experimental studies on state-derivative feedback control of bridge cable vibration using semiactive magnetorheological (MR) dampers. The semiactive feedback control is accomplished using only one MR damper and one accelerometer collocated near the lower end of the cable. Within the framework of reciprocal state space (RSS), the linear quadratic regulator (LQR) control technique is applied to formulate state-derivative feedback control law and derive the feedback and estimator gains for real-time control of cable vibration using MR dampers. The state-derivative feedback control strategy directly uses acceleration information for feedback and state estimation, which is usually the only measure available in practical cable vibration control implementation. More importantly, the control force commanded by the state-derivative feedback control strategy based on energy weighting is a dissipative force except for low velocity and small force, which is therefore implementable by the semiactive MR dampers without clipping. Numerical simulations of state-derivative feedback control for a stay cable in the cable-stayed Dongting Lake Bridge are conducted under sweeping sine excitation and sinusoidal step relaxation excitation, and then the experimental validation of the prototype cable is carried out in the bridge site with the help of the real-time control system dSPACE. Good agreement between the simulation and experimental results is observed.     

CFRP索和钢索斜拉桥地震响应分析与抗震验算

为了研究碳纤维增强复合材料(CFRP)索和钢索斜拉桥在地震响应和抗震性能方面的差异,以苏通长江公路大桥为参考建立了有限元动力学模型.采用等轴向刚度准则进行钢索和CFRP索的替换,利用时程分析法比较了不同索斜拉桥的地震响应值,并进行了抗震验算和评价.结果表明:相对钢索斜拉桥,CFRP索斜拉桥的自振频率有明显提高,位移和内力地震响应值减小,响应衰减较快,且抗震性能优势明显,其原因是CFRP索斜拉桥自重轻、索桥耦合振动的概率小、索的材料阻尼大等;所得结论可为CFRP索在大跨斜拉桥中的应用提供参考.     

多索预应力桁架结构优化设计

对影响多索预应力桁架结构优化设计的变量,包括索力值和截面尺寸进行研究。考虑了预应力作用阶段及预应力和荷载共同作用阶段的性态约束条件,建立了以结构重量最小为目标函数的数学优化模型。在求解方法上,用满应力准则法确定索力值和截面尺寸并将索力值的求解转化为线性规划模型。算例表明,方法具有较好的计算效率和收敛性。     

FRP索与钢索的求解计算和极限跨度

随着跨度的增大,自重对单索的影响就越明显,FRP(纤维增强复合材料）索的自重小,在大跨度结构中应用具有优势。单索的理论计算是索结构进行设计的基础。单索在自重作用下的求解,按照不同的假设,有弹性的悬链线解答、悬链线解答和抛物线解答。针对工程应用,以索端张拉轴力为已知量,推导了3种解答方法的求解方程,得到了关于张拉轴力的一元方程,方便了工程应用。另外,分别对斜拉索和水平索的悬链线解和抛物线解的精度进行了分析和比较,建议了2种近似求解方法的使用范围。根据求解结果,对FRP索和钢索的极限跨度进行了分析;结果表明FRP索有利于实现更大的跨度。FRP索的极限跨度可达钢索的4.4倍。     

袋式除尘器减震性能的研究

提出了袋式除尘器在水平地震作用下的计算模型,建立了结构的运动微分方程,分析了其抗震性能,得出了悬挂布袋对除尘器主体结构有良好的减震效果的结论。并对结构在3种不同地震波作用下进行了时程分析,发现场地土类别和地震波的特性对其减震率有一定的影响。     

结构变刚度/变阻尼控制若干问题的研究

尽管已有的研究证明,传统的半主动变刚度控制系统和变阻尼控制系统均可以有效地抑制结构在地震激励下的动力反应,然而最新的研究显示二者仍然存在明显的不足之处,需要进一步深入研究.本文首先就变刚度,变阻尼控制目前的研究现状分别进行了综合论述,然后重点探讨了二者各自存在的不足之处,并指出了值得关注的后续研究方向.     

预应力体外索的应用

通过北京学院南路立交及紫竹院立交两座预应力体外索钢桥的施工实践,对体外索的种类与选用、体外索的布置、锚具及转向器的设置、灌浆材料、预应力张拉、施工变形和施工程序等八个方面进行了总结,得出各自的优、缺点,以供同行参考。     

拉索预应力空间格结构的分析和设计

本文对拉索预应力空间网格结构的拉索布置、结构分析、节点构造等设计中的若干问题进行了论述,供工程设计参考.     

预应力体外索在叠合梁桥中的应用

结合广州市内环路工程中山一路西段的施工实践,介绍新型叠合梁结构中钢箱梁内预应力体外索的应用。     

具有耗能减震层的连体结构减震

以连体结构性能为研究视角,用模型测定减震性能,分析减震效果,结合结构工程实例,对连体结构、连廊结构进行设计,以及对结构抗震性能进行有效分析,分别从连廊结构、主体结构等方面对连体结构减震效果进行阐述,以期发挥连体结构的施工价值,增强减震性,维护建筑安全.     

带有多根预应力锚索的柔性桩设计计算方法

本文介绍了在预应力锚索桩设计计算方法中引入了斜拉桥设计计算中的初张、调索新概念 ,以实现桩身弯矩均匀的设计新思想 ,还提出了桩身混凝土预应力设计新概念。给出了一个示例 ,并与现行一般设计相比较 ,以便理解新的设计思想的合理性和重要性     

粘滞阻尼墙耗能减震结构的研究进展

本文阐述了粘滞阻尼墙的原理与特点,总结了国内外对这一耗能减震装置的试验研究与建立的本构模型,以及将其附加于结构之中所进行的研究与应用状况,探讨了附加粘滞阻尼墙结构的分析与设计方法,提出了今后需要研究的若干问题。     

附加粘弹性阻尼墙结构设计应用

利用结构设计软件Etabs对某部委全钢结构的办公大楼进行分析。原结构采用框架偏心支撑体系,有控结构则以粘弹性阻尼墙取代部分支撑,对2种结构体系在各种地震加速度峰值作用下的各项性能指标进行分析比较,得出结论：粘弹性阻尼墙可以有效减小结构的地震反应,提高了结构的抗震性能,且满足规范的各项要求。     

Blind Modal Identification in Frequency Domain Using Independent Component Analysis for High Damping Structures with Classical Damping

Output‐only modal identification methods are practical for large‐scale engineering. Recently, independent component analysis (ICA) which is one of the most popular techniques of blind source separation (BSS) has been used for output‐only modal identification to directly separate the modal responses and mode shapes from vibration responses. However, this method is only accurate for undamped or lightly damped structures. To improve the performance of ICA for high damping structures, this article presents an extended ICA‐based method called ICA‐F, which establishes a BSS model in frequency domain. First, the basic idea of BSS and ICA applied in modal identification is introduced in detail. The free vibration responses and the correlation functions of ambient responses can be cast into the frequency‐domain BSS framework just by mapping the time history responses to frequency domain through fast Fourier transform (FFT). Then, an ICA‐based method in frequency domain called ICA‐F is proposed to accurately extract mode shapes and modal responses for both light and high damping structures. A simulated 3 degree of freedom mass‐spring system and a 4‐story simulated benchmark model developed by the IASC‐ASCE Task Group in Health Monitoring are employed to verify the effectiveness of the proposed method. The results show that the proposed method can perform accurate modal identification for both light and high damping structures. Finally, the IASC‐ASCE experimental benchmark structure is also utilized to illustrate the proposed method applied to practical structure.     

电缆防火新技术

电缆的绝缘体大多是易燃物,超载、短路、遇到其他火源均易起火。缺乏防火保护的电缆尤其是众多电缆捆扎成的电缆束,起火后很容易被损坏。现提供两种符合国际标准和惯例的办法对电缆实施防火保护：对电缆穿墙处进行防火封闭、对电缆的部分或全部喷布防火涂层。为此提供的...