主动变刚度结构体系(AVS)多模态优化控制研究

依据原有状态控制律对AVS结构体系进行结构控制时 ,会出现高频响应失效问题 ,为此本文提出基于单步状态预测的控制律。借助结构模态控制技术 ,经推演而得出具有普遍工程应用意义的多自由度AVS结构体系的多模态优化控制律。通过仿真分析 ,可以看出本文方法较好地解决了高频控制响应失效问题 ,在取得与瞬时最优控制相当控制效果的同时 ,大大缩短了在线计算时间     

高层建筑多自由度结构体系AVS／D多振型控制

探讨了开关型半主动控制算法的研究现状。基于单步状态预测控制律 ,针对高层结构多自由度结构体系提出了AVS/D多振型开关控制律。通过算例与其它开关控制律的计算机仿真分析和比较 ,表明这种开关控制律是可行的、有效的 ,特别是在多自由度结构体系振动过程中有多个振型同时在受控结构的反应中起主要作用时 ,比其它振型开关控制律有更好的控制效果     

基于加速度趋近律的高层结构的滑模控制及其鲁棒性分析

本文采用加速度趋近律滑模控制算法对多自由度体系的地震响应进行了数字仿真研究。并且将该控制方法与LQR控制方法的控制效果和控制的鲁棒性进行了对比分析。仿真和分析结果表明此控制律的控制效果和鲁棒性均优于LQR控制方法 ,能够有效地减小结构的地震响应 ,同时具有较好的鲁棒性。基于加速度趋近律的滑模控制具有重要的实际应用价值     

建筑结构半主动控制振动台试验研究

本文讨论了作者进行的建筑结构半主动振动控制试验,用以检验主动变刚度/阻尼(AVS/D)控制系统犤6犦及瞬时最优半主动控制方法的有效性与实用性。试验结果表明:对比于对应的被动控制方式,AVS/D半主动控制系统不但能有效地控制结构在地震作用下的位移和加速度响应,而且克服了其它半主动控制系统存在的负面控制影响,对不同地震激励具有很强的控制鲁棒性,而且实现简单、易行,从而为进一步深入研究与应用于工程实际提供了试验依据。     

高层建筑结构动力时程响应分析的状态空间迭代法

本文把现代控制理论中的状态空间理论应用到高层建筑结构动力响应分析中，提出了状态空间迭代法分析高层建筑结构动力响应问题。根据结构动力方程，引入位移与速度为状态变量，导出状态方程，给出非齐次状态方程的解，进而建立状态空间迭代计算格式。文中结合工程实例，采用状态空间迭代法进行结构动力时程响应分析，其计算结果表明，具有较高的精度，特别对多自由度体系的多输入、多输出等问题的动力响应解法，效率较高。     

下部支承结构对网壳结构强震响应的影响研究

总结了关于考虑下部支承影响的网壳结构强震失效研究的最新研究成果。介绍了基于响应的荷载域全过程分析方法;通过建立精细化的数值模型,对考虑下部支承结构的单层球面网壳在强震作用下的特征响应进行了分析,得到了考虑下部支承结构的单层球面网壳在强震作用下的失效特征;通过大规模参数分析,详细地阐述了下部支承结构对网壳结构失效极限荷载的影响;提出了对于耦合体系的简化分析方法并初步研究了非线性下部支承结构对网壳结构失效的影响;讨论了下部支承结构非线性对网壳结构响应的影响。研究表明,非线性材料的支承结构也将明显改变耦合体系的响应规律及失效模式。     

双随机下刚性索穹顶结构的可靠性灵敏度分析

针对目前索穹顶结构研究中没有考虑荷载的随机性和结构本身的随机性的问题,采用基于正交设计响应面的Monte Carlo法对刚性索穹顶结构进行了双随机下的可靠性灵敏度分析.以一个跨度为60m,承受轴对称均布荷载作用的肋环型刚性索穹顶结构为例进行分析,得到了结构功能函数的响应面,进而采用Monte Carlo方法得到结构的失效概率以及各随机变量对于结构失效的灵敏度矩阵.结果表明,刚性索穹顶结构的失效概率较小,且应力控制的失效概率小于位移控制的失效概率,最外圈斜索的预应力水平、荷载、刚性杆件截面积对于结构失效较为敏感.在此基础上,与相应索穹顶结构比较,两种索穹顶结构的失效主要都是位移控制,且在位移控制下,最外圈斜索的预应力水平对于刚性索穹顶结构失效的敏感程度要比整体预应力水平对于相应索穹顶结构失效的敏感程度低,刚性索穹顶结构较相应索穹顶结构更为可靠.     

温度作用下大跨度索穹顶结构可靠度分析

基于响应面法,进行考虑温度作用的索穹顶结构在正常使用极限状态和承载能力极限状态下的可靠度分析。分析了在不同温差作用下索穹顶结构不同失效模式的可靠指标,并得到索穹顶结构在不同失效模式下的可靠性能大致与温度呈线性变化。最后采用蒙特卡罗法来检验响应面法的工程误差,比较结果表明响应面法在计算简便省时的情况下能保证良好的精度。     

高层建筑抗震设计AVS构件的优化布置

研究了主动变刚度系统中AVS构件(即钢性斜支撑)的优化布置问题,结合部分状态反馈的次最优控制理论中选择所采用的部分状态反馈的思想,提出了确定AVS系统中AVS构件的优化布置方法,并通过数值模拟对其有效性进行了验证。     

基于向量式有限元法的某开合屋盖结构关键拉杆失效分析(英文)北大核心CSCD

绍兴县体育中心体育场开合屋盖结构由固定屋盖和活动屋盖组成,活动屋盖可以在固定屋盖的轨道上滑动.根据建筑需求,固定屋盖的主桁架设计为扁拱状.为克服扁拱结构效率较低的缺点,主桁架下部安装了一系列实心拉杆形成弓形的结构.显然,拉杆是屋盖结构的关键受力构件,它的失效对整个屋盖结构的力学性能有很大影响.向量式有限元(VFIFE)是一种新型的结构分析数值方法,特别适用于处理动力和大变形问题.本文采用向量式有限元法对屋盖结构闭合和开启状态下关键拉杆的突然失效进行了分析,追踪了关键位置的位移、构件内力以及支座反力的动力响应过程.结果表明,对于单拉杆设计方式,开合屋盖在拉杆失效后呈现很强的动力响应;实际结构设计采用的并行多杆形式能有效减少拉杆失效产生的屋盖结构动力响应.     

PTRMD在多自由度结构中的减振性能及鲁棒性

将一种带碰撞的滚动型调谐质量阻尼器（PTRMD）应用于多自由度结构中,对其在多自由度结构体系中的减振性能及阻尼器频率失谐时的鲁棒性进行研究。通过拉格朗日方程推导得到分段运动方程,然后推广到多自由度结构中,建立了设有该装置的多自由度受控系统的动力方程,并利用数值方法求解。把PTRMD安装到6层结构中,对其在自由振动和强迫振动时的控制效果进行探讨,并与无碰撞的滚动型调谐质量阻尼器（TRMD）进行了比较,同时对它们在阻尼器频率偏离最优频率时的鲁棒性进行了分析。结果表明:在多自由度结构中安装PTRMD能有效减小结构的动力反应,得到满意的减振效果;相比TRMD,PTRMD具有减振性能好、控制频带宽、适用性强、受阻尼器频率变化的影响不大等优点,具有更广大的应用前景。     

Evaluation of modal incremental dynamic analysis,using input energy intensity and modified bilinear curve

In this paper, a technique for the study of nonlinear performance of structures in different levels of earthquakes is developed. In this method, the Incremental Dynamic Analysis (IDA) curves are not achieved from nonlinear dynamic analysis of multi‐degree‐of‐freedom (MDF) structure. However, the procedure of constructing these curves is based on modelling of the entire structure with several single‐degrees‐of‐freedom (SDF) structures and evaluating them through the modal pushover analysis method. An innovative idea for approximating pushover curves that is based on error distribution is introduced in this investigation. Furthermore, the total input energy applied towards the SDF oscillator, which gets converted into MDF structure, is used as intensity measure to impose the different levels of scaled earthquakes. This technique possesses all the advantages of the IDA method in studying the performance of structures in different levels of earthquake. In addition, it benefits from easy usage, high solving speed and less computational CPU time and in attendance with the modified bilinear curves. In this paper, six earthquake records have been applied over four different 4, 8, 12 and 16‐storey structures. The structural responses derived by this method, in the format of multi‐modal incremental curves, containing maximum displacement, drift, hinge rotation and hysteretic energy at the end of the earthquake, have been compared with the IDA method. Comparison of the results is found to have acceptable precision and reveals good agreement between two methods. Copyright © 2008 John Wiley & Sons, Ltd.     

Damage Identification for Hysteretic Structures Using a Mode Decomposition Method

This article investigates structural health monitoring (SHM) of multidegree of freedom (MDOF) structures after major seismic or environmental events. A recently developed hysteresis loop analysis (HLA) SHM technique has performed robustly for single degree of freedom (SDOF) and single mode dominant MDOF structures. However, strong ground motions can trigger higher vibration modes, resulting in irregular hysteresis loops and making this otherwise robust identification difficult. This study presents a new filtering tool, enabling reconstruction of single mode dominant restoring force‐displacement loops which can be readily used for HLA. The proposed filtering tool is based on a classic modal decomposition using optimized mode shape coefficients. The optimization process is carried out in a modal space and is based on decoupling frequency response spectra of interfering modes. Application of modal decomposition using the optimized mode shape coefficients allows for reconstruction of single‐mode dominant hysteresis loops, which can be effectively identified using HLA. The proposed filtering tool is validated on the reconstruction of hysteresis loops on an experimental bridge pier test structure with notable contributions from at least two modes. The results show the method eliminates the influence of all higher modes that contain significant energy content and yields the reconstruction of “smooth” single mode dominant hysteresis loops. The resulting SHM analysis on the reconstructed experimental hysteresis loops identified degradation in the elastic stiffness profiles, indicating damage within the structure and matching prior published results based on physical inspection of damage. The overall method presented increases the breadth of potential application of the HLA method and can be readily generalized to a range of MDOF structures.     

Numerical simulation model of vibration responses of rectangular plates embedded with piezoelectric actuators

A numerical simulation model for random large amplitude vibration control of composite plate using piezoelectric material is presented. The H_∞ control design is employed to suppress the large amplitude vibrations of composites plates under random loading. The numerical simulation model is developed and based on the finite element method. The finite element governing equation includes fully coupled structural and electrical nodal degrees of freedom, and consider the von Karman large amplitude vibration. The modal reduction method using the structural modes is adopted to reduce the finite element equations into a set of modal equations with fewer degrees of freedom. The modal equations are then employed for controller design and time domain simulation. In the simulations without control, the value of the linear mode to the nonlinear deflection is quantified; and the minimum number of linear modes needed for accurate model is obtained. In the simulations with control, it is shown that the truncated modes, which are neglected in the control design, deteriorate the controller performance. Generally, the vibration reduction level is not monotonically increasing with the size of the piezoelectric actuator. The optimal piezoelectric actuator size depends on the excitation level. For higher excitation level, optimal actuator size is larger. The H_∞ controller based on the linear finite element formulation gives better vibration reduction for small amplitude vibration, but it still gives reasonable performance for large amplitude vibration provided that the piezoelectric actuator is big and powerful enough.     

On the modal incremental dynamic analysis

In this article a new technique for the dynamic response of structures is investigated. This applied procedure can predict the approximate seismic performance of the structures and it is fast, inexpensive and results are reasonably acceptable. In fact, this novel method logically combines two different techniques, ‘incremental dynamic analysis (IDA)’ and ‘modal pushover analysis (MPA)’, presented by other researchers. This method will take advantage of both methodical ideas such as equivalent single degree of freedom of multi‐degree structures and the implementation of different scaled level of an earthquake record to the provided equivalent SDF structure. Using this procedure, simple approximate curves that present a realistic linear and non‐linear seismic behaviour of the structure due to the applied scaled level of earthquakes can easily be extracted. In this investigation, several four‐, eight‐ and 12‐storey structures are specified as the example models and are dynamically analysed. Next, three different scaled earthquakes, El Centro, Northridge and San Fernando, are applied to each example problem. The results of the presented technique, modal incremental dynamic analysis (MIDA), are then compared with the IDA method. Comparison of the results reveals good accuracy in building seismic demands evaluation. Finally, it is also shown that the MIDA method is simple enough to be carried out on most personal computers and the authors believe this technique will serve design engineers working in real design conditions. Copyright © 2005 John Wiley & Sons, Ltd.     

Displacement estimation of nonlinear structures using the force analogy method

Significant effort has gone toward developing accurate and efficient displacement estimation procedures for the nonlinear multi‐degree‐of‐freedom (MDOF) system. Although the dynamic nonlinear analysis is capable of providing the high computational precision through the step‐by‐step time integration method, the simplified method is still expected and imperative for seismic design practices. The work presented in this paper focuses on the implementation of using the modal superposition method to estimate displacement responses of the nonlinear MDOF system based on the force analogy method (FAM). The current research demonstrated that the equation of motion for the nonlinear MDOF system can be decoupled, but other two governing equations in the FAM about the internal force, such as the moment and force of structural members, are not decomposable. Thus, the FAM is incorporated with the modal pushover analysis (MPA) method to determine the basic parameters of each mode such that the modal superposition method can be suitable for the solution of the nonlinear MDOF system. The procedure presented here is an approximately estimation method due to the application of MPA method. However, the value and potential for the maximum displacement estimation of the nonlinear MDOF system were demonstrated through the application in a framed structure. Copyright © 2014 John Wiley & Sons, Ltd.     

Identification of the mode shapes of spatial tall multi‐storey buildings due to earthquakes: the new ‘modal time‐histories’ method

In the present article, a new method is presented which attempts to identify the dynamic characteristics (eigen frequencies, eigen periods, mode shapes and modal damping ratios) of spatial asymmetric tall multi‐storey buildings through measured seismic responses (accelerations). This new method is entitled ‘method of modal time‐histories’, because its main target is to identify the modal time‐histories of accelerations that are obtained by accelerograms recorded on the points of buildings where suitable accelerometers have been installed. In the case of an earthquake, the multi‐channel local network of accelerometers records the time‐histories of the accelerations of the building. In addition, in order to have a successful outcome, the instrumentation form of the multi‐channel local network on the building can potentially play the most important role. This paper, first, presents a relevant mathematical analysis that is adapted to the instrumentation form applied to the multi‐storey buildings and, second, outlines the new method, which consists of nine steps. Finally, in order to illustrate the theory, a suitable numerical example of an instrumented asymmetric five‐storey r/c building that has been oscillated by a weak earthquake is also provided. On the one hand, the identification of the dynamic characteristics of spatial asymmetric buildings contributes to the removal of the uncertainties of building models in order to perform advanced non‐linear analyses about inherent building seismic capacity. On the other hand, this method supports the simple monitoring of a building's ‘structural integrity’. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimal control of nonlinear frames by Newmark and distributed genetic algorithms

Active control of multi‐storey frame structures with nonlinear hysteretic response has been studied in this paper. A new nonlinear optimal control algorithm based on nonlinear Newmark integration method and distributed genetic algorithm (DGA) has been developed. The objective has been to reduce the response to below any desired level. In this study, DGA has been used to determine the weights in the control law corresponding to displacement, velocity and acceleration. The capabilities of the method has been assessed through simulation where an eight‐storey frame with bilinear hysteretic behaviour has been subjected to a white noise ground acceleration and controlled by the controllers designed by the new algorithm. An active tendon control system comprised of prestressed tendons and either a single actuator, which could apply a force to one of the floors, or eight actuators, which could fully control the frame, has been used. Also, the optimum actuator placement in the single actuator case has been studied. The designed controllers have been tested under both near and far‐field earthquakes and have performed successfully. Copyright © 2009 John Wiley & Sons, Ltd.     

Predictive instantaneous optimal control of inelastic structures based on ground velocity

One of the challenges confronting structural engineers in structural control is to find more efficient control algorithms to ensure better and more reliable control results to protect structures against the damaging effects of destructive environmental forces. In this paper, a simple control algorithm, namely the Predictive Instantaneous Optimal Control (PIOC) algorithm, is proposed by introducing a new state space form. Different from the classical ground acceleration‐based control algorithms, this new control algorithm uses earthquake ground velocity as the input. Since the earthquake ground velocity is not at high frequency as compared with the ground acceleration, it can be predicted at certain time steps beforehand in real‐time domain with higher accuracy. This ensures the synchronous execution of the proposed PIOC algorithm with real‐time application of the control force. To capture the damaging effects during earthquake ground motions, the force analogy method is used to characterize structures responding in the inelastic domain. Numerical studies are performed to compare the structural response with and without control using both single degree of freedom and multi‐degree of freedom structural models. Results show that the PIOC algorithm is effective in reducing the structural response under earthquake excitation. Copyright © 2006 John Wiley & Sons, Ltd.