地下结构非平稳随机地震响应分析

从有限元动力分析的基本原理出发,利用脉冲响应函数和傅立叶变换原理,研究了将地震荷载作为非平稳随机过程时地下结构随机地震响应分析方法,导出了非平稳随机地震加速度作用下地下结构动力响应的数字特征计算表达式。通过算例分析了某一隧道在7度非平稳随机地震作用下的位移和应力均方根响应。     

基于振型叠加法的顺层边坡非平稳随机地震响应及动力可靠度分析

为研究非平稳随机地震激励下顺层岩质边坡的动力可靠性问题,采用振型叠加法和虚拟激励法,建立含多层软弱结构面的顺层岩质边坡非平稳随机地震响应的快速算法,根据响应结果,采用首次穿越破坏准则,进一步推导出非平稳地震下顺层岩质边坡动力可靠度计算的解析表达式.在此基础上,通过MATLAB软件平台编写相应的程序以实现计算数据和结果图...     

网壳结构平稳与非平稳随机地震响应研究

对虚拟激励方法进行了研究,通过自编程序对单双层网壳的平稳与非平稳地震响应进行了分析,并列举一具体算例进行了说明,从而解决了网格结构中非平稳随机地震响应的问题,得出非平稳地震反应小于平稳地震反应的结论。     

基础转动结构随机地震响应分析的复模态法

对多自由度基础转动结构随机地震响应问题进行了系统研究。针对用第一振型将上部结构展开所得方程为非经典阻尼和非对称结构情况 ,用复模态法解耦 ,获得了以第一振型表示的结构地震响应的解析解 ,对单自由度体系 ,此解即为结构响应的精确解。该方法可用于隔震结构、加层减震结构、带TMD减震结构的随机响应分析与优化设计     

考虑地震非平稳性的隧道纵向抗震可靠度分析

考虑地震运动的非平稳性,将沉埋隧道地震反应分析的数学模型应用于隧道纵向随机地震响应及其抗震动力可靠度分析。从有限元动力分析的基本原理出发,利用脉冲响应函数和傅立叶变换原理,结合随机振动理论,研究了将地震荷载作为非平稳随机过程时隧道纵向随机地震响应及其抗震动力可靠度分析方法,建立了地下结构随机地震响应数字特征及其抗震动力可靠度的计算表达式。以南京长江越江隧道初步设计方案(沉管段)为例,计算了其在非平稳随机过程地震动作用下的动力反应均方根值和纵向抗震动力可靠度,并研究了管段接头的抗震可靠度。     

地震作用下复阻尼调频质量阻尼器减震结构优化设计

分析了简谐激励和平稳随机激励条件下,复阻尼调频质量阻尼器(TMD)和主结构的二自由度减震结构体系的稳态地震响应,建立了动力学平衡方程,推导了复阻尼TMD的阻尼和频率最优参数的理论公式,并分析了该二自由度减震结构体系在多条地震波作用下的减震效果,对比了复阻尼TMD和粘滞阻尼TMD减震效果的差异,结果表明:复阻尼TMD的减震效果接近于粘滞阻尼TMD的结果,在应用TMD减震技术时,复阻尼TMD也是一种选择。     

结构在水平与竖向地震同时作用的非平稳响应

本文对单自由度结构在水平与竖向地震同时作用下的随机地震响应问题进行了系统研究。首先用简明的推导方法,建立了结构参激随机振动方程;其次利用Stratonovich随机微分方程、It随机微分方程、FokkerPlanck方程和矩微分方程的相互转换关系,用统一的公式法,建立了结构响应矩方程;然后根据Hurwitz随机稳定准则,获得了结构一阶和二阶响应矩渐近稳定条件的解析判断式;最后针对非平稳水平地震激励的最典型四种强度包络函数,综合应用复模态法,获得了结构非平稳响应二阶矩的解析解,给出了算例,并综合分析了各种参数对结构响应和稳定性的影响。     

非平稳地震激励下结构随机响应及动力可靠性研究

基于美国西部121条基岩强震加速度记录,采用Hilbert-Huang变换(HHT)生成能真实反映地震记录频率和强度双非平稳特性的非均匀调制演变功率谱,并用经验统计方法建立了根据地震矩震级、震源距预测演变谱的统计模型。运用虚拟激励法得到具有特定震级、震源距的演变功率谱作用下结构的非平稳随机响应特性,同时结合首次超越理论,分析了结构的动力可靠度问题,并且与仅具有强度非平稳特性的均匀调制地震随机激励作用进行比较,结果表明,在总能量相同的情况下,双非平稳功率谱的激励会使结构的响应更大,结构更容易失效。     

土-桩-结构相互作用体系非平稳随机地震反应分析

目前,有关土-结构动力相互作用问题的研究基本上多限于确定性的或平稳随机激励下的响应分析.文中基于某基岩加速度反应谱,利用文献[7]的方法求取基岩非平稳随机地震功率谱密度函数,采用有限元方法建立土-桩-结构相互作用体系的三维分析模型,对在非平稳随机地震激励下土-桩-结构相互作用体系进行了反应分析.首先对三种不同场地条件下的土-桩-结构相互作用体系进行了动力特性分析;然后,对在非平稳随机地震激励下桩基承台的反应和自由场反应进行了比较,给出了结构的位移功率谱响应结果.     

刚性连体位置对非对称双塔连体结构动力可靠度的影响

考虑地震动的非平稳性,变化连体位置,对非对称双塔连体结构运用虚拟激励法进行非平稳随机激励下的动力可靠度研究。采用刚度退化的 Bouc-Wen 模型模拟塔楼各楼层的滞变特性,建立非线性化动力方程。运用混合精细积分法对每一时刻的响应进行求解,得到连体位置变化时非对称连体结构在非平稳随机激励下的时变方差。基于首次超越破坏准则与 Markov 假定,研究非平稳随机地震激励下连体结构的动力可靠度。运用上述理论,在8度罕遇地震作用下对某非对称双塔连体结构进行随机地震响应与动力可靠度分析。研究结果表明,地震作用下结构的层间位移响应呈现强烈的非平稳性,变化连体位置对连体结构的随机地震响应与动力可靠度将产生显著影响。     

Particle swarm optimization of tuned mass dampers

Tuned mass dampers (TMD) have been widely used to attenuate undesirable vibrations in engineering. Most optimization problems of TMD are solved by either numerical iteration technique or conventional mathematical methods that require substantial gradient information. The selection of the starting values is very important to ensure convergence. In this paper, we use a novel evolutionary algorithm of particle swarm optimization (PSO) for optimization of the required parameters of a TMD. Optimum parameters of the TMD system attached to a viscously damped single degree-of-freedom main system are obtained by minimizing some response quantities, for examples, the mean square displacement responses and displacement amplitude of the main system under various combinations of different kinds of excitations. The excitations considered include external force and base acceleration modeled as Gaussian white-noise random processes. Harmonic base acceleration with frequency invariant amplitude is also considered. The PSO can be used to find the optimum mass ratio, damper damping and tuning frequency of the TMD system and can be easily programmed for practical engineering applications. Explicit expressions of the optimum TMD parameters are given for engineering designers.     

Performance test of a tuned liquid mass damper for reducing bidirectional responses of building structures

In this study, a tuned liquid mass damper (TLMD) was proposed to reduce bidirectional responses of building structures, and its control performance was experimentally evaluated. The proposed TLMD with only one device body reduces bidirectional responses of building structures by behaving as a TMD and a TLCD in the weak and strong axial directions of a building floor plan, respectively. First, the control performance of a TLMD mounted on a scale‐downed single‐degree‐of‐freedom building model was experimentally evaluated by exciting this system with an actuator. Then, the real‐time hybrid shaking table testing method (RTHSTTM) was performed to assess the control efficiency of the total system by adopting the TLCD and the building model as the experimental and numerical parts, respectively. It was confirmed by comparing uncontrolled and controlled testing results that the proposed TLMD can be applied to reduce the responses in both the weak and strong directions of building structures. Also, the results from RTHSTTM showed that the performance of TLMD‐controlled building structure can be accurately evaluated by this method only using a TLMD as the experimental part. Copyright © 2008 John Wiley & Sons, Ltd.     

Optimizing parameters of tuned mass damper subjected to critical earthquake

Tuned mass damper (TMD) has been proposed as one of the vibration control methods for rehabilitation of buildings. Because the parameters of TMD can significantly affect the seismic performance of structures, many researches focused on finding the optimum parameters. Because earthquakes are random phenomena and future earthquakes in comparison with past earthquakes may be more destructive, the optimum design of TMD subjected to selected earthquakes can be nonconservative. Hence, the main contribution of this paper is to present the optimal design of TMD for the seismic vibration control of a structure subjected to a critical earthquake that produces the most severe response of a structure. In order to achieve this purpose, the parameters of TMD are optimized through minimizing the maximum displacement of the roof. First, three optimization methods are used to obtain the optimal parameters of TMD for a 10‐story shear building subjected to the critical earthquakes. Finally, the responses of the controlled and uncontrolled buildings such as the roof displacement, strokes, transfer function, and different forms of energy are compared. Results show that the optimum designs of TMD not only effectively reduce the roof displacement but also improve the seismic performance of the building.     

FPS型TMD控震效应分析

基于FPS(FrictionPendulumSystem)型TMD(TurnedMassDamper)控制的多层剪切型结构振动微分方程 ,通过时程计算分析了FPS型TMD控震响应规律。结果表明 ,合理设计的FPS型TMD控振系统可以改善结构的振动响应     

钢板夹层阻尼高频TMD两阶段设计方法

随着工业化的发展,建筑结构逐渐轻量化,机械设备逐渐重型化、高效化,这使得机械设备高频扰力导致的结构振动问题越来越突出;为了减轻结构的高频受迫振动响应,可以在结构振动响应较大的位置安装高频高阻尼比的钢板夹层阻尼悬臂梁式调谐质量阻尼器(tuned mass damper,TMD).由于TMD的弹性元件与阻尼元件相互耦合,因...     

Energy dissipation of tuned mass dampers during earthquake excitations

The effectiveness of energy‐dissipative tuned mass dampers (TMD) on structural dynamic responses have been studied extensively since its development in the 1970s. Its applications have recently been extended to the use of active multiple tuned mass dampers. However, the process of a damper in improving a structure's ability to dissipate the earthquake's input energy has never been investigated. In this research, the objective lies in studying the process of structural energy transfer and the ability for the structure to dissipate energy. Numerical simulations are performed to study the energy responses of structures with and without TMD installed. The effectiveness of TMD in reduction of energy responses is also studied by using energy spectra and in a case study of a six‐storey building. Results show that TMD is more effective in reducing the energy responses for structures with a moderate to long period of vibration than those for short period structures. In addition, TMD is very effective in reducing both the maximum kinetic energy and strain energy of the structure, while it is also effective in reducing the amount of damping energy that must be dissipated through the structure by providing an alternating route of damping energy dissipation through the TMD. Copyright © 2004 John Wiley & Sons, Ltd.     

Parametric control of structural responses using an optimal passive tuned mass damper under stationary Gaussian white noise excitations

In this study, the structural control strategy utilizing a passive tuned mass damper (TMD) system as a seismic damping device is outlined, highlighting the parametric optimization approach for displacement and acceleration control. The theory of stationary random processes and complex frequency response functions are explained and adopted. For the vibration control of an undamped structure, the optimal parameters of a TMD, such as the optimal tuning frequency and optimal damping ratio, to stationary Gaussian white noise acceleration are investigated by using a parametric optimization procedure. For damped structures, a numerical searching technique is used to obtain the optimal parameters of the TMD, and then the explicit formulae for these optimal parameters are derived through a sequence of curve-fitting schemes. Using these specified optimal parameters, several different controlled responses are examined, and then the displacement and acceleration based control effectiveness indices of the TMD are examined from the view point of RMS values. From the viewpoint of the RMS values of displacement and acceleration, the optimal TMDs adopted in this study shows clear performance improvements for the simplified model examined, and this means that the effective optimization of the TMD has a good potential as a customized target response-based structural strategy.     

Optimal design of active TMD for buildings control

Active TMD were previously designed assuming the structural parameters of the optimal passive TMD. However, the active control technique introduces to both the building and the TMD an active stiffness and active damping which change the structural parameters of the controlled structure. This paper presents a process for designing optimal active TMD for tall building control. It shows that the relationship between the first mode natural frequency of the building and the natural frequency of the tuned mass damper depends completely on the required degree of control in the building. A numerical example for a tall building subjected to stationary random wind forces is given.     

Study on self‐adjustable variable pendulum tuned mass damper

Pendulum tuned mass damper (PTMD) is usually used to control the horizontal vibration of a tall building. However, traditional PTMD is highly sensitive to frequency deviation and difficult to adjust its frequency. In order to improve this problem of traditional PTMD and protect a tall building more effectively, a novel PTMD, called self‐adjustable variable pendulum tuned mass damper (SAVP‐TMD), is proposed in this paper. On the basis of the acceleration ratio between TMD and primary structure, the SAVP‐TMD can retune itself by varying the length of the pendulum according to the improved acceleration ratio‐based adjustment algorithm. PTMD and primary structural accelerations are obtained from two accelerometers respectively, and the acceleration ratio is calculated in a microcontroller, then, the stepper motor will adjust the pendulum under the guidance of the microcontroller under a specific harmonic excitation. The improved acceleration ratio‐based adjustment algorithm is proposed and compared to solve the nonconvergent retuning problem. The SAVP‐TMD can be regarded as a passive damper including a frequency adjustment device. A single‐degree‐of‐freedom structure model is used to verify the effectiveness of SAVP‐TMD through both experimental study and numerical simulation. In order to further verify the effect of SAVP‐TMD in the MDOF structure, a five‐storey structure coupled with an SAVP‐TMD is proposed as a case study. The results of experiment, simulation, and case study all show that SAVP‐TMD can retune itself to the primary structural dominant frequency robustly, and the retuned PTMD has a better vibration control effect than the mistuned one.     

高层多塔连体结构连廊随机地震反应分析

在多点激励地震反应分析中,传统的随机振动分析方法存在数值积分耗时太长的问题。为了克服这一缺点,ANSYS通过对输入功率谱采用对数形式的分段线性表示,然后采用解析解积分方式进行随机振动求解,计算效率精确高效。采用该方法对一高位隔震多塔连体结构进行双向水平地震动作用下多点激励随机地震响应分析,并对空间变化地震动作用下连廊桁架杆件内力响应极大值的均值进行比较分析。分析结果表明:在水平双向地震动作用下,考虑行波效应和部分相干效应会使连廊杆件轴力有所增大,在设计时应引起重视。