高架桥地震反应半主动控制分析

本文探讨了高架桥结构地震反应LQR(Linear Quadratic Regulator)半主动控制算法以及考虑刚度退化的桥墩非线性计算模型，并利用Matlab语言编制的程序对其进行了数值仿真计算。结果表明，将隔震技术与利用MR阻尼器的半主动控制技术相结合，能够有效地减小高架桥的地震反应；MR阻尼器的设置位置以及结构的参数对控制效果有较大影响。考虑桥墩非线性影响将能得到更为接近实际的计算结果。     

高架桥梁地震响应模糊半主动控制

提出了使用MR阻尼器（Magnetorheological Damper）作为控制设备，以模糊集为基础的半主动控制算法，研究了8种模糊控制规则在高架桥梁地震响应中的控制效果。本文提出的模糊方法的优势在于算法自身的鲁棒性、处理非线性问题的能力和不需要结构的精确数学模型，算法需要的输入变量少，模糊算法的输出直接控制MR阻尼器的输入电压，与LQR-clipped算法不同，MR阻尼器的输入电压可以是零与最大值之间的任意值。根据高架桥梁的结构特点，将典型的墩-支座-桥面结构简化为一个两自由度的线性系统，计算了El Centro地震激励下，MR模糊半主动控制的地震响应，并分别与没有控制及其他控制时的地震响应进行了对比，分析了各种控制算法的控制效果。研究结果表明，MR模糊半主动控制算法可以达到LQR-clipped半主动的控制效果，且模糊控制所需要的控制力较小，为有效地发挥MR阻尼器的功能提供了一种简单的半主动算法。     

Polynomial friction pendulum isolators (PFPIs) for seismic performance control of benchmark highway bridge

The seismic response of a benchmark highway bridge isolated with passive polynomial friction pendulum isolators (PFPIs) is investigated and subjected to six bidirectional ground motion records. The benchmark study is based on a lumped mass finite-element model of the 91/5 highway overcrossing located in Southern California. The PFPI system possesses two important parameters; one is horizontal flexibility and the other is energy absorbing capacity through friction. The evaluation criteria of the benchmark bridge are analyzed considering two parameters, time period of the isolator and coefficient of friction of the isolation surface. The results of the numerical study are compared with those obtained from the traditional friction pendulum system (FPS). Dual design performance of the PFPI system suppressed the displacement and acceleration response of the benchmark highway bridge. The dual design hysteresis loop of the PFPI system is the main advantage over the linear hysteresis loop of the FPS. The numerical result indicates that the seismic performance of the PFPI system is better than that of the traditional FPS isolated system. Further, it is observed that variations of the isolation time period and coefficient of friction of the FPS and PFPI systems have a significant effect on the peak responses of the benchmark highway bridge.     

基于自供电磁流变阻尼器的隔震高架桥半主动控制

为解决结构振动控制的能量源问题,提出了一种新型自供电MR阻尼器智能减振系统。该系统由电磁调节式MR阻尼器、齿条齿轮加速器、永磁电机与控制器组成。基于广泛采用的隔震高架桥两自由度线性模型,定义了位移控制性能评价指标,引入了在汽车悬架系统设计中常用的Sky-hook控制策略,对隔震高架桥的减震性能进行了仿真分析。结果表明:通过优化设计的参数,自供电MR阻尼器的LQR-Clipped半主动控制与Skyhook控制都可以完全达到其相应的采用外部供电的MR阻尼器的控制效果,且接近理想的主动控制结果。     

Use of seismic early warning information to calibrate variable dampers for structural control of a highway bridge: evaluation of the system robustness

The seismic events occurred in recent years highlighted the extreme vulnerability of large part of the existing constructed facilities and the need to adopt innovative solutions to improve their seismic performance. With this purpose, the possible exploitation of a seismic early warning system (SEWS) in the framework of semi-active structural control using magnetorheological (MR) dampers is herein investigated. The main idea consists in the use of these time-varying properties devices to control an hosting structure by changing their behaviour according to an anticipate estimate, provided by the SEWS, of the peak ground acceleration (PGA) of the incoming earthquake. In this way, the dampers are able to adapt their mechanical characteristics to the specific earthquake obtaining the optimal seismic response. The present paper describes the application of this protection technique to a case-study problem, a highway bridge located in Southern California. The seismic response of the benchmark bridge is investigated by nonlinear time-history analyses by adopting 16 real earthquake ground excitations. These accelerograms cover a wide variety of magnitudes, distances to fault and soil types. Possible errors on estimation of PGA provided by SEWS and their effects on the proposed control system are also considered. The results obtained confirm that unavoidable errors in the PGA estimates provided by the SEWS do not propagate to the seismic response. Conversely, the proposed strategy turns out to damp these errors, resulting in a robust seismic behaviour of the protected structure.     

地震作用下公路桥梁碰撞的半主动控制研究

针对地震作用下公路桥梁的碰撞问题,采用接触单元法模拟桥梁之间的碰撞作用,并在此基础上研究了采用磁流变阻尼器的公路桥梁碰撞的半主动控制方法。通过对某公路桥梁的数值模拟发现,地震作用下桥梁之间的相互碰撞,将大幅增加桥梁的绝对加速度响应。采用磁流变阻尼器的半主动控制系统能够较好地降低结构的地震响应和消除地震作用下的碰撞。     

内蒙古地震预警基准台网监控能力评估

国家地震烈度速报与预警工程项目已启动,内蒙古自治区地震局已完成预警基准台站勘选工作。利用近震计算公式,利用已选定台址与现有台站噪声水平,评估内蒙古自治区预警基准站建成后地震监控能力。结果表明,呼和浩特、包头、鄂尔多斯和乌兰察布市地区,地震监测能力在1.0级,而赤峰—通辽地区监测能力将达0.5级。     

Ambient vibration based seismic evaluation of isolated Gülburnu highway bridge

This paper describes ambient vibration based seismic evaluation procedure of an isolated highway bridge. The procedure includes finite element modeling, ambient vibration testing, finite element model updating and time history analysis. Gülburnu Highway Bridge located on the Giresun–Espiye state highway is selected as a case study. Three dimensional finite element model of the bridge is created by SAP2000 software to determine the dynamic characteristics analytically. Since input force is not measured, Operational Modal Analysis is applied to identify dynamic characteristics. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to obtain experimental dynamic characteristics. Analytical and experimental dynamic characteristic are compared with each other and finite element model of the bridge is updated by changing of material properties to reduce the differences between the results. Analytical model of the bridge after model updating is analyzed using 1992 Erzincan earthquake record to determine the seismic behavior. EW, NS and UP components of the ground motion are applied to the bridge at the longitudinal, transverse and vertical directions, respectively. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of highway bridges. Maximum differences between the natural frequencies are reduced averagely from 9% to 2% by model updating. It is seen from the earthquake analyses that friction pendulum isolators are very effective in reducing the displacements and internal forces.     

Analysis of the observed seismic response of a highway bridge

Strong-motion accelerograms obtained on the San Juan Bautista 156/101 Separation Bridge during the 6 August 1979 Coyote Lake, California, earthquake are used to examine the response of this multiple-span bridge to moderate levels of earthquake loading. Although the bridge was not damaged, the records are of significant engineering interest as they are the first to be recorded on a highway bridge structure in North America. A technique of system identification is used to determine optimal modal parameters for linear models which can closely replicate the observed time-domain seismic response of the bridge. Time variations in frequency and damping in the horizontal response are identified using a moving-window analysis. A three-dimensional finite element model is developed to study the bridge response in detail. The first two horizontal modal frequencies computed from this model are in excellent agreement with information obtained during the system identification analysis provided the finite element model's expansion joints are locked, preventing relative translational motions from occurring across the joints. Locking is confirmed by the observed seismic deformations of the structure in the fundamental mode. Fundamental vertical frequencies of the individual spans, predicted by the finite element model, are in very good agreement with ambient vibration test data.     

多维Benchmark桥梁结构半主动控制策略

随着大跨度桥梁结构的广泛应用,作为生命线工程之一的桥梁结构振动问题备受关注。结构振动控制作为一种新方法,可以有效的减小结构振动响应。半主动控制只需较少的能量调节便可对最优控制力进行跟踪,进而成为研究的热点。传统的最优控制算法（LQR）需要计算复杂的Riccati方程,具有在线计算时间长等缺点。基于最优控制与计算结构力学之间的模拟理论,引入区段混合能的概念,将Riccati方程转化为区段矩阵的求解,采用水平双向布置MR阻尼器的方法对桥梁结构进行振动控制,考虑了桥梁结构3个方向的平动分量和转动分量,基于哈密顿体系提出了LQR半主动控制策略。最后,对Benchmark桥梁结构模型进行了仿真计算,结果表明:提出的LQR半主动控制策略是有效的。     

Fuzzy logic control of bridge structures using intelligent semi-active seismic isolation systems

Passive supplemental damping in a seismically isolated structure provides the necessary energy dissipation to limit the isolation system displacement. However, damper forces can become quite large as the passive damping level is increased, resulting in the requirement to transfer large forces at the damper connections to the structure which may be particularly difficult to accommodate in retrofit applications. One method to limit the level of damping force while simultaneously controlling the isolation system displacement is to utilize an intelligent hybrid isolation system containing semi-active dampers in which the damping coeffic ient can be modulated. The effectiveness of such a hybrid seismic isolation system for earthquake hazard mitigation is investigated in this paper. The system is examined through an analytical and computational study of the seismic response of a bridge structure containing a hybrid isolation system consisting of elastomeric bearings and semi-active dampers. Control algorithms for operation of the semi-active dampers are developed based on fuzzy logic control theory. Practical limits on the response of the isolation system are considered and utilized in the evaluation of the control algorithms. The results of the study show that both passive and semi-active hybrid seismic isolation systems consisting of combined base isolation bearings and supplemental energy dissipation devices can be beneficial in reducing the seismic response of structures. These hybrid systems may prevent or significantly reduce structural damage during a seismic event. Furthermore, it is shown that intelligent semi-active seismic isolation systems are capable of controlling the peak deck displacement of bridges, and thus reducing the required length of expansion joints, while simultaneously limiting peak damper forces. Copyright © 1999 John Wiley & Sons, Ltd.     

基于能量方程的建筑结构半主动控制

基于地震作用下结构的能量响应方程,本文提出根据结构吸收能量、相对动能和变形能的变化(对时间的一次导数)进行结构的“开-关”半主动减震的控制律;在物理坐标系中对这3种控制律的动力特征和控制效果,以及作动器参数的选取进行了分析。本文针对建筑结构进行了数值仿真。计算结果表明,本文提出的控制律可以有效地减小了结构的位移响应,对随机不确定的地震波均具有良好的减震效果,适应性强,而且控制器参数合理。其中根据结构变形能推导的控制律的半主动控制效果优于其它2种控制律。     

Semi-active model predictive control for 3rd generation benchmark problem using smart dampers

A semi-active strategy for model predictive control (MPC), in which magneto-rheological dampers are used as an actuator, is presented for use in reducing the nonlinear seismic response of high-rise buildings. A multi-step predictive model is developed to estimate the seismic performance of high-rise buildings, taking into account of the effects of nonlinearity, time-variability, model mismatching, and disturbances and uncertainty of controlled system parameters by the predicted error feedback in the multi-step predictive model. Based on the predictive model, a Kalman-Bucy observer suitable for semi-active strategy is proposed to estimate the state vector from the acceleration and semi-active control force feedback. The main advantage of the proposed strategy is its inherent stability, simplicity, on-line real-time operation, and the ability to handle nonlinearity, uncertainty, and time-variability properties of structures. Numerical simulation of the nonlinear seismic responses of a controlled 20-story benchmark building is carried out, and the simulation results are compared to those of other control systems. The results show that the developed semi-active strategy can efficiently reduce the nonlinear seismic response of high-rise buildings.     

Towards earthquake early warning for the Rion-Antirion bridge,Greece

Patras is the third largest city in Greece and an ideal candidate for earthquake early warning (EEW) applications due to its high seismic hazard, its existing research infrastructure and the presence of critical structures such as the Rion-Antirion bridge. Patras is located a few hundred kilometres from the Hellenic Arc, where very strong and potentially damaging earthquakes occur. This distance is large enough to allow a few tens of seconds of warning time prior to significant shaking, provided earthquakes are timely detected by a dense seismic network. Within the framework of the EC-funded project REAKT, the Virtual Seismologist (VS) EEW software was installed at Patras Seismological Laboratory. Its initial performance evaluation is presented here. In general VS provides magnitudes similar to the official, manually revised ones. Given the current station density and network telemetry, the average time that VS needs to deliver the first magnitude estimate is rather large, of the order of tens of seconds and not yet satisfactory for routine operational use of EEW. Even so, the system is able to provide up to 10 s of warning time prior to S-wave arrivals for events occurring on the Hellenic Arc. Our results indicate that the seismic networks in Greece need enhancements for regional EEW, either by adding stations or by upgrading the hardware to reduce delays. The application of an EEW system in the area is promising and, once operational, capable of mitigating earthquake risk.     

Model-data fusion for seismic performance evaluation of an instrumented highway bridge

The paper presents a computationally efficient algorithm to integrate a probabilistic, non-Gaussian parameter estimation approach for nonlinear finite element models with the performance-based earthquake engineering (PBEE) framework for accurate performance evaluations of instrumented civil infrastructures. The algorithm first utilizes a minimum variance framework to fuse predictions from a numerical model of a civil infrastructure with its measured behavior during a past earthquake to update the parameters of the numerical model that is, then, used for performance prediction of the civil infrastructure during future earthquakes. A nonproduct quadrature rule, based on the conjugate unscented transformation, forms an enabling tool to drive the computationally efficient model prediction, model-data fusion, and performance evaluation. The algorithm is illustrated and validated on Meloland Road overpass, a heavily instrumented highway bridge in El Centro, CA, which experienced three moderate earthquake events in the past. The benefits of integrating measurement data into the PBEE framework are highlighted by comparing damage fragilities of and annual probabilities of damages to the bridge estimated using the presented algorithm with that estimated using the conventional PBEE approach.     

Highway bridge seismic design: Summary of FHWA/MCEER project on seismic vulnerability of new highway construction

The Federal Highway Administration (FHWA) sponsored a large, multi-year project conducted by the Multidisciplinary Center for Earthquake Engineering Research (MCEER) titled “Seismic Vulnerability of New Highway Construction” (MCEER Project 112), which was completed in 1998. MCEER coordinated the work of many researchers, who performed studies on the seismic design and vulnerability analysis of highway bridges, tunnels, and retaining structures. Extensive research was conducted to provide revisions and improvements to current design and detailing approaches and national design specifications for highway bridges. The program included both analytical and experimental studies, and addressed seismic hazard exposure and ground motion input for the U.S. highway system; foundation design and soil behavior; structural importance, analysis, and response; structural design issues and details; and structural design criteria. Supported by: the Federal Highway Administration under contract number DTFH61-92-C-00112.     

福建省地震台网预警能力评估

由于常用的均方根值法和噪声功率谱法不能消除不同传感器记录的噪声干扰,为提高噪声水平计算的准确度,本文选用最大概率峰值位移作为背景噪声评估指标。基于可靠的噪声数据,借鉴震级-最大距离监测能力法并考虑预警时效,提出了地震预警最小震级评估方法,系统评估福建三类传感器网及其融合网的地震预警最小震级和预警首报时间。结果表明：测震强震融合网的地震预警最小震级高于单测震网,但明显低于强震网;强震烈度计融合网与单烈度计网的结果相近;三网融合后95%区域的地震预警最小震级约为M_L3.2。由于烈度计网比测震和强震网密集,其预警首报时间最短;三网融合相对于单测震网或单强震网,其震后地震预警首报时间得到了明显缩短,预计95%区域的首报时间为4—6 s。本文研究为福建省的台网布局的优化和重点区域监测能力的提升提供了参考依据。     

城市高架桥模糊简化TS主动控制的优化设计

首先利用遗传算法全局寻优的特性找到LQR控制中的最优权系数,然后得到控制力的状态表达式u=-GZ,在此基础上利用简化的模糊推理算法设计Takagi-Sugeno模糊控制器,对某城市高架桥计算模型的上部结构位移进行了MATLAB下的仿真控制分析,并取得了一定的控制效果。并通过分析可知:模糊控制系统可以对难以建立精确数学模型的结构进行有效的控制。     

基于半主动控制的MR阻尼器控制力优化

本文研究半主动控制系统中磁流变(MR)阻尼器的控制力优化问题,从而提高MR阻尼器的半主动控制效果。文中首先建立了多自由度结构MR阻尼器控制系统的运动方程;然后根据MR阻尼器的出力特性提出了结构控制的半主动控制律,并对控制率中MR阻尼器的最大控制力设计值提出了不同的优化取值方法;最后仿真分析了MR阻尼器的不同最大控制力设计值对不同自由度结构的控制效果。研究表明,当设计值取最优控制力的平均绝对值或均方根值时,MR阻尼器的最大控制力比最优控制力的最大值降低了85%,而控制效果降低不多,可以满足对结构的控制要求;降低最大控制力设计值后,不但可以充分发挥MR阻尼器的出力性能,而且可以缩小MR阻尼器的设计尺寸,便于工程应用。