多维地震作用下偏心结构的磁流变阻尼器半主动控制

理论研究与震害经验表明,地震时结构会产生不可忽略的平动与扭转耦合的空间振动。本文提出了基于线性最优控制理论的部分状态反馈次优控制策略和基于遗传算法的控制策略,以Marlab和Simulink为平台,采用磁流变阻尼器对双向水平地震作用下的偏心结构平．扭耦联反应进行半主动控制。对-6层双向偏心框架结构进行控制效果仿真分析的结果证明,本文提出的2种控制策略是有效的。     

漂浮体系悬索桥拟静态纵向运动特性及其控制

营运状况下漂浮体系悬索桥加劲梁纵向运动产生的过大累积行程会引起伸缩缝和塔梁纵向阻尼器等连接构件的性能退化和疲劳损坏.探索加劲梁纵向运动过大累积行程的成因,并找出降低累积行程的控制措施是确保悬索桥健康运营的关键.首先,以江阴长江大桥实测位移时程数据为基础,对不同频谱特性的位移成分进行分解,并统计了不同位移成分的循环次数和...     

白云母对岩盐断层带摩擦速度依赖性影响的实验研究

为更好地理解层状硅酸盐对断层强度、滑动速度依赖性及地震活动特征的影响,利用双轴摩擦实验对含白云母岩盐断层带在干燥及含水条件下摩擦的速度依赖性进行了实验研究,并观测了摩擦滑动过程中的声发射,分析了断层带的微观结构.实验结果表明,干燥条件下含白云母岩盐断层带在0.1 ～ 100μm/s的速度范围内表现为黏滑和速度弱化,增大σ2会使断层带从速度弱化向速度强化转化,速度依赖性转换出现在0.1 μm/s,其中断层滑动表现为稳滑或应力释放时间较长的黏滑事件;含水条件下含白云母岩盐断层带在0.05 ～0.01μm/s的速度范围内表现为速度强化,0.1 ～10μm/s的速度范围内表现为速度弱化,50～100μm/s的速度范围内又转换为速度强化行为.含白云母岩盐断层带在干燥条件下一次黏滑伴随一个或一丛声发射事件,而在含水条件下与稳滑相对应,滑动过程中并未记录到声发射事件.显微结构观察表明,速度弱化域的主要变形机制是岩盐颗粒的脆性破裂和局部化的滑动;干燥条件下,速度强化域的主要变形机制是岩盐颗粒的均匀破裂;含水条件下2个速度强化域对应不同的微观机制,高速域的速度强化受控于岩盐颗粒在白云母相互连结形成的网状结构上的滑动及其均匀碎裂作用,而低速域的速度强化还受岩盐的压溶作用控制.通过与岩盐断层带摩擦实验结果对比可知,白云母的存在对于燥岩盐断层带摩擦滑动方式和速度依赖性没有显著影响,而在含水条件下白云母的存在使得岩盐断层带滑动趋于稳定.实验结果为分析含层状硅酸盐断层的强度和稳定性提供了依据.此外,在速度依赖性转换域上观察到的应力缓慢释放的现象进一步证实了在岩盐断层带摩擦滑动过程中观察到的现象,这对慢地震机制研究具有参考意义.     

基于H∞理论的磁流变阻尼器半主动容错控制

建筑结构的半主动控制系统中的传感器,在强震作用下可能因出现故障而影响控制效果。以磁流变阻尼器为例,研究半主动容错控制系统的设计方法。首先,研究了基于状态观测器的半主动H∞控制器设计方法,并将之应用到建筑结构采用磁流变阻尼器的减振控制中;运用改进Bouc-Wen模型,计算磁流变阻尼器的阻尼力,通过求解一个代数Riccati方程和一个状态观测方程,得出了基于状态观测器的H∞主动控制律;再对其采用Clipped-optimal方法实施半主动控制策略。然后,针对传感器故障,利用观测器组的输出残差对故障进行在线诊断,并通过几个观测器状态值的比较得到故障的大小,并据此对传感器的测量值进行修正,从而消除故障对闭环系统的影响,最终实现半主动H∞容错控制。仿真结果表明,该方法具有很好的容错控制效果。     

新型开孔H型钢阻尼器有限元分析

设计了分别开椭圆形孔和菱形孔的2种新型H型钢耗能器,阐述了它们的构造与耗能原理。采用有限元软件ABAQUS对开椭圆形孔、菱形孔和条形孔这3种新型耗能器的耗能性能进行数值分析,研究了开孔形状、肢宽与肢高等参数对新型耗能器耗能性能的影响。分析结果表明：新型H型钢耗能器具有饱满的滞回曲线,屈服位移较小、耗能性能稳定,耗能器的屈服位移、初始刚度和等效阻尼比随各肢钢板宽度增大（或高度减小）而增大;在开孔率相近或者肢宽相同的情况下,菱形孔H型钢耗能器的等效阻尼比要比条形孔和椭圆形孔的大,且应力分布更加均匀。     

Semi‐active tuned mass damper building systems: Application

Seismic performance attributes of multi‐story passive and semi‐active tuned mass damper (PTMD and SATMD) building systems are investigated for 12‐story moment resisting frames modeled as ‘10+2’ stories and ‘8+4’ stories. Segmented upper portion of the stories are isolated as a tuned mass, and a passive viscous damper or semi‐active resetable device is adopted as energy dissipation strategy. The semi‐active approach uses feedback control to alter or manipulate the reaction forces, effectively re‐tuning the system depending on the structural response. Optimum tuned mass damper control parameters and appropriate matching SATMD configurations are adopted from a companion study on a simplified two‐degree‐of‐freedom system. Statistical performance metrics are presented for 30 probabilistically scaled earthquake records from the SAC project. Time history analyses are used to compute response reduction factors across a wide range of seismic hazard intensities. Results show that large SATMD systems can effectively manage seismic response for multi‐degree‐of freedom systems across a broad range of ground motions in comparison to passive solutions. Specific results include the identification of differences in the mechanisms by which SATMD and PTMD systems remove energy, based on the differences in the devices used. Additionally, variability is seen to be tighter for the SATMD systems across the suites of ground motions used, indicating a more robust control system. While the overall efficacy of the concept is shown the major issues, such as isolation layer displacement, are discussed in detail not available in simplified spectral analyses, providing further insight into the dynamics of these issues for these systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Testing of dynamically substructured,base‐isolated systems using adaptive control techniques

Experimental techniques for testing dynamically substructured systems are currently receiving attention in a wide range of structural, aerospace and automotive engineering environments. Dynamic substructuring enables full‐size, critical components to be physically tested within a laboratory (as physical substructures), while the remaining parts are simulated in real‐time (as numerical substructures). High quality control is required to achieve synchronization of variables at the substructuring interfaces and to compensate for additional actuator system(s) dynamics, nonlinearities, uncertainties and time‐varying parameters within the physical substructures. This paper presents the substructuring approach and associated controller designs for performance testing of an aseismic, base‐isolation system, which is comprised of roller‐pendulum isolators and controllable, nonlinear magnetorheological dampers. Roller‐pendulum isolators are typically mounted between the protected structure and its foundation and have a fundamental period of oscillation far‐removed from the predominant periods of any earthquake. Such semi‐active damper systems can ensure safety and performance requirements, whereas the implementation of purely active systems can be problematic in this respect. A linear inverse dynamics compensation and an adaptive controller are tailored for the resulting nonlinear synchronization problem. Implementation results favourably compare the effectiveness of the adaptive substructuring method against a conventional shaking‐table technique. A 1.32% error resulted compared with the shaking‐table response. Ultimately, the accuracy of the substructuring method compared with the response of the shaking‐table is dependent upon the fidelity of the numerical substructure. Copyright © 2009 John Wiley & Sons, Ltd.     

近场地震动下偏心结构的减震控制研究

本文选用远场宽频地震Kanai-Tajimi模型与近场地震He-Agrawal速度脉冲模型,对现有的典型近场地震记录进行了非线性数值拟合。通过调整脉冲分量与宽频分量的比值,得到了不同脉冲分量的地震波,分析了在合成近场地震波作用下,设置粘滞阻尼器时偏心结构的动力反应,并与未设置阻尼器时结构的地震响应进行了对比,同时也对能反映结构偏心特性的参数进行了分析研究。通过数值模拟与仿真分析,得到了一些对实际工程设计有意义的结论。     

Experimental assessment of dynamic lateral resistance of railway concrete sleeper

The single tie (sleeper) push test (STPT) is a common method to evaluate the lateral resistance of a railway track sleeper. This methodology evaluates the lateral resistance phenomenon in a static manner despite the fact that the majority of the exerted loads on a railway track have a dynamic nature. For this reason, a mass–spring–damper numerical model was created to investigate the dynamic lateral interaction between an isolated sleeper and ballast layer in the presence of various lateral impact loads. On the basis of the model outputs, a pendulum loading test device (PLTD) was designed and developed in the laboratory. In this regard, a cylindrical hammer with modifiable mass and triggering angle was installed on a steel frame for imposing lateral impact load on an instrumented concrete sleeper. The graphs of the sleeper–ballast interaction force versus the sleeper lateral displacement were extracted for different masses and triggering angles of the hammer. Considering a same condition for sleeper, the maximum value of this interaction force was called the dynamic lateral resistance (DLR) and static lateral resistance (SLR) respect to the dynamic and static states of lateral loading. Comparing the values of the sleeper DLRs and SLR indicated that unlike the constant SLR of 6.5 kN, the DLR was in the range 2–10.2 kN in the impact load domain of 3–40 kN. However, as a key finding, the average slopes of the DLR and SLR graphs were equivalent in the dynamic and static tests.     

Earthquake response analyses of a full‐scale five‐story steel frame equipped with two types of dampers

The seismic performance tests of a full‐scale five‐story passively controlled steel building were conducted on the E‐Defense shaking table in Japan in March 2009. Before the tests, a blind prediction contest was held to allow researchers and practitioners from all over the world to construct analytical models and predict the dynamic responses of the steel frame specimen equipped with buckling‐restrained braces (BRBs) or viscous dampers (VDs). This paper presents the details of two refined prediction models made and results obtained before the tests. When the proposed analytical modeling techniques are adopted as in the two refined prediction models, the overall prediction accuracy is about 90%. Sensitivity studies conducted after the tests are also presented in this paper. The effects of varying each modeling feature on the response simulation accuracy have been investigated. The analytical results suggest that considering concrete full‐composite actions for beam members could improve prediction accuracy by about 20% against using the simplified bare steel beam model. Adopting refined BRB stiffness computed from incorporating finite‐element gusset stiffness only improves the overall prediction accuracy by 0.9%. Considering the BRB dynamic loading test results for analytical BRB strength reduces the error by 1.9%. For the VD frame, incorporating the brace and VD stiffness could improve the overall prediction accuracy by about 15%. Copyright © 2012 John Wiley & Sons, Ltd.