Parameter identification of hysteretic model of rubber-bearing based on sequential nonlinear least-square estimation

In order to evaluate the nonlinear performance and the possible damage to rubber-bearings （RBs） during their normal operation or under strong earthquakes, a simplified Bouc-Wen model is used to describe the nonlinear hysteretic behavior of RBs in this paper, which has the advantages of being smooth-varying and physically motivated. Further, based on the results from experimental tests performed by using a particular type of RB （GZN 110） under different excitation scenarios, including white noise and several earthquakes, a new system identification method, referred to as the sequential nonlinear least- square estimation （SNLSE）, is introduced to identify the model parameters. It is shown that the proposed simplified Bouc- Wen model is capable of describing the nonlinear hysteretic behavior of RBs, and that the SNLSE approach is very effective in identifying the model parameters of RBs.

Trust-region based instantaneous optimal semi-active control of long-span spatially extended structures with MRF-04K damper

In the field of civil engineering, magnetorheological fluid （MRF） damper-based semi-active control systems have received considerable attention for use in protecting structures from natural hazards such as strong earthquakes and high winds. In this paper, the MRF damper-based semi-active control system is applied to a long-span spatially extended structure and its feasibility is discussed. Meanwhile, a _trust-region method based instantaneous optimal semi-active control algorithm （TIOC） is proposed to improve the performance of the semi-active control system in a multiple damper situation. The proposed TIOC describes the control process as a bounded constraint optimization problem, in which an optimal semi- active control force vector is solved by the trust-region method in every control step to minimize the structural responses. A numerical example of a railway station roof structure installed with MRF-04K dampers is presented. First, a modified Bouc- Wen model is utilized to describe the behavior of the selected MRF-04K damper. Then, two semi-active control systems, including the well-known clipped-optimal controller and the proposed TIOC controller, are considered. Based on the characteristics of the long-span spatially extended structure, the performance of the control system is evaluated under uniform earthquake excitation and travelling-wave excitation with different apparent velocities. The simulation results indicate that the MR fluid damper-based semi-active control systems have the potential to mitigate the responses of full-scale long-span spatially extended structures under earthquake hazards. The superiority of the proposed TIOC controller is demonstrated by comparing its control effectiveness with the clipped-optimal controller for several different cases.

基于扩展卡尔曼滤波的非线性带滑移滞变系统的实时估计

利用扩展卡尔曼滤波方法对Baber与Noori提出的带滑移滞变模型进行了参数的实时估计。考虑到该方法在收敛性上对参数初始值的选取的依赖性较强 ,提出了一种用于确定各参数初始估计值的方法。

基于EKF方法的橡胶隔震支座参数识别实验研究

采用Bouc-Wen模型建立橡胶隔震支座的非线性动力学方程,基于已有研究成果,缩减模型参数简化模型,建立不同数量参数的迟滞模型模拟橡胶隔震支座的非线性特性。对橡胶隔震支座进行振动台实验,基于测得的加速度信号和广义卡尔曼滤波(Extended Kalman filter,EKF)方法在线识别橡胶隔震支座的参数和位移。对不同参数数量的Bouc-Wen模型在不同地震波激励下,EKF方法识别得到的橡胶隔震支座模型参数一致,且识别的位移和实际测量得到的位移曲线吻合良好,验证了本文所得模型参数的有效性和准确性及模型简化的合理性,也证明了EKF方法在橡胶隔震支座参数识别中的有效性。

滞回结构随机地震反应概率密度演化分析

在工程实际中,要合理地评估复杂结构在地震作用下的整体性能,需要考虑结构参数的随机性。概率密度演化理论可以直接获取随机结构动力反应的概率密度函数及其演化过程。本文以广义F-偏差最小化作为代表点选取准则,采用扩展的Bouc-Wen滞回模型,对具有随机参数的滞回非线性多自由度结构进行了地震动反应概率密度演化分析。结果表明,随机结构的动力反应具有显著且复杂的演化特征,这些特征可以通过概率密度演化理论进行精细化分析。

基于扩展有限元进行钢筋混凝土柱捏拢效应的机理分析

预测地震荷载下钢筋混凝土柱的力学性能,对评估震后混凝土结构的安全性和震害损失具有重要意义。由于混凝土材料在受力过程中的复杂性,目前对钢筋混凝土结构力学性能的模拟主要依靠数值方法。已有的数值模拟方法大都基于有限元法,将混凝土视为连续体,通过人为定义参数来指定混凝土的滞回本构,因此存在一定的主观性与局限性。该文结合扩展有限元法与断裂准则,直接模拟混凝土裂缝的开展与闭合,并考虑钢筋和混凝土的粘结滑移作用,通过数值计算,直接再现了钢筋混凝土结构在低周反复荷载下的力学行为。模拟方法得到了试验的验证,与结果吻合较好。该文进一步分析了钢筋混凝土柱的滞回行为中混凝土、钢筋的各自作用和相互抵消行为,从细观的角度,在机理上揭示了捏拢效应出现的三个主要原因。