Robust H∞ control for aseismic structures with uncertainties in model parameters

This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LMI toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 El Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters.     

Seismic spatial effects on long-span bridge response in nonstationary inhomogeneous random fields

The long-span bridge response to nonstationary multiple seismic random excitations is investigated using the PEM (pseudo excitation method). This method transforms the nonstationary random response analysis into ordinary direct dynamic analysis, and therefore, the analysis can be solved conveniently using the Newmark, Wilson-θ schemes or the precise integration method. Numerical results of the seismic response for an actual long-span bridge using the proposed PEM are given and compared with the results based on the conventional stationary analysis. From the numerical comparisons, it was found that both the seismic spatial effect and the nonstationary effect are quite important, and that both stationary and nonstationary seismic analysis should pay special attention to the wave passage effect.     

海洋平台随机冰力谱的识别

将海冰对结构的作用看作是随机激励,利用海洋平台原型结构冰激振动的实测响应数据,用逆虚拟激励法(1PEM)识别了平台的冰载荷谱,结果表明逆虚拟激励法识别效果满足工程实际的需要,有较好的应用前景。     

随机地震响应的确定性算法

本文给出一个适宜于在电子计算机上执行的线性系统随机响应计算方法,并将它应用于海洋平台结构分析程序DASOS-J中。它的特点是易学易用,而且不因存在非比例阻尼矩阵或靠得很近的结构自振频率而在随机响应计算中引入误差,这是目前常用的其它方法不易做到的。     

考虑行波效应的车桥系统地震响应分析

借助虚拟激励法,本文研究了非一致水平地震作用下三维车桥耦合时变系统的非平稳随机振动问题。通过轮轨间位移协调关系将列车和桥梁运动方程进行耦合,建立了考虑行波效应的多点地震激励下列车-桥梁时变系统运动方程。水平地震激励假设为均匀调制多点异相位完全相干随机激励;轨道不平顺激励假设为多点异相位完全相干平稳随机激励。采用时变系统的虚拟激励法将这些随机激励分别转化为一系列虚拟的确定性激励,然后通过数值积分求解相应的虚拟响应,进而方便地得到系统随机响应的时变功率谱密度函数和标准差等。数值算例中,通过Monte Carlo法验证了本文随机振动分析方法的正确性和有效性,并讨论了地震波视波速、场地土条件等对系统随机响应的影响。     

分层岩层介质中平稳随机地震波传播的精细解法

随机波在分层介质中的传播是地震工程中很重要的一类问题。将岩层考虑为分层介质。岩层是各向异性的,各层性质不同,岩层位于基岩上面,并且认为基岩比岩层刚很多,在基岩处给出随机激励。在频率和波数域中,将控制方程化为常微分方程求解。对常微分方程,应用两点边值问题的精细积分法进行求解。因此,近年来发展的应用于结构随机振动的虚拟激励法,可应用于当前分层岩层响应的计算,给出数值结果,并与一些经典结果进行了比较,证明了该方法的合理性。     

毗邻建筑考虑局部场地效应时的LQG控制

本文基于虚拟激励法和留数定理推导出毗邻建筑考虑局部场地效应时在平稳随机地震激励下的LQG控制问题的闭合解。利用此闭合解进行场地土参数研究表明,场地土参数对位移和加速度响应的影响是不同的,甚至是相反的。因此对于给定的LQG控制加权阵Q和R,场地土的卓越频率和阻尼比变化对减震效果有显著影响,应予以重视。     

非平稳随机地震响应的精确高效算法

本文推广了文献[1]分析平稳随机地震响应的精确高速算法,使得在演变随机激励下线性结构的非平稳地震响应很容易地获得了解决。对一些重要的包络函数g(t),本文通过简单的频域分析求出了精确的时变功率谱密度。     

Seismic spatial effects on dynamic response of long-span bridges in stationary inhomogeneous random fields

The seismic analysis of long-span bridges subjected to multiple ground excitations is an important problem.The conventional response spectrum method neglects the spatial effects of ground motion, and therefore may result in questionable conclusions. The random vibration approach has been regarded as more reliable. Unfortunately, so far,computational difficulties have not yet been satisfactorily resolved. In this paper, an accurate and efficient random vibration approach -- pseudo excitation method (PEM), by which the above difficulties are overcome, is presented. It has been successfully used in the three dimensional seismic analysis of a number of long-span bridges with thousands of degrees of freedom and dozens of supports. The numerical results of a typical bridge show that the seismic spatial effects, particularly the wave passage effect, are sometimes quite important in evaluating the safety of long-span bridges.