大型工程结构模态识别的理论和方法研究

【作者】 姚志远；

【导师】 汪凤泉；

【作者基本信息】 东南大学 ， 测试计量技术及仪器， 2004， 博士

【摘要】 工程结构的模态识别有着广泛的应用前景,识别的模态参数能够被用来估计结构的损伤和确定结构未来的响应,因此,该技术能使用在桥梁的健康检测和大型建筑的主动控制中。传统识别方法利用被测试的输入和输出数据识别结构的振动模态,但是,对于大型工程结构无论是实施人工激励还是测试外部激励都是困难的。九十年代后期,环境振动识别方法受到广泛的关注,该方法利用测试的振动数据识别结构的模态参数,主要的识别方法有时间序列方法、ITD 方法、ERA 方法和随机子空间识别方法。系统辨识方法源于控制工程,它们利用离散的测试数据识别离散模型的模型参数,并将模型参数转换成结构的模态参数。事实上,结构的振动模型是连续的动力学模型,基于连续模型参数识别的思想方法,本文提出利用离散的测试数据直接识别结构的模态参数的基本理论和方法。全面地研究环境振动识别方法的基本理论,系统地分析环境振动识别方法的主要方法,讨论它们的优点和不足;建立结构动力学的有限元模型和试验模型,分析有限元模型与试验模型之间的相互关系;改进谐波识别中的MUSIC识别方法和相关函数识别方法,给出大型结构模态识别的连续型的子空间分解识别方法和相关函数识别方法,这个方法是多元谐波识别方法;提出直接识别结构的物理参数和模态参数的最小二乘方法,这个方法利用导数的近似值代替导数值,并运用最小二乘方法识别结构的物理参数,讨论导数近似值的选择方法,分析算法的收敛性;通过仿真计算和模型实验,研究高层框架结构的模态参数识别,验证子空间分解识别方法、相关函数识别方法和最小二乘识别方法的有效性,算法的稳定性;从理论和试验两个方面分析和研究噪声对识别精度的影响,影响识别精度的因素,以及部分模态成分的模态参数不能够被识别的原因。本文完善工程结构模态识别的方法体系,提出更加稳定高效的识别方法,这些方法能够被使用在桥梁的健康检测和建筑的主动控制中。更多还原

【Abstract】 The modal identification for engineering structures can be widely applied in civil engineering, and the identified modal parameters is used to estimate structural damages and determine future responses of the structure. Hence, this method can be used in health monitoring of bridges and active control of huge architectures. The measured input and output data of structures are used to estimate the modal parameters for the traditional identification methods, but it is diffculty to exert artificial excition on huge engineering structures or measure the exterior excition of huge engineering structures. In the later of 1990s, it is widely interested of ambient vibration method to identify the structural modal parameters according to the measured output data. There are many traditional identification methods, such as the time series analysis, ITD method, ERA method and stochastic subspace method. System identification originates from the control engineering and is utilized to estimate the model parameters of discrete models by the discrete data and transform model parameters to structural modal parameters. In fact, the discussed structural vibration models are continuous models. Based on the parameters identification methods of continuous models, this paper puts forward the basic theory and method to estimate directly structural modal parameters by discrete output data. Firstly, this paper investigated roundly the basic theory of the ambient vibration method, analyzed systematically the main methods of ambient vibration identification, and discussed their advantages and disadvantages. Then we established the finite element model of structural dynamics and test model and analyzed their mutual relation, improved MUSIC method and correlation function method in the harmonic identification, and gave the subspace method and correlation function method based on continuous model, which is multi-harmonic retrieve technique. And then, this paper also puts forward least-squares method to estimate directly structural physical and modal parameters; this approach replaced the derivative operator in the continuous time model with an equivalent approximation, and estimated the physical parameters of structures by the least-squares method. And then, we discussed the approximation methods of derivative and their convergence. Finally, this paper researched the modal parameters of a frame structure by the simulation and test. The results demonstrated that subspace method, correlation function method and the least-squares method are effective and stable respectively. The influence of noise on identification precision, the effect factor of the computing precision and the reason of missing estimation some modes were analyzed and discussed. This paper improved the system of the modal identification for engineering structures. The research results show that those methods are of simplicity and effectiveness, and they can be used in health monitoring and vibration control for bridges and architectures.更多还原