【作者】 周云；

【导师】 易伟建；

【作者基本信息】 湖南大学 ， 结构工程， 2008， 博士

【摘要】 近二十年来,基于动力信息的结构损伤诊断研究受到人们的广泛关注,学者在这一领域开展大量的研究。由于土木工程结构的复杂性,人们对结构的建模忽略了很多关键因素,例如没有考虑土与结构动力相互作用的影响。人们多利用低阶模态进行损伤诊断研究,对损伤敏感的高阶模态研究和利用较少。用于结构损伤诊断的动力信息还受到环境因素和测量噪声的影响,存在着不确定性。本文以弹性地基板和弹性地基上的钢筋混凝土框架结构为对象展开参数识别和损伤诊断研究工作,主要内容如下:?1.对模态参数识别方法进行了研究,比较最小二乘复指数法(LSCE)与?PolyMAX?方法,发现?PolyMAX?方法识别高阻尼高阶模态的能力较强。在实验室条件下对弹性地基上自由板进行了脉冲锤击法模态实验,讨论了? Winkler?地基和双参数地基板振动的特点,指出实际工程中地基板的振动仅存在“近似刚体模态”。利用? Vlasov?地基上厚薄板通用元建立地基板振动的通用方法,通过反分析识别得到地基的物理参数。?2.在实验室条件下对地基上的一座钢筋混凝土框架结构进行了模态实验研究。随着框架结构的浇筑过程,进行了随着层数增加的逐层位移模态测试,得到了各种工况下结构的模态值。然后进行了应变模态测试,得到各阶应变模态测试结果。分别考虑了重复实验,模态参数分析方法,温度变化,力大小不均等因素造成的模态参数不确定性。发现模态参数识别方法的影响不能忽略。随温度的升高,结构模态频率降低。锤击力增大导致结构频率的降低。对于非稳态信号的处理,利用?HHT?的识别得到的结果比?FFT?更好。?3.对本文框架结构进行了物理参数识别研究。上部结构采用弯剪缩聚型模型,下部基础采用地基阻抗函数模型。基于不同工况识别得到的结构模态参数结果,利用灵敏度方法进行了各种工况下的结构和地基参数同步识别,得到了模态参数随结构变化的规律。由于灵敏度方法易出现病态问题,采用遗传算法结合模拟退火技术形成遗传退火混合算法,提高了遗传算法的全局寻优能力。利用遗传退火混合算法进行参数识别,识别结果优于灵敏度方法的结果。?4.引入模态局部化的概念,通过算例讨论了刚度完好连续梁由于支座位置变化和支座刚度变化导致的模态局部化的问题,在理论上是特征空间的扩张的问题。利用一座? 3?层框架首层梁的模态实验证实了框架梁也具有连续梁的类似特性,并分析了框架中千斤顶对于结构动力特性的影响。对本文框架结构柱的研究发现,连续梁的模态局部化现象也存在于框架柱中,通过在首层柱单元上加质量博士学位论文?块的方法,从实测结果证实了“高灵敏度的高阶模态”的存在。?5.建立了基于贝叶斯理论进行损伤诊断的基本框架,利用基于马尔可夫链的蒙特卡罗模拟(MCMC)的方法计算贝叶斯统计问题,编制了?MCMC?计算程序。通过一个三层剪切型框架结构的计算模型,分别计算了单损伤与多损伤,不同准则的比较,不同噪声水平下方法的比较,表明? MCMC?方法能有效地诊断结构的损伤。对本文框架结构局部加强柱部位进行了损伤前和损伤后的各? 5?次试验,利用两步法得到的后验期望估计准确诊断了损伤的位置。同时发现地基参数对于结构动力特性有着明显的影响。更多还原

【Abstract】 In these two decades, extensive attention has been focused on the researches about structural damage identification based on dynamic information, the studies in this field have been widely conducted by the scholars. Due to the complexity of civil engineering structures, many key factors are neglected in structural modeling, such as the influence of the soil-structure dynamic interaction is not considered. The lower modes are often used in damage identification, however the higher modes which are more sensitive to the damage have seldom been researched and utilized. The dynamic information is also influenced by the environment and the measurement noise, so there exist uncertain factors. In this paper the researches on the slab and frame on elastic foundation are studied in this paper, the main works are as follows.1. The researches have been done on modal parameter identification method. Compared with LSCE method, PolyMAX method has better abilities on identifying higher modes and higher damping modes. Modal experiments on free-edged elastic foundation slabs were done by hammer-hitting excitation method in the laboratory. The vibration characters of the slabs on Winkler foundation and on two parameter foundation are discussed, it is indicated that‘approximate rigid modes’exist in the slab on real soil condition. The generalized method analyzing the thick-thin slab on Vlasov foundation has been researched, the physical parameters of the foundation are identified by the inverse analysis.2. The modal experiment on a reinforced concrete frame structure on soil foundation was done in laboratory. The displacement mode experiment was done with increasing of the storey, the modal experimental results of four cases were obtained. The strain mode experiment was done and the strain modes were also obtained. Four different factors influencing the uncertainty of modal parameters are considered, including repeated experiments, modal analysis method, varieties of the temperature and the varieties of hitting force magnitude. It is found that the influence of modal parameter identification method can not be neglected. With the increase of the temperature, the modal frequencies are decreased. Modal frequencies of the structures are also decreased with the higher hitting force. HHT method is better on identifying the non-stationary signals than FFT method.3. Physical parameter identification is carried out on the frame structure. The bending shear condensation model is used as the upper structure model, and impedance function model is used as the foundation model. By using the modal parameter identification results in different Cases, the sensitivity method is used to identify the structure’s and foundation’s parameters in the same time, the regulation of the modal parameter changing with story height is obtained. Due to the ill-posed problems often occurred in sensitivity method, the simulated annealing algorithm is used to combine with genetic algorithm, so GAHA is produced and the global searching ability is developed. GAHA is used in parameter identification, the identified results are better than the results calculated by sensitivity method.4. The concept of modal localization is introduced, the modal localization phenomenon caused by changing support location and support stiffness in continuous beam like structure is discussed by numerical examples, it is due to the expansion of the eigenvalue space in theory. The modal experiments on the fist story beam of a three story height frame structure testify the frame beam has the similar dynamic characters just like continuous beam, the jack’s influence on the dynamic characters of frame structure is discussed. By researching on the column of the frame structure, it is found that modal localized phenomenon in continuous beam like structure occurred in frame column, by adding the mass on the column element of first story, the‘high sensitive higher mode’is found in experimental results.5. The basic frame work of damage identification based on Bayesian statistical theory is established, Markov Chain’s Monte Carlo simulation (MCMC) is used to calculate Bayesian problem. Calculating program of MCMC is compiled. By calculating a three storey shear frame structure, the cases on the single damage location and multiple damage locations, the different criterion and the method under different noise level are compared. It is indicated that Bayesian method based on MCMC method can identify the structural damage effectively. At last, five experiments were conducted before damage and after damage on the frame structure which local column is strengthened, the damage location can exactly be found by using posterior expectation estimation in two step method. It is found that the foundation parameter has obvious influence on structural dynamic characters.更多还原