【作者】 孙威；

【导师】 阎石；

【作者基本信息】 大连理工大学 ， 结构工程， 2009， 博士

【摘要】 随着我国社会经济的不断发展,各种大型复杂工程结构不断涌现,土木工程结构健康监测技术逐渐成为学术界的研究热点。近十几年来,智能材料结构在工程领域中的成功应用,为实现真正意义上的结构健康监测提供了有效的途径。以压电陶瓷为代表压电智能材料具有集传感和驱动一体化的优越特性,适合于结构健康监测领域。同时,压电材料还具有响应速度快、线性关系好、能耗低、造价低廉且易加工成型等优点。因此,将压电材料作为基本元件,研发一套方便、实用的结构健康监测系统也符合我国当前的国情。本论文基于上述背景,对利用压电陶瓷材料进行混凝土结构健康监测的相关技术进行详细研究,具体工作包括以下几个方面:(1)针对混凝土结构的特点以及压电陶瓷片的材料特性,研制开发了一种新型的、适用于混凝土结构的压电陶瓷传感器件——“智能骨料”。它既是混凝土结构健康监测的智能元件,又具有普通骨料的功能,很好地解决了压电传感器与主体结构相结合时出现的各种实际问题。在此基础上,对压电智能混凝土结构损伤主动监测系统的线性性能、灵敏度、重复性及频率响应特性等基本性能进行了试验研究。结果表明,该系统具有良好的性能,这为进一步开展健康监测研究奠定了试验基础。(2)依据应力波在固体中的传播特点,提出了考虑几何扩散影响的修正衰减系数公式,并对应力波在混凝土介质中传播的衰减规律和以压电陶瓷片作为声源的声场在混凝士介质中的分布规律等问题进行了研究。结果表明,应力波在混凝土介质内传播,衰减系数与频率之间近似满足三次多项式关系;同时以压电陶瓷片作为声源,其声场在混凝土内部的分布较为分散。该试验结果为合理布置传感器提供了依据。(3)对利用波动法的混凝土结构主动损伤识别技术进行了研究。通过研究混凝土构件裂缝损伤及其发展对主动监测信号的幅值、频率及相位等参量的影响,找出各参数随损伤程度增加的变化规律。结果表明,信号幅值对裂缝损伤的变化最为敏感,且随损伤程度的不断增加呈现出不断衰减的趋势。因此,利用波动法的压电智能混凝土结构损伤主动识别技术中,主动监测信号的幅值可作为损伤识别的主要特征参量。在此基础上进一步从理论上证明了信号幅值作为损伤特征参量的有效性。(4)在以信号幅值作为特征参量的基础上,提出了利用信号能量衰减的损伤程度判定方法。针对混凝土结构形体较大的特点,提出利用传感器列阵的损伤近似定位方法。对混凝土构件进行了损伤监测试验,结果证明提出的损伤识别方法的有效性。同时通过主被动损伤监测对比试验,表明本文提出的方法适合用于混凝土结构的长期健康临测领域。(5)以dSPACE系统为平台搭建了压电智能混凝土结构的健康监测系统。结合压电智能混凝土结构长期健康监测的特点,提出了相应的结构健康监测策略,为大型混凝土结构健康监测提供必要的技术支持。在此基础上,对荷载作用下的压电智能混凝土框架结构的进行了健康监测试验。试验结果表明,通过分析传感器采集到的监测数据能够有效的反映存在的损伤以及结构健康状态的发展趋势。更多还原

【Abstract】 Nowadays, various kinds of large and complex engineering structures have constantly appeared with the continuous development in economy and society of our country. The technology of structural health monitoring (SHM) has become the research hotspot in the civil engineering fields. In decades, the successful application for smart material and structure (SMS) technology in the civil engineering has opened a successful path to realize the real and meaningful SHM.Smart piezoelectric materials such as the piezoelectric ceramic have a superior characteristic of dual functions of actuating and sensing which make it suitable for the SHM technology. Meanwhile, the piezoelectric materials have many other advantages of fast response, good linear relationship, low energy consumption, low cost and easy processing. Therefore, developing a convenient and practical SHM system based on piezoelectric materials will accord well with Chinese conditions. In the background, the SHM technology for concrete structures using piezoelectric ceramic is researched in details in the paper and the work includes as follows:Firstly, a kind of new sensor which is named "smart aggregate" and suitable for health monitoring in concrete structures is researched and developed according to the characteristic of the concrete and the piezoelectric ceramic. The new smart sensor has the functions of both smart elements and the normal aggregate in concrete materials and can be used to solve problems caused by the combination of two materials. On this basis, an experimental research designed for validating the system of the active structural health monitoring (ASHM) for smart piezoelectric concrete is finished. The results show that many indexes of the system such as linearity, sensitivity, frequency response characteristic and repeatability are very good and it is helpful to establish the foundation for further development in the SHM field.Secondly, according to the characteristic of wave propagation in the concrete, an attenuation coefficient considering the geometrical attenuation during the wave spreading was proposed. Furthermore, the law of the stress wave propagating in the concrete media and the sound field distribution generating by the vibration of PZT patches in the concrete are experimentally researched. The results show that the attenuation coefficient is the function of the cubic polynomial of frequency and the sound field around the PZT patch are scattered. The results also lay a basis for reasonably placing the sensors in the monitored structure. Thirdly, the active damage identification technology for concrete structures was researched. The variable law of amplitude, frequency and phase of the detecting signal caused by the increase of the damage level are established by the parameter research of the concrete crack damage. The results show that the amplitude of the stress signal is the best sensitive to the change of damage among the parameters and it will gradually decay with the increase of damage degree. Therefore, the amplitude of the signal can be used as the most important characteristic parameter for the active damage identification technology based on wave method. The effectiveness for the amplitude of signal being used as the characteristic parameter has been proved by a theoretical analysis approach.Fourthly, a damage degree identification method based on the energy attenuation is proposed on the basis of the signal amplitude being used as characteristic parameter. A damage locating method based on the transducers array is also proposed for the huge scale property of concrete structure. The damage detection tests for the concrete specimens are carried on to validate the efficiency of the array. The results show that the proposed damage identification method is very effective and that it’s suitable for the long-term health morning by compare of the results between the active and the passive monitoring tests.Fifthly, a health monitoring system for smart piezoelectric concrete structure based on the dSAPCE software is set up. Combining the property of the long term health monitoring and the smart piezoelectric concrete structure, a relevant SHM strategy was also proposed to provide a technical support and a guideline for the large scale concrete structure health monitoring. Then, a health morning test for a large scale RC frame structure is carried on in the laboratory. The experimental results show that the damage state and the development tendency of the monitored structure could also be effectively reflected by analyzing the data collected from the long term used sensors.更多还原