【作者】 狄生奎；

【导师】 李慧； 杜永峰；

【作者基本信息】 兰州理工大学 ， 结构工程， 2011， 博士

【摘要】 结构健康监测是近年来发展起来的一项新兴的应用技术,主要应用于结构的在线实时连续监测、检查以及损伤探测等,实施结构健康监测的目的是增加和提高运营结构的可靠性、安全性和耐久性,确保结构完成正常的使用寿命,降低结构的维修成本。近年来这项技术被广泛应用于桥梁、水坝等大型工程项目运营过程的健康监测,同时土木工程界在实现对结构损伤及时识别的同时,也在尝试对识别出损伤的桥梁在不影响交通的情况下实现快速及时的修复。本文全面论述了国内外基于动力检测的健康监测方法和智能材料损伤识别及应急修复的相关文献,对其理论意义、研究应用前景、研究成果和存在问题做了全面的分析与比较。在此基础上研究了基于模态曲率、柔度模态的结构损伤识别方法以及形状记忆合金应用于结构健康监测和自修复的性能。以一个横向弯曲振动的连续直梁为研究对象,求解了梁在任意支撑条件下的运动微分方程的一般表达式,依据模态理论,将该微分方程的解表示为结构各阶模态的叠加形式并利用模态振型的正交性,求得结构的曲率频响函数,依据曲率频响函数的特征,对结构进行位移模态试验测得结构的弯曲位移模态后,就可以得到结构的曲率模态振型。对一简支梁模型进行动力测试,测试出结构各个实验工况下损伤前后的频率、相应振型,计算得到模态曲率差曲线,并且和有限元计算的结构模态曲率差的损伤识别结果进行对比,验证了用模态曲率差来识别简支梁损伤的可行性、适用性,探讨了损伤位置、模态阶次、损伤程度等对损伤识别结果的影响和敏感性。为了将模态曲率差理论应用于本论文的工程应用背景,分析了应用模态曲率差识别直梁结构与曲梁结构的理论区别,推导了曲梁结构的曲率振型模态的计算公式,设计了一个下承式系杆钢管混凝土拱桥试验模型,利用有限元程序理论计算了不同损伤状况下拱肋的模态曲率差,绘制了模态曲率差曲线,理论计算结果表明,模态曲率差可以用于对拱桥拱肋的损伤识别；开展室内动力测试试验,测试了各个工况下系杆拱桥模型的加速度响应,并进行曲率模态振型的转化后,绘制了模态曲率差曲线并和有限元分析结果进行了对比,说明模态曲率差可以应用于拱肋结构的损伤识别。为了在低阶频率下能够对结构的损伤实现比较好的识别,对基于模态柔度矩阵的损伤识别理论进行了论述,推导了基于模态柔度的损伤识别的基本理论公式,指出了模态柔度在低阶频率下对结构频率有着较好的敏感性,本文构造了一个基于模态柔度矩阵的损伤识别灵敏度参数,用于对结构进行损伤识别。对一钢梁模型进行理论模拟,提取结构的频率及相应振型,将模态振型转化为本文构造的损伤识别灵敏度参数ζ,绘制了损伤识别灵敏度参数ζ与结构单元位置的柱状图,从图中可以明显的看出,损伤识别灵敏度ζ对结构单损伤或多损伤有着显著的敏感性,可以应用于结构的损伤识别；对模型梁进行了动力测试,提取结构频率、相应振型,并转化为模态柔度和损伤识别灵敏度后,和理论计算结果进行对比,验证了基于本文构造的损伤灵敏度参数方法的正确性和可行性。为了研究或实现结构的自监测与应急自修复,制作了3组嵌入形状记忆合金(Shape Memory Alloy简称SMA)的钢筋混凝土梁,将SMA作为传感元件和驱动元件复合到混凝土梁中对梁的裂缝进行监测和应急自修复研究。试验采取通电激励的方式加热合金丝,为此专门研制了可控低压直流电源；通电激励加热合金丝,对SMA应用于结构健康监测的相变行为、电阻率的导电敏感性和力学性能进行了测试；对SMA置入混凝土的抗滑移性能进行了分析和测试；研究表明：当混凝土梁开裂程度较小,裂缝宽度小于0.3mm的情况下,合金丝电阻变化率与混凝土裂缝宽度间的线性关系非常明显,试验过程表明在消除合金丝滑移的情况下,且裂缝宽度在1.5mm范围内,SMA电阻变化率与混凝土梁的裂缝宽度成线性关系,SMA作为传感元件用于结构健康监测是可行的,完全可通过对合金电阻变化率的测定来监测混凝土梁裂缝损伤情况；当混凝土开裂且裂缝宽度大于2.0mm时,对形状记忆合金进行通电加热,SMA驱动效应发生可以使混凝土梁裂缝愈合；在对SMA敏感性测试试验过程中,SMA丝在发生轴向变形后,其电阻随着SMA丝的长度改变而且较为敏感；在对混凝土梁的自修复性能测试试验过程中发现,并不是SMA预张拉越大越好,预拉控制在极限拉应变的20%-30%为宜。以一个下承式钢管混凝土拱桥作为工程研究的应用背景,对结构进行了全面的有限元分析,在此基础上采用环境激励的方式对拱桥进行了全面的动力测试,对该桥主跨一阶竖向、一阶扭转、次跨一阶竖向、一阶扭转、全桥一阶横向振型等测试结果进行了全面的分析与比较,和有限元计算结果进行对比分析后发现：实测结果与理论分析结果基本吻合；拱肋竖向的振动和桥面竖向振动同步,拱肋竖向振动的频率稍大于桥面频率；试验结果表明,在完全环境激励情况下,足以识别出桥梁的振动模态；该拱桥振型第一阶模态是桥面的横向振动,地震反应分析时要特别注意桥面横向地震反应；扭转振型在振型序列中位置靠后,阶数较高,说明该结构抗扭刚度较大,对抗风比较有利；该桥实测频率基本都大于有限元计算结果,说明该桥刚度较好；对该拱桥采用空间有限元分析结果和实测结果基本一致。将拱桥主跨振型与第4章试验模型的振型进行对比后发现,实际结构的模态振型与试验模型的结果有着很好的一致性,可以将模态曲率差应用于拱桥拱肋的损伤识别研究。本文的研究工作在基于动力的桥梁损伤识别与健康监测和SMA智能结构的自监测与应急自修复方面做了一些有益的尝试,为今后桥梁结构健康监测与应急自修复的研究提供了一些基本的试验结果与理论支持,供今后开展基于动力和嵌入SMA的混凝土结构健康监测与自修复研究参考。更多还原

【Abstract】 Structural health monitoring (SHM) is an emerging applied new technology in recent years, dealing with continuous health monitoring of structure online, test and damage identification, the ultimate goal is to increase and improve the reliability, safety and durability, and to ensure the structure can finish the design life and reduce the maintenance costs. The technology is applied to monitor the large scale engineering, such as bridges, dams and so on. The timely repairing without influencing traffic is concerned when the damage identification can be realized at the same time.The research of the dissertation sums up a large number of references of the curvature mode, flexibility mode and intelligent material at home and abroad, makes a relatively comprehensive discussion on its theoretical significance, study application, research achievements and existing problems, studies the health monitoring methods based on the curvature mode, flexibility mode and SMA. Main research works can be summed up in five aspects.A beam with vertical bending vibration is taken as the research object, and general formula of differential equation was solved in any supported conditions. According to the modal theory, Solution of the differential equation was expressed as mode superposition of each mode, substituted into the differential equations and considering orthogonally of mode shapes, curvature FRF was obtained. Based on the characteristics of curvature FRF, after the displacement mode of the structure was measured by experimental test, curvature mode of the structure can be obtained. Dynamic test of a simple support beam was finished before and after damage, the corresponding curve of curvature mode was calculated by test result, the result of the finite element analysis and experimental result were compared, it is shown that mode curvature can be used to identify the damage of structure. The influence and sensitivity of the damage location, modal order, and damage degree were discussed to the accuracy of identification result.In order to use the modal curvature in one of concrete-filled steel tube (CFST) engineering, the theory difference of damage identification between straight and curve beam were analyzed, the modal curvature formula of curve beam curvature is derived. A CFST model was designed in the labratory, the difference mode curvature was calculated by finite element program of different damage condition of the arch rib, the theoretical result shows that modal curvature can be used to damage identification of arch ribs; dynamic experimental tests was carried out to get the acceleration response of the structure of various conditions, and modal curvature was transformed, the results of experiment and finite element analysis were compared, it is shown that modal curvature changes at the node arch ribs were injured. The result illustrate that the method can identify single damage and multiple damages of arch rib.In order to identify the complex structure in low order frequency, damage identification theory of the modal flexibilityis analyzed, the damage identification parameter was put forward based on modal flexibility matrix theory, a sensitivity parameter of difference flexibility matrix was used to identify the damage of a steel beam, extract the frequency and the corresponding structural vibration model after finite element simulation, the result shows the proposed damage identification sensitivity parameter can locate the damage position of single damage or multiple damages of the beam obviously; The dynamic test of the steel beam was carried out in the laboratory, and collected the structural dynamic parameters with single injury and multiple injuries in various conditions, structural frequency, corresponding mode shapes and modal flexibility were extracted sensitivity parameter curve were drawn, it is shown that the experimental sensitivity parameter can identify the damage easily. The compared result of finite element calculation and experiment illustrated that the sensitivity parameter can be applied to structural damage identification.In order to research or realize the self-monitoring and emergency self-repairing of structure,3 groups reinforced concrete beam embedded with SMA were made in the laboratory, shape memory alloy (SMA) was used to self-monitoring and self-repairing emergency as sensing and actuating element. The SMA were heated by electricity, the low-voltage DC power was developed; the function of sensitivity and mechanics of SMA were tested by supplying electricity heating SMA line; bond-slip between the SMA and concrete were analyzed and tested; it is shown from the experiment when the width of concrete beam crack is less than 0.3mm,there are very good linear relationship between SMA resistance rate and concrete crack width, and when the width is within the 1.5mm the SMA resistance rate and concrete crack width is linear relationship, it is shown that it is possible for the SMA to be used as sensing element in structural health monitoring. When the width of concrete beam is more than 2mm, SMA drive effect take places and can make the crack of concrete healing by heating the SMA, During the test experiment of SMA sensitivity, the resistance is very sensitive to the length change of SMA; In the self-healing properties experiment, it is found that it is suitable to control the pre-tensioned SMA at ultimate tensile strain of 20%-30%.At last, one of CFST arch bridge was analyzed by finite element program, and comprehensive dynamic test was carried out under ambient excitation. incentive to conduct a, first order vertical, reverse mode of the main and sub-span, first order transverse mode of full-span were tested and analyzed comprehensively, it is found that test result is consistent with the finite element result; The vertical vibration of arch rib and deck are synchronization, vertical vibration frequency of arch rib is slightly greater than deck frequency; it is shown it can identify the vibration mode under the full environment excitation; The first order mode is the transverse vibration mode of the deck, seismic response analysis of bridge deck have to be pay special attention to transverse seismic response. The torsion vibration model is higher than other mode, it illustrate that the torsion rigidity of structure is strong that it is favorable to against wind; The measured frequency of bridge is greater than the calculated frequency, it is shown that the bridge stiffness is better. The test results of main span of the bridge and the experimental results in the chapter 4 were compared,there are very good consistency.更多还原