基于嵌入式压电材料的不规则多腔钢管混凝土缺陷监测及谱元法机理研究

Currently, the construction of super high-rise building structures in China is developing very quickly. Due to its perfect mechanical behavior, the Concrete Filled Steel Tubes (CFSTs) have been widely employed in super high-rise building structures, and the cross section of the CFSTs becomes larger with a complicated multi-box shape. The development of efficient detection methodology for concrete core defects and the interface debonding damage between concrete core and steel tube of large scale complicated irregular CFSTs is very crucial because most of the current available nondestructive technologies including ultrasonic method are unsuitable for them. In this study, a piezoelectric ceramic material based on embedded piezo intelligent block (EPIB) is developed firstly and a novel concrete defects and the interface debonding damage detection approach is proposed based on the stress wave propagation. The developed EPIBs are employed to investigate the characters of stress wave propagation in concrete and steel-concrete composite members. Then, series experimental study on the concrete core defects and the interface debonding damage detection for single-box CFST scale models and complicated irregular multi-box CFSTs is carried to verify the detectability of the proposed approach. Based on the energy spectrum analysis, wavelet packet energy and wavelet packet spectrum analysis, novel damage indices are defined and the effect of the signal types and the frequency bands on the detectability of the proposed method is discussed. The principle and the arrangement of the EPIB for the defect detection of different CFSTs are discussed. Finally, the mechanism of the proposed concrete core defect and interface damage detection approach with EPIB for concrete, steel-concrete composite members, scale single-box CFSTs and full scale multi-box CFSTs is numerically analyzed with Spectral Element Method(SEM). Experimental and analytical results show the proposed approach provides a novel way for the concrete core defect and interface damage detection of CFSTs for super high-rise building structures.

我国超高层建筑建设正处于快速发展期。钢管混凝土以其优良的结构性能在超高层建筑中的应用日益广泛，且截面大并呈多腔组合趋势发展。大型复杂不规则多腔钢管混凝土构件中大体积混凝土缺陷以及钢管壁与核心混凝土界面粘结性能的监测与评估是亟待解决的课题，传统手段如超声波法无法适用。本项目将充分发挥压电陶瓷智能材料的优势，研发基于压电陶瓷的嵌入式压电智能块，提出基于应力波传播的复杂不规则多腔钢管混凝土缺陷监测新方法；在研究混凝土以及钢-混凝土组合构件中应力波传播特性的基础上，开展不同截面型式和不同缺陷的单腔钢管混凝土缩尺比例构件和复杂多腔钢管混凝土足尺构件的系统试验，探讨所提出的方法对不同缺陷形式和程度识别能力；基于监测信号的功率谱、小波包能量以及小波包能量谱分析结果定义新型损伤指标，探讨不同信号类型和频率下对损伤的分辨能力以及嵌入式压电智能块的布置方案和原则；运用谱元法进行数值模拟揭示其物理机理。

钢管混凝土构件以其承载力高和抗震性能好等力学特性在我国超高层建筑和桥梁结构中广泛应用，现有研究表面其界面与核心混凝土缺陷会对其力学性能产生负面影响，对其缺陷进行有效检测具有重要意义。本项目充分发挥压电陶瓷智能材料的优势， 提出基于压电陶瓷的不规则多腔钢管混凝土缺陷检测方法，并对其机理进行研究，具有重要理论和方法论意义和工程应用价值。本项目的主要研究内容和所取得的主要成果如下：（1）分别开展了基于压电陶瓷激励和应力波测量的单腔、对称规则多腔和复杂不规则多腔钢管混凝土柱钢管-混凝土界面剥离和内部混凝土缺陷的检测试验研究，验证了所提出方法的可行性。（2）开展了基于压电阻抗测量的钢管混凝土柱界面剥离缺陷检测试验研究。以某大比例复杂不规则截面多腔钢管混凝土巨型柱为试验对象，分别利用机电耦合阻抗法对界面剥离缺陷进行检测，验证了该方法的可行性。（3）分别利用波传播分析法和压电陶瓷机电耦合阻抗法进行型钢混凝土柱界面缺陷检测试验研究。结果表明，两种方法均可以有效检测不规则钢骨混凝土柱的界面剥离缺陷。（4）建立了压电材料与钢管混凝土多物理场耦合数值模型，分析了界面剥离缺陷程度对压电陶瓷传感器测量信号的影响，数值模拟结果验证试验发现的基本规律。（5）开发了钢管混凝土结构二维平面应力波分析的谱元法模型，验证了应力波法检测界面剥离缺陷的机理，谱元法计算效率高。（6）建立了压电材料与管道结构的超声与机械多物理场耦合数值分析模型，研究运用纵向导波检测管道结构缺陷的机理，对接收信号的时程分析可较为准确定位缺陷位置。项目预定工作均全面完成，并进行了适当拓展，形成含SCI二区期刊在内的国际国内重要学术期刊论文和发明专利，成果在国内具有重要影响的超高层建筑上应用，培养了博士和硕士研究生，进一步加强了国际合作与交流。项目成果形成一定国际影响，负责人受邀担任英国物理协会IOP Smart Materials and Structures专辑Focus Issue on Interface Monitoring using Smart Sensors的客座编辑。