FRP加固钢梁界面剥离损伤的瑞利波检测技术数值研究

发布时间：2019-05-29 23:31

【摘要】：随着近年来空间大跨度钢结构的快速发展，因为原有结构承载力不足而运用FRP（Fiber Reinforced Plastics）加固的钢结构亦越来越多，对大跨度FRP加固钢结构进行界面剥离损伤无损检测，对于FRP加固钢结构的养护维修，保证大型重要钢结构建筑物加固后的安全性和可靠性具有重要的意义。本文主要研究如何利用瑞利波群速度频散曲线的变化规律检测出界面剥离损伤长度。瑞利波在FRP加固钢梁的表层传播时，瑞利波的频散特性会发生变化，瑞利波速度频散曲线反应了瑞利波的频散特性。为了研究如何利用瑞利波频散信息进行损伤识别，文中建立了FRP与钢材二层介质的有限元模型，研究了瑞利波在FRP加固钢梁表面的产生机理和传播特性，并从波场快照中识别出瑞利波，确定了瑞利面波波场数值模拟各种影响参数，模拟了FRP加固钢梁的界面剥离损伤，介绍了求解瑞利波群速度频散曲线的互相关分析法。通过理论公式求出的瑞利波速与有限元模拟出的瑞利波速的对比验证有限元模拟的准确性。文中对全跨FRP加固钢梁进行了二维有限元模拟，分析了剥离损伤和钢梁裂纹对瑞利波传播的影响，，进行了其对应的瑞利波群速度频散曲线正演计算，从中找出了界面剥离损伤与瑞利波群速度频散曲线变化规律之间的联系。当出现界面剥离损伤时，同一检波点对间的瑞利波群速度在一些频段幅值降低，瑞利波群速度频散曲线在相应频段内呈现向下平移的趋势，且界面剥离损伤长度越大，曲线向下平移量越大；同一结构中不同检波点对之间的瑞利波群速度频散曲线的差异与界面剥离损伤有一定的联系。文中使用欧几里德距离和角分离度度量了频散曲线间的差异，认为当两条曲线的角分离度大于0.9时，说明检测过程采集的数据是有效的，相应的欧几里德距离可以作为界面剥离损伤检测的指标。文中以此为基础提出了FRP加固钢梁界面剥离损伤检测方法。文中提出了将归一化平均欧几里德距离作为界面剥离损伤程度的检测指标。建立非全跨FRP加固钢梁的三维有限元模型，使用基于模型的损伤检测方法进行FRP加固钢梁界面剥离损伤的模拟检测。分析了最小可检测尺寸的三个影响因素和文中检测方法的比较优势。
[Abstract]:With the rapid development of space long-span steel structure in recent years, more and more steel structures strengthened by FRP (Fiber Reinforced Plastics) are strengthened because of the insufficient bearing capacity of the original structure. Nondestructive testing of interfacial peeling damage of long-span FRP strengthened steel structure is carried out. It is of great significance for the maintenance and maintenance of steel structures strengthened with FRP to ensure the safety and reliability of large and important steel structure buildings. In this paper, how to detect the interfacial peeling damage length by using the variation law of the velocity dispersion curve of the Rayleigh wave group is studied. When the Rayleigh wave propagates on the surface of the steel beam strengthened by FRP, the dispersion characteristics of the Rayleigh wave will change, and the dispersion curve of the Rayleigh wave velocity reflects the dispersion characteristics of the Rayleigh wave. In order to study how to use Rayleigh wave dispersion information for damage identification, the finite element model of FRP and steel two-layer medium is established, and the generation mechanism and propagation characteristics of Rayleigh wave on the surface of steel beam strengthened by FRP are studied. The Rayleigh wave is identified from the wave field snapshot, the influence parameters of the wave field numerical simulation are determined, the interfacial peeling damage of the steel beam strengthened by FRP is simulated, and the cross-correlation analysis method for solving the velocity dispersion curve of the Rayleigh wave group is introduced. The accuracy of the finite element simulation is verified by the comparison between the Rayleigh wave velocity calculated by the theoretical formula and the Rayleigh wave velocity simulated by the finite element method. In this paper, the two-dimensional finite element simulation of steel beams strengthened with full-span FRP is carried out, the effects of peeling damage and cracks on the propagation of Rayleigh waves are analyzed, and the corresponding velocity dispersion curves of Rayleigh wave groups are calculated forward. The relationship between the interfacial peeling damage and the velocity dispersion curve of the Rayleigh wave group is found out. When the interface peeling damage occurs, the amplitude of the Rayleigh wave group velocity between the same detection point pairs decreases in some frequency bands, and the velocity dispersion curve of the Rayleigh wave group tends to shift downward in the corresponding frequency band, and the longer the interface peeling damage is, the larger the interface peeling damage length is. The larger the downward translation of the curve is, the greater the downward translation of the curve is. The difference of velocity dispersion curve between different detection point pairs in the same structure is related to the interfacial peeling damage. In this paper, Euclidean distance and angular separation degree are used to measure the difference between dispersion curves. It is considered that when the angular separation degree of the two curves is more than 0.9, the data collected in the detection process are effective. The corresponding Euclidean distance can be used as an index for interfacial peeling damage detection. Based on this, a method for detecting interfacial peeling damage of steel beams strengthened with FRP is proposed in this paper. In this paper, the normalized average Euclidean distance is used as the detection index of interfacial peeling damage. The three-dimensional finite element model of steel beams strengthened with non-full-span FRP is established, and the damage detection method based on the model is used to simulate the interfacial peeling damage of steel beams strengthened by FRP. The three influencing factors of the minimum recoverable size and the comparative advantages of the detection methods in this paper are analyzed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU393.3;TU317

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