基于分形理论和小波分析的桥梁结构损伤识别研究

发布时间：2018-05-09 15:16

本文选题：桥梁结构 + 损伤识别　；参考：《天津大学》2014年硕士论文

【摘要】：桥梁结构由于其结构本身性能退化及外部因素的影响会发生损伤、裂纹等形式的破坏。结构一旦发生破坏,将造成重大的人员伤亡,威胁社会的安定与国家的长治久安。因此,防患于未然,为了避免重大桥梁事故的发生,对已有桥梁结构进行健康状况监测,探索一种简便有效的检测方法,便具有重要的学术价值及实用意义。本文以小波分析和分形维数为基本工具,以结构的振动信息为基础进行桥梁结构损伤识别(主要进行损伤定位),主要进行了以下几方面的研究:首先提出了一种基于分形理论与振型相结合的损伤定位方法;损伤的存在使结构的振型曲线在损伤位置的不规则程度变大,而Katz分形维数可用来定量描述曲线的这种不规则程度,因此利用Katz滑动窗沿振型曲线滑动,得到各测点的分形维数,并将含裂纹简支梁与完好简支梁各测点分形维数相比较便可进行损伤识别;并将分析裂纹处于结构不同位置、裂纹相对深度的大小及裂纹条数对损伤定位效果的影响。其次引入小波分析的概念,并通过小波的多分辨率分析功能,对冲击荷载作用下多阶模态叠加振动响应进行有效的分离,以其中识别效果最好的一阶模态响应为处理对象,定义相对小波能量分形维数差与一阶加速度响应分形维数差两种损伤,并对损伤进行定位,通过简支梁的数值模拟及实验进行验证。最后通过结合小波能量与模态柔度曲率差都对损伤敏感的特性,提出一种相对小波包能量柔度曲率差损伤指标来判断损伤位置;并与仅基于相对小波包能量曲率差的方法进行比较,通过连续梁的数值模拟及连续梁的试验验证说明该方法的可行性。
[Abstract]:Because of the degradation of the structure itself and the influence of the external factors, the bridge structure will be damaged and damaged in the form of cracks. Once the structure is destroyed, it will cause heavy casualties and threaten the stability of the society and the long-term stability of the country. Therefore, in order to avoid the occurrence of major bridge accidents, it is of great academic value and practical significance to monitor the health status of existing bridge structures and to explore a simple and effective detection method. In this paper, wavelet analysis and fractal dimension are used as the basic tools. Based on the vibration information of the structure, the damage identification of bridge structure is carried out (the damage location is mainly carried out in the following aspects): firstly, a damage location method based on fractal theory and vibration mode is proposed; The existence of damage increases the degree of irregularity in the damage position of the structure, and the fractal dimension of Katz can be used to quantitatively describe the irregularity of the curve. Therefore, the Katz sliding window is used to slide along the mode curve. The fractal dimension of each measuring point is obtained, and the damage identification can be carried out by comparing the fractal dimension of simply supported beam with crack with that of intact simply supported beam, and the analysis crack is located in different position of structure. The influence of the relative depth of crack and the number of cracks on the effect of damage location. Secondly, the concept of wavelet analysis is introduced, and the multi-resolution analysis function of wavelet is used to effectively separate the multi-order modal superimposed vibration response under impact load, and the first-order modal response, which is the best one, is taken as the processing object. The relative wavelet energy fractal dimension difference and the first order acceleration response fractal dimension difference are defined, and the damage location is carried out, which is verified by the numerical simulation and experiment of the simply supported beam. Finally, by considering the sensitivity of wavelet energy and modal flexibility curvature difference to damage, a damage index of relative wavelet packet energy flexibility curvature difference is proposed to judge the damage location. Compared with the method based on relative wavelet packet energy curvature difference, the feasibility of this method is verified by numerical simulation of continuous beam and experiment of continuous beam.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U446

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