【作者】 李萍；

【导师】 浣石；

【作者基本信息】 广州大学 ， 结构工程， 2018， 硕士

【摘要】 经济的快速发展离不开交通系统的可靠支持,而桥梁在交通系统中扮演着重要角色。在长期的运营过程中,各种病害作用会造成桥梁的损伤,进而影响桥梁的使用安全,因此及时对桥梁损伤进行识别和处理就显得很重要。以往的桥梁损伤识别方法都是针对桥梁整体进行损伤的诊断,以桥梁局部为研究对象的损伤识别研究却很少。因此,本文以简支梁局部损伤为研究对象,采用冲击荷载作为激励,利用测点振动响应和CEEMD分解的HHT变换,对简支梁桥的损伤识别指标及其对应的损伤识别方法进行了研究。通过模型试验和数值计算相结合的方法进行了验证性研究,结果表明,本文提出的损伤识别指标和损伤识别方法能够对局部损伤进行识别,数值模拟与试验分析对损伤的敏感性趋势是一致的。本文主要内容和成果如下:1、简述了桥梁健康监测、损伤识别方法、振动信号处理的研究现状。介绍了多种桥梁损伤识别方法,总结了各类方法存在的不足之处;重点分析了EMD分解方法在桥梁振动信号处理中的优势。2、在基于经验模态分解(EMD)、总体平均经验模态分解(EEMD)以及改进的总体平均经验模态分解(CEEMD)的希尔伯特-黄变换(HHT)方法的基础上,将改进的总体经验模态分解(CEEMD)方法应用到受损简支梁的振动信号分析中,在模态混叠不严重的情况下,分离出了单一频率成分信号,解决了以往频谱分析不能单独分离出某一阶频率的问题。3、在ANSYS中对三维简支梁模型进行模态分析,建立简支梁固有频率以及固有频率变化率FCR损伤识别指标,研究了简支梁局部损伤位置、损伤程度对固有频率、固有频率变化率FCR的影响,定量分析了固有频率、固有频率变化率FCR角度准确识别损伤程度、损伤位置的效果。4、在ANSYS/LS-DYNA中模拟简支梁桥在冲击荷载作用下的动态过程,提出了在动态加载方式下,对采集的简支梁振动加速度信号进行基于CEEMD的HHT变换分析,以测点IMF频谱变化、信号边际谱分布变化识别损伤的方法。对CEEMD分解出的固有模式函数IMF进行频谱分析和边际谱分析,通过比较受损简支梁激励源信号穿过损伤后测点横向加速度信号冲击频率、边际谱分布与未损简支梁对应位置测点的冲击频率、边际谱分布可知,受损简支梁测点冲击高阶频率是增加的;边际谱在高阶频率区间的分布也是有增加的。即通过激励源信号穿过损伤后测点IMF频谱变化和边际谱分布变化可以达到局部损伤识别的目的。5、建立了一种可进行冲击加载激励的桥梁局部损伤识别的模型试验,包括实验装置、测量模块和数据处理模块。通过数值模拟结果与试验结果比较得出,受损简支梁激励源信号穿过损伤后测点冲击高阶频率是增加的,以及边际谱在高频区间的分布也是增加的结论,从而验证了提出的局部损伤识别方法是可行的。更多还原

【Abstract】 The rapid economic development depends on the reliable support of the transportation system in which the bridge plays an important role.During the long-term operation process,various diseases may damage to the bridge,and there by affect the safety of the bridge.Therefore,it is very important to recognize and handle the bridge damage in time.The previous method of bridge damage identification is to diagnose the damage of the whole bridge.However,few studies focus on the damage identification based on the bridge part.Therefore,in this paper,the damage of the simply supported beam will be studied by using the impact load as the excitation.The vibration response of the measured point and the HHT transformation of the CEEMD decomposition have also been adopted.We will study the damage index and the corresponding damage identification method of the simply supported beam.A validation experiment has been carried out by a combination of model experiments and numerical calculations.The results show that the damage identification index and damage identification method proposed in this paper can identify the local damage.Numerical simulation and experimental analysis are consistent with the sensitivity trend of damage.The main research contents and achievements of this article are as follows:1.Review the research on health monitoring of bridge,damage identification methods,and vibration signal processing.A variety of bridge damage identification methods and the corresponding shortcomings have been summarized.Particularly,the advantages of EMD decomposition methods in bridge vibration signal processing will be analyzed.2.Based on Empirical Mode Decomposition(EMD),Ensemble Empirical Mode Decomposition(EEMD),and Complementary Ensemble Empirical Mode Decomposition(CEEMD)with Hilbert-Huang transformation(HHT)method,a complete global empirical mode decomposition(CEEMD)has been applied to the analysis for the vibration signals of damaged simple supported beams.Under the condition where the modal aliasing is not serious,a single frequency component signal is separated,which cannot be separated byprevious frequency spectrum analysis.3.The modal analysis of the three-dimensional simple-supported beam model has been performed in ANSYS to establish the damage identification index of the natural frequency and rate of change of the natural frequency of the simply-supported beam.The effect of local damage position and damage degree of the simply supported beam on the natural frequency and natural frequency change rate was studied.Quantitative analysis of the natural frequency,natural frequency change rate of the angle to accurately identify the degree of damage,damage the effect of the location.4.By using the ANSYS/LS-DYNA,the dynamic process of a simple-supported beam bridge under impact load has been simulated,and the dynamic acceleration loading method is used to analyze the vibration acceleration of the simply supported beam based on the CEEMD-HHT transformation.Points IMF spectrum changes,signal marginal spectrum distribution changes to identify damage.Spectral analysis and marginal spectrum analysis are performed on the intrinsic mode function IMF decomposed by CEEMD.By comparing the excitation source signal of the damaged simple beam with the lateral acceleration signal of the damaged point,the impact frequency and the distribution of the marginal spectrum are equal to those of the undamaged simply supported beam.It can be seen from the impact frequency and the marginal spectrum distribution of the location measurement points that the impact high-order frequencies of the damaged simple beam are increased,and the distribution of the marginal spectrum in the high-order frequency range is also increased.That is,the purpose of local damage identification can be achieved by exciting the source signal through the IMF spectrum change and the distribution of marginal spectrum after the damage.5.A model test for local damage identification of bridges that can be excited by impact loading is established,including experimental devices,measurement modules,and data processing modules.Comparing the numerical simulation results with the experimental results,it can be concluded that the impingement source signal after the damage of the simply supported beam passes through the post-damage measurement point and the higher-order frequency of the impact increases,and the distribution of the marginal spectrum in the high-frequency range also increases.The proposed local damage identification method is feasible.更多还原