【作者】 尤吉；

【导师】 姚天曙；

【作者基本信息】 安徽农业大学 ， 农业机械化工程， 2007， 硕士

【摘要】 模态参数反映了工程结构的质量、刚度以及阻尼的信息。若有局部损伤的存在,工程结构的模态参数就会发生相应改变,通过监测工程结构的模态信息即可获得其状态信息,因此,利用分析工程结构的模态参数可以进行工程结构的损伤识别诊断。本研究主要进行了以下工作:1.分析了模态柔度差值对结构进行了损伤识别方法的特点。采用简支梁的单元体刚度下降的方式模拟梁不同程度、不同位置的损伤状况。利用模态柔度差值对结构进行损伤识别。虽然利用模态柔度差值比利用结构固有频率和固有振型对损伤有着更好的识别效果,但通常都需要用到工程结构损伤前的模态信息,因此一般用于大型工程结构的适时监测,在工程结构中一般受到检测条件约束。2.分析了利用曲率模态振型进行损伤识别的特点。对简支梁进行损伤识别时发现:当工程结构发生损伤时,位移模态振型曲线的变化很小,难以识别结构的损伤状况;而曲率模态振型对工程结构的损伤很敏感,利用曲率模态振型进行损伤识别可以有更好的效果。而且曲率模态法不依赖结构损伤前的原始参数,不同程度的损伤能表征为曲率的突变,仅需依据损伤点的曲率突变就能够进行结构损伤识别。但不足之处是:曲率突变在数值上的变化难以评价,存在漏判的现象。需要借助于多阶曲率模态分别对结构进行综合分析,工作量大,过程复杂,这在实际应用中也有一定的局限性。3.提出了利用柔度差值曲率进行结构损伤识别的原理和方法,选用简支梁和悬臂梁的模拟损伤实例进行详细分析,得到了较为满意的结果:同一单元产生不同程度损伤时,损伤单元柔度差值曲率随着损伤加重而增大,可以此作为损伤部位损伤程度比较的依据;柔度差值曲率对简支梁损伤比较敏感,即使损伤只有15%,从曲线上也能观察到明显的变化;从简支梁第二单元不同程度损伤的柔度差值曲线可以看出,即使损伤单元处在支座附近,从曲线上也能对损伤位置进行定位。因此柔度差值曲率法具有灵敏度高、可靠性强,从图形和数据两个方面对损伤位置和程度辩识皆比较简便,可操作性强,便于应用于工程实际,具有其他方法无可比拟的通用性和可靠性。更多还原

【Abstract】 Modal parameters of the structure reflect the information of its quality, stiffness and damping. So we can get the state information of structures by monitoring its modal parameters. In this paper, the research is damage identification of engineering structure based on modal parameters.The main researches in this paper are as following:1. Analyzing the characters of damage identification of engineering structure based on flexibility difference. In a simple beam example, it calculates the stiffness decreased of the beam damaged in various degree and units by the decrease of unit’s stiffness. It discerns the damage of the beam by the flexibility difference and tells the method’s advantage comparing with the methods based on structure’s natural frequency or the mode of vibration. But it also points out this method need the mode information before damaging, which is often difficult to acquire in actual engineering structure and it is generally used in monitoring of large-scale engineering structures.2. Analyzing the characters of damage identification of engineering structure based on structural curvature modal. The identification application of the simple beams based on structural curvature modal confirms that: When structure has damage, structural displacement’s change is so small that we can’t discern the damage by it. But structural curvature modal is sensitive to the damage, and we can use it to discern the damage. Though the curvature modal method need not rely on the structural parameters before damage, it only relies on the curvature’s sudden change. The valuing of the curvature’s sudden change is difficult and the method also has the problems of wrong location. To avoid it, we should apply multi-modal in factual application. So it has limitation in practice.3. In order to solve these problems, it sets forth the methods and principles of discerning engineering structures damage by the flexibility difference curvature. It use some examples to confirm that: Flexibility difference curvature can be the basis of judging the damage degree; Even if only 15% damage, the flexibility difference curvature cure change is also significant; Though the second unit which is near to bearing of beam has varying degrees of damage, the location of the damage can be acquire. So the method has notable advantages such as high sensitivity, strong reliability, visualization and simplicity in amount and graph analysis, unparalleled reliability and applicability, it could be apply in the factual project structures.更多还原