【作者】 丁北斗；

【导师】 吕恒林；

【作者基本信息】 中国矿业大学 ， 结构工程， 2010， 博士

【摘要】 对在役网架结构进行结构检测和检验,及时发现在役网架结构的损伤,对可能出现的灾害提出预警,评估其安全性已经成为未来工程的必然要求,也是土木工程学科发展的一个重要领域,具有重要的理论意义和应用价值。围绕网架结构安全性评定,本文从基于环境激励网架结构模态分析与损伤识别角度进行了三个核心问题的研究:(1)基于环境激励获取网架结构真实模态参数的方法研究;(2)根据结构模态参数进行网架结构损伤识别理论研究;(3)在役网架结构安全性评定的系统构建研究。基于环境激励的模态分析方法有很多种,如随机子空间法、峰值拾取法等,本文考虑到各种模态分析方法的优劣,采用多种模态分析方法对采集到的基于环境激励下的动测数据进行分析,识别结构的模态,并形成一套获取结构模态参数的流程。建立基于模态应变能法网架结构损伤识别理论。该理论结合网架结构的特点,以网架结构未损伤模型或有限元模型为参考模型,通过测试网架结构在役状态的模态参数,从而计算出网架结构各单元的模态应变能,就可以判定网架结构的可靠性状态。根据构造不同损伤工况的网架结构损伤识别数值算例表明,该方法实现了网架结构的损伤识别。建立基于动测结果采用直接优化算法的网架结构有限元模型修正损伤识别理论。该理论根据网架结构损伤识别特点,选择适当损伤识别参数,实现网架结构的损伤识别。同时构造桁架结构数值算例,验证采用直接优化算法为基础的网架结构有限元模型修正损伤识别理论的有效性。进行一32根杆件13个节点的四角锥网架结构模型以及一1258根杆件341个节点的在役四角锥网架结构动测试验,对网架结构基于环境激励模态分析有效性和损伤识别理论进行试验验证。模态试验分析表明,基于环境激励模态分析能够获取网架结构的模态参数,尤其对于大型网架结构,效果更明显。基于环境激励的模态分析方法中,峰值拾取法和随机子空间法,均能较为有效的获取结构的模态参数。与有限元模态分析结果比较而言,峰值拾取法对于低阶模态参数比较稳定可信,而随机子空间法对于高阶模态参数比较稳定可信。损伤识别理论的试验验证表明,基于模态应变能法损伤识别理论和基于有限元模型修正法网架结构损伤识别理论对于在役网架结构,在环境影响或者各种外界的作用下,结构损伤比较平均情况下,是可以达到网架结构损伤判定的目标。对于具体损伤部分和损伤细节,还需要结合更多的检测手段做进一步的检测和鉴定。提出并建立在役网架结构安全性评定系统。该系统由表观质量检查、基于静测方法的使用性能检测和基于动测的损伤识别三部分构成,以网架基本尺寸、挠度以及模态参数作为指标,实现在役网架结构的安全性评定,并结合具体在役网架结构安全性评定的实施,以验证该系统的有效性,进而为后续研究在役网架结构的寿命评估、预测提供可靠的依据。更多还原

【Abstract】 The inspection and testing of the grid structure in service in time to discover the damage that may arise disaster, early warning, assessment of structure safety has become a necessary requirement for future projects, but also the development of a civil engineering discipline important areas, has important theoretical significance and application value.Surrounding the safety assessment of grid structure, from the point of modal analysis and damage detection of the grid structure based on ambient vibration,the article carried out the three core issues:(1) The method research to obtain the true modal parameters of grid structure based on ambient vibration;(2) The theory research of grid structure damage detection according to the structural modal parameters;(3) The research of the safety assessment system of grid structure in service.There are many modal analysis ways based on ambient vibration such as the random subspace method, the peak picking method. This article takes into account the merits of modal analysis methods, using a variety of modal analysis method to analyze the collected ambient excitation-based dynamic test data to identify the modal parameter,and form a set of structural modal parameters obtained process.This paper has established the structural damage detction method based on modal strain energy method.The method considering characteristics of grid structure which reference model of this method is undamaged grid structure model or the finite element model, as long as testing out the state of in-service modal parameters of the grid structure to calculate the grid structure of the unit modal strain energy, then ,can determine the reliability of the grid structure of the state. At the same time, given the grid structure damage identification numerical example, to construct a different grid structure damage cases, through the development of procedures that can automatically identify the grid structure of the damage.This paper has also established the finite element model updating damage detection method of grid structure adopting direct optimization algorithms based on dynamic test results. According to the characteristics grid structure,the theory which select the appropriate damage identification parameters to achieve the same damage identification of the grid structure considering characteristics of grid structure. To verify the model updating method based on direct damage identification method , a numerical example of truss structure is adopted to verify the validity .To execute the dynamic testing of experimental model which has 32 bars and 13 node of pyramid grid structure and a pyramid grid structure in service which has 1258 bars and 341 node,verify the effectivness of modal analysis and damage detection theory of grid structure under ambient excitation .Modal test analysis showed that modal analysis methods under ambient excitation, can obtain more effective modal parameters ,especially for large-scale grid structure, the effect is more pronounced. Based on ambient vibration modal analysis method, the peak picking method and the random subspace method can both obtain more effective modal parameters .The results compared with the finite element analysis results shows that the modal parameters obtained by the peak picking method, is relatively stable and credible to the low modal parameters, while the modal parameters obtained by stochastic subspace method is relatively stable and credible to the high modal parameters.Experimental verification of damage detection showed that the grid structure damage detection method based on modal strain energy and based on the finite element model updating, can achieve the target of damage detection of grid structure,if the environmental impact of various external effects on the structure is of the average. For details of the specific injury and damage parts, the means of deeper detection and identification of further testing is necessary.Propose and establish safety assessment system of grid structure in service, which is composed of the apparent quality inspection, measurement methods based on static testing and modal parameters based on dynamic testing ,which indexes is the basic grid size, deflection and modal parameter, and realize the safety assessment.of grid structure in service. Combined with the implementation of the safety assessment of the actural grid structure, to verify the effectiveness of the system, and prepare for further study of the life assessment , prediction of grid structure in service.更多还原