【作者】 王卓；

【导师】 闫维明；

【作者基本信息】 北京工业大学 ， 结构工程， 2009， 博士

【摘要】 北京奥运会所使用的比赛及训练场馆广泛采用了空间结构的形式。网壳结构是空间结构中的一种主要形式,其具有跨越能力强、造型美观、受力合理、施工简便等优点,为奥运场馆屋盖结构较多地采用,如奥运自行车比赛馆,其屋盖采用双层球面网壳结构;奥运羽毛球比赛馆,其屋盖采用弦支球面网壳结构,等等。网壳结构在保证奥运场馆新颖、美观、形式多样的同时,其复杂的动力学特性给结构的参数识别和损伤检测提出了新的挑战。本文重点针对网壳结构的模态参数识别、模态局部化和跃迁、损伤检测开展了系统深入的研究;此外,本文还对两类常见的建筑结构——层剪切结构和混凝土梁式结构的参数识别和损伤检测问题进行了有价值的研究和探索。取得的研究成果分述如下:1.提出了一种适用于网壳结构的模态测试技术。该技术联合使用单点瞬态冲击激励技术和模态参数识别的复模态指示函数法,通过单点瞬态冲击激励位置的优化选取,最大程度地孤立或分离待识别模态,在较大程度上减轻结构响应中重频(或近频)模态之间的互相干扰;复模态指示函数法作为一种先进的频域模态识别方法,能够快速、自动地确定结构模态参数,优于传统的峰值检测法。对所提出的模态测试技术进行了数值模拟,结果表明,该技术能够在一定程度上保证网壳结构模态参数识别的有效性和准确性。2.较为系统地研究了网壳结构的模态局部化和跃迁现象。通过对网壳结构子结构的算例分析,证实了两类现象在理论上是存在的;利用矩阵摄动法分析了两类现象的发生机理,即网壳结构模态局部化和跃迁现象发生的内因是结构固有频率的密集分布,外因是结构物理参数的小量变化;部分采用本文提出的网壳结构模态测试技术,对一个凯维特型单层球面网壳结构进行了模型试验,试验结果验证了模态局部化现象的存在性;阐述了模态局部化和跃迁对网壳结构抗震计算和损伤检测的重要影响;以一个单层球面网壳结构为例,进行了同一地面运动激励下,包含不同初始几何缺陷的网壳结构的线性动力反应分析,分析结果表明,与不考虑初始几何缺陷相比,某些杆件的轴压力峰值显著增大。因此,初始几何缺陷所导致的网壳结构模态局部化对结构线性动力反应的影响是不可忽略的,建议在网壳结构的抗震计算中予以足够的重视。3.针对网壳结构的轻度损伤,基于模态局部化和跃迁现象,提出了一种性质优良的损伤特征向量。该向量的构造简单,仅使用网壳结构的少数振型和少量的测试自由度。通过一个网壳结构的算例分析,对所提出的损伤特征向量的性质进行了检验。结果表明,该向量不仅具有较好的空间可分辨性、损伤敏感性和噪声鲁棒性,并且对结构有限元模型误差具有一定的适应性。进一步,通过一个凯维特型单层球面网壳结构模型的损伤试验,验证了损伤特征向量的良好性质。4.提出了一种基于高阶模态振型差的网壳结构损伤区域检测设想,并进行了试验探索。该设想首先对网壳结构进行区域划分并按区域布置传感器;然后利用单点随机激励获得结构的高阶模态响应,再由随机减量技术和Ibrahim时域辨识算法获取结构高阶模态参数;最后,利用损伤前后高阶模态振型差值的最大值来指示损伤区域。对一个单层椭球面网壳结构模型进行了损伤区域的检测试验,试验分析结果初步验证了所提出设想的可行性。5.针对环境激励下层剪切结构的刚度识别问题,提出了一种新的解决方法。该方法采用自然激励技术实现结构随机响应向确定性响应的过渡,推演了层剪切结构自由振动的参数解耦方程,以简化识别过程和降低计算量。将自然激励技术、参数解耦方法和扩展卡尔曼滤波算法三者有机结合,为环境激励下层剪切结构的刚度识别提供了一个较好的解决方案。分别以六自由度和十自由度的层剪切结构为例,对该方法进行了数值模拟和试验验证,结果表明,该方法能够比较准确地识别结构层间刚度,具有较好的工程应用前景,可用于框架结构建筑、连续梁桥以及力学模型可简化为链状多自由度系统的工程结构的健康监测中。6.对钢筋混凝土简支梁加载损伤后的阻尼特征进行了试验研究,提出了一种描述结构阻尼特征的新指标——相邻周期耗能比,并通过试验分析给出了该指标与简支梁弯曲裂缝损伤的关系。试验通过静力加载模拟简支梁的损伤累积过程,通过突加荷载试验跟踪简支梁阻尼特征随加载损伤等级的变化,深入分析和比较了阻尼比、相邻周期耗能比二者随裂缝损伤状态的变化机理,研究结果表明,相邻周期耗能比指标能够比较敏感地反映裂缝型损伤的程度变化,并具有很好的噪声鲁棒性,可以作为钢筋混凝土梁式结构的损伤检测指标。更多还原

【Abstract】 Space structures are extensively used as roof structures of competition and training gymnasiums in Beijing Olympic Games. A latticed shell structure belongs one of main structural styles in space structures. It has a large span, a beautiful design, a reasonable stress and a convenient construction, so it is used as the roof structures of some Olympic gymnasiums. For example, the roof of Olympic Cycling Gymnasium is a double-layer spherical latticed shell structure; the roof of Olympic Badminton Gymnasium is a suspended spherical latticed shell structure. A latticed shell structure ensured these Olympic gymnasiums novel, artistic and multiform. But at the same time, its complex dynamical property brings some new challenge to structural parameter identification and damage detection. The main research targets of this dissertation are modal parameter identification, mode localization and transition, damage detection of latticed shell structures. Moreover, for two kinds of common structures, inter-story shearing structures and RC beam structures, the problems of parameter identification and damage detection were also researched. The research results are as follows:1. A modal testing technique for latticed shell structures is presented. The technique combines the technique of single-point transient shock excitation and the complex mode indication function method for modal parameter identification. Through the optimal position selection of single-point transient shock excitation, the mode identified can be isolated or separated to a great extent, and the interference between repeated frequencies modes (or closed frequencies modes) in structural response can be lightened to some extent. The complex mode indication function method is an advanced modal identification method in frequency domain. It can determine modal parameters automatically with a high-speed, so it is better than traditional peak-pick method. Numerical simulation was done to the modal testing technique. The results show that the technique has good validity and accuracy to some extent.2. Mode localization and transition of latticed shell structures were researched systematically. Through a numerical simulation example of a latticed shell substructure, the existence of mode localization and transition phenomena is verified in theory. The mechanism of two phenomena is analyzed by the matrix perturbation theory. It shows that the internal cause of two phenomena is the intensive frequencies of latticed shell structures and the external cause is the slight change of structural physical parameters. Using the modal testing technique presented in this dissertation partly, a model experiment was done to a Kiewitt single-layer spherical latticed shell structure. The experiment results prove that the phenomenon of mode localization is existent indeedly. The important impact of two phenomena is expounded in the areas of earthquake resistant calculation and damage detection of latticed shell structures. And using a single spherical latticed shell structure as an example, structural linear dynamic response under the same ground movement are calculated and analyzed by considering different initial geometrical imperfections. The results show that comparing with the case of ignoring initial geometrical imperfections, the peak values of axial pressure of some members augment remarkably. Thus, mode localization caused by initial geometrical imperfections can make linear dynamic response of latticed shell structures change remarkably, so it should be considered adequately in the seismic calculation of latticed shell structures.3. For the slight damage of latticed shell structures, a damage characteristic vector with good properties is presented based on the phenomena of mode localization and transition. The vector is simple, and it is composed of some low-order modes and a few testing freedoms. Through a numerical simulation example of a latticed shell structure, the properties of the damage characteristic vector are tested. The results show that the vector not only has good identifiable ability, damage sensitivity and noise robustness, and it can keep its adaptability to some extent to the error of structural finite element model. Furthermore, through a damage experiment of a Kiewitt single-layer spherical latticed shell structure model, the properties of damage characteristic vector are verified.4. A trial experiment is done on the damage region detection of latticed shell structures based on the difference of high-order modes. The experiment is to divide a latticed shell structure into several regions and place sensors in accordance to these regions firstly, then to acquire structural high-order modal response by single-point random excitation and identify the modal parameters by random decrement technique and Ibrahim time domain method, at last, to locate damage regions by the difference of high-order modes before and after damage. Through a damage detection test of a single-layer ellipsoidal latticed shell structure model, the feasibility of the method is verified basicly.5. The problem of inter-story stiffness identification for shearing structures under ambient excitation is researched and a new method is presented. In the method, the transition from structural random response to deterministic response is realized by the natural excitation technique (NExT). The parameter-decoupled free vibration equation of shearing structures is deduced, and the equation can simplify the process of identification and reduce the amount of calculation. Through the effective combination of the NExT, the parameter-decoupled method and the extended Kalman filter (EKF) algorithm, a good scheme is presented for inter-story stiffness identification of shearing structures under ambient excitation. Using shearing structures with six-degree-of-freedom and ten-degree-of-freedom as examples, the scheme is tested by numerical simulation and experimental verification. The results show that the inter-story stiffness can be identified with accuracy basically, and the scheme can be applied in frame constructions, continuous bridges and engineering structures whose mechnical models can be simplified as chain multiple degree of freedom systems.6. The damping characteristic of a simple-supported RC (reinforced concrete) beam after damage is researched, and a new index of damping characteristic (adjacent periods’dissipative ratio, APDR) is presented. The relationship between new index and bend-crack damage of RC beam is given by experimental analysis. In the experiment, the accumulated damage of beam is realized by static load test, and the change of damping characteristic with loading damage is tracked by shock load test. The mechanism of damping ratio’s change and APDR’s change with crack damage states are analyzed and compared deeply. The results show that the APDR index is sensitive to the severity of crack damage, and it has good noise robustness. So it can be used as a damage detection index of RC beams. Keywords latticed shell structure; parameter identification; damage detection; mode更多还原