超高耸结构台风期间动力特性监测

主要做了以下几个方面的工作:(1)利用GPS等多种传感器,建立广州新电视塔的健康监测系统;(2)采用一种仅基于输出响应的模态识别算法(频域分解法),结合台风期间所测得的加速度响应识别了广州新电视塔的前十阶模态参数;(3)用图、表和有限元模型描述了电视塔在台风期间的形变状态,揭示其动力特性。具有理论创新和较好的应用借鉴作用。     

基于GPS的高耸结构动态特性监测

在土木工程领域,GPS作为一种新的结构振动健康监测方法正受到广泛关注.以在建的广州新电视塔(塔高610 m)为研究背景,利用RTK-GPS测量技术对其在台风以及一般风荷载作用下的动态特性进行了监测试验,获得了电视塔核心筒顶部一个测点沿其短轴和长轴方向的动位移时程曲线,位移曲线的谱分析结果表明,利用动态GPS观测能精确地识别出高耸结构物的低阶振动频率,其识别结果同加速度计识别结果以及有限元模型分析结果吻合很好.研究结果表明,在高耸结构施工监控和健康监测中,应用动态GPS技术进行环境激励动态特性监控是一种有效的方法.     

重力坝动力特性测试方法模型试验研究

目前水工结构的动力破坏特性越来越受到关注,其中动力特性是其研究的一个重要方面。通过模型试验的方法研究重力坝模型动力特性的测试方法。重点研究了环境激励法测试结构动力特性的效果,并与传统测力法进行了比较。试验结果表明采用环境激励的方法,可只根据结构的振动响应数据,有效地测试结构的动力特性。并且在不同大小环境激励下结构的振型没有发生变化,频率与阻尼比变化很小。试验结果还表明通过环境激励法与通过传统激励法测试的振型、频率与阻尼比相差很小,可认为采用这两种方法测试的结构动力特性一致。同时还说明环境激励法可有效地测试有损伤结构的动力特性。试验结果为使用环境激励法测试实际在线重力坝结构的动力特性提供了依据。     

广州新电视塔整体结构振动台试验研究

广州新电视塔塔高610m,由一座高达454m的主塔和一个高156m的天线桅杆构成,建成后将是世界第一高电视塔。广州大学工程抗震研究中心试验室设计了一个1/50结构模型,并对其进行了多种地震波的49种工况下的振动台试验。测试了模型结构的动力特性、阻尼比及其各种地震作用下的加速度、位移、扭转和应变反映,分析了模型结构的破坏情况,并根据试验结果和相似理论,研究了原型结构的地震反应。试验及分析结果表明,模型结构第1阶、第2阶振型频率与原型结构计算换算频率相差15%―18%左右,第3阶、第4阶频率相差30%左右,其对应阻尼比依次为3.317%、2.277%、1.555%和1.259%,其扭转、平动第一周期比为0.211,且在多遇、设防烈度和罕遇地震作用下结构最大层间位移角平均分别为1/320、1/154和1/72,显示结构在经历多遇地震,设防烈度地震和罕遇地震作用后,结构总体上满足设计目标的抗震设防要求。     

基于数码摄像技术的高耸结构动态特性监测

在结构健康监测领域,基于数码摄像的图像处理技术作为一种新的结构振动监测方法正受到广泛关注。以主结构建成后的广州新电视塔为研究背景,利用工业数码摄像机对其在一般风荷载作用下的动态特性进行监测试验,并与GPS和加速度计同时测量。数据分析结果表明,利用数码摄像系统获得的塔顶动位移时程曲线与GPS获得的动位移曲线吻合得较好;利用数码摄像技术能够准确的识别高耸结构的低阶振动频率,其获得的结构一阶振动频率,与GPS、加速度计识别结果以及有限元分析结果吻合得很好。研究结果表明,在高耸结构的健康监测中,应用数码摄像技术进行结构动态特性监测是一种有效的新方法。     

复杂形体超高钢结构电视塔抗震性能分析研究

宁夏超高钢结构电视塔结构高度216m,桅杆长度104m。建筑体型为底部小、上部大、中部略呈细腰形且设计有三段楼层共计28层的花瓶状形体。楼层不连续分布导致结构质量和侧向刚度沿竖向分布不均匀,结构几何形式复杂,对抗震要求高。     

高层结构动力特性试验研究

本文通过１：５０比尺的有机玻璃模型对广州市某办公综合大楼进行实验模态分析，并对该结构的动力特性进行分析。     

带限位TMD的抗风动力可靠度研究

摘要：针对实际高层高耸结构在设置TMD控制装置时,存在空间位置有限、TMD行程受限的问题,进行了带限位TMD的抗风动力可靠度研究。首先,采用虚拟激励法计算复杂高耸结构—TMD体系在脉动风荷载下的随机风振响应;然后,基于随机振动的首次超越破坏准则,研究TMD装置在容许行程范围内不同重现期风荷载下的动力可靠度。并以国内在建的第一高塔-广州新电视塔为工程算例,验证了该研究在实际设计中所具有的重大工程意义。     

浮式风机变桨故障后停机的动力特性研究

浮式风机变桨故障后紧急顺桨停机可能会引起风机传动系统、机舱设备、塔筒和浮式基础荷载和弯矩的巨大波动。采用空气动力-水动力-控制系统-结构动力全耦合非线性方法模拟了不同海况下的全潜式浮式风机变桨系统故障,分析了风机低速轴弯矩、机舱加速度、塔筒弯矩和浮式基础的运动响应变化。结果表明,在变桨故障后紧急顺桨停机工况下,风机系统内部所受荷载和弯矩与正常运行相比有明显增加,在优化控制方法后,即变桨故障后高速轴刹车并减速顺桨,风机系统内部增加的荷载和弯矩得到有效缓解。     

地震激励下桩-土非线性耦合作用对桩基动力响应特性的影响

为探讨桩-土非线性耦合作用对桩基动力响应特性的影响,以桩-土-结构耦合系统为研究对象,建立三维非线性有限元模型。采用Drucker-Prager非线性土体本构模型,利用罚函数法实现桩-土-结构界面间的非线性耦合作用,引入无反射边界条件,并考虑重力因素,得到了水平和竖直方向组合地震激励下桩-土非线性相互作用对桩基地震响应的影响。结果表明,考虑桩-土接触非线性,桩基的加速度响应峰值减小,桩土之间出现明显的分离现象,桩基剪力和弯矩峰值有所增加。通过对桩基轴力的校核,桩基不承受拉力,不会发生拔桩现象。     

互谱能量法在激励力未知条件下对结构的诊伤研究

众多结构损伤诊断的方法都是基于结构有限元模型，或者是基于结构激励力已知条件下进行的系统参数识别技术。然而，由于大型结构物激励力不易测试，这些方法应用于土木工程结构物存在着一定的局限性。因此。发展基于环境激励下抗噪声性能较好的结构损伤诊断方法对于土木工程结构物安全监测显得尤为重要。提出一个新的互谱能量法，实现了在环境激励力未知条件下对结构进行损伤诊断。互谱能量法诊断结构损伤无需已知结构本身的材料特性，无需系统参数识别，不是基于结构的有限元模型，仅基于结构动力可测试部分输出响应信号以及结构单元拓扑分布即可实现结构的损伤诊断。为了验证所提互谱能量法的有效性，数值模拟两跨连续梁结构，仅仅利用有限的动力测试信号，并且结构测试信号中加入了较大的噪声模拟实际的测试环境，研究结果表明互谱能量法能够有效地诊断出结构单一，多损伤位置的损伤，抗噪声能力较强。     

基于HHT的液压缸动态特性分析新方法

提出了一种基于Hilbert-Huang变换的液压缸动态特性分析的新方法：运用经验模态分解,把周期激励下液压缸油液压力波动信号分解为多个从高频到低频的本征模态函数分量,依据各分量的Hilbert边际谱以及自由振动频率信息,对各分量分类并以此为基础重构信号,提取出反映液压缸动态特性的自由振动分量。此方法在某试验台液压缸动态特性分析中,取得了良好的效果,提取出的自由振动分量,可以作为评价液压缸动态特性好坏的依据。     

Structural Health Monitoring of an Annular Component using a Statistical Approach

Abstract:  For aerospace components there is undoubtedly a critical need to detect incipient damage in the structure, as any microscopic crack or defect can potentially lead to catastrophic failure and loss of human life. This paper investigates the scattering of an ultrasonic-guided wave into a hollow cylinder-like structure, under both damaged and undamaged conditions. Hollow cylinder structures are widely used not only in aerospace components but also in other engineering applications. The wave was sequentially transmitted and captured by means of a 'real-time data-acquisition system' combined with integrated disc-shaped piezoceramic transducers. The integration of the tested structure and the transducers formed a structural health monitoring system. Wave responses were recorded from both of the structural conditions for the purpose of damage identification using a novelty detection method called 'outlier analysis'. The principal component analysis method of reducing the dimensionality of the feature space is also presented in this paper, with its main aim being to visualise how the data sets behave as a function of the structural conditions.     

Health Monitoring of Aerospace Structures Using Fibre Bragg Gratings Combined with Advanced Signal Processing and Pattern Recognition Techniques

Abstract: The main purpose of this work is to develop an innovative system for structural health monitoring of aerospace composite structures based on real‐time dynamic strain measurements. The dynamic response of a composite panel, which represents a section of a typical aeronautical structure, is measured using fibre Bragg grating (FBG) dynamic sensors. Damage is simulated by slightly varying locally the mass of the panel at different zones of the structure. A finite element model of the structure has been developed to simulate the dynamic behaviour based on the modal superposition principle. The numerical model was calibrated against experimental results, and it was used for the placement of the FBG sensors. The proposed damage detection algorithm utilises the collected dynamic response data, and through various levels of data processing, an artificial neural network identifies the damage size and location. Feature extraction is the first step of the algorithm. Novel digital signal processing techniques, such as the wavelet transform, are used for feature extraction. The extracted features are effective indices of damage location and its extension. The classification step comprises a feed‐forward back propagation network, whose output determines the simulated damage location. Finally, dedicated training and validation activities are carried out by means of numerical simulations and experimental procedures.     

Electro-Mechanical Impedance (EMI)-Based Incipient Crack Monitoring and Critical Crack Identification of Beam Structures

Fatigue-induced damage is often progressive and gradual in nature. Fatigue is often deteriorated by corrosion in ageing structures, creating maintenance problems, and even causing catastrophic failure. This ushers the development of structural health monitoring (SHM) and nondestructive evaluation (NDE) systems. Recent advent of smart materials applicable in SHM alleviates the shortcomings of the conventional techniques. Autonomous, real-time, remote monitoring becomes possible with the use of smart piezoelectric transducers. For instance, the electro-mechanical impedance (EMI) technique, employing piezoelectric transducers as collocated actuators and sensors, is known for its ability in damage detection and characterization. This article presents a series of lab-scale experimental tests and analysis to investigate the feasibility of fatigue crack detection and characterization employing the EMI technique. This study extends the work by Lim and Soh [1 Y. Y. Lim and C. K. Soh . Smart Materials and Structures 20 : 125001 ( 2011 ).[Crossref], [Web of Science ®] , [Google Scholar]] to incorporate the phases involving crack initiation and critical crack. It is suggested that the EMI technique is effective in characterizing fatigue induced cracking, even in its incipient stage. Micro-crack invisible to the naked eyes can be detected by the technique especially when employing the higher frequency range of 100–200 kHz. A quick and handy qualitative-based critical crack identification method is also suggested by visually inspecting the admittance frequency spectrum.     

Evaluation of power extraction circuits on piezo‐transducers operating under low‐frequency vibration‐induced strains in bridges

The concept of piezoelectric energy harvesting (PEH) provides a promising solution for perpetually running low‐power electronic devices such as wireless sensor networks by harvesting ambient vibrations generated from civil structures such as long span bridges, city flyovers, elevated metro corridors, which are constantly under dynamic loads. However, its successful industrial‐scale deployment on civil structures is still not realised because of the low‐frequency of vibrations (typically <5 Hz) encountered there, coupled with the low levels of voltage generation. The vast majority of PEH‐related studies have only focused on PEH configurations and geometries, Often entailing secondary structures. d₃₁ mode, which is the most natural mode of excitation, has not been investigated in depth for piezo‐patches directly bonded on the main structure. Studies, which have focused on electronic conditioning circuitry, have been restricted to typically high‐voltage and high‐frequency scenarios only. This paper focuses on systematically studying the issues inflicting energy harvesting from the ambient vibrations induced flexural strains civil structures, such as city flyovers, using piezo elements in d₃₁ mode. Vibration measurements are first undertaken from a typical city flyover consisting of steel girders supporting a reinforced concrete (RC) deck. The basic site measurements are employed to perform a laboratory‐based parametric study to investigate the influence of parameters such as vibration frequency, voltage, and circuit components like diodes on PEH. On the basis of the experimental results, it can be concluded that power in microwatts range can be typically harvested from these civil structures through directly bonded piezo patches in d₃₁ mode. However, there are still issues associated with electronic circuitry accompanying harvesters, such as diodes and storage elements. The same are summarised and future directions envisioned.     

基于连续碳纤维/树脂智能材料的梁结构应变模态表征

研制了一种具有动态传感功能的碳纤维/树脂智能层,可用于结构的应变模态诊断.通过不同加载频率下的单向拉伸实验揭示了这种智能材料对低频动态载荷的响应能力,并理论分析了动态响应误差的影响因素.在此基础上将碳纤维/环氧树脂智能层连续敷设于悬臂梁结构表面代替传统的点式应变片,进行应变模态测试.测试结果表明,碳纤维/环氧树脂智能层可以较精确地反映结构的前三阶固有频率,并较好地表征结构的前三阶应变模态振型.对悬臂梁局部附加质量后重新进行了模态试验,结果表明:附加质量后,智能层反映的结构固有频率显著下降;同时,在附加质量所在的节点位置,智能层反映的应变模态振型有突变产生,说明智能层所表征的应变模态对结构物性参数变化具有识别能力,采用智能层与采用应变片的实验结果一致.此外,基于碳纤维/树脂智能层的可覆盖性,采用有限的测点全面捕捉了结构的应变模态信息,并在测试中通过在可疑区域内逐步增加测点,实现了结构物性参数变化的定位.     

一种改进的近邻多损伤“移相叠加”成像方法

近邻多损伤成像是Lamb波成像研究中的一个难点。在传统“移相叠加”方法基础上提出一种改进的近邻多损伤成像方法。为了避免或减轻相邻损伤散射信号间的混叠,该方法利用双面激励产生较高空间分辨率的单模式Lamb波监测信号。同时,根据Lamb波在传播中的能量衰减情况,引入衰减补偿因子来减小监测信号对不同位置监测灵敏度的差异。理论分析和实验均证明了上述两处改进对于提高近邻多损伤成像质量的有效性。