空间网架结构的动力性能脉动法测试及分析

为研究某体育场网架结构,利用脉动法对该结构1/10缩尺模型进行了动力特性测试。利用谱分析技术对所采集的数据进行分析,得出该结构的自振频率和各阶振型。根据实际模型,运用ANSYS软件建立有限元计算模型,得到该模型的各阶自振频率和模态的理论值。将试验结果与有限元分析结果进行对比,结果表明:实测结构自振周期小于理论分析值,模态相似。     

随机子空间法在海上风电结构模态参数识别中的应用

频率、阻尼比等是海上风电结构动力分析的重要设计参数.但是,环境激励下海上风电结构实测振动响应噪声水平高、信噪比低,应用传统随机子空间方法(SSI)进行海上风电结构模态参数识别十分困难.对海上风电高桩承台基础进行现场测试,并对环境激励下海上实测数据进行模态参数识别,旨在获取结构频率及阻尼信息.为提升模态参数识别精度,应用奇异值分解技术实现模型定阶,模型阶次得到了合理确定;同时,应用稳定图分析技术,噪声模态得到有效识别.结果表明:结合模型定阶与稳定图分析技术,随机子空间法可以比较准确地获得环境激励下的海上风电基础结构的频率及阻尼信息.     

基于随机子空间法的系杆拱桥模态测试分析

通过对某座采用顶推法施工的大跨径钢管混凝土系杆拱桥进行模态测试,基于随机子空间法进行模态分析,得到了桥梁结构前6阶振动模态参数;采用桥梁结构分析软件MIDAS建立有限元模型并对桥梁进行模态分析,提取了与实测前6阶模态振型相对应的模态参数。经过比较发现,桥梁实测模态振型、自振频率与理论分析结果相吻合,实测系杆拱桥的动力特性满足要求,同时验证了随机子空间法是桥梁结构模态分析的一种有效方法。     

框架—剪力墙结构动力特性测试研究和有限元分析

采用脉动法对某框架剪力墙结构的教学实验楼进行动力特性测试,获取结构的模态参数;基于ANSYS分析软件,建立结构三维有限元模型,在考虑和不考虑填充墙两种情况下,分别对结构进行模态分析;对比计算结果,实测结果和考虑填充墙的模型吻合较好,分析影响动力特性的因素,由于填充墙刚度的影响,结构的频率明显变大,振型位移曲线,则更偏于剪切型,其中对纵向影响更明显。其研究成果对今后其他的同类工程具有一定的参考价值。     

网架模型结构模态分析的试验研究

实验模态分析是综合运用线性振动理论、动态测试技术、数字信号处理和参数识别等手段,进行系统识别的过程。模态分析是有效的结构检测和安全评估的方法之一,它是根据测量模态参数(固有频率、阻尼比、振型、模态刚度、模态质量)相对于正常值产生的变化,并通过相关分析与识别来判断结构安全程度的一种先进方法。本文通过对网架模型结构进行试验模态分析,研究了试验模态技术在实际运用中的试验方法,识别系统的模态参数并与有限元分析进行比较,有限元结果与实测频率有一定的不同,但前四阶模态频率的差值百分比均在9%以内,说明实测的结果与有限元分析是比较吻合的。     

环境激励下结构模态参数识别在简支梁实验中的应用实例

本文简要介绍了环境激励下结构模态参数识别方法及其特点,还阐述了实测数据的时域和频域表示及离散傅立叶变换简介,并进行了简支梁模态试验,通过理论分析比较得出初步结论。     

脉动风作用下结构基本模态的定义和识别

顾名思义,基本模态应该是结构所有模态中最重要的一阶模态,在动力响应分析中具有不可或缺的作用.传统习惯将第一阶模态作为基本模态,这对于风振响应分析是不恰当的.本文通过对模态应变能公式进行定性分析,归纳出脉动风作用下模态应变能最大的那阶模态的振型所具有的基本特征,并将这阶模态定义为结构在脉动风作用下的基本模态.按照这个定义,脉动风作用下高层、高耸结构的基本模态位于第一阶,这与传统定义相同;而对于平均风荷载全为吸力的小矢跨比穹顶结构,脉动风作用下基本模态位于高阶.脉动风空间相关性的强弱对这两种类型结构的影响正好相反.算例分析表明,模态贡献系数可以准确地识别出基本模态在模态序列中的阶次.     

哈尔滨工业大学(深圳)

正大型复杂土木工程结构健康监测技术结构健康监测系统实测结构响应,体现足尺结构真实荷载工况下的承载能力和工作性能,用于跟踪结构响应变化过程、全面理解和认识结构行为、揭示结构响应内在规律、验证设计参数、解决施工不确定性因素等工程实际问题。哈尔滨工业大学(深圳)自主研发大型土木工程的结构健康监测系统,对其荷载、环境及响应进行监测,实时评定结构健康状况。哈尔滨工     

SVSA系统在某高层建筑结构动力特性测试中的应用研究

实测高层建筑结构的动力特性具有重要的意义。介绍了一种实测高层建筑结构动力特性的方法:结合同济大学土木工程学院自主开发的SVSA系统,利用环境激励下结构的脉动响应,确定结构物的动力特性。首先简述了该套测试系统的工作原理及使用方法,然后通过对同济大厦A座的现场实测,得到结构的自振频率与阻尼比,画出结构的前几阶平动振型,最后将测试结果与数值模型的分析结果进行对比,对比的结果显示,数值模型的分析结果与实测动力特性之间存在一定的误差,结构的计算周期约为实测周期的1.6倍。本文对于高层建筑结构的动力特性实测具有一定的应用参考价值。     

双协调自由界面模态综合方法在框架结构上的应用研究

本文研究双协调自由界面模态综合方法,并将其运用于土木工程结构中。首先介绍了双协调自由界面模态综合方法的基本思路和公式推导,进而提出了相应的模态截取准则。最后,通过一个11层的框架结构进行数值模拟。数值模拟分析结果验证了双协调自由界面模态综合方法在土木工程结构上应用的可行性,进一步通过算例对比,证明了本文提出的双协调自由界面模态综合方法的模态截取准则的正确性,为今后大型结构子结构研究方法提供了必要的理论基础。     

Modal identification with uncertainty quantification of large-scale civil structures via a hybrid operation modal analysis framework

In operational modal analysis (OMA), only structural responses are typically available. In this context, bias and variance (uncertainty) errors may exist in modal estimates (especially damping estimates), resulting in inaccurate determination of the modal properties of large-scale structures under harsh excitations. To this end, a hybrid OMA framework based on the modal decoupling, the natural excitation technique, the random decrement technique (RDT), and improved eigensystem realization algorithm (ERA) with the automated stabilization diagram is presented to perform high-accuracy modal estimates with uncertainty quantification for large-scale structures under normal and severe ambient excitations. The accuracy and effectiveness of the hybrid framework for identifying the modal parameters are validated by numerical simulation study of a framework structural model. Furthermore, the hybrid framework is applied to analyze recorded acceleration responses of a supertall building with 600-m height under normal excitations and typhoon condition to verify its applicability in field measurements. The numerical simulation and field measurement studies demonstrate that the hybrid framework can not only perform precise modal estimations with uncertainty quantification through a single ambient vibration measurement but also effectively reveal the variations of modal properties of supertall structures under harsh excitations from multiple perspectives. This paper aims to enhance the reliability and accuracy of modal estimation for engineering structures and further provide insight into the variations of dynamic properties of large-scale civil structures under severe excitations.     

Variational mode decomposition based modal parameter identification in civil engineering

An out-put only modal parameter identification method based on variational mode decomposition (VMD) is developed for civil structure identifications. The recently developed VMD technique is utilized to decompose the free decay response (FDR) of a structure into to modal responses. A novel procedure is developed to calculate the instantaneous modal frequencies and instantaneous modal damping ratios. The proposed identification method can straightforwardly extract the mode shape vectors using the modal responses extracted from the FDRs at all available sensors on the structure. A series of numerical and experimental case studies are conducted to demonstrate the efficiency and highlight the superiority of the proposed method in modal parameter identification using both free vibration and ambient vibration data. The results of the present method are compared with those of the empirical mode decomposition-based method, and the superiorities of the present method are verified. The proposed method is proved to be efficient and accurate in modal parameter identification for both linear and nonlinear civil structures, including structures with closely spaced modes, sudden modal parameter variation, and amplitude-dependent modal parameters, etc.     

优化技术在土建结构设计中的应用

近年来国内外对土建结构设计的优化进行了大量工作。优化的对象涉及结构工程的各个方面。本文试图综述各国在土建结构设计中运用优化技术的概况,类如梁、懔条、框排架、桥梁、桅杆以及建筑体系等,着重于所采用的数学模型与经济效果。评述仅限于实际应用的范围,并不包括有关的全部文献,本文正讨论了在建立优化数学模型时土建结构在目标函数、约束条件以及设计变量上的一些特点和问题。     

大跨度门式刚架结构地震响应分析方法研究

近年来,由于门式刚架结构设计施工存在一些问题,导致工程安全事故屡见不鲜,尤其在地震作用下,较多门式刚架工程发生垮塌,造成了巨大的经济损失。以某大跨度门式刚架厂房为例,利用ANSYS有限元分析软件建立其三维计算模型,进行地震作用下的振动响应分析。首先,通过模态分析得到门式刚架的各阶振型和自振频率;然后,分别进行谱分析和地震反应时程分析。分析表明,谱分析的结果偏于安全,而地震反应时程分析的结果可以作为谱分析结果的复核检验。     

Spurious mode distinguish by modal response contribution index in eigensystem realization algorithm

Modal identification process has played an important role for civil engineering structures. Among the identification methods, eigensystem realization algorithm is one of the most popular one. However, the noises in practical environment can influent the effectiveness of eigensystem realization algorithm, which can introduce spurious modes due to the overestimated physical order for the structure. This paper proposes a new index named the modal response contribution index (MRCI) for the eigensystem realization algorithm, which can determine the structural physical order and then distinguish spurious mode more precisely. First, the structural responses are divided into different modal response by the well‐known modal superposition theory. Then the square root summation of each modal response is obtained and named as MRCI. A modified stabilization diagram is also presented, which increases the row number of Hankel matrix with the determined order by MRCI. The straight lines formed by the stable points in the modified stabilization diagram designate the structural modal parameters. Finally, one numerical example and the monitoring data of a practical cable‐stayed bridge are employed. The results show that the proposed MRCI and modified stabilization diagram can identify the structural physical mode more precisely.     

Modal parameter identification of Tsing Ma suspension bridge under Typhoon Victor: EMD-HT method

This paper aims to identify the natural frequencies and modal damping ratios of the Tsing Ma suspension bridge during Typhoon Victor using the newly emerged empirical mode decomposition (EMD) method in conjunction with the Hilbert-transform (HT) technique. Stationary tests on the acceleration responses of the bridge recorded at different locations and in different directions during Typhoon Victor are first carried out to classify the recorded response data. Natural frequencies and modal damping ratios identified by the EMD-HT method are then compared with those obtained by the traditional fast Fourier transform (FFT)-based method. The modal parameters identified by the EMD-HT method from the bridge responses recorded at different locations are compared with each other to check their consistency. Furthermore, the variations of natural frequency and total modal damping ratio with vibration amplitude and mean wind speed are examined. The results demonstrated that the EMD-HT method is applicable to modal parameter identification of large civil structures under typhoons. The EMD-HT method and the FFT-based method produced almost the same natural frequencies but the FFT-based method gave higher modal damping ratios than the EMD-HT method in general.     

Structural dynamic parameter identification of Saige building based on distributed synchronous acquisition method

在大型复杂工程结构上进行现场模态测试时，由于结构规模体量大并存在空间隔断，导致数据采集设备与传感器之间快速布设数据传输线困难。因此，有必要解决不同位置分布式同步采集设备时间精确同步问题，研发易于快速安装的分布式数据采集和无线传输设备。为此，提出基于“北斗”卫星授时的结构振动分布式同步采集算法，集成分布式同步采集硬件与研发数据在线采集和无线传输软件，获取大型复杂工程结构不同空间位置时间同步动态响应，基于随机子空间算法自[JP2]动识别工程结构服役状态下真实的模态参数。在赛格大厦振动事件溯源工作中，该系统成功捕捉到5月20日12:00—13:00[JP]结构共振时第69层与桅杆底部的加速度响应，发现四次共振均以频率2.12 Hz振动主导。基于该系统在环境激励条件下的现场模态测试，识别结构前19阶动力学参数，发现频率2.12 Hz是主体结构弯扭耦合和桅杆面内对称振动模态。基于现场激振测试识别频率2.12 Hz对应的阻尼比，发现阻尼比随着振幅的增加突然减小然后逐步增加，较低的阻尼比是导致赛格大厦发生共振的原因之一。     

基于分布式同步采集的赛格大厦结构动力学参数识别

在大型复杂工程结构上进行现场模态测试时,由于结构规模体量大并存在空间隔断,导致数据采集设备与传感器之间快速布设数据传输线困难。因此,有必要解决不同位置分布式同步采集设备时间精确同步问题,研发易于快速安装的分布式数据采集和无线传输设备。为此,提出基于“北斗”卫星授时的结构振动分布式同步采集算法,集成分布式同步采集硬件与研发数据在线采集和无线传输软件,获取大型复杂工程结构不同空间位置时间同步动态响应,基于随机子空间算法自动识别工程结构服役状态下真实的模态参数。在赛格大厦振动事件溯源工作中,该系统成功捕捉到5月20日12:00—13:00结构共振时第69层与桅杆底部的加速度响应,发现四次共振均以频率2.12 Hz振动主导。基于该系统在环境激励条件下的现场模态测试,识别结构前19阶动力学参数,发现频率2.12 Hz是主体结构弯扭耦合和桅杆面内对称振动模态。基于现场激振测试识别频率2.12 Hz对应的阻尼比,发现阻尼比随着振幅的增加突然减小然后逐步增加,较低的阻尼比是导致赛格大厦发生共振的原因之一。     

Wavelet‐based approach of time series model for modal identification of a bridge with incomplete input

Identification of modal parameters of a bridge from its earthquake responses is crucial for performing damage assessment of the structure. However, all the input base excitations of the bridge may not be measured because of economic concerns and sensor malfunctions. Consequently, evaluating the modal parameters of a bridge under the consideration of incomplete input measurements is a challenging and important task. An approach that combines the continuous Cauchy wavelet transform with an autoregressive time‐varying moving average with exogenous input (AR‐TVMA‐X) model is proposed in this study to identify the modal parameters of a multispan bridge under multiple support earthquake excitations with incomplete measurements. The efficiency and efficacy of the proposed approach are first validated using numerically simulated responses of a three‐span continuous beam subjected to multiple support nonstationary excitations. A standard procedure of using the proposed approach to identify the modal parameters is established according to comprehensive studies on the effects of noise in the data, the number of supports whose excitations are used in the AR‐TVMA‐X model, and the orders of the AR‐TVMA‐X model on the accuracy of identifying the modal parameters. This procedure is further applied to process the earthquake responses of a two‐span cable‐stayed 510‐m‐long bridge to demonstrate the engineering applicability of the proposed approach.