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Time-domain and frequency-domain approaches to identification of bridge flutter derivatives

Zhengqing CHEN

《结构与土木工程前沿（英文）》 2009年第3卷第2期页码 173-179 doi: 10.1007/s11709-009-0034-1

摘要： Flutter derivatives are essential for flutter analysis of long-span bridges, and they are generally identified from the vibration testing data of a sectional model suspended in a wind tunnel. Making use of the forced vibration testing data of three sectional models, namely, a thin-plate model, a nearly streamlined model, and a bluff-body model, a comparative study was made to identify the flutter derivatives of each model by using a time-domain method and a frequency-domain method. It was shown that all the flutter derivatives of the thin-plate model identified with the frequency-domain method and time-domain method, respectively, agree very well. Moreover, some of the flutter derivatives of each of the other two models identified with the two methods deviate to some extent. More precisely, the frequency-domain method usually results in smooth curves of the flutter derivatives. The formulation of time-domain method makes the identification results of flutter derivatives relatively sensitive to the signal phase lag between vibration state vector and aerodynamic forces and also prone to be disturbed by noise and nonlinearity.

关键词： long-span bridges wind-induced vibration flutter derivatives forced vibration test time-domain method frequency-domain method

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基于频率域全波形反演的隧道超前探测研究 Article

于明羽, 程飞, 刘江平, 彭代诚, 田志坚

《工程（英文）》 2022年第18卷第11期页码 197-206 doi: 10.1016/j.eng.2021.06.018

摘要：

地震超前探测方法是获取隧道前方复杂地质体结构的重要手段，对隧道工程的安全建设和灾害防治极为重要。针对目前隧道地震超前探测方法在获取掌子面前方地质体结构和物性参数时存在精度不足的问题，本文将高分辨率成像的声波频率域全波形反演方法应用于地震隧道超前探测，并研究了频率组选择策略以及观测系统对反演效果的影响，实现了隧道前方不良地质体的结构成像与物性反演。研究结果显示：本文基于常规频率域声波全波形反演的频率组选择策略，提出的覆盖垂直波数和抗混叠相结合的频率组选择策略，能够有效获得隧道前方地质体的空间结构和物性参数，并提高反演分辨率；本文通过线性增加隧道观测系统侧边长度，讨论不同隧道双边观测系统长度对反演成像的影响，得出侧边长度近似于掌子面宽度5 倍时反演效果最佳，超过该范围后继续增加侧边观测长度对反演结果影响可忽略；最后采用研究结果对复杂的多地层模型进行反演，得出掌子面前方复杂地层的准确结构形态和物性参数，验证了本文方法的可行性。

关键词：隧道超前探测全波形反演频率选择策略观测系统设计

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Frequency domain a9ctive vibration control of a flexible plate based on neural networks

Jinxin LIU, Xuefeng CHEN, Zhengjia HE

《机械工程前沿（英文）》 2013年第8卷第2期页码 109-117 doi: 10.1007/s11465-013-0252-z

摘要：

A neural-network (NN)-based active control system was proposed to reduce the low frequency noise radiation of the simply supported flexible plate. Feedback control system was built, in which neural network controller (NNC) and neural network identifier (NNI) were applied. Multi-frequency control in frequency domain was achieved by simulation through the NN-based control systems. A pre-testing experiment of the control system on a real simply supported plate was conducted. The NN-based control algorithm was shown to perform effectively. These works lay a solid foundation for the active vibration control of mechanical structures.

关键词： active vibration control (AVC) neural network (NN) low frequency noise frequency domain control multi-frequency control

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长寿命路面疲劳寿命预测的频域分析方法

魏保立,郭成超,崔璨

《中国工程科学》 2017年第19卷第6期页码 80-85 doi: 10.15302/J-SSCAE-2017.06.012

摘要：

笔者分别从沥青路面和水泥混凝土路面两个方面分析了路面疲劳寿命预测的相关方法。重点对疲劳寿命预测的频域分析方法进行了较为详细的分析，结合车辆–道路耦合振动系统模型，对路面不平整引起的车辆与道路之间的随机振动进行了分析，指出车辆–道路耦合振动的随机功率谱密度是进行路面疲劳寿命预测的一种手段和方法，并提出了相应的预测步骤，旨在为长寿命路面的设计和性能评价提供参考。

关键词：长寿命路面疲劳寿命预测随机振动功率谱密度

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心电图信号的频域分析

涂承媛,曾衍钧,李树信

《中国工程科学》 2002年第4卷第12期页码 66-70

摘要：

提出了一种简便有效的、由心电图（ECG）曲线提取QRS-T复合波的新方法，从而获得P波（当房颤未发生时）或f波（当房颤时）；利用功率谱、自相关、互相关等信号处理技术，对它进行了处理和分析，特别是，比较了未房颤时和发生房颤时的相关信息的显著差别。

关键词：心电图（ECG） QRS-T复合波 P波房颤波（f波）频数直方图功率谱自相关互相关

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H_∞ control in the frequency domain for a semi-active floor isolation system

Yundong SHI, Tracy C BECKER, Masahiro KURATA, Masayoshi NAKASHIMA

《结构与土木工程前沿（英文）》 2013年第7卷第3期页码 264-275 doi: 10.1007/s11709-013-0214-x

摘要： A floor isolation system installed in a single floor or room in a fixed base structure is designed to protect equipment. With this configuration, the input motions to the floor isolation from the ground motions are filtered by the structure, leaving the majority of the frequency content of the input motion lower than the predominant frequency of the structure. The floor isolation system should minimize the acceleration to protect equipment; however, displacement must also be limited to save floor space, especially with long period motion. Semi-active control with an control was adopted for the floor isolation system and a new input shaping filter was developed to account for the input motion characteristics and enhance the effectiveness of the control. A series of shake table tests for a semi-active floor isolation system using rolling pendulum isolators and a magnetic-rheological damper were performed to validate the control. Passive control using an oil damper was also tested for comparison. The test results show that the control effectively reduced acceleration for short period motions with frequencies close to the predominant frequency of the structure, as well as effectively reduced displacement for long period motions with frequencies close to the natural frequency of the floor isolation system. The control algorithm proved to be more advantageous than passive control because of its capacity to adjust control strategies according to the different motion frequency characteristics.

关键词： semi-active floor isolation H_∞ control MR damper shaping filter shaking table test

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基于频域的多变量广义预测控制（MIMO-GPC）稳定性分析

孙青林,陈增强,袁著祉

《中国工程科学》 2004年第6卷第10期页码 39-44

摘要：

提出了基于频域的多变量广义预测控制（MIMO-GPC）稳定性分析方法，推导了MIMO-GPC的闭环反馈结构，给出了基于闭环特征多项式的MIMO-GPC的稳定性判据和奈奎斯特稳定性判据。这些判据可作为MIMO-GPC控制器参数设计的重要依据。

关键词：多变量广义预测控制频域分析稳定性判据

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An efficient stochastic dynamic analysis of soil media using radial basis function artificial neural network

P. ZAKIAN

《结构与土木工程前沿（英文）》 2017年第11卷第4期页码 470-479 doi: 10.1007/s11709-017-0440-8

摘要： Since a lot of engineering problems are along with uncertain parameters, stochastic methods are of great importance for incorporating random nature of a system property or random nature of a system input. In this study, the stochastic dynamic analysis of soil mass is performed by finite element method in the frequency domain. Two methods are used for stochastic analysis of soil media which are spectral decomposition and Monte Carlo methods. Shear modulus of soil is considered as a random field and the seismic excitation is also imposed as a random process. In this research, artificial neural network is proposed and added to Monte Carlo method for sake of reducing computational effort of the random analysis. Then, the effects of the proposed artificial neural network are illustrated on decreasing computational time of Monte Carlo simulations in comparison with standard Monte Carlo and spectral decomposition methods. Numerical verifications are provided to indicate capabilities, accuracy and efficiency of the proposed strategy compared to the other techniques.

关键词： stochastic analysis random seismic excitation finite element method artificial neural network frequency domain analysis Monte Carlo simulation

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Damage identification in connections of moment frames using time domain responses and an optimizationmethod

《结构与土木工程前沿（英文）》 2021年第15卷第4期页码 851-866 doi: 10.1007/s11709-021-0739-3

摘要： Damage is defined as changes to the material and/or geometric properties of a structural system, comprising changes to the boundary conditions and system connectivity, adversely affecting the system’s performance. Inspecting the elements of structures, particularly critical components, is vital to evaluate the structural lifespan and safety. In this study, an optimization-based method for joint damage identification of moment frames using the time-domain responses is introduced. The beam-to-column connection in a metallic moment frame structure is modeled by a zero-length rotational spring at both ends of the beam element. For each connection, an end-fixity factor is specified, which changes between 0 and 1. Then, the problem of joint damage identification is converted to a standard optimization problem. An objective function is defined using the nodal point accelerations extracted from the damaged structure and an analytical model of the structure in which the nodal accelerations are obtained using the Newmark procedure. The optimization problem is solved by an improved differential evolution algorithm (IDEA) for identifying the location and severity of the damage. To assess the capability of the proposed method, two numerical examples via different damage scenarios are considered. Then, a comparison between the proposed method and the existing damage identification method is provided. The outcomes reveal the high efficiency of the proposed method for finding the severity and location of joint damage considering noise effects.

关键词： damage identification beam-to-column connection time-domain response optimization

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framework for underground structures in layered ground under inclined P-SV waves using stiffness matrix and domain

《结构与土木工程前沿（英文）》 2023年第17卷第1期页码 10-24 doi: 10.1007/s11709-022-0904-3

摘要： A numerical framework was proposed for the seismic analysis of underground structures in layered ground under inclined P-SV waves. The free-field responses are first obtained using the stiffness matrix method based on plane-wave assumptions. Then, the domain reduction method was employed to reproduce the wavefield in the numerical model of the soil–structure system. The proposed numerical framework was verified by providing comparisons with analytical solutions for cases involving free-field responses of homogeneous ground, layered ground, and pressure-dependent heterogeneous ground, as well as for an example of a soil–structure interaction simulation. Compared with the viscous and viscous-spring boundary methods adopted in previous studies, the proposed framework exhibits the advantage of incorporating oblique incident waves in a nonlinear heterogeneous ground. Numerical results show that SV-waves are more destructive to underground structures than P-waves, and the responses of underground structures are significantly affected by the incident angles.

关键词： underground structures seismic response stiffness matrix method domain reduction method P-SV waves

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基于频域的PID广义预测控制器的鲁棒性分析

王繁珍,陈增强,姚向峰,袁著祉

《中国工程科学》 2006年第8卷第10期页码 66-70

摘要：

推导了PID广义预测控制器(PID-GPC)的闭环反馈结构, 采用小增益定理获得了存在建模误差(MPM)情况下PID-GPC鲁棒稳定的一个充分条件。然后在频域内分析了PID-GPC控制器的参数选择对其鲁棒性的影响。

关键词：预测控制鲁棒性频域小增益定理 PID控制

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Analytical method of capsizing probability in the time domain for ships in the random beam seas

LIU Liqin, TANG Yougang, LI Hongxia

《结构与土木工程前沿（英文）》 2007年第1卷第3期页码 361-366 doi: 10.1007/s11709-007-0048-5

摘要： The methods for constructing safe basins of ships and predicting their survival probability in random waves were studied. The nonlinear differential equation of the rolling motion of ships in random beam seas was established considering nonlinear damping, nonlinear restoring moment, and random waves. The random rolling differential equation was solved in the time domain by applying the harmonic acceleration method and by synthetically considering the instantaneous state of ships and the narrowband wave energy spectrum. The numerical simulation of random capsizing course was brought forward, the safe basins were constructed for safe navigation, and the survival probabilities of ships were calculated. As an example, the safe basins on the rolling initial value plane were constructed for a 30.27-meter-long fishing vessel according to different initial conditions and random wave parameters. The survival probabilities of the fishing vessel under different significant wave heights were predicted. Thus, the survival probabilities of ships in random seas can be predicted quantitatively by the proposed method.

关键词： different survival probability different significant nonlinear differential narrowband

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Improved numerical method for time domain dynamic structure-foundation interaction analysis based onscaled boundary finite element method

DU Jianguo, LIN Gao

《结构与土木工程前沿（英文）》 2008年第2卷第4期页码 336-342 doi: 10.1007/s11709-008-0054-2

摘要： Based on the reduced set of base function in scaled boundary finite element method (SBFEM), an improved time domain numerical approach for the dynamic structure-foundation interaction analysis was proposed. With reasonable choice of the number of base functions, the degrees of freedom on the structure-foundation interface were reduced and the associated computation for the calculation of convolution integral was greatly reduced. The results of this proposed approach applied to the calculation of a gravity dam and an arch dam. The acceleration frequency response functions were calculated and the influences affected by different reduced set of base functions as well as full set were compared. It was found that a higher degree of reduced set of base functions resulted in a significant increase of computational efficiency but a little bit of loss in accuracy. When the reduced set was decreased by 60%, the efficiency may be increased to up to five times, while the loss of accuracy of peak value of response will be less than 4%. It may be concluded that the proposed approach is suitable for large-scale structure-foundation interaction analysis.

关键词： structure-foundation interface computational efficiency different suitable numerical approach

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Oscillation frequency of simplified arterial tubes

Hui AN, Fan HE, Lingxia XING, Xiaoyang LI

《机械工程前沿（英文）》 2009年第4卷第3期页码 300-304 doi: 10.1007/s11465-009-0038-5

摘要： To construct the spatial kinetic equation of an arterial tube and obtain its radial natural frequency, a linear-elastic and small deformation condition is assumed. The theoretical analysis is first presented and the finite element method is then used to numerically simulate the spatial kinematics. The results show that the first-order frequency is 15.8 Hz and the obtained exact analytical solutions agree well with numerical solutions, which proves that the theoretical analysis and numerical simulation are both correct.

关键词： spatial kinematics natural frequency finite element method

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基于钻头运动诱发套管头振动信号检测的井眼防碰监测方法

何保生,刘刚,王平双,文敏

《中国工程科学》 2011年第13卷第5期页码 74-78

摘要：

针对海上加密调整井的井眼防碰问题，设计了一种井筒防碰地面监测预警系统，并进行了现场应用。系统利用加速度传感器监测通过套管传输到套管头上的钻头振动信号，利用数据采集、信号滤波放大和专门编制的监测软件记录分析传感器采集的振动信号，通过对信号的时域、频域分析，确定信号特征与井间相对距离的关系，识别钻头对风险井套管的趋近或碰撞。应用结果表明，该系统能有效感知通过地层、套管传输到套管头的钻头振动信号，并能识别出钻头对风险邻井的趋近，验证了系统在设计理论和方法上的可行性，为加密调整井的井眼防碰、保证钻井安全提供了一种有效的手段。

关键词：调整井防碰风险井振动信号时域分析频域分析