Search

For the issue of flow induced vibration of spillway emersed radial gates under partially opening conditions, a fluid structure coupling transfer mathematical model for gates and spillway flow was constructed by using Computational Fluid Dynamics (CFD) software Fluent and Computational Structural Dynamics (CSD) software Mechanical APDL. Calculated and analyzed the vibration characteristics of the gate during discharge, developed a gate flow induced vibration back analysis program based on the principle of modal superposition, and achieved back analysis of the dynamic response results of the gate flow induced vibration. Taking the exposed arch gate of a certain project in Wujiang as an example for forward and backward analysis, the results indicate that the fluctuating pressure on the gate panel obtained from the Large Eddy Simulation (LES) turbulent model exhibits characteristics of low frequency, narrowband, and approximately gaussian distribution. The structural dynamic field of the gate is calculated by combining modal coordinates, vibration mode vectors, and stress vectors. The results of the back analysis of the dynamic displacement field and dynamic stress field are basically consistent with the results of the full method forward analysis, demonstrating the rationality of the back analysis method and the applicability of the program. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There are extremely high requirements for the surface quality and integrity of parts in the automotive, aerospace, and die/mold industry. Meanwhile, due to the advantages of large workspace, strong flexibility, and low cost, the hybrid robots have shown broad application prospects in the above fields of machining or manufacturing. However, limited by the stiffness of robot joints and links, the surface topography of the milled workpiece is more susceptible to the dynamic response caused by the variation of robot postures and cutting forces. The simulation of the surface topography in the robotic milling process remains a challenging goal. This paper focuses primarily on the dynamic displacement of end effector for the TriMule hybrid robot as well as its impact on the topography of the milled surface. In this paper, a framework model for predicting the topography of milled surface is developed first, and then further perfected by incorporating the dynamic displacement of the robot-tool system in the machining process. In this method, the dynamic model of the robot milling process is developed based on the stiffness of the TriMule hybrid robot within the entire workspace. After that, the finite element method is introduced to discretize the tool and workpiece, and the topography of the milled surface can be regenerated through the Boolean operations and the Z-MAP method. Finally, a series of validation experiments are conducted and the results indicate that the proposed model can be used to predict the topography of the surface milled by the hybrid robot in different postures. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Variometric approach (VA) technique has been introduced as an alternative to real-time kinematics and real-time precise point positioning techniques. As the ability of the variometric approach to detect short-term dynamic behaviors in real-time mode in applications such as Global Navigation Satellite Systems (GNSS)-seismology and structural health monitoring is demonstrated, the demand for open-source VA software is increasing. However, open-source software that is capable of VA processing in real-time mode based on single- and dual-frequency multi-GNSS observations is scarce. In view of this fact, we have developed an open-source VA processing software called PPPH-VA that can evaluate single- and dual-frequency multi-GNSS observations in real-time mode. PPPH-VA is developed in the MATLAB environment, and it can simultaneously process GPS, GLONASS, Galileo, BeiDou-2, and BeiDou-3 data with the VA technique in real-time mode, employing both single- and dual-frequency observations. We evaluated PPPH-VA using shake table experiments based on real data, and the results demonstrate that it provides high accuracy in terms of detection of dynamic displacements. Toolbox can successfully detect the dominant frequencies of short-term dynamic behaviors and is capable of determining the amplitude values corresponding to the peak frequency at the sub-mm level. Moreover, in the time domain, it can obtain dynamic behaviors with an accuracy of millimeters. [ABSTRACT FROM AUTHOR]

Measuring the structure's displacement plays a very important role in ensuring the safe operation of railway bridges in general and urban railway bridges in particular. In Vietnam, traditional methods using high-precision mechanical gauges have been used to measure the displacement of railway bridges. However, these methods need a lot of effort in installation and traffic control during implementation. These methods are based on the static principle: The test loads are placed on the bridge structure, and then the structure's displacement is observed. The safety assessment and analysis results are guaranteed by multiplying the dynamic coefficients, leading to some assessments that may not be close to the actual exploitation of the bridge structure. Therefore, the current study presents a new solution for measuring the displacement of railway bridge structures. This method uses Linear Variable Differential Transformer (LVDT) sensors to record the continuous displacement of the structure during the time the train passes over the bridge. Through field measurements combined with a finite element analysis model, the research focuses on developing and applying LVDT sensors in urban railway bridge structure health monitoring. At the same time, the potential of developing this method in Vietnam in the future is evaluated. [ABSTRACT FROM AUTHOR]

Global navigation satellite system (GNSS) receivers are commonly utilized for the displacement monitoring of long-span bridges. It is necessary for the structural early warning and identification to accurately extract the trend and dynamic displacement components from the original GNSS displacement signal. In this study, the solution for the component extraction is proposed by an improved variational mode decomposition (VMD) method, which is conducted by the recursive data-driven strategy (hereinafter referred to as RD-VMD). Further, the structural health monitoring (SHM) data of a long-span suspension bridge are used for validation. Firstly, the fourth-order Butterworth low-pass filter (BF) and ensemble empirical mode decomposition (EEMD) are compared to the proposed method for the trend extraction, and the comparison shows that the extraction error by RD-VMD is 1 cm smaller than those by the other two methods from the measured displacement with heavy vehicle passing. Then the measured modes during 168 h identified from the acceleration signals, the GNSS displacement signals, and the dynamic displacement sequences extracted by RD-VMD are compared. Consequently, the extracted dynamic displacement has the highest success rate of modal identification among the three data types. Especially for the second vertical mode, the effective identification results from the dynamic displacement sequences are at least 25% more than those from the other two data types. The statistical results show that the extracted dynamic displacement can be used for automated modal identification. Therefore, the feasibility of the proposed component extraction method is validated by the SHM data. [ABSTRACT FROM AUTHOR]

AF1410 is a low carbon high alloy ultra-high strength steel. It not only has high strength and high toughness, but also has a high stress corrosion resistance. However, due to the characteristics of hard quality and poor thermal conductivity, AF1410 is a difficult material to process. In the process of milling, the geometric factors of process parameters, the flexible deformation of milling cutter and the flutter of the process system all affect the surface roughness, which makes it difficult to predict the surface roughness of milling parts. In order to solve this problem, a prediction model for surface topography of ultrahigh strength steel AF1410 was studied. To solve this problem, this paper studies the formation of milling surface topography, considers the dynamic displacement of the milling system, proposes a modeling method of surface topography based on the dynamic characteristics of the milling system and forms a prediction model. On this basis, the surface topography of ultra-high strength steel is simulated and analyzed, and the accuracy of the model is verified by experiments. The study realizes the prediction of milling surface topography of AF1410 parts and reveals the formation mechanism of milling surface topography from geometric and physical perspectives. [ABSTRACT FROM AUTHOR]

• Time delays present in SHM system are demonstrated and analyzed. • A multi-sensor data fusion rule is developed for joint monitoring of displacements. • An algorithm based on correlation analysis is proposed to synchronize signals. • Fusing acceleration and inclination to capture 2D dynamic displacement trajectory. • More modal frequency components are proved to be carried by fusion displacement. Accurate identification of dynamic displacements and mode shapes is essential for determining the operating conditions of super high-rise buildings. However, existing structural health monitoring studies typically rely on a limited number of sensors to investigate the individual direction responses, disregarding the overall behaviors, which is inadequate for super high-rise buildings with considerable flexibility. Furthermore, extended monitoring periods resulting in time delays restrict the possibility of using additional sensors for joint monitoring. Based on the theory of multi-sensor data fusion, this study provides a new solution to identify the overall dynamic displacements and mode shapes through fusing acceleration and inclination, both of which can be directly measured in the structural health monitoring system. First, the time delays extracted from the measured data are presented and classified into two groups to facilitate data processing. Then, a multi-sensor data fusion rule based on the similarity of signal components is proposed to establish the relationships between inclinometers and accelerometers of different types, heights, and orientations, and a signal synchronization algorithm based on cross-correlation theory is employed in terms of the fusion rule. The proposed algorithm and fusion method are effectively validated by numerical simulations in both synchronized and unsynchronized cases and compared with other displacement estimation methods. Finally, the fusion displacement is derived by fusing the synchronized inclination and acceleration using the Kalman filtering algorithm. A full-scale field experiment on the 632 m high Shanghai Tower is conducted to verify the applicability of the proposed method to actual super high-rise buildings. It is demonstrated that the fusion displacement derived from the measured data after synchronization exhibits excellent characteristics in both time and frequency domains. This is further evidenced by the successful identification of the two-dimensional dynamic displacements and the first nine mode shapes of the Shanghai Tower during the approach of Typhoon Krosa. [ABSTRACT FROM AUTHOR]

We present the performance of real-time (RT)-precise point positioning (PPP) and GNSS-based variometric approach for displacement analysis stand-alone engine (VADASE) methods in capturing dynamic motions in real time. To examine the effectiveness of the two RT methods, different cases, including harmonic motions in various frequency and amplitude ranges, two ground motions similar to those experienced during a real earthquake, and step motions, were generated using a shake table. RT-PPP and VADASE results based on global positioning systems (GPS) observations at a 20 Hz sampling rate were compared with results of the linear variable differential transformer (LVDT) sensor and relative positioning (RP) in the frequency and time domains. Frequency-domain outcomes demonstrated that both RT-based techniques can precisely detect dominant frequencies of the tested motions. However, the time domain results showed that the VADASE can capture the dynamic displacements slightly better than the RT-PPP. While the RMSE values of the differences between the RT-PPP technique and the LVDT vary between 2.3 and 11.6 mm, these values ranged from 1.4 to 6.00 mm for the VADASE approach. Results of earthquake simulation and step motion tests indicated that the VADASE provides more accurate and reliable results than the RT-PPP. It was concluded that the RT-PPP and VADASE approaches can significantly contribute to real-time determination of accurate displacement and natural frequencies of engineering structures and seismic waveforms. They have potential benefits for structural health monitoring, earthquake/tsunami early warning systems, and rapid risk assessment applications. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Geology & Oilfield Development in Daqing is the property of Editorial Department of Petroleum Geology & Oilfield Development in Daqing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: Identifying fundamental characteristics of a structure provide key information for structural health monitoring (SHM). To date, numerous researchers have reported tools and algorithms that can perform system identification, with a large portion of their application being contact‐based sensors. Although dynamic responses of structures can be directly measured from contact‐based sensors, the lifespan of those sensors being much shorter than that of the structure, requiring labor to deploy and maintain the sensors, etc., has led to the use of non‐contact‐based sensors. Among various non‐contact‐based sensors, some researchers have investigated the use of light detection and ranging (Lidar) sensors, which remotely acquire three‐dimensional ranging information, mostly for static displacement measurement during construction. Thus, this paper presents an approach for system identification of structures using dynamic displacement measured from a multi‐channel Lidar sensor. Hardware and mechanical attributes that limit the direct use of raw data from the Lidar are explored. Then, strategies to adjust the tilt axes and reduce the range uncertainties and data synchronization are proposed. Subsequently, two types of laboratory‐scale structures are prepared for validation: a flexible cantilever beam and a four‐story shear building. In both of the structures, the Lidar showed less than 5% error in estimating the first natural frequencies. Also, the mode shape has been estimated with high precision. The results demonstrate the ability of the Lidar for identifying dynamic characteristics of a structure. The potable feature of the Lidar will further allow full‐scale monitoring of a large‐scale civil infrastructure for SHM. [ABSTRACT FROM AUTHOR]

This study investigates the ability of traditional-PPP (Precise Point Positioning) and PPP-AR (Ambiguity Resolution) techniques in structural health monitoring and Global Navigation Satellite Systems (GNSS)-seismology applications, and the contribution of multi-GNSS observations to both methods. To evaluate the performances of the methods, harmonic oscillations with amplitudes ranging from 5 mm to 10 mm and frequency between 0.3 Hz and 1.2 Hz, representing possible structural motions, were generated using a shake table. Furthermore, the 1989 Loma Prieta earthquake was simulated to examine the performance of PPP techniques in GNSS-seismology applications. The data collected at 20 Hz sampling rate were evaluated employing the traditional-PPP and PPP-AR techniques using only-Global Positioning System (GPS) and GPS/Galileo satellite observations, and the results were compared with Linear Variable Differential Transformer (LVDT) data in the frequency and time domain. Although the outcomes revealed that the frequency and amplitude values obtained from both methods with different satellite combinations in the frequency domain were comparable to each other, they clearly demonstrate that the superiority of the PPP-AR technique over the traditional-PPP technique in the time domain and the contribution of multi-GNSS observations. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Display omitted] • Low-cost GNSS & IMU MEMS receiver and software for vibration detection was validated. • The low-cost sensor system meets the requirements of precise vibration monitoring. • Coupled low-cost sensor solution provides displacements with mm-level error. • Coupled low-cost sensor solution outperforms GNSS-only one in vibration monitoring. We assess the performance of the self-developed receiver coupling dual-frequency low-cost GNSS chipset and IMU MEMS sensor. The system also comprises software dedicated to vibration monitoring based on relative kinematic positioning in a post-processing mode. The observation assessment reveals high accuracy of low-cost GNSS and MEMS accelerometer data. The Septentrio Mosaic X5 chipset exhibits competitive to high-grade receivers' phase observation noise, outperformance in code noise level and observation auto-correlation at a level that may be neglected even in high-rate applications. The evaluation of the MEMS accelerometer data proves that the sensor accuracy is adequate for vibration monitoring. With the shake table experiment, we examine the performance of vibration recovery. An advantage of the coupled solution over a GNSS-only one is documented with a 15 % reduction of the amplitude error. The backward smoothing of coupled solutions drives the next 20 % error drop. Finally, the high performance of the coupled solution based on low-cost GNSS & accelerometer is confirmed by a mean amplitude error of 0.4 mm. The frequency analyses indicate that both coupled and single-sensor solutions precisely detect the vibration frequencies; however, they also confirm the outperformance of the former over the latter. The power spectra of the recovered displacement time series accentuate the benefits of GNSS + accelerometer fusion and backward filtering for reducing displacement noise. [ABSTRACT FROM AUTHOR]

Due to the special damming methods and materials of the tailings dam, the dam body is easy to lose stability and is damaged under the action of the earthquake, which poses a threat to the life and property of downstream residents. Aiming at the dynamic response of tailings dam, based on the finite element analysis method, the dynamic response of tailings dam is analyzed by using the equivalent linear principle. The dynamic displacement, response acceleration, dynamic stress, and liquefaction distribution of an upstream tailings dam under seismic load are analyzed and calculated. The calculation results show that the tailings dam is in a stable state under the static action. The maximum acceleration amplification factor along the river appears at the node of 3 h/4. dam height. The maximum principal stress and the minimum principal stress of the accumulation dam are compressive stress. The maximum dynamic displacement of the dam body along the river and vertically is small. The post-processing program is written in MATLAB language to generate the dam liquefaction area under different seismic time histories. The results show that the liquefaction area is mainly concentrated in the shallow area of the sedimentary beach below the phreatic line and does not penetrate the whole dam. [ABSTRACT FROM AUTHOR]

Railway bridges are susceptible to over-height truck collisions and to address this issue, it is necessary to attenuate the effect of these impacts to ensure the safety of transportation operations. This study experimentally investigates the effectiveness of crash beams as a cushioning mechanism for railway bridges against collisions. Over-height truck and railway bridge impact events were simulated in a 1:5 scale experiment. The design parameters such as the stiffness of the crash beam and the bridge supports were scaled to evaluate different levels of attenuation. Seventeen experiments were conducted with five configurations consisting of four different types of crash beams and one no-crash beam arrangement. The results show that crash beams attenuate bridge total peak dynamic displacement responses between 14.5% and 35.7%, depending on the intensity of the impact and crash beam type. In addition, the results show that the average effectiveness in attenuating residual deformation for all four crash beams ranges from 43.03% to 83.40%. Finally, various designs and their effectiveness against lateral impacts with different speeds are discussed. The overall scope of this research is to provide objective information about the design of crash beams for railway bridges based on their response to over-height truck collisions at various speeds. [ABSTRACT FROM AUTHOR]

A series of experiments are carried out with a stick–slip earthquake model consisting of two granite blocks under biaxial compression loading. The mechanical stresses, strains, and acoustic emission are recorded. The model is subjected to calibrated mechanical impacts. The stages of exponential acceleration of motions of the sides of the contact are recorded, but this feature is not universal. The energy of the impacts was lower by three orders of magnitude than the energy accumulated by the model, which indicates a triggering mechanism of slip initiation. A series of impacts resulting in small displacements partially reduced the accumulated energy. If a large displacement was initiated by an impact, its energy was even higher compared to displacements that were not caused by impacts. The experiments revealed the difficulties in solving the problem of reduction of earthquake hazard by elastic pulses. [ABSTRACT FROM AUTHOR]

• A machined surface prediction model in peripheral milling operations is developed considering the dynamics of whole machine tool. • The location errors and roughness parameters are used to evaluate the quality of machined surfaces. • The reliability analysis method of machining quality is proposed considering the multiple failure modes. • The influences of key parameters on the machined surface machining quality and reliability are analyzed. The performance improvement of machine tools can be constrained by limited understanding of machined surfaces and machining quality reliability. In this paper, attentions are paid to the prediction of machined surface and the reliability analysis of machining quality for a three axis vertical machining center using peripheral milling operations. The prediction model of the machined surface in peripheral milling operations is developed considering the kinematic trajectories of all flutes, the run-out of tool, as well as the dynamic displacements of the cutter and workpiece. The dynamic displacements of the cutter and workpiece can be analytically calculated by the dynamics models of the tool and workpiece clamping systems of the machine tool. The location errors and roughness parameters are used to evaluate the quality of machined surfaces, and the reliability analysis method of machining quality is proposed considering the multiple failure modes. The proposed prediction method is verified during the peripheral milling of workpiece under different cutting conditions. The influences of some parameters on the machined surface are analyzed, and the machining quality reliability of the machine tool is also calculated and analyzed. This study can provide a theoretical basis for the design and optimization of machine tools and cutting tools, as well as the optimum design of processing conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

Global Positioning System (GPS) technology is reported in the literature as a reasonable alternative for the structural health monitoring (SHM) of bridges. However, more validations of GPS technology must be performed to extract the associated risk of bridges, particularly applying probabilistic concepts. This paper presents a probabilistic approach to evaluating the safety of bridges using real-time dynamic displacements obtained via geodetic-grade GPS receivers. The implementation of the probabilistic approach is demonstrated by the evaluation of the serviceability condition of a real-scale bridge. The structural evaluation involved the continuous extraction of GPS displacement data over the course of 1 h at three different periods of the day from Monday to Sunday. A comprehensive probabilistic study is developed based on dynamic displacements in terms of reliability index and probability of failure. Finally, based on the findings documented in this paper, the detection of unsafe serviceability conditions of bridges is possible by integrating GPS technology and the probabilistic approach presented in this research, which may help to inform decisions about the improvement or retrofit of bridge structures. [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

GNSS technology (known especially for GPS satellites) for measurement of deflections has proved very efficient and useful in bridge structural monitoring, even for short stiff bridges, especially after the advent of 100 Hz GNSS sensors. Mode computation from dynamic deflections has been proposed as one of the applications of this technology. Apart from formal modal analyses with GNSS input, and from spectral analysis of controlled free attenuating oscillations, it has been argued that simple spectra of deflections can define more than one modal frequencies. To test this scenario, we analyzed 21 controlled excitation events from a certain bridge monitoring survey, focusing on lateral and vertical deflections, recorded both by GNSS and an accelerometer. These events contain a transient and a following oscillation, and they are preceded and followed by intervals of quiescence and ambient vibrations. Spectra for each event, for the lateral and the vertical axis of the bridge, and for and each instrument (GNSS, accelerometer) were computed, normalized to their maximum value, and printed one over the other, in order to produce a single composite spectrum for each of the four sets. In these four sets, there was also marked the true value of modal frequency, derived from free attenuating oscillations. It was found that for high SNR (signal-to-noise ratio) deflections, spectral peaks in both acceleration and displacement spectra differ by up to 0.3 Hz from the true value. For low SNR, defections spectra do not match the true frequency, but acceleration spectra provide a low-precision estimate of the true frequency. This is because various excitation effects (traffic, wind etc.) contribute with numerous peaks in a wide range of frequencies. Reliable estimates of modal frequencies can hence be derived from deflections spectra only if excitation frequencies (mostly traffic and wind) can be filtered along with most measurement noise, on the basis of additional data. [ABSTRACT FROM AUTHOR]

Accurate measurement of dynamic displacement is important for the structural health monitoring and safety assessment of supertall structures. However, the displacement of a supertall structure is difficult to be accurately measured using the conventional methods because they are either inaccurate or inconvenient to be set up in practice. This study provides an accurate and economical method to measure dynamic displacement of supertall structures accurately by fusing acceleration and strain data, which are generally available in the structural health monitoring system. Dynamic displacement is first derived from the measured longitudinal strains based on geometric deformation without requiring mode shapes. An optimization technique is utilized to optimize the deployment of strain sensors for achieving more accurate strain-derived displacement. The strain-derived displacement is then combined with measured acceleration via a multi-rate Kalman filtering approach. Applications to a numerical supertall structure and a laboratory cantilever beam verify that the proposed method accurately estimates displacement including both high-frequency and pseudo-static components, under different noise cases and sampling rates. A full-scale field test on the 600 m-high Canton Tower is implemented to validate the applicability of the proposed method to real supertall structures. Error analysis demonstrates that the data fusion displacement is more accurate than the global position system-measured displacement in the time and frequency domains. [ABSTRACT FROM AUTHOR]

In this paper, we propose a dynamic displacement estimation method for large-scale civil infrastructures based on a two-stage Kalman filter and modified heuristic drift reduction method. When measuring displacement at large-scale infrastructures, a non-contact displacement sensor is placed on a limited number of spots such as foundations of the structures, and the sensor must have a very long measurement distance (typically longer than 100 m). RTK-GNSS, therefore, has been widely used in displacement measurement on civil infrastructures. However, RTK-GNSS has a low sampling frequency of 10–20 Hz and often suffers from its low stability due to the number of satellites and the surrounding environment. The proposed method combines data from an RTK-GNSS receiver and an accelerometer to estimate the dynamic displacement of the structure with higher precision and accuracy than those of RTK-GNSS and 100 Hz sampling frequency. In the proposed method, a heuristic drift reduction method estimates displacement with better accuracy employing a low-pass-filtered acceleration measurement by an accelerometer and a displacement measurement by an RTK-GNSS receiver. Then, the displacement estimated by the heuristic drift reduction method, the velocity measured by a single GNSS receiver, and the acceleration measured by the accelerometer are combined in a two-stage Kalman filter to estimate the dynamic displacement. The effectiveness of the proposed dynamic displacement estimation method was validated through three field application tests at Yeongjong Grand Bridge in Korea, San Francisco–Oakland Bay Bridge in California, and Qingfeng Bridge in China. In the field tests, the root-mean-square error of RTK-GNSS displacement measurement reduces by 55–78 percent after applying the proposed method.

Monitoring the dynamic responses of bridge structures has received considerable attention. It is important to synchronously measure both the quasi-static and dynamic displacements of bridge structures. However, the traditional accelerometer method cannot capture the quasi-static displacement component, although it can detect the dynamic displacement component. To this end, a novel composite instrument of a smartstation was proposed to monitor vibration displacements of footbridges. Full-scale experiments were conducted on a footbridge to validate the feasibility of the composite instrument-based monitoring method. A Chebyshev filter and wavelet algorithms were developed to process the composite instrument measurements. It was concluded that the measurement noise of the composite instrument was mainly distributed in a frequency range of 0–0.1 Hz. In two case studies with displacement peaks of 5.7–10.0 mm and 1.3– 2.5 mm, the composite instrument accurately identified the quasi-static and dynamic displacements. The composite instrument will be a potential tool for monitoring structural dynamics because of its enhanced overall performance.

Paper presents dynamic field test and analysis results of a three span railway steel continuous truss bridge over river Neris in Jonava. Bridge was originally constructed in 1914. In the period of the World War II and afterwards the bridge was many time destroyed by German and Soviet armies. In 1948 the new railway bridge was constructed. Object of the present paper is to evaluate dynamic behaviour of the railway bridge after 67 years in service. Experimental dynamic analysis was divided into resonance-vibration, forced-vibration and free vibration studies. Resonance-vibrations of the bridge were excited by separate actions of shock loading and standard locomotive 2M62. Forced-vibrations were measured under the action of locomotive 2M62. Additionally, free vibration tests under passage of freight and passenger trains have been carried out. Structural dynamic response of the bridge was analysed using Brüel & Kjær LAN XI dynamic test system and software. As a result, main dynamic parameters of the bridge were obtained. The main results include: mode shapes, frequencies of natural and forced vibrations, damping ratios, maximum amplitudes of accelerations, dynamic displacements. The obtained values were compared to the requirements of different design codes. Based on the achieved results concluding remarks and recommendations regarding the condition of the bridge after long-term period in service were presented.

Cutter displacements and deflections induce a significant amount of surface error in machined thin-walled parts and are a major obstacle to achieving higher productivity in a five-axis milling operation. In this study, a milling force model for the five-axis flank milling process was established and implemented by calculating and simulating the cutter dynamic displacement to investigate the dynamic response of ruled surface impeller blades in the milling process. A machining trajectory and related machining parameters were selected to calculate the dynamic milling forces in the X and Y directions for each analysis time using the calculation method. Using ANSYS software, the milling forces in three directions were input into the finite element model of the ball-end milling tool. The deformation was analyzed using post-processing for the ruled surface milling. Then, the milling parameters related to the dynamic displacement of the tool in the side milling blade were trained and optimized using a back-propagation neural network and particle swarm optimization algorithm during the side milling of the ruled surface. In addition, processing experiments were performed based on the optimized parameters. The blade roughness tests indicated that the surface quality was considerably improved after optimization, thus verifying the feasibility of the optimization method. [ABSTRACT FROM AUTHOR]

The Euler subtle motion amplification algorithm is applied to bridge vibration analysis. Firstly, a series digital images of bridge structures are collected continuously by ordinary civil camera, and then the micro vibration of the bridge is amplified by the related algorithm of Euler motion amplification. The time history images of the bridge specimen under the conventional video sampling frequency are obtained by decomposing the amplified digital image. Finally, the holographic dynamic displacement measurement results of the test bridge are obtained by analyzing the edge features of the mark points in the image sequences. Compared with the displacement sensor and the dial indicator, the analysis method presented is feasible, and can meet the application requirements of bridge dynamic displacement measurement.It is possible to carry out preliminary quantitative analysis of some vibration characteristics of bridges, and to identify micro vibration displacements of bridge structure. [ABSTRACT FROM AUTHOR]

GPS has been extensively used in measurement of displacements of long, flexible bridges, but we summarize evidence that geodetic instruments, GPS (GNSS) and RTS (robotic total stations), in combination with accelerometers, can be used to measure with safety semi-static and dynamic deflections of stiff bridges with main natural frequencies > 1–3 Hz. This is possible through a methodology derived from controlled, supervised learning experiments, field evidence and structural constraints. This methodology permits to understand the noise characteristics of dynamic displacement measurements and to develop techniques to suppress their noise, and has the following characteristics: (i) it is based on redundant/collocated sensors in order to control measurement uncertainty, avoid blunders and compensate for weaknesses inherent in each type of sensor; (ii) focusses on controlled excitations with structural/logical constraints, mostly free attenuating oscillations leading to direct estimation of first modal frequencies. This methodology was applied, refined, validated and exemplified in the study of several types of bridges in Greece, covering among others, cases of progressive decay and of soil-structure interactions. [ABSTRACT FROM AUTHOR]

Real-time dynamic displacement and spectral response on the midspan of Jiangyin Bridge were calculated using Global Navigation Satellite System (GNSS) and a speedometer for the purpose of understanding the dynamic behavior and the temporal evolution of the bridge structure. Considering that the GNSS measurement noise is large and the velocity/acceleration sensors cannot measure the low-frequency displacement, the Variational Mode Decomposition (VMD) algorithm was used to extract the low-frequency displacement of GNSS. Then, the low-frequency displacement extracted from the GNSS time series and the high-frequency vibration calculated by speedometer were combined in this paper in order to obtain the high precision three-dimensional dynamic displacement of the bridge in real time. Simulation experiment and measured data show that the VMD algorithm could effectively resist the modal aliasing caused by noise and discontinuous signals compared with the commonly used Empirical Mode Decomposition (EMD) algorithm, which is guaranteed to get high-precision fusion data. Finally, the fused displacement results can identify high-frequency vibrations and low-frequency displacements of a mm level, which can be used to calculate the spectral characteristics of the bridge and provide reference to evaluate the dynamic and static loads, and the health status of the bridge in the full frequency domain and the full time domain.

Dynamic displacement measurement of objects can be challenging due to the limitations of conventional methods and pricey instrumentation of unconventional methods, such as laser scanners. In this research, Close Range Photogrammetry (CRP) is used as an affordable non-contact method to measure 3D dynamic displacements. It is proposed as a reliable alternative to traditional dynamic deformation measurement methods such as displacement sensors or accelerometers. For this purpose, dynamic displacements of a three-dimensional one-story building frame model on a one-dimensional shake table are determined by using the traditional method of attached accelerometer and CRP. The results of the CRP method are compared with the results of the traditional methods as well as numerical models. The results show a good agreement which evidences the reliability of the CRP with regular cameras.

Considering the lack of precision in transforming measured micro-electro-mechanical system (MEMS) accelerometer output signals into elevation signals, this paper proposes a bridge dynamic displacement reconstruction method based on the combination of ensemble empirical mode decomposition (EEMD) and time domain integration, according to the vibration signal traits of a bridge. Through simulating bridge analog signals and verifying a vibration test bench, four bridge dynamic displacement monitoring methods were analyzed and compared. The proposed method can effectively eliminate the influence of low-frequency integral drift and high-frequency ambient noise on the integration process. Furthermore, this algorithm has better adaptability and robustness. The effectiveness of the method was verified by field experiments on highway elevated bridges.

Detection of potential damages is of much significance for aging bridges, which has attracted extensive attention in recent years. In this paper, a damage detection method is proposed utilizing dynamic displacement of a bridge under a moving vehicle. First, the theoretical basis of this method is elaborated. The idea is to use the static component of displacement measurements under a moving vehicle, and to use the calculated curvature change to identify damage in bridges. In order to obtain the static component, a technique is proposed for curvature calculation. Second, the proposed method is verified with two examples. In the first example, a finite element model of a single span bridge under a moving vehicle is used to show reliability of the method. Both vehicle-bridge interaction and road surface roughness are considered in the analysis. Parametric study on damage intensity, data acquisition location, vehicle passing path, and damping ratio provides guidance for application in real bridges. In the second example, a field test on a prestressed concrete viaduct is conducted to calibrate its finite element model. Artificial damage, that is, concrete crack and tendon rupture, was created, and the proposed method is used to identify the damage. Analysis results show capability of the method. Finally, conclusions are drawn, and suggestions are given for application of the proposed method on damage detection of real bridges. [ABSTRACT FROM AUTHOR]

Paper presents dynamic field test and analysis results of a three span railway steel continuous truss bridge over river Neris in Jonava. Bridge was originally constructed in 1914. In the period of the World War II and afterwards the bridge was many time destroyed by German and Soviet armies. In 1948 the new railway bridge was constructed. Object of the present paper is to evaluate dynamic behaviour of the railway bridge after 67 years in service. Experimental dynamic analysis was divided into resonance-vibration, forced-vibration and free vibration studies. Resonance-vibrations of the bridge were excited by separate actions of shock loading and standard locomotive 2M62. Forced-vibrations were measured under the action of locomotive 2M62. Additionally, free vibration tests under passage of freight and passenger trains have been carried out. Structural dynamic response of the bridge was analysed using Brüel & Kjær LAN XI dynamic test system and software. As a result, main dynamic parameters of the bridge were obtained. The main results include: mode shapes, frequencies of natural and forced vibrations, damping ratios, maximum amplitudes of accelerations, dynamic displacements. The obtained values were compared to the requirements of different design codes. Based on the achieved results concluding remarks and recommendations regarding the condition of the bridge after long-term period in service were presented. [ABSTRACT FROM AUTHOR]

Vibration measurements provide useful information about a structural system's dynamic characteristics and are used in many fields of science and engineering. Here, we present an alternative noncontact approach to measure dynamic displacements of structural systems using digital videos. The concept is that intensity measured at a pixel with a fixed (or Eulerian) coordinate in a digital video can be regarded as a virtual visual sensor. The pixels in the vicinity of the boundary of a vibrating structural element contain useful frequency information, which we have been able to demonstrate in earlier studies. Our ultimate goal, however, is to be able to compute dynamic displacements, i.e., actual displacement amplitudes in the time domain. In order to achieve that, we introduce the use of simple black-and-white targets that are mounted on locations of interest on the structure. By using these targets, intensity can be directly related to displacement, turning a video camera into a simple, computationally inexpensive, and accurate displacement sensor with notably low signal-to-noise ratio. We show that subpixel accuracy with levels comparable to computationally expensive block matching algorithms can be achieved using the proposed targets. Our methodology can be used for laboratory experiments, on real structures, and additionally, we see educational opportunities in K-12 classroom. In this paper, we introduce the concept and theory of the proposed methodology, present and discuss a laboratory experiment to evaluate the accuracy of the proposed black-and-white targets, and discuss the results from a field test of an in-service bridge. [ABSTRACT FROM AUTHOR]

In this paper, a dynamic displacements-based model updating method using a motion capture system (MCS) is proposed. The dynamic characteristics from MCS are used to find the parameters that minimize the difference between updated model and direct measurement. Using a multi-objective optimization algorithm of non-dominated sorting genetic algorithm-II, the number of objective functions for model updating is set to the same number of modes under consideration, and all the objective function are simultaneously minimized. To consider the contribution of each mode on model updating and to avoid biased results, a rule for weighting of solutions associated to each mode based on modal participation factors is suggested and tested. Using a free vibration experimental test of a three-story shear model, the performance of model updating method is verified by the comparison of the dynamics characteristics between the updated model and direct measurement by MCS. In addition, time histories of displacements from the updated model are compared with the direct measurement. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a smoothing based Kalman filter to estimate dynamic displacement in real-time by fusing the velocity measured from a laser Doppler vibrometer (LDV) and the displacement from a light detection and ranging (LiDAR). LiDAR can measure displacement based on the time-of-flight information or the phase-shift of the laser beam reflected off form a target surface, but it typically has a high noise level and a low sampling rate. On the other hand, LDV primarily measures out-of-plane velocity of a moving target, and displacement is estimated by numerical integration of the measured velocity. Here, the displacement estimated by LDV suffers from integration error although LDV can achieve a lower noise level and a much higher sampling rate than LiDAR. The proposed data fusion technique estimates high-precision and high-sampling rate displacement by taking advantage of both LiDAR and LDV measurements and overcomes their limitations by adopting a real-time smoothing based Kalman filter. To verify the performance of the proposed dynamic displacement estimation technique, a series of lab-scale tests are conducted under various loading conditions. [ABSTRACT FROM AUTHOR]

Fiber optic interferometry has been used to detect small displacements in diverse applications. Counting the number of fringes in fiber-optic interferometry is challenging due to the external effects induced in dynamic systems. In this paper, a novel interference fringe counting technique is developed to convert the intensity of interference data into displacements in the range of micrometers to millimeters while simultaneously resolving external dynamic effects. This technique consists of filtering the rough experimental data, converting filtered optical interference data into displacements, and resolving dynamic effects of the experimental system. Filtering the rough data is performed in time by using the moving average method with a window size of 400 data points. Filtered optical data is further converted into displacement by calculating relative phase differences of each data point compared to local maximum and local minimum points. Next, a linear curve-fit is subtracted from the calculated displacement curve to reveal dynamic effects. Straightness error of the lead screw driven stage, dynamics of the stepper motor, and profile of the reflective surfaces are investigated as the external dynamic effects. Straightness error is characterized by a 9th order polynomial function, and the effect of the dynamics of the stepper motor is fitted using a sinusoidal function. The remaining part of the measurement is the effect of roughness and waviness of the reflective surfaces. As explained in the experimental setup part, two fiber-optic probes detect the vertical relative displacements in the range of 1-50 µm, and the encoder probe detects 13.5 mm horizontal displacement. Thus, this technique can detect three order of magnitude different dynamic displacements with sub-micrometer resolution. The current methodology can be utilized in different applications which require measuring straightness error of lead-screw driven stages, large area surface profile of specimens, and vibration of actuators such as stepper motors. [ABSTRACT FROM AUTHOR]

In this paper, we observed physically adsorbed CO molecules on C 60 surface being displaced by impinging noble gas atoms (He, Ne, Ar, Kr), either through a dynamic displacement process or an exothermic replacement process, depending on their adsorption energies. This displacement mechanism could shift from one to the other depending on the surface coverage and temperature. Furthermore, rotational energy of the impinging molecules may also contribute to the dynamic displacement process by supplying additional energy. [ABSTRACT FROM AUTHOR]

Most of the existing bridge superstructure damage detection methods are based on acceleration or strain response due to ambient excitation. This paper proposes a bridge damage detection procedure that utilizes vehicle-induced displacement response without requiring prior knowledge about the traffic excitation and road surface roughness. This study is partially motivated by the recent advances in convenient measurement of structural displacements enabled by video-based sensors. Vehicle-bridge interaction analysis shows that when subjected to moving vehicles, the bridge displacement response is dominated by the first-order mode component. This justifies the proposed damage detection method that only requires the first-order mode shape curvature. While conventionally the mode shapes are extracted based on operational modal analysis, the first-order mode shape is extracted by directly analyzing the power spectral density functions of measured bridge displacement responses under vehicle excitations. Numerical simulations are carried out to investigate the feasibility and performance of the proposed damage detection method using three damage scenarios including damage at single, double, and multiple locations, each involving several extents of damage defined by the reduction in element stiffness. The results reveal that all the damage cases can be successfully identified. Furthermore, the damage detection performance is evaluated for cases involving different classes of road surface roughness and less measurement points. The study demonstrates the potential of the proposed model-free and time-efficient method for damage detection of bridge structures. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

For the complex problems of ground-track-wheels coupling system excitation characteristics， a dynamics model of the tracked vehicle suspension system was established leaving out the track impacts. The theoretical calculations of the road wheels dynamic displacement were realized through kinetic equation. It was then simulated under various working conditions. A multi-body dynamics simulation model was proposed. Comparing the simulation result with that of the theoretical calculations， the change regulation of the road wheels dynamic displacement with the vehicle speed was analyzed. The results provide a theoretical reference for designing and developing the tracked vehicle. A technical support for loading excitation directly on road wheels about vehicle road simulation system is provided as well. [ABSTRACT FROM AUTHOR]