Identification Of Dynamic Characteristics Research Articles

Safety–Function–Environment Evaluation System for Large-Span Cable-Supported Bridges: Theory and Case Studies

Compared with common bridges, large-span cable-supported bridges contain more components, are located in a more complex environment, and play a more important role in traffic system sustainability. Throughout the service life, it is more necessary to evaluate their safety, functionality, and environmental status. In this study, a comprehensive evaluation system is proposed to fill the gap using advanced sensor-guided structural health monitoring data and probability-based digital twins. Safety evaluation is the basis of the system and can be divided into overall and component levels. The former includes an over-limit analysis of main structural responses and degradation identification of dynamic characteristics. The abnormal areas discovered in this phase and the hot spots prompted by prior information during the design process will be checked in the latter. The functional assessment of this system is mainly based on checklist-type inspection and is often carried out together with appearance inspection and non-main structural component detection. Environmental assessment includes the monitoring and analysis of wind fields, temperature, humidity, foundation scour, and traffic flow and is the source of external information in the aforementioned two modules. The temperature and humidity of the example bridges are basically uniformly distributed along the spatial dimension, fluctuating over a period of one day.

DInSAR–SBAS satellite monitoring of infrastructures: how temperature affects the “Ponte della Musica” case study

Continuous monitoring of the structural health of strategic structures and transport infrastructures plays a crucial role in providing an effective assessment of the safety conditions and in timely planning of the ordinary and extraordinary maintenance programme. Deformation monitoring and dynamic characteristic identification are some commonly used strategies for this purpose. One of the main challenges of recent years in the field of structural health monitoring is the use of data deriving from satellite interferometry, capable of providing information on structural deformations at a local and territorial scale. Despite the solidity and dependability of satellite-based methods for assessing ground deformation over time, when it comes to structural surveillance, there are certain circumstances under which satellites are incapable of accurately assessing displacements. This is particularly true for structures that are sensitive to temperature variations. The paper uses the “Ponte della Musica–Armando Trovajoli” in Rome as a case study to explore these aspects in more depth. This bridge has a steel arch structure with a prestressed concrete deck below it. It represents an example in which satellite differential interferometry does not allow obtaining useful information on displacement, at least for the most deformable portion of the deck, and therefore also on any pathological movements. This work proposes a 3D digital twin of the bridge, appropriately calibrated through experimental measurements of the environmental vibrations performed on the bridge. This will allow to evaluate the role played by thermal deformations related to air temperature variations and thus better understand the connection between physiological deformations and satellite limits.

BPF-WT combined filtering method for indirect identification of bridge dynamic characteristics

The indirect measurement method of extracting the dynamic characteristics of the bridge structure from the dynamic response of passing vehicles is a new method for bridge structure health monitoring, which has the advantage of cost-effectiveness. However, how to improve the accuracy of the indirect measurement method to identify the dynamic characteristics of the bridge is the current research focus. In this paper, combining the characteristics and advantages of bandpass filter (BPF) and wavelet transform (WT), a simple and effective joint filtering method BPF-WT is proposed for indirect identification of bridge dynamic characteristics. This method can eliminate the peak caused by the known vehicle frequency, and realize the layer-by-layer decomposition and reconstruction of the signal through the advantage of WT, to achieve the purpose of automatically executing the packet filtering task. This paper takes a simple trolley as an example to conduct a scaled test study to identify the dynamic characteristics of a bridge and proves that the BPF-WT joint filtering method can perform bridge dynamics under three conditions: different vehicle weights, different driving speeds, and driving on bridge decks with different roughness. Characteristic identification results and their influence rules. According to the research findings, the method of combined filtering suggested in this paper can efficiently filter out the noise produced by the vehicle’s frequency and the surroundings. This method can also distinctly detect the initial three frequencies of the bridge. Therefore, it demonstrates the practicality and efficiency of the BPF-WT combined filtering technique, which has a broad range of potential applications.

Dynamic characteristic identification of a bridge using BPF-WT combined filtering method

ABSTRACT The application of indirect identification of dynamic characteristics of bridge structures is largely hindered due to the complexity of bridge dynamic characteristics identification environment factors and signal processing. We propose a new combined filtering method by Bandpass filter with Wavelet Transform, which combines wavelet transform and bandpass filter to break through the problem of low accuracy of indirect recognition method due to the influence of vehicle frequency and other environmental noise. This new method not only gives full play to the advantages of bandpass filters but can easily reduce the peak caused by the known vehicle frequency. It realises the layer-by-layer decomposition and reconstruction of signals through wavelet transform advantage, to achieve the effect of automatic grouping filtering. The influencing factors of the new method are analysed by a customised trolley as an example to identify the dynamic characteristics of the structure. This paper also combines this method with virtual vehicles on ABAQUS and SIMPACK software to identify the dynamic characteristics of a simply supported box girder bridge. The effectiveness and reliability of this method in identifying bridge dynamic characteristics are further verified.

A mechanism-data hybrid-driven framework for identifying dynamic characteristic of actual chemical processes

As a prerequisite of accurate process analysis, prediction and optimization, the precise identification of process dynamic characteristics is of great significance. Traditional identification methods and data-driven technologies suffer from low accuracy and noise interference when facing the identification of actual chemical process. In this contribution, a mechanism-data hybrid-driven framework is developed to simultaneously capture the delay time and dynamic response of process variables. Combining non-parametric identification method, theoretical model and big data analysis technology, the proposed framework is able to derive more accurate and reliable identification results from the distributed control system (DCS) data directly, avoiding drawbacks brought by single method. The presented framework successfully identifies the flowrate dynamic properties of an actual deethanization process, and outperforms traditional approaches including finite impulse response model and Welch's averaged periodogram method. The contribution is significant for dynamic characteristic identification of actual chemical process, facilitating the developments of high-accuracy models for process prediction, control and intelligent optimization.

Dynamic characteristics identification of RC beams subjected to impact damage

Structural dynamic characteristics are essential parameters for detecting structural damage. This study conducted impact and static loading tests on six reinforced concrete (RC) beams, and the plastic energy dissipation of the reinforced concrete beams under both loading conditions is be essentially consistent. The random decrement technique and Hilbert-Huang transform (RDT-HHT) combined approach is used to identify the first three mode dynamic characteristics (frequency and damping ratio) of impact-damaged reinforced concrete beams. An approach based on finite element (FE) plastic damage distribution is proposed to obtain the continuous flexural stiffness of damaged reinforced concrete beams. Both the global stiffness and Rayleigh method are used to predict the natural frequency. The results show that the first three mode frequencies of the damaged reinforced concrete beams decrease, whereas their damping ratios increase. Specifically, the first mode frequency reduction of reinforced concrete beams under impact damage is slightly lower than that under static damage, while the second and third mode frequencies exhibited a greater decrease. The increase in damping of the damaged reinforced concrete beams is mainly related to the damage extent, damage distribution, and damage location. Furthermore, the first and third mode damping ratios of reinforced concrete beams increase more significantly than the second mode damping ratio after damage, primarily because the most severe damage occurred at the location (mid-span) with the maximum curvature of the first and third mode modal shapes. Due to the more concentrated distribution and more severe local damage of impact damaged reinforced concrete beam, the increase in the first and third mode damping ratios after impact damage is more pronounced compared to static damage. The global stiffness method overestimates the frequency of damaged reinforced concrete beams. Whereas the Rayleigh method utilizes a reasonable first mode modal shape function and the continuous flexural stiffness to predict the structural frequency after damage, the first mode frequency predicts after damage with an error of less than 3%. It is recommended to consider changes in both frequency and damping to assess the extent of impact damage in structural components.

A general data quality evaluation framework for dynamic response monitoring of long-span bridges

The structural health monitoring system (SHM) of long-span bridges inevitably produces low-quality data. It is important to evaluate the data quality and screen out normal data. Most existing studies on data anomaly detection have focused on abnormal data with abnormal waveforms in time domain. Usually there are pseudo-normal data in the SHM system, which seems normal in time domain. However, the pseudo-normal data of bridge dynamic responses may cause wrong dynamic characteristics identification. In this study, the existing data anomaly detection was further expanded to data quality evaluation, and both obvious abnormal and pseudo-normal data are evaluated. A general data quality evaluation framework for dynamic response monitoring of long-span bridge structures was proposed. The time–frequency characteristics of monitoring data were obtained by continuous wavelet transform, and the data quality was classified and evaluated by constructing and training a convolutional neural network (CNN). The proposed framework was verified by using acceleration monitoring data of a cable-stayed bridge. The results reveal that this framework solves the problem that CNN cannot detect pseudo-normal data through time-domain characteristics, and improves the accuracy of data quality evaluation by using time–frequency information of the monitoring data. The acceleration monitoring data of a suspension bridge and a single pylon cable-stayed bridge were used to demonstrate the feasibility of the cross-object application of the proposed framework. The evaluation accuracy for the acceleration data quality of the suspension bridge exceeded 96%. After the reinforced training of a small number of pseudo-normal data samples, the evaluation accuracy for the acceleration data quality of the cables of the cable-stayed bridge reached 96.8%. The framework shows a good generalization capacity and robustness in cross-object applications.

Parameter design and performance evaluation of tuned mass damper (TMD) for seismic control of structure considering soil-structure interaction (SSI)

Tuned mass damper (TMD) is a practical tool for reducing structural vibration. The current TMD design often use the dynamic characteristics of structures with fixed base. However, in terms of resisting earthquakes especially when the soil-structure interaction (SSI) effect is prominent, the TMD designed for the fixed base situation behaves unfavorably and even amplifies the structural response. In this paper, a parameter design and performance evaluation of TMD for seismic control of structure considering SSI is studied. The contents include the SSI modeling, structural dynamic characteristic identification, and TMD parameter designing. A seismic SSI model that the soil is simulated by an accurate lumped parameter models (LPMs) is built firstly. A simple and practical method is then used to identify the structural dynamic characteristic of SSI model. The identified structural frequency is used to compute the parameters of TMD. Finally, two types of structures, three kinds of soils, and 100 ground motions are applied to comprehensively evaluate the TMD performance through the comparison with the fixed-ground-based design and optimization-algorithm-based design. The research shows the TMD designed by the proposed method can show a good performance and robustness.

A State-of-the-Art Review on Chatter Stability in Machining Thin−Walled Parts

Thin−walled parts are widely used in many important fields because of performance and structural lightweight requirements. They are critical parts because they usually carry the core functions of high−end equipment. However, their high−performance machining has been facing severe challenges, among which the dynamics problem is one of the most important obstacles. The machining system is easily subjected to chatter due to the weak rigidity of the thin−walled structure and slender cutting tool, which significantly deteriorates the surface quality and reduces the machining efficiency. Extensive studies aiming at eliminating machining chatter have been carried out in the recent decades. This paper systematically reviews previous studies on the identification of system dynamic characteristics, modeling and prediction of chatter stability, and chatter elimination/suppression methods and devices. Finally, existing problems are summarized, and future research is concluded.

Experimental identification of dynamic characteristics of welded stiffened structures based on model updating

Complex engineering systems are generally manufactured using joints. This paper proposes a methodology for accurately identifying the stiffness and damping properties of welded stiffened plates. The results of the substructure based finite element models are compared with the actual experimental data. Discrepancies have been observed between the finite element and experimental results. Eigensensitivity studies have been carried out to select the updating parameters. The stiffness and viscous damping properties of the stiffened plate are identified using model updating. The accuracy of the proposed methodology has been validated by matching the predicted finite element FRF with the experimental FRF.

СТРАТЕГІЇ РОЗВИТКУ МІЖНАРОДНИХ ГОТЕЛЬНИХ МЕРЕЖ

The article is devoted to the study of the development strategies of international hotel chains. The purpose of the study is to reveal the peculiarities of organization of international hotel companies, to identify the advantages of the hotel chain form, to classify and characterize typical development strategies of hotel chains. General logical methods of analysis, synthesis, analogy, comparison and generalization were used, which ensured the systematization of scientific, statistical, scientific and journalistic information of publicly available organizational and economic data on the functioning of hotel chains. The key place in the study is given to the method of classification with the identification of qualitative, quantitative and dynamic characteristics of hotel operators. The article analyzes the conditionality of the development of hotel chains as a result of fierce competition in the business environment. It was found that the strength resources of hotel chains ensure their high and long-term stability. The advantages of managing finances, marketing, quality, and strategy in hotel chains compared to independent hotels are highlighted and analyzed. The study classifies and characterizes the main types of hotel chain development strategies, in particular, global geographic expansion, consistent focused local expansion strategy, brand portfolio expansion, real estate portfolio development, external orientation strategy, geographic advantage orientation, segmentation strategy, cost leadership strategy, internal orientation strategy, branding strategy, etc. The study revealed the diversification of international hotel chains as a reflection of significant competition in the segment of four-star and five-star hotels of well-known brands. The authors state that the future of hotel chains will depend on the convergence of growing competitiveness with a diverse customer base that is constantly evolving and looking for unique and personalized experiences. The results of classifying the strategy of hotel chains can be used by market operators to select the optimal model of competitiveness, which determines the practical significance of the study.

Identification of Multimodal Dynamic Characteristics of a Decurrent Tree with Application to a Model-Scale Wind Tunnel Study

Wind tunnel tests of scaled model trees provide an effective approach for understanding fluctuating wind loading and wind-induced response of trees. For decurrent trees, vague multimodal dynamic characteristics and ineffective estimation of leaf mass are two of the main obstacles to developing aeroelastic models. In this study, multimodal dynamic characteristics of the decurrent tree are identified by field measurements and finite element models (FEM). It was found that the number of branches swaying in phase determines the magnitude of effective mass fraction of branch modes. The frequencies of branch modes with larger effective mass fraction were considered as a reference for an aeroelastic model. In addition, an approach to estimate leaf mass without destruction was developed by comparing trunk frequency between field measurements and FEM. Based on these characteristics of the prototype, the scaled, aeroelastic model was constructed and assessed. It was found that the mismatch of leaf stiffness between the model and the prototype leads to mismatch of leaf streamlining and damping between them. The Vogel exponent associated with leaf streamlining provides a possible way to ensure consistency of leaf stiffness between the model and prototype.

Monitor wind characteristics and wind‐induced responses of a skyscraper during two typhoons

SummarySkyscrapers are wind‐sensitive structures due to their large slenderness ratio and good flexibility. Understanding the wind characteristics and wind‐induced response from the actual data provides first‐hand information for wind resistance design. This paper reports the wind properties and dynamic performance of a 632 m high‐rise building in Shanghai during the passage of typhoons Jongdari and Rumbbia. Field measurements obtained from the structural health monitoring system include acceleration and wind speed. The data analysis of turbulence intensity, turbulence integral length, and gust factor are compared and discussed. For the identification of dynamic characteristics, the stochastic subspace method and enhanced frequency domain decomposition method are employed to identify the modal parameters. Besides, the comfort assessment using peak value and root mean square of accelerations is compared with different standards. Studying the wind characteristics during the passage of typhoons and their impact on high‐rise buildings in a metropolis is expected to gain an insight into the dynamic mechanism of high‐rise buildings and collect a database for wind resistance design in typhoon‐prone regions.

Dynamic analysis of composite rod fastening rotor system considering multiple parameter influence

Dynamic performances of composite rod fastening rotor system are analyzed considering the integration of multiple parameters. A dynamic modeling method of multi-disk rod fastening rotor system is proposed based on the composite rotor structure and the influences of multiple parameters. The interaction of system parameters and fault features are revealed in the composite rod fastening rotor system. The dynamic analysis discloses the influence of fault degree and multiple parameters on the nonlinear behaviors. The results show that the dynamic characteristics of the rod fastening rotor system alter under the crack fault. The evolution of nonlinear performances is displayed in the analysis of multiple parameters. The analysis results contribute to the identification of dynamic characteristics for rod fastening rotor system and fault detection of gas turbine rotor system.

Characterization and identification of static and dynamic hammer tail characteristics in infrared temperature field of leaking steam

Characterization and identification of static and dynamic hammer tail characteristics in infrared temperature field of leaking steam

Identification of stiffness and damping of the weld in stiffened plates using model updating

Stiffened structures form an integral part of the ship structure. The fatigue life and the load-carrying capacity of the ship structure are dependent on the stiffened panels. Stiffened structures are formed by welding beam stiffeners on bare plates. The current study proposes a methodology to accommodate the welding uncertainties in the theoretical model. The uncertainties in the strength and damping of the weld line are incorporated, using coupling spring and dampers. The coupling elements couples the beam and plate subsystems of the stiffened structure assembly. A representative model of a stiffened structures is developed. Model updating on the representative model is carried out based on simulated experimental data using the inverse eigensensitivity method. The coupling spring stiffnesses were identified using model updating. The algorithm was verified for the ability to capture the variability of strength along the weld line. The variation in damping due to welding was determined on the updated model using a damping identification technique, which requires prior knowledge of accurate stiffnesses of the weld. Studies were carried out to investigate the robustness of the proposed algorithm by inducing random noise in the modal parameters. The generated Frequency Response Function (FRF) was verified to be sufficiently stable against the random perturbations of the modal parameters. It can be concluded from the numerical studies that the proposed algorithm can be used for the identification of dynamic characteristics of the welded stiffened plates with confidence.

Simulation evaluation of dynamic characteristic identification accuracy of sliding bearing considering test error

Aiming at the dynamic characteristics test bench of sliding bearings, the dynamic model is established. Based on the forward and inverse dynamic problems of the bearing, a simulation evaluation method for the identification accuracy of the sliding bearing dynamic characteristics is proposed and the algorithm is verified. The identification errors of dynamic characteristic coefficients under different excitation frequencies are analyzed, the sensitivities of single frequency excitation method and dual-frequency excitation method to test error are contrastively analyzed, and the influence laws of dynamic characteristic identification accuracy of sliding bearing are evaluated. Based on which the traditional single frequency excitation method has been improved. The dynamic characteristic test should be carried out respectively in the low frequency range and the high frequency range. The main stiffness and cross damping are the average of two tests, the main damping is the identification value in the high frequency, and the cross stiffness is the identification value in the low frequency. That will effectively reduce the impact of test error. The obtained data and laws could support the improvement of the dynamic characteristics test method of sliding bearings and the confirmation of test parameters, thereby the accuracy of dynamic characteristics identification is improved.

Measurement problems of miniature electrical machines

The article presents the issue related to experimental research on the determination of static and dynamic properties of miniature electrical machines. The tested objects are, for example, micromotors with body diameters in the order of single millimetres, or linear drives with millimetre dimensions. The main measurement problems were presented and the specificity of these measurements was characterized. First of all, electromechanical time constants have small values due to small values of masses or mass moments of inertia. The force quantities (forces and torques) generated by such actuators also require the use of unconventional measuring transducers. The research may concern the identification of static and dynamic characteristics, but also methods of dynamic measurement of the quantities used in the control of such micromachines are presented. Practical examples of original measurement methods and systems are presented.

An enhanced indirect video-based measurement procedure for dynamic structural system identification applications

A video-based indirect sensing procedure for dynamic identification purposes is presented. To overcome major limitations of video-based methods in real on-site measurements, a novel three step pre-modification, magnification, post-modification process is developed. This process includes revision of the initial input video record in order to delete disturbing objects, utilizing a magnification method to filter the frequency content of the monitored motion and using a revision step for elimination of noises generated during magnification process. Finally, a set of digital signal and image processing analyses are performed on the modified video using virtual visual sensor technology. Based on the results of this research, motion signals of the monitored object are detected. The proposed approach has been used for identification of dynamic characteristics of two historic masonry minarets in Istanbul. Results shows that the proposed procedure is able to assess the dynamic characteristics of the monitored structure with a high-level of accuracy.

Optimal sensor placements for system identification of concrete arch dams

This paper investigates the optimal sensor placements and capabilities of this procedure for dynamic characteristics identification of arch dams. For this purpose, a prototype arch dam is constructed in laboratory conditions. Berke arch dam located on the Ceyhan River in city of Osmaniye is one of the highest arch dam constructed in Turkey is selected for field verification. The ambient vibration tests are conducted using initial candidate sensor locations at the beginning of the study. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are used to extract experimental dynamic characteristics. Then, measurements are repeated according to optimal sensor locations of the dams. These locations are specified using the Effective Independence Method. To determine the optimal sensor locations, the target mode shape matrices which are obtained from ambient vibration tests of the selected dam with a large number of accelerometers are used. The dynamic characteristics obtained from each ambient vibrations tests are compared with each other. It is concluded that the dynamic characteristics obtained from initial measurements and those obtained from a limited number of sensors are compatible with each other. This situation indicates that optimal sensor placements determined by the Effective Independence Method are useful for dynamic characteristics identification of arch dams.