Using a Single-DOF Test Vehicle to Simultaneously Retrieve the First Few Frequencies and Damping Ratios of the Bridge

2021 ◽  
pp. 2150108
Author(s):  
Y. B. Yang ◽  
K. Shi ◽  
Z. L. Wang ◽  
H. Xu ◽  
B. Zhang ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Contact Point ◽  
Vehicle Speed ◽  
Test Vehicle ◽  
Closed Form Solutions ◽  
Random Decrement Technique ◽  
Mode Decomposition ◽  
Random Decrement ◽  
Contact Response ◽  
The Hilbert Transform

Bridge damping ratios are extracted via the skillful use of the single-degree-of-freedom (DOF) test vehicle for the first time in this paper. Central to the simultaneous retrieval of the first few frequencies and damping ratios from the contact (point) response of the bridge is the use of the variational mode decomposition (VMD) and random-decrement technique (RDT). Closed-form solutions are newly derived for the vehicle and contact responses of the damped bridge and validated later numerically. Using the proposed method, one calculates first the mono-component from the contact response by the VMD; then extracts the free-decay response for each mode by the RDT; and finally identifies the frequency and damping ratio by the Hilbert transform. The parametric study confirms that: (1) the contact response outperforms vehicle’s response in retrieving bridge frequencies and damping ratios; (2) the first few frequencies can be identified with robustness for reasonable levels of road roughness, vehicle speed, bridge damping and noise; (1) good result is obtained for the first damping ratio, in spite of the traditional uncertainty existing with damping; and (2) ongoing traffic can enhance the proposed method for bridge identification.

Adaptive Amplifier for a Test Vehicle Moving Over Bridges: Theoretical Study

2020 ◽  
pp. 2150042
Author(s):  
Y. B. Yang ◽  
Z. L. Wang ◽  
K. Shi ◽  
H. Xu ◽  
J. P. Yang
Keyword(s):  
Dynamic Responses ◽  
Vehicle Speed ◽  
Test Vehicle ◽  
Vehicle Performance ◽  
Single Degree Of Freedom ◽  
Closed Form Solutions ◽  
Numerical Studies ◽  
Element Simulation ◽  
Road Roughness ◽  
Overall Performance

A vibration amplifier is first proposed for adding to a test vehicle to enhance its capability to detect frequencies of the bridge under scanning. The test vehicle adopted is of single-axle and modeled as a single degree-of-freedom (DOF) system, which was proved to be successful in previous studies. The amplifier is also modeled as a single-DOF system, and the bridge as a simple beam of the Bernoulli–Euler type. To unveil the mechanism involved, closed-form solutions were first derived for the dynamic responses of each component, together with the transmissibility from the vehicle to amplifier. Also presented is a conceptual design for the amplifier. The approximations adopted in the theory were verified to be acceptable by the finite element simulation without such approximations. Since road roughness can never be avoided in practice and the test vehicle has to be towed by a tractor in the field test, both road roughness and the tractor are included in the numerical studies. For the general case, when the amplifier is not tuned to the vehicle frequency, the bridge frequencies can better be identified from the amplifier than vehicle response, and the tractor is helpful in enhancing the overall performance of the amplifier. Besides, the amplifier can be adaptively adjusted to target and detect the bridge frequency of concern. For the special case when the amplifier is tuned to the vehicle frequency, the amplifier can improve the vehicle performance by serving as a tuned mass damper, as conventionally known. This case is of limited use since it does not allow us to target the bridge frequencies. Both bridge damping and vehicle speed are also assessed with their effects addressed.

scholarly journals Structural Responses of a Supertall Building Subjected to a Severe Typhoon at Landfall

2020 ◽  
Vol 10 (8) ◽  
pp. 2965 ◽  
Author(s):  
Zhi Li ◽  
Jiyang Fu ◽  
Yuncheng He ◽  
Zhen Liu ◽  
Jiurong Wu ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Measurements ◽  
Amplitude Dependence ◽  
Modal Shape ◽  
Stochastic Subspace Identification ◽  
Random Decrement Technique ◽  
Random Decrement ◽  
Combined Use ◽  
Structural Responses

Typhoon Mangkhut (1822) was one of the strongest tropical cyclones that ever impacted the south coast of China in past decades. During the passage of this typhoon, the structural health monitoring (SHM) system installed on a 303 m high building in this region worked effectively, and high-quality field measurements at nine height levels of the building were collected successfully, which provides a valuable opportunity to explore the dynamic properties of the building and the associated wind effects. In this study, the typhoon wind characteristics are presented first based on in-situ measurements at two sites. Acceleration responses of the building is then investigated, and the building’s serviceability is assessed against several comfort criteria. This study further focuses on the identification of modal parameters (i.e., natural frequency, damping ratio, and modal shape) via two methods: stochastic subspace identification (SSI) method and a method based on combined use of spectral analysis and random decrement technique (RDT). The good agreement between the two results demonstrates the effectiveness and the accuracy of the adopted methods. The obtained results are further compared with the stipulations in several technical codes as well as simulation results via finite element method to examine their performances in this real case. The amplitude dependence of natural frequencies and damping ratios of the studied building are also stressed.

Tendency of Damping Ratio of Floating Artificial Base by Experiment and Measurement

2005 ◽  
Author(s):  
Koichi Maruyoshi ◽  
Osamu Saijo
Keyword(s):  
Vibration Mode ◽  
Damping Ratio ◽  
Experimental Models ◽  
Radiation Damping ◽  
Elastic Behavior ◽  
Structural Damping ◽  
Floating Structure ◽  
Vibration Data ◽  
Random Decrement Technique ◽  
Random Decrement

It is important to estimate both added mass and radiation damping of floating artificial base, which is floating structure, in fluid-structure interaction problem. When a floating artificial base shows elastic behavior, its damping contains both structural damping and radiation damping. Therefore it is difficult to estimate the damping. We aimed to grasp tendencies of damping, when a floating artificial base shows elastic behavior, by both experiment and field measurement. The experimental modal analysis using elastic plate models was carried out and tendencies of damping ratio of experimental models were grasped. Besides, damping ratio of an existent floating artificial base was calculated from measured vibration data by the Random Decrement Technique (RDT). In our experimental results, the damping ratio became larger value in lower vibration mode, and then it decreased in higher vibration mode. In higher vibration mode, we could not confirm radiation damping. It is thought that structural damping accounts for nearly all of obtained damping ratio. Consequently, it is appropriate that damping ratio of the floating artificial base is evaluated as Rayleigh type damping.

Contact-Point Response for Modal Identification of Bridges by a Moving Test Vehicle

2018 ◽  
Vol 18 (05) ◽  
pp. 1850073 ◽  
Author(s):  
Y. B. Yang ◽  
Bin Zhang ◽  
Yao Qian ◽  
Yuntian Wu
Keyword(s):  
Finite Element ◽  
Closed Form ◽  
Frequency Response Function ◽  
Contact Point ◽  
Modal Identification ◽  
Mode Shapes ◽  
Test Vehicle ◽  
Closed Form Solutions ◽  
Road Surfaces ◽  
Vehicle Response

The response of the contact point of the vehicle with the bridge, rather than the vehicle itself, is proposed for modal identification of bridges by a moving test vehicle. To begin, approximate closed-form solutions were derived for the vehicle and contact-point responses, and they were verified by finite element solutions. The contact-point acceleration is born to be free of the vehicle frequency, an annoying effect that may overshadow the bridge frequencies in case of rough surface. From the frequency response function (FRF) of the vehicle with respect to the contact point, it was shown that the contact-point response generally outperforms the vehicle response in extracting the bridge frequencies because it could identify more frequencies. In the numerical simulations, the contact-point response was compared with the vehicle response for various scenarios. It is concluded that in each case, say, for varying vehicle speeds or frequencies, for smooth or rough road surfaces, with or without existing traffic, the contact-point response outperforms the vehicle response in extracting either the frequencies or mode shapes of the bridge.

Random Decrement Technique Based on the Sampling Methods

2011 ◽  
Vol 243-249 ◽  
pp. 5413-5419
Author(s):  
Chuan Xiong Zhang ◽  
Wen Hai Shi ◽  
Zheng Nong Li
Keyword(s):  
Sampling Method ◽  
Sampling Methods ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Structural System ◽  
Random Decrement Technique ◽  
Linear Dynamic ◽  
Random Decrement ◽  
Effective Use

This paper presents the random decrement (RD) technique based on the sampling method for parameter identification of linear dynamic system. The development of RD technique was elaborated briefly in the aspects of identifying the dynamic properties, and then this paper summarized the corresponding parameters recognition problems due to the quantity and quality of measured sampling segments. Detailed analysis of two kinds of sampling method (the probability-proportional-to-size and two-stage sampling) is conducted to investigate its adaptation range in extracting RD signatures. The results of two simulated examples indicates that in view of the different vibration parameter recognition situation, the above provided RD technique based on different sampling methods could improve the quality of RD signature obviously, and lead to a quite accurate frequency and the damping ratio of structural system under the effective use of all measured sampling segments.

scholarly journals A Feature Extraction Method Based on VMD and RDT and Its Application in Engine Crankshaft Bearing Fault

2018 ◽  
Author(s):  
Gang Ren ◽  
Jide Jia ◽  
Jianmin Mei ◽  
Xiangyu Jia ◽  
Jiajia Han
Keyword(s):  
Feature Extraction ◽  
Extraction Method ◽  
Random Noise ◽  
Permutation Entropy ◽  
Noise Robustness ◽  
Feature Extraction Method ◽  
Bearing Fault ◽  
Random Decrement Technique ◽  
Mode Decomposition ◽  
Random Decrement

The vibration signal of the engine contains strong background noise and many kinds of modulating components, which is difficult to diagnose. Variational mode decomposition (VMD) is a recently introduced adaptive signal decomposition algorithm with a solid theoretical foundation and good noise robustness compared with empirical mode decomposition (EMD). VMD can effectively avoid endpoint effect and modal aliasing. However, VMD cannot effectively eliminate the random noise in the signal, so the random decrement technique is introduced to solve the problem. Based on the crankshaft bearing fault simulation experiment, the four kinds of wear state vibration signals are decomposed by VMD, and the modal components with smaller permutation entropy are selected as fault components. Then the fault component is processed by the random decrement technique, and the Hilbert envelope spectrum of the fault component is obtained. Compared with the fault feature extraction method based on EMD and EEMD, the feature extraction results of the proposed method are better than those of the above two methods. The simulation analysis and the simulation test of the crankshaft bearing fault verify the effectiveness of the proposed method.

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