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.

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.

Operational Modal Analysis of Broaching Machine

2012 ◽  
Vol 159 ◽  
pp. 170-175
Author(s):  
Lv Gao Lin ◽  
Shen Shun Ying ◽  
Shu Qiong Chen ◽  
Xiao Tian Lv
Keyword(s):  
Cutting Force ◽  
Natural Frequency ◽  
Fundamental Frequency ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Modal Parameters ◽  
Modal Shape ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Cutting Velocity

Modal parameters for LG51SH broaching machine from operational responses are studied to examine the dynamic properties of mechanical structure. The operational modal is analyzed using PolyMAX method with responsive data of key point in broaching machine, which is excited in practical broaching operation and tested by LMS SCADAIII-105 system. The identified steady state modal, representative modal shape, modal damping ratio and natural frequency in broaching are presented. The test and analysis result shows that there are natural frequency of 38Hz and 192Hz, which are close to multiple of the fundamental frequency of cutting force in broaching, 6Hz, therefore, reasonable cutting velocity should be adopted to void producing fundamental frequency of cutting force in broaching.

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.

Identification of modal parameters from non-stationary responses of high-rise buildings

2021 ◽  
pp. 136943322110339
Author(s):  
Lunhai Zhi ◽  
Feng Hu ◽  
Qiusheng Li ◽  
Zhixiang Hu
Keyword(s):  
Damping Ratio ◽  
Modal Identification ◽  
Frame Structure ◽  
Modal Parameters ◽  
Strong Wind ◽  
Modal Parameter ◽  
Civil Structures ◽  
High Rise ◽  
Random Decrement Technique ◽  
Structural Responses

A key issue in the control, health monitoring, and condition assessment of civil structures is the estimation of structural modal parameters based on measured structural responses. However, field measurements of structural responses from civil structures under strong wind or earthquake excitations usually exhibit non-stationary feature and therefore cannot be adequately deal with by traditional modal identification methods. In this study, a novel procedure is integrated for modal parameter identification of civil structures from non-stationary structural responses on the basis of the variational mode decomposition (VMD) technique. First, the VMD algorithm is applied to decompose measured vibration signals into individual mode components. Then, the random decrement technique (RDT) is employed to obtain free vibration response of each mono component. Next, normalized Hilbert transform (NHT) is used to estimate modal natural frequency and damping ratio. The performance of the developed approach is evaluated using simulated non-stationary responses of a frame structure, and the identified results are validated. The effects of crucial factors such as levels of noise involved in structural response and data length on the modal parameter estimations are examined through detailed parametric study. Furthermore, the approach is applied to modal identification based on field measured non-stationary responses of a high-rise building during Typhoon Nida. The case study illustrates that the integrated method is an efficient tool for estimating the modal parameters of civil structures from non-stationary structural responses.

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.

scholarly journals The use of random decrement technique for long term health monitoring of concrete structures

2021 ◽  
Author(s):  
Rana Morsy
Keyword(s):  
Damage Detection ◽  
Health Monitoring ◽  
Nuclear Power ◽  
Concrete Beams ◽  
Dynamic Properties ◽  
Offshore Platforms ◽  
Random Decrement Technique ◽  
Power Stations ◽  
Random Decrement ◽  
Detection Approach

This investigation deals with the development of an advanced strategy for Structural Health Monitoring (SHM) of concrete beams and girders for important structures such as bridges, offshore platforms and nuclear power stations using smart monitoring systems, including an effective diagnostic approach for damage detection with a reliability-based performance ranking. The proposed strategy can be classified into four main sections: identification of the existence of damage, determination the localization of the damage, estimation the level of damage, and assessing the seriousness of the damage regarding the structure’s service life. Random Decrement (RD) is an accurate dynamic analysis diagnostic tool that has been used effectively for SHM; the technique has been used within various fields in mechanical, aerospace, and, recently, civil engineering. The damage detection approach is based on the RD technique. A theoretical, numerical, and experimental investigation has been conducted on concrete beams using the RD technique for damage detection in terms of changes in the dynamic properties and used at successive multiple points under certain leading point conditions to determine the location of damage through the development of the Multi-Channel Random Decrement (MCRD).

scholarly journals The use of random decrement technique for long term health monitoring of concrete structures

2021 ◽  
Author(s):  
Rana Morsy
Keyword(s):  
Damage Detection ◽  
Health Monitoring ◽  
Nuclear Power ◽  
Concrete Beams ◽  
Dynamic Properties ◽  
Offshore Platforms ◽  
Random Decrement Technique ◽  
Power Stations ◽  
Random Decrement ◽  
Detection Approach

This investigation deals with the development of an advanced strategy for Structural Health Monitoring (SHM) of concrete beams and girders for important structures such as bridges, offshore platforms and nuclear power stations using smart monitoring systems, including an effective diagnostic approach for damage detection with a reliability-based performance ranking. The proposed strategy can be classified into four main sections: identification of the existence of damage, determination the localization of the damage, estimation the level of damage, and assessing the seriousness of the damage regarding the structure’s service life. Random Decrement (RD) is an accurate dynamic analysis diagnostic tool that has been used effectively for SHM; the technique has been used within various fields in mechanical, aerospace, and, recently, civil engineering. The damage detection approach is based on the RD technique. A theoretical, numerical, and experimental investigation has been conducted on concrete beams using the RD technique for damage detection in terms of changes in the dynamic properties and used at successive multiple points under certain leading point conditions to determine the location of damage through the development of the Multi-Channel Random Decrement (MCRD).

scholarly journals A System Identification-Based Damage-Detection Method for Gravity Dams

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Masoud Mirtaheri ◽  
Mojtaba Salkhordeh ◽  
Masoud Mohammadgholiha
Keyword(s):  
Wavelet Transform ◽  
Dynamic Properties ◽  
Structural Response ◽  
Cost Effective ◽  
The Body ◽  
Mode Shapes ◽  
Damage Scenarios ◽  
Hilbert Huang Transform ◽  
Random Decrement Technique ◽  
Random Decrement

Dams are essential infrastructures as they provide a range of economic, environmental, and social benefits to the local populations. Damage in the body of these structures may lead to an irreparable disaster. This paper presents a cost-effective vibration-based framework to identify the dynamic properties and damage of the dams. To this end, four commonly occurred damage scenarios, including (1) damage in the neck of the dam, (2) damage in the toe of the structure, (3) simultaneous damage in the neck and the toe of the dam, and (4) damage in the lifting joints of the dam, are considered. The proposed method is based on processing the acceleration response of a gravity dam under ambient excitations. First, the random decrement technique (RDT) is applied to determine the free-vibration of the structure using the structural response. Then, a combined method based on Hilbert–Huang Transform (HHT) and Wavelet Transform (WT) is presented to obtain the dynamic properties of the structure. Next, the cubic-spline technique is used to make the mode shapes differentiable. Finally, Continuous Wavelet Transform (CWT) is applied to the residual values of mode shape curvatures between intact and damaged structures to estimate the damage location. In order to evaluate the efficiency of the proposed method in field condition, 10% noise is added to the structural response. Results show promising accuracy in estimating the location of damage even when the structure is subjected to simultaneous damage in different locations.

scholarly journals Evaluation of Dynamic Properties of Sodium-Alginate-Reinforced Soil Using A Resonant-Column Test

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2743
Author(s):  
Seongnoh Ahn ◽  
Jae-Eun Ryou ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
...  
Keyword(s):  
Shear Modulus ◽  
Sodium Alginate ◽  
Shear Failure ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Reinforced Soil ◽  
Resonant Column ◽  
Column Test ◽  
Alginate Solution ◽  
Resonant Column Test

Ground reinforcement is a method used to reduce the damage caused by earthquakes. Usually, cement-based reinforcement methods are used because they are inexpensive and show excellent performance. Recently, however, reinforcement methods using eco-friendly materials have been proposed due to environmental issues. In this study, the cement reinforcement method and the biopolymer reinforcement method using sodium alginate were compared. The dynamic properties of the reinforced ground, including shear modulus and damping ratio, were measured through a resonant-column test. Also, the viscosity of sodium alginate solution, which is a non-Newtonian fluid, was also explored and found to increase with concentration. The maximum shear modulus and minimum damping ratio increased, and the linear range of the shear modulus curve decreased, when cement and sodium alginate solution were mixed. Addition of biopolymer showed similar reinforcing effect in a lesser amount of additive compared to the cement-reinforced ground, but the effect decreased above a certain viscosity because the biopolymer solution was not homogeneously distributed. This was examined through a shear-failure-mode test.

scholarly journals Identification of Dynamic Parameters of Pedestrian Walking Model Based on a Coupled Pedestrian–Structure System

2021 ◽  
Vol 11 (14) ◽  
pp. 6407
Author(s):  
Huiqi Liang ◽  
Wenbo Xie ◽  
Peizi Wei ◽  
Dehao Ai ◽  
Zhiqiang Zhang
Keyword(s):  
Negative Correlation ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Testing ◽  
The Body ◽  
Structural Vibration ◽  
Pedestrian Dynamics ◽  
Structure Interaction ◽  
Mass Spring ◽  
Stiffness And Damping

As human occupancy has an enormous effect on the dynamics of light, flexible, large-span, low-damping structures, which are sensitive to human-induced vibrations, it is essential to investigate the effects of pedestrian–structure interaction. The single-degree-of-freedom (SDOF) mass–spring–damping (MSD) model, the simplest dynamical model that considers how pedestrian mass, stiffness and damping impact the dynamic properties of structures, is widely used in civil engineering. With field testing methods and the SDOF MSD model, this study obtained pedestrian dynamics parameters from measured data of the properties of both empty structures and structures with pedestrian occupancy. The parameters identification procedure involved individuals at four walking frequencies. Body frequency is positively correlated to the walking frequency, while a negative correlation is observed between the body damping ratio and the walking frequency. The test results further show a negative correlation between the pedestrian’s frequency and his/her weight, but no significant correlation exists between one’s damping ratio and weight. The findings provide a reference for structural vibration serviceability assessments that would consider pedestrian–structure interaction effects.

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