Experimental investigation on coupled vibration characteristics of wind-excited tall buildings

2020 ◽  
Vol 23 (9) ◽  
pp. 1948-1959
Author(s):  
Wei Hao ◽  
Qingshan Yang
Keyword(s):  
Fourier Transform ◽  
Wind Speed ◽  
Complex Geometry ◽  
Damping Ratio ◽  
Time History ◽  
Tall Buildings ◽  
Vibration Characteristics ◽  
Coupled Vibration ◽  
Coupled Response ◽  
Standard Deviations

Contemporary tall buildings constructed with high-strength and light-weight materials become relatively flexible and lightly damped, and the fluctuating wind forces acting on the buildings may cause excessive vibrations, especially at the vicinity of vortex lock-in wind speed, where the natural frequency of the buildings is synchronized with the vortex shedding frequency. Given that tall buildings tend to be designed with unconventional shape involving innovative structural systems and complex geometry, the correlations among three force components may accentuate building motions significantly. In this study, the coupling characteristics between the alongwind and crosswind vibrations of tall buildings with symmetric shape and distinct natural frequencies in two directions are investigated through a serious of aeroelastic model tests. The response standard deviations and power spectral densities are calculated, respectively, based on the displacement data measured at multiple levels of wind speed and structural damping ratio. Then the coupled response is extracted from the alongwind response in frequency domain through Fourier transform and inverse Fourier transform, and the standard deviations of the coupled response are calculated based on time history analysis, which are compared with that of the crosswind response to investigate the relationship between the alongwind and crosswind motions. Moreover, the amplitude ratio, phase difference, and coherence of the response components are also calculated for further discussing the coupling effects and examining the coupled vibration characteristics.

Response Law and Influencing Factors of the Soil under Action of Pile Driving Vibration Based on Midas/GTS

2013 ◽  
Vol 353-356 ◽  
pp. 979-983
Author(s):  
Dong Zhang ◽  
Jing Bo Su ◽  
Hui De Zhao ◽  
Hai Yan Wang
Keyword(s):  
Damping Ratio ◽  
Large Diameter ◽  
Time History ◽  
Pile Driving ◽  
Analysis Model ◽  
Vibration Load ◽  
History Analysis ◽  
Study Results ◽  
Propagation Law ◽  
Dynamic Time

Due to the upgrade and reconstruct of a high-piled wharf, the piling construction may cause the damage of the large diameter underground pipe of a power plant nearby. For this problem, a dynamic time-history analysis model was established using MIDAS/GTS program. Based on the analysis of the pile driving vibration and its propagation law, some parameters, such as the modulus of the soil, the Poissons ratio of soil, the action time of vibration load and the damping ratio of the soil that may have an effect on the response law of the soil, were studied. The study results not only serve as an important inference to the construction of this case, but also accumulate experience and data for other similar engineering practices.

A Family of Efficient Sloshing Liquid Dampers for Suppression of Wind-Induced Instabilities

2003 ◽  
Vol 9 (3-4) ◽  
pp. 361-386 ◽  
Author(s):  
V. J. Modi ◽  
A. Akinturk ◽  
W. Tse
Keyword(s):  
Energy Dissipation ◽  
High Efficiency ◽  
Damping Ratio ◽  
Real Life ◽  
Wind Tunnel Test ◽  
Tall Buildings ◽  
Two Phases ◽  
Liquid Dampers ◽  
Obstacle Geometry ◽  
Floating Particles

Bluff structures in the form of tall buildings, smokestacks, control towers, bridges, etc., are susceptible to vortex resonance and galloping type of instabilities. One approach to vibration control of such systems is through energy dissipation using sloshing liquid dampers. In this paper we focus on enhancing the energy dissipation efficiency of a rectangular liquid damper through the introduction of two-dimensional obstacles as well as floating particles. The investigation has two phases. To begin with, a parametric free vibration study aimed at the optimization of the obstacle geometry is undertaken to arrive at configurations promising increased damping ratio and hence higher energy dissipation. The study is complemented by an extensive wind tunnel test program, which substantiates the effectiveness of this class of damper in suppressing both vortex resonance and galloping type of instabilities. Simplicity of design, ease of implementation, minimal maintenance, reliability as well as high efficiency make such liquid dampers quite attractive for real-life applications.

scholarly journals Evaluation of bearing capacity of reinforced concrete box ribbed arch bridge based on dynamic load test

2021 ◽  
Vol 233 ◽  
pp. 01047
Author(s):  
Mao He ◽  
Xin Fu ◽  
Shunchao Chen
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Load ◽  
Damping Ratio ◽  
Vibration Characteristics ◽  
Load Test ◽  
Driving Safety ◽  
Original Material ◽  
Arch Bridge ◽  
Dynamic Load Test ◽  
And Function

Dynamic load test is to measure the natural vibration characteristics of the bridge structure or the forced vibration characteristics under dynamic load, and to evaluate the driving performance, driving safety and comfort of the bridge through dynamic load test. In order to evaluate the stress state and working performance of a reinforced concrete box-ribbed arch bridge, the load test of the bridge is carried out. Dynamic load test is used to test the inherent fundamental frequency, damping ratio and impact coefficient of the bridge through pulsation test and sports car test. Through the experiment with the key parts of the stress (strain) and displacement load and other important data, through analysis and study, the comprehensive analysis of the phenomenon of calculation and test, a comprehensive performance evaluation structure and function whether meet the design requirements, to provide technical basis for the safety of the bridge operation, and provide the original material for the bridge maintenance and management in the future.

Response of higherise buildings to ground motion from underground nuclear detonations

1969 ◽  
Vol 59 (6) ◽  
pp. 2343-2370
Author(s):  
John A. Blume
Keyword(s):  
Ground Motion ◽  
Las Vegas ◽  
Spectral Response ◽  
Vertical Plane ◽  
Time History ◽  
Tall Buildings ◽  
Response Spectra ◽  
Statistical Parameters ◽  
Typical Data ◽  
Earthquake Design

abstract Typical data obtained thus far in the AEC nuclear test program on the response of highrise Las Vegas buildings to ground motion from distant nuclear events including Boxcar and Benham are presented, together with measured building response to distant earthquakes and to wind gusts. Major variations in response spectra are shown over the city for a specific event, from period band to period band at the same location for different events, and statistical parameters are shown for the randomness of spectral response. The peak response of tall buildings is shown for the top levels in translation and in orbital motion, and in the vertical plane with simultaneous multi-level measurements. The variation of peak modal response is shown with elapsed time, modal combinations are noted, and an example of time-history computed response is compared to measured response. It is shown that highrise Las Vegas buildings respond to ground motion with considerable amplification, that the fundamental modes tend to dominate the peak responses although there are exceptions, that there can be significant modification of loading conditions because of simultaneous motion in the two horizontal axes even though a building is symmetric, and that some building periods vary with amplitude and history of non-damaging prior response while others do not. In general there are indications that code earthquake design criteria are by no means conservative.

scholarly journals Determination of Fat, Protein, and Lactose in Raw Milk by Fourier Transform Infrared Spectroscopy and by Analysis with a Conventional Filter-Based Milk Analyzer

1996 ◽  
Vol 79 (3) ◽  
pp. 711-717 ◽  
Author(s):  
Dominique Lefier ◽  
Remy Grappin ◽  
Sylvie Pochet
Keyword(s):  
Fourier Transform ◽  
Fourier Transform Infrared ◽  
Raw Milk ◽  
Milk Composition ◽  
Milk Samples ◽  
Bulk Milk ◽  
Different Seasons ◽  
Standard Deviations ◽  
True Protein ◽  
Single Calibration

Abstract The accuracy of fat, crude protein (CP), true protein (TP), and lactose determinations of raw milk by Fourier transform infrared (FTIR) spectroscopy and by analysis with a conventional filter-based milk analyzer was assessed in 6 trials performed over a 10-month period. At each trial, 30 bulk milk samples collected from 15 European countries and 11 reconstituted milks made from raw milk components were analyzed. When calibrations were performed with reconstituted milks at each trial, accuracy standard deviations for fat, CP, TP, and lactose were, respectively, 0.050,0.048,0.035, and 0.076 g/100 g for the filter instrument and 0.047, 0.046,0.042, and 0.065 g/100 g for the FTIR instrument. When a single calibration was made instead of calibrations at each trial, accuracy standard deviations increased for the filter instrument to 0.130, 0.119,0.121, and 0.083 for fat, CP, TP, and lactose, respectively, and for the FTIR instrument to 0.082, 0.053,0.044, and 0.084 g/100 g. Because the FTIR instrument provides more spectral information related to milk composition than does the filter instrument, single-calibration FTIR analysis of milk samples collected in different seasons is more accurate. Using reconstituted milks, prepared such that there is no correlation between fat, CP, and lactose, provides a more robust calibration than using genuine bulk milk, especially when milks with unusual composition are analyzed.

scholarly journals An investigation into the mechanical damping characteristics of catenary contact wires and their effect on aerodynamic galloping instability

2003 ◽  
Vol 217 (2) ◽  
pp. 63-71 ◽  
Author(s):  
M. T. Stickland ◽  
T. J. Scanlon ◽  
I. A. Craighead ◽  
J Fernandez
Keyword(s):  
Wind Speed ◽  
East Coast ◽  
Damping Ratio ◽  
Friction Damper ◽  
Wind Speeds ◽  
Damping Characteristics ◽  
Damped Oscillation ◽  
Mechanical Damping ◽  
The Uk ◽  
Wire System

Measurement of the damped oscillation of a section of the UK East Coast Main Line (ECML) catenary/contact wire system was undertaken, and the natural frequency and mechanical damping were found to be 1.4Hz and 0.05 respectively. This information was used to assess the effect of increasing the mechanical damping ratio on the susceptibility of the system to an aerodynamic galloping instability. The section of line tested was known to gallop at wind speeds of approximately 40 mile/h, and theoretical and experimental work verified this. A friction damper arm was designed and three units were fitted to the section of line affected. The introduction of increased mechanical damping was found to raise the mechanical damping coefficient of the line to between 0.095 and 0.18, and the mathematical analysis produced a theoretical wind speed for galloping oscillation of between 75 and 141 mile/h respectively. For over a year since the units were fitted, no problems with galloping instability have been observed.

Structural behaviour of water sloshing damper with embossments subject to random excitation

2004 ◽  
Vol 31 (1) ◽  
pp. 120-132 ◽  
Author(s):  
Young-Kyu Ju
Keyword(s):  
Standard Deviation ◽  
Vibration Control ◽  
Structural Model ◽  
Structural Characteristics ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Random Excitation ◽  
Water Tank ◽  
Structural Behaviour ◽  
Peak Displacement

To improve the serviceability of tall buildings, several types of vibration control systems have been developed. The tuned liquid damper (TLD) has advantages, such as simple adjustment of natural frequency, easy installation, and low maintenance. Since water tanks at the top of tall buildings can be directly modeled as a TLD system, it is more practical than any other vibration control system in Korea. Since most of the tanks in Korea have embossments on the wall, the structural characteristics are different from those of tanks used in other countries. As the damping ratio of the TLD depends on several factors, such as the magnitude and frequency of applied load, the shape of the tank, wall roughness, and so forth, it is difficult to evaluate the control performance of the tank exactly. In this study, the characteristics of the water sloshing damper with embossments (WSDE) are evaluated and the equation for equivalent damping ratio is proposed. To clarify the damping effect of a high-rise building with a damping device subject to random excitation, an experiment of a coupled structural model with a water tank was conducted. The parameters were mass ratio of water to model structure, number of wire screens, and shape factor of the water tank. The peak displacement, acceleration response, and standard deviation of the experimental results are analyzed. The coupled structural model with a water tank shows lower maximum and standard deviation responses than those of the structural model alone.Key words: water sloshing damper with embossment, vibration control, structural test, tall buildings.

Increasing Damping Ratios in a Tuned Liquid Damper Using Damping Bars

2007 ◽  
Vol 353-358 ◽  
pp. 2652-2655 ◽  
Author(s):  
Ki Pyo You ◽  
Young Moon Kim ◽  
Cheol Min Yang ◽  
Dong Pyo Hong
Keyword(s):  
Passive Control ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Shaking Table ◽  
Water Tank ◽  
Tuned Liquid Damper ◽  
Structural Vibrations ◽  
Existing Structures ◽  
Long Time ◽  
Wind Induced Vibration

Wind-induced vibration of tall buildings have been of interest in engineering for a long time. Wind-induced vibration of a tall building can be most effectively controlled by using passive control devices. The tuned liquid damper(TLD) is kind of a passive mechanical damper, which relies on the sloshing liquid in a rigid tank. TLD has been successfully employed in practical mitigation of undesirable structural vibrations because it has several potential advantages: low costs, easy installation in existing structures, and effectiveness even against small-amplitude vibrations. Shaking table experiments were conducted to investigate the characteristics of the shallow water sloshing motion in a rectangular tank. To increase the damping ratio of the rectangular water tank, triangle sticks were installed at the bottom of water tank. This installation increased the damping ratio by amaximum of 40-70%.

Non-Linear Coupled Dynamics of a Flexible Propeller-Shaft System Supported by Water Film Bearings

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Chang-Gang Lin ◽  
Ming-Song Zou ◽  
Can Sima ◽  
Li-Bo Qi ◽  
Yue Yu
Keyword(s):  
Nonlinear Vibration ◽  
Damping Ratio ◽  
Water Film ◽  
Vibration Characteristics ◽  
Superposition Method ◽  
Propeller Shaft ◽  
Chaotic Motions ◽  
Mode Superposition Method ◽  
Shaft System ◽  
Slice Method

Abstract A slice method to determine the boundary conditions between the stern bearing and shaft by dividing the journal in the stern bearing into several slice elements along the axial direction is proposed for the first time. A comprehensive finite element model considering the nonlinear force of the water film and the flexibility of the propeller blade is established for a propeller-shaft system. The long bearing approximation is adopted to calculate the pressure distribution around each journal element in the stern bearing. The mode superposition method is employed. The nonlinear equation of motion is solved iteratively using the Newmark method. A parametric study is implemented to analyze the nonlinear vibration characteristics of the system. It is shown that the real motion state of the journal in the stern bearing can be simulated more precisely by the slice method proposed. The responses of the system alternate among period-one, quasi-periodic, multi-periodic, and chaotic motions as the rotating speed increases. The damping ratio has a significant effect on the dynamic characteristics of the propeller-shaft system. The motion of the system is unstable when the damping ratio is very small. At this time, the modes of the flexible propeller blades can be excited readily. The slice method, which can also be extensively used in similar rotor-bearing systems in the engineering field, is very simple and efficient to analyze the nonlinear vibration characteristics of a flexible propeller-shaft system supported by water film bearings.

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