Dynamic Forces of Swaying Human and Responses of Temporary Demountable Grandstand Based on Experiment and Simulation

Shock and Vibration ◽

10.1155/2018/2791491 ◽

2018 ◽

Vol 2018 ◽

pp. 1-22

Author(s):

Lin He ◽

Jian Yuan ◽

Feng Fan ◽

Cong Liu

Keyword(s):

Force Plate ◽

Dynamic Responses ◽

Experimental Program ◽

Force Model ◽

Lateral Vibration ◽

Structural Dynamic ◽

Important Research Topic ◽

Dynamic Forces ◽

Semiempirical Formula ◽

Stiffness And Damping

Modern temporary demountable structures must be designed to withstand the dynamic forces which generated by crowd occupants. The human forces and that cause the dynamic responses of structure have become an important research topic. In this paper, the human swaying forces and responses of temporary demountable grandstand are studied through an experimental program. The dynamic forces that were induced by participants who have swayed 0.5–1.8 Hz are recorded by a triaxial human biomechanics force plate, and the structural dynamic responses of a temporary grandstand occupied twenty swaying human are investigated. The constraint parameters of swaying force model which derives from a semiempirical formula are developed and can be represented for crowd. Crowd can able to induce excessive lateral vibration of structure due to the lower frequency of temporary grandstand and make them in panic. The dynamic responses of a large temporary grandstand are predicted by finite element method, and the results show that a person was considered as a load with stiffness and damping, and the structural lateral dynamic responses are higher than the model of person just only considered as load.

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Investigation of Dynamic Responses and Vibration Serviceability of Temporary Grandstands by a 3 DOF Interaction Model due to Swaying Motion

Shock and Vibration ◽

10.1155/2022/6217148 ◽

2022 ◽

Vol 2022 ◽

pp. 1-32

Author(s):

Jian Yuan ◽

Suhui Yu ◽

Cong Liu ◽

Chengqiang Gao ◽

Wei Wang ◽

...

Keyword(s):

Damping Ratio ◽

Force Plate ◽

Interaction Model ◽

Reference Value ◽

Experimental Results ◽

Shaking Table ◽

Dynamic Responses ◽

Random Waves ◽

Lateral Direction ◽

Structural Dynamic

Excessive vibration of temporary grandstand by the crowd has lateral rhythmic motions, which attracted increasing attention in the recent years. This paper focuses on experiments where a temporary grandstand occupied by 20 participants is oscillated by a shaking table with a series of random waves and the crowd-induced rhythmic swaying motions at lateral direction, respectively. The dynamic forces that were induced by participants who have swayed at 0.5–1.8 Hz are recorded by a tri-axial human biomechanics force plate. A new relationship between the annoyance rate and structural acceleration at logarithmic coordinate is investigated and proposed, and the swaying load model is given. Based on these experimental results, a simplified three-degree-of-freedom lumped dynamic model of the joint human–structure system is reinterpreted. Afterwards, combined with a feasible range of crowd/structural dynamic parameters, a series of interaction models are analyzed, the vibration dose value (VDV) of the structure is obtained and discussed, and the notable parameters for interaction model are predicted. The experimental results show that the lateral serviceability limit is 1.29 m/s1.75 and the upper boundary is 2.32 m/s1.75. The dynamic response of model indicated that the VDV of structure will be decreased with increasing the mass of static crowd and damping ratio of the dynamic crowd. The max response of the model is α ≤ 0.6, f2 = 1.8 Hz or α > 0.6, f2 = 1.5 Hz or f1 = 2.5–3.5 Hz. It may be used as a reference value in vibration safety and serviceability assessment of TDGs, to estimate realistically the vibration response on the occasions when the crowds are swaying.

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Mechanistic Force Modeling for Broaching Process

International Journal of Manufacturing Engineering ◽

10.1155/2014/485712 ◽

2014 ◽

Vol 2014 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Raghavendra Kamath Cholpadi ◽

Appu Kuttan

Keyword(s):

Dynamic Model ◽

Natural Frequency ◽

Experimental Work ◽

Model Parameters ◽

Force Model ◽

Damping Coefficients ◽

Force Modeling ◽

Dynamic Forces ◽

Stiffness And Damping ◽

Experimental Corroboration

There is a demand for mechanistic force model that can predict and simulate the broaching process. In this paper, an attempt has been made for mechanistic force modeling of the broaching operation and experimental corroboration with the simulated result. The stiffness and damping coefficients for dynamic model are computed from the natural frequency of the broaching system and actual damped natural frequency has been obtained experimentally. Experimental work has been carried to compute the dynamic model parameters such as mass, stiffness, and damping coefficients. The simulated dynamic forces are illustrated graphically and are closely in agreement with the results obtained through manual broaching process.

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A New Structural Dynamic Model for Pump Mechanical Seals Vibration Analysis Incorporating Squeeze Motion of O-Ring Seals and General Dynamic Motion of the Pump Housing and the Pump Shaft

Journal of Tribology ◽

10.1115/1.4038867 ◽

2018 ◽

Vol 140 (6) ◽

Cited By ~ 1

Author(s):

Dara Childs

Keyword(s):

Reaction Force ◽

Excitation Frequency ◽

Nonlinear Function ◽

Force Model ◽

Mechanical Seals ◽

Structural Dynamic ◽

Damping Matrix ◽

Stiffness Matrices ◽

Force Components ◽

Stiffness And Damping

New models are developed for flexibly mounted stator (FMS) and flexibly mounted rotor (FMR) mechanical seals that incorporate the radial reaction force components produced by supporting O-rings due to relative squeezing motion across the O-rings. Supporting data come from tests done in relation to O-ring supports for ball bearing races. The reaction-force model is linear but a nonlinear function of excitation frequency. The model accounts for the axial displacement doz of the O-ring from the mass center of the seal stator (FMS configuration) or seal rotor (FMR configuration), which couples the radial and pitch–yaw motion of the model's stiffness and damping matrices. Greens' coned-face-seal model is used to define the reaction moment arising across the seal faces via stiffness and damping matrices. The damping matrix does not coincide with Green's. His is constant; the matrix developed here contains terms that are harmonic at twice theprecession frequency. When averaged over one precession cycle, the new average damping matrix coincides with Green's result. When the averaged damping matrix is used, the resultant model is linear. However, because of the viscoelastic reaction-force and reaction-moment models used for the O-ring coefficients, most of the stiffness and damping matrices are strong functions of the assumed precession frequency. The new FMR model contains a skew-symmetric stiffness matrix due to the O-ring damping terms. In rotordynamics, skew symmetric stiffness matrices due to internal damping in the rotor can lead to rotordynamic instabilities.

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Wind tunnel tests and dynamic analysis of wind-induced response of a transmission tower on a hill

Advances in Structural Engineering ◽

10.1177/13694332211033960 ◽

2021 ◽

pp. 136943322110339

Author(s):

Jian Guo ◽

Changliang Xiao ◽

Jiantao Li

Keyword(s):

Wind Tunnel ◽

Wind Field ◽

Dynamic Responses ◽

Interactive Effects ◽

Induced Response ◽

Transmission Tower ◽

Structural Dynamic ◽

Wind Tunnel Tests ◽

Hill Slope ◽

The Hill

A hill with a lattice transmission tower presents complex wind field characteristics. The commonly used computational fluid dynamics (CFD) simulations are difficult to analyze the wind resistance and dynamic responses of the transmission tower due to structural complexity. In this study, wind tunnel tests and numerical simulations are conducted to analyze the wind field of the hill and the dynamic responses of the transmission tower built on it. The hill models with different slopes are investigated by wind tunnel tests to measure the wind field characteristics, such as mean speed and turbulence intensity. The study shows that the existence of a transmission tower reduces the wind speed on the leeward slope significantly but has little effect on the windward slope. To study the dynamic behavior of the transmission tower, a hybrid analysis procedure is used by introducing the measured experimental wind information to the finite element tower model established using ANSYS. The effects of hill slope on the maximum displacement response of the tower are studied. The results show that the maximum value of the response is the largest when the hill slope is 25° compared to those when hill slope is 15° and 35°. The results extend the knowledge concerning wind tunnel tests on hills of different terrain and provide a comprehensive understanding of the interactive effects between the hill and existing transmission tower regarding to the wind field characteristics and structural dynamic responses.

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Model Test and Numerical Analysis of an Offshore Bottom Fixed Pentapod Wind Turbine Under Seismic Loads

Volume 6: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2016-54499 ◽

2016 ◽

Cited By ~ 1

Author(s):

Wenhua Wang ◽

Zhen Gao ◽

Xin Li ◽

Torgeir Moan ◽

Bin Wang

Keyword(s):

Wind Turbine ◽

Wind Wave ◽

Seismic Analysis ◽

Wind Farms ◽

Dynamic Responses ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Test Model ◽

Structural Dynamic ◽

Load Conditions

In the last decade the wind energy industry has developed rapidly in China, especially offshore. For a water depth less than 20m, monopile and multi-pile substructures (tripod, pentapod) are applied widely in offshore wind farms. Some wind farms in China are located in high seismicity regions, thus, the earthquake load may become the dominant load for offshore wind turbines. This paper deals with the seismic behavior of an offshore wind turbine (OWT) consisting of the NREL 5MW baseline wind turbine, a pentapod substructure and a pile foundation of a real offshore wind turbine in China. A test model of the OWT is designed based on the hydro-elastic similarity. Test cases of different load combinations are performed with the environmental conditions generated by the Joint Earthquake, Wave and Current Simulation System and the Simple Wind Field Generation System at Dalian University of Technology, China, in order to investigate the structural dynamic responses under different load conditions. In the tests, a circular disk is used to model the rotor-nacelle system, and a force gauge is fixed at the center of the disk to measure the wind forces during the tests. A series of accelerometers are arranged along the model tower and the pentapod piles, and strain gauges glued on the substructure members are intended to measure the structural dynamic responses. A finite element model of the complete wind turbine is also established in order to compare the theoretical results with the test data. The hydro-elastic similarity is validated based on the comparison of the measured dynamic characteristics and the results of the prototype modal analysis. The numerical results agree well with the experimental data. Based on the comparisons of the results, the effect of the wind and sea loads on the structural responses subjected to seismic is demonstrated, especially the influence on the global response of the structure. It is seen that the effect of the combined seismic, wind, wave and current load conditions can not be simply superimposed. Hence the interaction effect in the seismic analysis should be considered when the wind, wave and current loads have a non-negligible effect.

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Identification of Viscously Damped Distributed Structural Dynamic Systems

13th Biennial Conference on Mechanical Vibration and Noise: Modal Analysis, Modeling, Diagnostics, and Control — Analytical and Experimental ◽

10.1115/detc1991-0365 ◽

1991 ◽

Author(s):

R. Chander ◽

M. Meyyappa ◽

S. Hanagud

Keyword(s):

Dynamic Systems ◽

Beam Theory ◽

Continuous Functions ◽

Model Parameters ◽

Unknown Parameters ◽

Structural Dynamic ◽

Domain Identification ◽

Forcing Function ◽

Cardinal Splines ◽

Stiffness And Damping

Abstract A frequency domain identification technique applicable to damped distributed structural dynamic systems is presented. The technique is developed for beams whose behavior can be modeled using the Euler-Bernoulli beam theory. External damping of the system is included by means of a linear viscous damping model. Parameters to be identified, mass, stiffness and damping distributions are assumed to be continuous functions over the beam. The response at a discrete number of points along the length of the beam for a given forcing function is used as the data for identification. The identification scheme involves approximating the infinite dimensional response and parameter spaces by using quintic B-splines and cubic cardinal splines, respectively. A Galerkin type weighted residual procedure, in conjunction with the least squares technique, is employed to determine the unknown parameters. Numerically simulated response data for an applied impulse load are utilized to validate the developed technique. Estimated values for the mass, stiffness and damping distributions are discussed.

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Road Vehicle-Bridge Interaction considering Varied Vehicle Speed Based on Convenient Combination of Simulink and ANSYS

Shock and Vibration ◽

10.1155/2018/1389628 ◽

2018 ◽

Vol 2018 ◽

pp. 1-14 ◽

Cited By ~ 1

Author(s):

Helu Yu ◽

Bin Wang ◽

Yongle Li ◽

Yankun Zhang ◽

Wei Zhang

Keyword(s):

Reaction Force ◽

Sudden Change ◽

Vertical Direction ◽

Dynamic Responses ◽

Force Model ◽

Vertical Acceleration ◽

Vehicle Speed ◽

Road Vehicle ◽

The Road ◽

Bridge Model

In order to cover the complexity of coding and extend the generality on the road vehicle-bridge iteration, a process to solve vehicle-bridge interaction considering varied vehicle speed based on a convenient combination of Matlab Simulink and ANSYS is presented. In this way, the road vehicle is modeled in state space and the corresponding motion equations are solved using Simulink. The finite element model for the bridge is established and solved using ANSYS. The so-called inter-history iteration method is adopted to realize the interaction between the vehicle model and the bridge model. Different from typical method of road vehicle-bridge interaction in the vertical direction, a detailed longitudinal force model is set up to take into account the effects of varied vehicle speed. In the force model, acceleration and braking of the road vehicle are treated differently according to their mechanical nature. In the case studies based on a simply supported beam, the dynamic performance of the road vehicle and the bridge under varied vehicle speeds is calculated and discussed. The vertical acceleration characteristics of the midpoint of beam under varied vehicle speed can be grouped into two periods. The first one is affected by the load transform between the wheels, and the other one depends on the speed amplitude. Sudden change of the vertical acceleration of the beam and the longitudinal reaction force are observed as the wheels move on or off the bridge, and the bridge performs different dynamic responses during acceleration and braking.

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Research on Stiffness and Damping Characteristics of Fixed Oily Porous Materials Joint Interface

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.422.575 ◽

2011 ◽

Vol 422 ◽

pp. 575-579

Author(s):

Chong Nian Qu ◽

Liang Sheng Wu ◽

Jian Feng Ma ◽

Yi Chuan Xiao

Keyword(s):

Porous Material ◽

Porous Materials ◽

Parallel Plate ◽

Joint Interface ◽

Force Model ◽

Equivalent Stiffness ◽

Contact State ◽

Damping Characteristics ◽

Stiffness And Damping ◽

Damping Model

In this document, using the anti-squeezed force model in the narrow parallel plate when fluid is squeezed, the equivalent stiffness and damping model is derived. It is further verified that it can increase the stiffness and damping while there are oil between the joint interfaces theoretically. Because the contact state of oily porous material can divide into liquid and solid parts, the document supposes that it is correct and effective to think the stiffness and damping of the two parts as shunt connection.

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