scholarly journals Experimental and Numerical Study on Dynamics of Two Footbridges with Different Shapes of Girders

2020 ◽  
Vol 10 (13) ◽  
pp. 4505 ◽  
Author(s):  
Anna Banas ◽  
Robert Jankowski
Keyword(s):  
Natural Vibration ◽  
Numerical Study ◽  
Numerical Results ◽  
Vibration Exciter ◽  
Structural Vibrations ◽  
Impulse Load ◽  
Different Shapes ◽  
Comfort Criteria ◽  
Good Agreement

The paper presents the experimental and numerical results of the dynamic system identification and verification of the behavior of two footbridges in Poland. The experimental part of the study involved vibration testing under different scenarios of human-induced load, impulse load, and excitations induced by vibration exciter. Based on the results obtained, the identification of dynamic parameters of the footbridges was performed using the peak-picking method. With the impulse load applied to both structures, determination of their natural vibration frequencies was possible. Then, based on the design drawings, detailed finite element method (FEM) models were developed, and the numerical analyses were carried out. The comparison between experimental and numerical results obtained from the modal analysis showed a good agreement. The results also indicated that both structures under investigation have the first natural bending frequency of the deck in the range of human-induced excitation. Therefore, the risk of excessive structural vibrations caused by pedestrian loading was then analysed for both structures. The vibration comfort criteria for both footbridges were checked according to Sétra guidelines. In the case of the first footbridge, the results showed that the comfort criteria are fulfilled, regardless of the type of load. For the second footbridge, it was emphasized that the structure meets the assumptions of the guidelines for vibration severability in normal use; nevertheless, it is susceptible to excitations induced by synchronized users, even in the case of a small group of pedestrians.

Numerical Modeling of Near Fault Seismic Ground Motion for Denali Fault

2021 ◽  
Vol 12 (2) ◽  
pp. 0-0
Keyword(s):  
Ground Motion ◽  
Peak Ground Acceleration ◽  
Numerical Study ◽  
Ground Motions ◽  
Numerical Results ◽  
Fault Rupture ◽  
Ground Acceleration ◽  
Denali Fault ◽  
Near Fault ◽  
Good Agreement

An effective earthquake (Mw 7.9) struck Alaska on 3 November, 2002. This earthquake ruptured 340 km along Susitna Glacier, Denali and Totschunda faults in central Alaska. The peak ground acceleration (PGA) was recorded about 0.32 g at station PS10, which was located 3 km from the fault rupture. The PGA would have recorded a high value, if more instruments had been installed in the region. A numerical study has been conducted to find out the possible ground motion record that could occur at maximum horizontal slip during the Denali earthquake. The current study overcomes the limitation of number of elements to model the Denali fault. These numerical results are compared with observed ground motions. It is observed that the ground motions obtained through numerical analysis are in good agreement with observed ground motions. From numerical results, it is observed that the possible expected PGA is 0.62 g at maximum horizontal slip of Denali fault.

Numerical Study of Discrete Masonry Structures under Static and Dynamic Loading

2016 ◽  
pp. 254-291 ◽  
Author(s):  
Rossana Dimitri ◽  
Giorgio Zavarise
Keyword(s):  
Static Loading ◽  
Numerical Study ◽  
Structural Response ◽  
Systematic Investigation ◽  
Numerical Results ◽  
Continuum Approximation ◽  
Promising Tool ◽  
Different Shapes ◽  
Optimal Configurations ◽  
Static And Dynamic Loading

Much of the world's architectural heritage consists of Unreinforced Masonry (URM) structures whose preservation is a topical subject. To prevent possible collapse of multi-block systems in hazardous conditions, a promising tool to investigate their structural response is represented by numerical modelling with the Discrete Element Method (DEM). Gothic buttresses of trapezoidal and stepped shapes are first analysed comparatively under static loading, defining the optimal configurations. Numerical results are verified against the analytical predictions of overturning and sliding resistances, based on a continuum approximation of masonry. The DEM is then successfully adopted to assess the first-order seismic behavior of arches and buttressed arches with different shapes as compared to predictions based on limit analysis. A systematic investigation on dynamic behavior failure domains and on modes of collapse of URM structures is finally performed for varying input parameters, as needed to gain more confidence on the numerical results.

A 3D BOUNDARY ELEMENT METHOD FOR DETERMINATION OF ACOUSTIC EIGENFREQUENCIES CONSIDERING ADMITTANCE BOUNDARY CONDITIONS

1993 ◽  
Vol 01 (04) ◽  
pp. 455-468 ◽  
Author(s):  
Z. S. CHEN ◽  
G. HOFSTETTER ◽  
H. A. MANG
Keyword(s):  
Boundary Element Method ◽  
Boundary Conditions ◽  
Boundary Element ◽  
Large Scale ◽  
Numerical Study ◽  
Numerical Algorithms ◽  
Numerical Results ◽  
Simple Problem ◽  
Element Method

A 3D boundary element method for the determination of the acoustic eigenfrequencies of car compartments, characterized by a unified treatment of Robin, Dirichlet, and Neumann boundary conditions, is presented. The drawback of frequency-dependent matrices of the eigenvalue problem is overcome by means of the Particular Integral Method. Thus, the standard numerical algorithms for the extraction of eigenvalues can be applied. The numerical study contains both a comparison of numerical results with analytical solutions of a simple problem with different types of boundary conditions and a comparison of numerical results of a large-scale problem with respective numerical results, computed on the basis of the finite element method. In addition, for the latter example, different numerical algorithms for the eigenvalue extraction are examined.

Identification of Excitation Forces and Prediction of the Radiation by Measured Structural Vibrations from an Underwater Structure

2013 ◽  
Vol 457-458 ◽  
pp. 1139-1143
Author(s):  
Ji Gang ◽  
Q. Zhou ◽  
Chun Wen Huang
Keyword(s):  
Experimental Data ◽  
Frequency Domain ◽  
Transfer Matrix ◽  
Numerical Results ◽  
Structural Vibrations ◽  
Cylindrical Model ◽  
Underwater Structure ◽  
Good Agreement

An approach identifying the excitation forces based on structural vibrations measured is proposed in the paper. Based on the transfer matrix predicted by FEM/BEM and the vibration vector measured, excitation forces in frequency domain are identified. Further more, acoustic from the underwater structure is predicted by FEM/BEM. To verify the approach, experiment on was carried out for a shaker driven underwater immerged cylindrical model made of steel. Excitations are identified by accelerations measured on the shell. With the forces provided, the radiation of the shell is predicted and compared with that measured. The numerical results are shown to be in good agreement with experimental data.

scholarly journals Numerical Contribution to Airflow Study Through a Generic Merchant Ship Models

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Wind Tunnel ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Numerical Code ◽  
Generic Models ◽  
Merchant Ship ◽  
Acceleration And Deceleration ◽  
Low Speed Wind Tunnel ◽  
Good Agreement

The merchant ships are continuously recruited by the world meteorological organization (WMO) as Voluntary Observing Ship (VOS) for the collect of meteorological parameters at the ocean surface. VOS meteorological observation includes many parameters such as the wind speed measured by anemometers. This measurement is biased by the presence of ship and superstructure. Little work was carried out in this field. Between them we find the experimental work at a low speed wind tunnel of Southampton University which studies the airflow distortion over simple models (generic models) of VOS merchant ship. This study presents numerical results of a 3D simulation analyzing airflow effect above the bridge of a generic merchant ship models involved in VOS. For this purpose three-dimensional, stationary and turbulent, numerical simulation has been achieved the flow over the bridge of a tanker and a container ship at 1/ 46 scale using a numerical code and CFX code with turbulence k-ε models. This numerical study allows us to know the position of the line of equality as well as the zone of acceleration and deceleration of the flow. The results obtained numerically by numerical code and CFX code are compared with those obtained experimentally in the wind tunnel of Southampton University. Numerical results are in a good agreement with experimental results and can be used as a reference to find the position of the equality line and to know the error range in of the anemometer velocity reading.

The Effect of Stratification Ratio on the Macrostructure of Stratified Swirl Flames: Experimental and Numerical Study

2018 ◽  
Author(s):  
Xiao Han ◽  
Davide Laera ◽  
Aimee S. Morgans ◽  
Yuzhen Lin ◽  
Chih-Jen Sung
Keyword(s):  
Fluid Dynamics ◽  
Numerical Study ◽  
Large Eddy Simulations ◽  
Flame Dynamics ◽  
Large Eddy ◽  
Swirling Flame ◽  
Different Shapes ◽  
Flame Quenching ◽  
Simulation Results ◽  
Good Agreement

The present article reports experimental and numerical analyses of the macrostructures featured by a stratified swirling flame for varying stratification ratio (SR). The studies are performed with the Beihang Axial Swirler Independently-Stratified (BASIS) burner, a novel double-swirled full-scale burner developed at Beihang University. Experimentally, it is found that depending on the ratio between the equivalence ratios of the methane-air mixtures from the two swirlers, the flame stabilizes with three different shapes: attached V–flame, attached stratified flame and lifted flame. In order to better understand the mechanisms leading to the three macrostructures, large eddy simulations (LES) simulations are performed via the open source Computational Fluid Dynamics software OpenFOAM using the incompressible solver Reacting Foam. Changing the SR, simulation results show good agreement with experimentally observed time-averaged flame shapes, demonstrating that the incompressible LES are able to fully characterize the different flame behaviours observed in stratified burners. When the LES account for heat loss from walls, they better capture the experimentally observed flame quenching in the outer shear layer. Finally, insights into the flame dynamics are provided by analysing probes located near the two separate streams.

Numerical and Qualitative Analysis of a Single Particle Behavior in a Shear Driven Flow in Equilateral Triangular Cavity

2013 ◽  
Vol 465-466 ◽  
pp. 557-561
Author(s):  
Muhammad Ammar Nik Mutasim ◽  
Nasir Ali ◽  
M.S. Idris ◽  
Ahmed N. Oumer
Keyword(s):  
Fluid Flow ◽  
Numerical Study ◽  
Flow Speed ◽  
Numerical Results ◽  
Driven Cavity ◽  
The Past ◽  
Particle Flows ◽  
Equivalent Time ◽  
Surrounding Fluid ◽  
Good Agreement

Intesive research works have been done on solid particle flows for the past decades. However, prediction of accurate relationship between the particle and the surrounding fluid is still challenging. This study focuses on the experimental and numerical study of behavior of a particle flow in a lid-driven cavity of equilateral triangular shape. Numerical analysis was done using Finite Difference Method (FDM) with stream function vorticity approach. The center location of the fluid flow was treated assumed to be the particle motion. To check the validaty of the numerical results, experiment was done. The particle and fluid used for the experiment were water and silk, respectively. The particle is considered to be slightly buoyant towards water. In the experiment the fluid flow was based on horizontal translating motion where the particle was initially at rest at the bottom wall of the cavity. The fluid flow speed is set to laminar flow with Reynolds Number, Re = 0 to 1000. It was found that the silk particle moved to the preferential path of the primary vortex at equivalent time of 13 seconds. Generally, the experimetal and numerical results for the streamlines were in good agreement.

Numerical Study of Liquid-Liquid Vertical Dispersed Flows

2012 ◽  
Author(s):  
Kofi Freeman K. Adane ◽  
Syed Imran A. Shah ◽  
R. Sean Sanders
Keyword(s):  
Turbulent Flows ◽  
Volume Fraction ◽  
Numerical Study ◽  
Continuous Phase ◽  
Numerical Results ◽  
Mean Velocity ◽  
Ansys Cfx ◽  
Oil In Water ◽  
Dispersed Flows ◽  
Good Agreement

Numerical simulations of liquid-liquid dispersed flow in a vertical pipe (38mm) have been carried out using the two-fluid approach implemented in a commercial CFD code, ANSYS CFX. A dispersion of oil in water (where water is the continuous phase) was studied. Both fluids were considered as turbulent flows. The k-ε model was used for the continuous phase, with the eddy viscosity of the dispersed phase estimated from that of the continuous phase. A comparison of the present numerical results with previous experimental and numerical results in terms of volume fraction, mean velocity and turbulent kinetic energy is discussed. In general, good agreement between the simulation results and experimental measurements was observed.

scholarly journals Determination of plastic properties by instrumented spherical indentation: Expanding cavity model and similarity solution approach

2009 ◽  
Vol 24 (3) ◽  
pp. 1045-1053 ◽  
Author(s):  
Peng Jiang ◽  
Taihua Zhang ◽  
Yihui Feng ◽  
Rong Yang ◽  
Naigang Liang
Keyword(s):  
Similarity Solution ◽  
Numerical Study ◽  
Sensitivity Analyses ◽  
Contact Radius ◽  
Spherical Indentation ◽  
Cavity Model ◽  
Plastic Properties ◽  
Solution Approach ◽  
Good Agreement

The present paper aims to develop a robust spherical indentation-based method to extract material plastic properties. For this purpose, a new consideration of piling-up effect is incorporated into the expanding cavity model; an extensive numerical study on the similarity solution has also been performed. As a consequence, two semi-theoretical relations between the indentation response and material plastic properties are derived, with which plastic properties of materials can be identified from a single instrumented spherical indentation curve, the advantage being that this approach no longer needs estimations of contact radius with given elastic modulus. Moreover, the inconvenience in using multiple indenters with different tip angles can be avoided. Comprehensive sensitivity analyses show that the present algorithm is reliable. Also, by experimental verification performed on three typical materials, good agreement of the material properties between those obtained from the reverse algorithm and experimental data is obtained.

The Effect of Stratification Ratio on the Macrostructure of Stratified Swirl Flames: Experimental and Numerical Study

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Xiao Han ◽  
Davide Laera ◽  
Aimee S. Morgans ◽  
Yuzhen Lin ◽  
Chih-Jen Sung
Keyword(s):  
Numerical Study ◽  
Large Eddy Simulations ◽  
Flame Dynamics ◽  
Large Eddy ◽  
Swirling Flame ◽  
Computational Fluid Dynamics Cfd ◽  
Different Shapes ◽  
Flame Quenching ◽  
Simulation Results ◽  
Good Agreement

The present paper reports experimental and numerical analyses of the macrostructures featured by a stratified swirling flame for varying stratification ratio (SR). The studies are performed with the Beihang Axial Swirler Independently Stratified (BASIS) burner, a novel double-swirled full-scale burner developed at Beihang University. Experimentally, it is found that depending on the ratio between the equivalence ratios of the methane–air mixtures from the two swirlers, the flame stabilizes with three different shapes: attached V-flame, attached stratified flame, and lifted flame. In order to better understand the mechanisms leading to the three macrostructures, large eddy simulations (LES) are performed via the open-source computational fluid dynamics (CFD) software OpenFOAM using the incompressible solver ReactingFoam. Changing SR, simulation results show good agreement with experimentally observed time-averaged flame shapes, demonstrating that the incompressible LES are able to fully characterize the different flame behaviors observed in stratified burners. When the LES account for heat loss from walls, they better capture the experimentally observed flame quenching in the outer shear layer (OSL). Finally, insights into the flame dynamics are provided by analyzing probes located near the two separate streams.

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