Experimental Study on Dynamic Behaviors of Concrete Bridge in China Existing Railway Speed Increase to 200~250km/h

2012 ◽  
Vol 193-194 ◽  
pp. 1123-1128
Author(s):  
Peng Hui Liu ◽  
Yi Qian Yang ◽  
Jing Chuan Yao ◽  
Wei Wang ◽  
Zhen Sheng Dong
Keyword(s):  
Experimental Data ◽  
Natural Frequency ◽  
Critical Parameters ◽  
Maximum Speed ◽  
Dynamic Factor ◽  
Concrete Bridge ◽  
Dynamic Behaviors ◽  
Speed Increase ◽  
Multiple Unit ◽  
Lateral Rigidity

On April fifteenth, 2007, the 4 vertical and 2 horizontal railway lines were increased the sixth time by the Chinese Ministry of Railways. The electrical multiple unit (EMU) was running at speed of 200km/h in these sections. In some sections, the EMU maximum speed has reached 250km/h. Dynamic behaviors of bridges and piers under the loads of the train were analyzed with different spans and types in existing speed-raising trunk lines. The critical parameters, such as lateral and vertical natural frequency, dynamic factor, lateral amplitude, lateral natural frequency and lateral amplitude of pier and so on, which play important roles in dynamic behaviors of bridge, are analyzed by experimental data. The lateral rigidity and dynamic behaviors of bridge including beams and piers are the most obvious problems in existing speed-raising lines. Based on years of research, especially lots of dynamic behavior tests of concrete bridge in recent year, the dynamic behaviors of bridges are analyzed comprehensively considering the vibration of bridge and train characteristics. Many results are got and used in the relevant codes.

A Dynamic Test of Fully Prestressed Concrete Beams

2011 ◽  
Vol 368-373 ◽  
pp. 2483-2490
Author(s):  
Yao Ting Zhang ◽  
Yi Zheng ◽  
Hong Jian Li
Keyword(s):  
Experimental Data ◽  
Elastic Modulus ◽  
Theoretical Analysis ◽  
Natural Frequency ◽  
Axial Force ◽  
Prestressed Concrete ◽  
Concrete Beams ◽  
Dynamic Test ◽  
Modified Formula

A dynamic test of two unbonded fully prestressed concrete beams has been conducted. The results indicate that the natural frequency of beams increases with the prestress force, which is opposite to the analytical arguments for homogeneous and isotropic beams subject to axial force. This paper explains the change in frequencies by discussing the change in the elastic modulus. A modified formula is also proposed, and the experimental data agree well with the theoretical analysis.

scholarly journals Determination of the Firing Pin Critical Velocity and the Critical Power in the Percussive Initiation of Primer Caps

2016 ◽  
Vol 7 (4) ◽  
pp. 33-66
Author(s):  
Andrzej FARYŃSKI ◽  
Andrzej DŁUGOŁĘCKI ◽  
Jarosław DĘBIŃSKI ◽  
Łukasz SŁONKIEWICZ
Keyword(s):  
Experimental Data ◽  
Critical Velocity ◽  
Hot Spot ◽  
Pulse Power ◽  
Critical Parameters ◽  
Simplified Model ◽  
Initiation Mechanism ◽  
The Mean ◽  
Institute Of Technology ◽  
Explosive Reaction

This work involved testing of the probability of initiating a KWM-3 type of primer cap as a function of the firing pin velocity upon impact. The tested firing pin was accelerated to the required velocity by a falling mass. The measurements under this work were made with a measurement system and methodologies developed at Air Force Institute of Technology (AFIT) in Warsaw (Poland). The percussive pulse velocity and power was altered by modifying the percussive mass to keep the initiating pulse energy constant at two levels: Ewe = 272 mJ and 343 mJ. The firing pin velocity values estimated by experimental data to bring a 50% probability of percussive primer cap initiation were within the interval vi50% = 0.34÷0.51 m/s. It was found that the mean primer cap ignition delay rose from approx. 0.7 ms at a percussion velocity of 1.5 m/s to 6 ms at 0.17 m/s. The experimental data suggest the values of Ewe x vi50% = 0.136. A simplified model was proposed for the deformation of the primer cap base and compressed pyrotechnical mixture shape. The model served to determine the approximate time trend for the penetration of the primer cap by the firing pin, including velocity, power and emitted energy, by assuming a complete energy transfer from the percussive mass to the primer cap. The mean initiating pulse power calculated from the model at the vi50% interval was Pavg = 120÷180 W, whereas the maximum initiating pulse power was Pmax = 170÷250 W. The calculated time values for firing pin penetration were very close to the aforementioned primer cap ignition delays at the respective velocity and percussive mass values. This indirectly indicates nearly complete energy transmission from the percussive masses to the primer caps. A location was identified within the compressed pyrotechnical mixture shape volume which could form the hot spot for initiation of the explosive reaction. Based on the calculation results using the simplified model, and assuming that the energy and diffusive heat flux output to and from the explosive reaction initiation hot spot were equivalent, the expression of Ewe x vi50% derived from the result was approx. 0.18. This means that the two critical parameters of primer cap initiation: (i) velocity, which can be identified with vi50% (and the respective power) and (ii) Ewe50%, i.e. the energy threshold below which the probability of primer cap initiation is less than 0.5, are interrelated. Aside from the initiation mechanism proposed and applied to calculate the firing pin critical velocity, this work discusses several other initiation mechanisms, all of which were ruled out during the testing process.

Limitations of the Power Spectral Density as an Indicator of Test Severity

2011 ◽  
Vol 54 (2) ◽  
pp. 116-128 ◽  
Author(s):  
Mark Paulus
Keyword(s):  
Experimental Data ◽  
Spectral Density ◽  
Frequency Shift ◽  
Natural Frequency ◽  
Power Spectral Density ◽  
Low Frequency ◽  
Poor Correlation ◽  
Frequency Change ◽  
Power Spectral

This paper presents a set of experimental data comparing repetitive shock (RS) vibration, single-axis electrodynamic (ED) vibration, and multi-axis ED vibration. It was found that multi-axis testing is more severe than single-axis testing at the same level. In addition, weaknesses were found in the RS system at low frequency. Smoothing of the data or poor line resolution was also shown to change the overall severity of a test. A poor correlation was shown between the power spectral density (PSD) and the rate of natural frequency change (RFC) over a wide frequency shift. The change in natural frequency caused the initial PSD to be an ineffective indicator of test severity. Quantification of the severity of the test profile can be accomplished through characterization of the RFC.

Identification of Natural Frequency of Bearing Rotor Based on GA-SVM

2012 ◽  
Vol 443-444 ◽  
pp. 27-33
Author(s):  
Tian Ran Ma ◽  
Fei Hu Qin ◽  
Rui Xue Liu ◽  
Feng Jie Zhang
Keyword(s):  
Experimental Data ◽  
Support Vector Machine ◽  
Natural Frequency ◽  
Rolling Bearing ◽  
Linear Mapping ◽  
Support Vector ◽  
Non Linear ◽  
Experimental Values ◽  
Rotor Structure ◽  
Good Agreement

During identify natural frequency of bearing rotor, due to the complex non-linear relationship among the factors which influence natural frequency, so it is hard to establish a complete and accurate theoretical model. Based on the generalization and approximation of non-linear mapping capability of support vector machine (SVM) and the powerful ability of global optimization of the genetic algorithm (GA), the paper through optimizing the SVM by GA, establishes combined Genetic Support Vector Machine (GA-SVM). The method establishes the mapping between the natural frequency of a rolling bearing rotor and the various parameters, which reduces the rotor structure for the study similar to the natural frequency of the calculation of the workload greatly. Using the model to indentify the natural frequency of bearing rotor under different parameters, then compare identification value with experimental values shows that projections in good agreement with the experimental data.

scholarly journals Dynamic Behaviors of Gantry Cranes. 5th Report. Natural Frequency.

1992 ◽  
Vol 58 (545) ◽  
pp. 30-35
Author(s):  
Masajiro ABE ◽  
Hiroshi ITO ◽  
Yongxiang REN ◽  
Kinya ICHIMURA
Keyword(s):  
Natural Frequency ◽  
Dynamic Behaviors ◽  
Gantry Cranes

A Preliminary Study of Whirl Instability for Pressurized Gas Bearings

1962 ◽  
Vol 84 (4) ◽  
pp. 511-518 ◽  
Author(s):  
R. H. Larson ◽  
H. H. Richardson
Keyword(s):  
Experimental Data ◽  
Natural Frequency ◽  
Stability Criterion ◽  
Journal Bearings ◽  
Rigid Rotor ◽  
Gas Bearings ◽  
Preliminary Study ◽  
Bearing System

Experimental data are presented for the threshold of whirl instability for a short, rigid rotor supported in externally pressurized compensated gas journal bearings. The effects of supply pressures from zero to 200 psig and of radial clearances from 0.0006 to 0.0032 in. are discussed for one type of bearing configuration. A simple stability criterion is presented which explains qualitatively the observed trends. Whirl instability was observed when the frequency of rotation of the shaft exceeded from two to six times the lowest natural frequency of the shaft-bearing system.

Development and Comparison of a Heat-Transfer Correlation for Supercritical Refrigerants

2017 ◽  
Author(s):  
Nicholas Tarsitano ◽  
Khalil Sidawi ◽  
Igor Pioro
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Fluxes ◽  
Critical Parameters ◽  
Future Research ◽  
Supercritical Conditions ◽  
Wide Range ◽  
Heat Transfer Correlations ◽  
R 134A ◽  
Correlation Accuracy

The objective of this paper is to act as a collection of multiple different heat-transfer correlations and to check their accuracy when compared to experimental data obtained in supercritical-pressure refrigerants (R-22 and R-134a). This paper is also intended to collect as much relevant data of heat transfer in supercritical refrigerants as possible for future research. The experimental data have been retrieved from graphs within a wide range of operating parameters. This study is in support of potential use of supercritical refrigerants as modeling fluids instead of supercritical water. The use of refrigerants as modelling fluids instead of water will allow to decrease costs and technical difficulties during experiments at supercritical pressures and widen operating ranges, because the critical parameters of refrigerants are significantly lower than those of water. The research was completed by collecting graphed data from several different experimental series using both R-22 and R-134a data. The advantage of comparing different refrigerants for determining correlation accuracy is to increase the predictability for other potential experiments using refrigerants. All data are taken from bare-tube experiments to produce a relative baseline for heat-transfer characteristics. These experiments have been performed within the following range: Inner tube diameter ranging between 4.4 mm to 13 mm, pressure ranging between 4.3 MPa to 5.5 MPa, and at a number of various mass and heat fluxes. Sixteen potential heat-transfer correlations have been selected and used in this assessment. The correlation by Watts and Chou [1] and Cheng et al. [2] were shown to have the lowest root-mean-square error. Other correlations with the reasonable accuracy include Mokry et al. [3] and Swenson et al. [4] correlations. However, it was decided to develop a new correlation based on these refrigerant data in an attempt to increase the prediction accuracy. Therefore, based on the Mokry et al. [3] correlation a modified correlation was developed, which generalized the experimental Freon data with higher accuracy than the know correlations. This correlation is intended to create a basis for further study on the use of refrigerants as modeling fluids. While Freon has similar properties to water at supercritical conditions, the different molecular properties causes factors to affect each fluid differently. For refrigerants at supercritical conditions, the factors that seem to have the most effect are the dynamic viscosity and density of a fluid.

scholarly journals Strut-and-tie computer modelling of reinforced concrete bridge portal frames

2002 ◽  
Vol 35 (3) ◽  
pp. 165-189 ◽  
Author(s):  
N. H. T. To ◽  
J.M. Ingham ◽  
S. Sritharan
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Computer Program ◽  
Computer Modelling ◽  
Concrete Bridge ◽  
Tension Stiffening ◽  
Reinforced Concrete Bridge ◽  
Strut And Tie ◽  
Force Displacement ◽  
Stiffening Effect

Nonlinear inelastic force-displacement response envelopes of full-scale reinforced concrete bridge portal frames are predicted in this paper by representing the frame using strut-and-tie models. The nonlinear strut-and-tie analyses, which included the tension stiffening effect, were performed using the computer program Drain-2DX. Strut-and-tie analytical results were found to correlate satisfactorily with the experimental data and to provide superior prediction to that generated using conventional planar frame models.

scholarly journals Implementation of a DPU-Based Intelligent Thermal Imaging Hardware Accelerator on FPGA

Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 105
Author(s):  
Abdelrahman S. Hussein ◽  
Ahmed Anwar ◽  
Yasmine Fahmy ◽  
Hassan Mostafa ◽  
Khaled Nabil Salama ◽  
...  
Keyword(s):  
Thermal Imaging ◽  
Visual Analysis ◽  
Computational Cost ◽  
General Purpose ◽  
Maximum Speed ◽  
Heat Map ◽  
Speed Increase ◽  
Custom Hardware ◽  
Battery Energy ◽  
Hardware Platforms

Thermal imaging has many applications that all leverage from the heat map that can be constructed using this type of imaging. It can be used in Internet of Things (IoT) applications to detect the features of surroundings. In such a case, Deep Neural Networks (DNNs) can be used to carry out many visual analysis tasks which can provide the system with the capacity to make decisions. However, due to their huge computational cost, such networks are recommended to exploit custom hardware platforms to accelerate their inference as well as reduce the overall energy consumption of the system. In this work, an energy adaptive system is proposed, which can intelligently configure itself based on the battery energy level. Besides achieving a maximum speed increase that equals 6.38X, the proposed system achieves significant energy that is reduced by 97.81% compared to a conventional general-purpose CPU.

scholarly journals The Issue of the Free Surface of Adsorbent in the Description of a Monolayer Mobile Gas Adsorption on Solids

2019 ◽  
Vol 69 (4) ◽  
pp. 33-44
Author(s):  
Jerzy K. Garbacz ◽  
Jerzy Ciechalski ◽  
Mariusz Kozakiewicz
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Theoretical Basis ◽  
Adsorption Layer ◽  
Gas Adsorption ◽  
Adsorption Equilibrium ◽  
Critical Parameters ◽  
Two Dimensional ◽  
Homogeneous Surface ◽  
Adsorption Equation

AbstractThis paper characterises the concept of monolayer mobile gas adsorption on a homogeneous surface of a solid. The theoretical basis of the phenomenological variant of the description of adsorption equilibrium in the system in question are discussed. The essential features of the solutions to date are discussed, and the effect of the free surface of adsorbent on the form of the final adsorption equation is stressed.An alternative concept of the free surface based on the modified two-dimensional analogue of Reiss, Frisch and Lebowitz equations is also presented. The obtained adsorption equation was tested for critical parameters of two-dimensional condensation of the adsorption layer, and then used to describe the experimental data available in literature. The verification carried out confirmed the correctness and usefulness of the proposed concept.

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