scholarly journals Nondestructive Detection of Gaps between Railway Track Slabs and Soil Foundation Using Leaked Air Waves

2020 ◽  
Vol 10 (10) ◽  
pp. 3347
Author(s):  
Seongbaek Park ◽  
Hojin Cho ◽  
Yujin Lim
Keyword(s):  
Nondestructive Test ◽  
Acoustic Waves ◽  
Concrete Slab ◽  
Soft Soil ◽  
Concrete Surface ◽  
Test System ◽  
Railway Track ◽  
Accelerometer Data ◽  
Element Analysis ◽  
Time Frequency

Gaps generated underneath railway track slabs may cause unstable conditions. Such gaps can form because of different reasons, including settlement of soft soil, unsuitable construction of a concrete slab on loosely compacted soil, and drastic stiffness change in a transition zone between the bridge deck and embankment. The gaps underneath railway track slabs are not easily detectable by common nondestructive test methods. A nondestructive test (NDT) based on a wavelet time–frequency concept is proposed for the practical purpose of detecting gaps under track slabs. The method uses a microphone sensor to catch leaked Rayleigh acoustic waves in the air and an accelerometer to measure surface Rayleigh waves on the slab. In order to investigate the possibility of developing the test system, a finite element analysis (FEA) was performed to simulate Rayleigh wave generation on the concrete surface and in the air. A test system module composed of a microphone and an accelerometer, data acquisition system (DAQ), and an analyzer program was also assembled for a small backyard pilot test. It was verified that the new NDT test system could be successfully adapted for detecting gaps underneath railway track slabs and track bed soil.

scholarly journals An impact echo method to detect cavities between railway track slabs and soil foundation

2021 ◽  
Vol 68 (1) ◽  
Author(s):  
Pierre Anthyme Bahati ◽  
Viet Dinh Le ◽  
Yujin Lim
Keyword(s):  
Open Space ◽  
Concrete Slab ◽  
Test Methods ◽  
Railway Track ◽  
Element Analysis ◽  
Impact Echo ◽  
Time Frequency ◽  
Railway Tracks ◽  
Soil Foundation ◽  
The Impact

AbstractThe impact echo technique is one of the most useful non-destructive test methods for determining the thickness of concrete or detecting possible cracks or cavities in the internal parts of a concrete structure without damaging the surface. Many types of unstable conditions in railway tracks, including various modes of irregularities, may occur when cavities are generated directly under a concrete slab track or when a slight open space is made under a loose sleeper. In this study, we developed a nondestructive testing (NDT) system for detecting abnormalities in concrete tracks and performed 3D numerical simulations using the ABAQUS finite element analysis (FEA) program to investigate the impact echo response from a concrete track slab with different sizes of cavities. Sections of concrete slab were simulated as solid body masses under the railway tracks with gaps in the bodies themselves or with cavities existing between the track concrete layer (TCL) and the hydraulically stabilized base (HSB). We investigated the locations and depths of the cavities and gaps in the model concrete slab using the acoustic impact echo response based on the frequency response of the elastic waves generated in the slab. In addition, a Short-time Fourier Transform (STFT) and a wavelet technique were adopted for a time frequency analysis. Our study demonstrated that the impact echo technique developed in this study by FEA and NDT can measure and confirm the location and depth of cavities in concrete slabs.

Tire Cornering Simulation Using an Explicit Finite Element Analysis Code

1998 ◽  
Vol 26 (2) ◽  
pp. 109-119 ◽  
Author(s):  
M. Koishi ◽  
K. Kabe ◽  
M. Shiratori
Keyword(s):  
Finite Element Method ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Test System ◽  
Experimental Results ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Explicit Finite Element ◽  
Explicit Finite Element Analysis ◽  
Element Method

Abstract The finite element method has been used widely in tire engineering. Most tire simulations using the finite element method are static analyses, because tires are very complex nonlinear structures. Recently, transient phenomena have been studied with explicit finite element analysis codes. In this paper, the authors demonstrate the feasibility of tire cornering simulation using an explicit finite element code, PAM-SHOCK. First, we propose the cornering simulation using the explicit finite element analysis code. To demonstrate the efficiency of the proposed simulation, computed cornering forces for a 175SR14 tire are compared with experimental results from an MTS Flat-Trac Tire Test System. The computed cornering forces agree well with experimental results. After that, parametric studies are conducted by using the proposed simulation.

scholarly journals Time-frequency analysis of acoustic waves in an integrated acousto-optical modulator based on LiNbO3

2020 ◽  
Vol 1697 ◽  
pp. 012174
Author(s):  
A V Varlamov ◽  
S I Ivanov ◽  
A P Lavrov ◽  
A V Shamray
Keyword(s):  
Frequency Analysis ◽  
Acoustic Waves ◽  
Optical Modulator ◽  
Time Frequency Analysis ◽  
Time Frequency

Finite Element Analysis of Composite Ceramic-Concrete Slab Constructions Exposed to Fire

2016 ◽  
Vol 861 ◽  
pp. 88-95
Author(s):  
Balázs Nagy ◽  
Elek Tóth
Keyword(s):  
Composite Structures ◽  
Elevated Temperatures ◽  
Cfd Simulation ◽  
Concrete Slab ◽  
Composite Ceramic ◽  
Reinforced Concrete Beam ◽  
Element Analysis ◽  
Standard Fire ◽  
Using Data ◽  
Dynamics Simulations

In this research, conjugated thermal and fluid dynamics simulations are presented on a modern hollow clay slab blocks filled pre-stressed reinforced concrete beam slab construction. The simulation parameters were set from Eurocode standards and calibrated using data from standardized fire tests of the same slab construction. We evaluated the temperature distributions of the slabs under transient conditions against standard fire load. Knowing the temperature distribution against time at certain points of the structure, the loss of load bearing capacity of the structure is definable at elevated temperatures. The results demonstrated that we could pre-establish the thermal behavior of complex composite structures exposed to fire using thermal and CFD simulation tools. Our results and method of fire resistance tests can contribute to fire safety planning of buildings.

Sensitivity Analysis of Smoothed Particle Hydrodynamics in PAM-CRASH for Modeling of Soft Soils

2013 ◽  
Author(s):  
Ranvir Dhillon ◽  
Moustafa El-Gindy ◽  
Rustam Ali ◽  
David Philipps ◽  
Fredrik Öijer ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Soft Soil ◽  
Strength Criterion ◽  
Model Parameters ◽  
Rapid Progression ◽  
Element Analysis ◽  
Particle Modeling ◽  
Modeling Techniques ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

The rapid progression of computational power and development of non-mesh particle modeling techniques provides solutions to problems which are not accurately modeled using traditional finite element analysis techniques. The field of soft soil modeling has been pressing on in recent years and the smoothed particle hydrodynamics (SPH) modeling method in PAM-CRASH provides opportunity for further advancement in accuracy. This research focuses on the development of soft soil models using SPH with verification using pressure-sinkage and shear strength criterion. Soil model parameters such as geometry and contact model are varied to determine the effect of the parameters on the behaviour of the soft soil and relationships are developed. The developed virtual soil models are compared against existing soils to determine which soils are accurately modeled and further refinements are made to validate the models with existing empirical data.

On-Site Experimental Testing to Study the Vibration of Composite Floors

2014 ◽  
Vol 601 ◽  
pp. 231-234
Author(s):  
Cristian Lucian Ghindea ◽  
Dan Cretu ◽  
Monica Popescu ◽  
Radu Cruciat ◽  
Elena Tulei
Keyword(s):  
Dynamic Characteristics ◽  
Experimental Testing ◽  
Concrete Slab ◽  
Human Perception ◽  
Experimental Tests ◽  
International Standards ◽  
Structural Element ◽  
Element Analysis ◽  
Floor Slabs ◽  
Composite Floors

As a general trend, in order to reduce material consumption or to reduce the mass of the structures, composite floor slabs solutions are used to achieve large spans floor slabs. This solutions led to floors sensitive to vibrations induced generally by human activities. As a verification of the design concepts of the composite floors, usually, it is recommended a further examination of the floor after completion by experimental tests. Although the experimental values of the dynamic response of the floor are uniquely determined, the processing can take two directions of evaluation. The first direction consist in determining the dynamic characteristics of the floor and their comparison with the design values. Another way that can be followed in the processing of the experimental results is to consider the human perception and comfort to the vibration on floors. The paper aims to present a case study on a composite floor, with steel beams and concrete slab, tested on-site. Both aspects of data processing are analyzed, in terms of the structural element, and in terms of the effect on human perception and comfort. Experimentally obtained values for the dynamic characteristics of the floor are compared with numerical values from finite element analysis, while the second type of characteristic values are compared with various human comfort threshold values found in international standards.

Application of Optimized Digital Filters and Asymmetrically Trimmed Mean to Improve the Accuracy of Dynamic Egg Weighing

2017 ◽  
Vol 60 (4) ◽  
pp. 1099-1111
Author(s):  
Jianyi Zhang ◽  
Yibin Ying ◽  
Huanyu Jiang ◽  
Haijun Wang ◽  
Chunwei Yang ◽  
...  
Keyword(s):  
Frequency Analysis ◽  
Digital Filters ◽  
Load Cell ◽  
Location Estimation ◽  
Egg Mass ◽  
Accelerometer Data ◽  
Trimmed Mean ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Dynamic Weighing

Abstract. Rolling poultry eggs through a weighing rail is a simple, fast, and efficient way to measure mass. However, disturbances generated primarily by the rolling eggs vary with the rolling state and speed as well as with the egg mass and shape. These disturbances distort the load cell signal in the form of a stochastic strong amplitude fluctuation, and eliminating these fluctuations completely is a difficult task. A piezoelectric accelerometer was used to measure the vibration disturbances. The smoothed pseudo-Wigner-Ville distribution (SPWVD), which is a type of time-frequency analysis, was used to analyze the vibration disturbances using the accelerometer data. The results indicated that the disturbances were non-stationary, and the frequency characteristics were time-varying. Preliminary experiments showed that the commonly used low-pass filtering and subsequent average-based mass estimation method (AME) did not result in a satisfactory weighing accuracy. To meet the requirement of fast and accurate dynamic weighing of eggs, this research proposed a sorting-based mass estimator (SME) that consisted of an optimized digital filter and asymmetrically trimmed mean. The SME regarded the mass measurement as a problem of location estimation of non-Gaussian and heavy-tailed random variables, given the short observation time and the presence of outliers (disturbances). Four types of digital filters in the SME were selected to pre-filter the load cell data. The relevant parameters of the digital filters and asymmetrically trimmed mean in the SME were optimized using a grid search. Experimental results showed that the proposed SME effectively improved the weighing accuracy, and almost all of the egg weighing errors were less than 1 g with a processing speed of up to 5 eggs s-1. Compared with the AME, the overall mean error was reduced by approximately 86% to 93%, and the overall standard deviation of the error (SDE) was reduced by approximately 41% to 50%. Keywords: Asymmetrically trimmed mean, Digital filters, Dynamic weighing, Egg mass, Time-frequency analysis.

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