A Novel Single-Phase Flying-Inductor Buck-Boost Inverter

Javad Sadeghi Chevinly,Yam P. Siwakoti,Mojtaba Forouzesh,Frede Blaabjerg 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

In this paper a new single-phase flying-inductor buck-boost inverter is proposed. The inverter operates on the principle of flying-inductor, and it has the capability to buck or boost the input voltage without increasing the number of required components. In addition, the inverter is free from electrolytic capacitors, which helps to improve reliability and lifetime of the inverter. The operating principle of the proposed inverter has been analyzed and discussed. Finally, experimental results from a 250 W prototype validates the performance of the proposed topology.

Development of non-destructive method of detecting steel bars corrosion in bridge decks

Javad Sadeghi,Farshad Hashemi Rezvani 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.5

One of the most common defects in reinforced concrete bridge decks is corrosion of steel reinforcing bars. This invisible defect reduces the deck stiffness and affects the bridge’s serviceability. Regular monitoring of the bridge is required to detect and control this type of damage and in turn, minimize repair costs. Because the corrosion is hidden within the deck, this type of damage cannot be easily detected by visual inspection and therefore, an alternative damage detection technique is required. This research develops a non-destructive method for detecting reinforcing bar corrosion. Experimental modal analysis, as a non-destructive testing technique, and finite element (FE) model updating are used in this method. The location and size of corrosion in the reinforcing bars is predicted by creating a finite element model of bridge deck and updating the model characteristics to match the experimental results. The practicality and applicability of the proposed method were evaluated by applying the new technique to a two spans bridge for monitoring steel bar corrosion. It was shown that the proposed method can predict the location and size of reinforcing bars corrosion with reasonable accuracy.

Application of neural networks in evaluation of railway track quality condition

Javad Sadeghi,Hossein Askarinejad 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1

Due to the significant costs and time consumed for track visual inspections, most railway industries rely only on geometry data obtained from automated inspections for the assessments of railway track quality conditions. This is the main limitation of the current practices,which may lead to inappropriate determinations of maintenance and repair schedules. This research attempts to rectify this deficiency by developing a methodology for the establishment of correlations between the track structural conditions and the data obtained from automated inspections. The aim is to provide the possibility of having a rational understanding of the structural defects of track (the causes of track irregularities) without conducting visual inspections. Neural network technique is implemented for this purpose. A vast amount of field data obtained from comprehensive visual and automated inspections of different railways are utilized to develop the neural network models. The results obtained in this research reveals that the neural network technique has a very good capability in establishing correlations between track geometrical defects and track structural problems. The application of the developed models in a number of railway tracks indicates that the proposed methodology is an effective approach in the prediction of track structural defects.

Effect of nonlinearity of fastening system on railway slab track dynamic response

Javad Sadeghi,Mohammad Seyedkazemi,Amin Khajehdezfuly 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.6

Fastening systems have a significant role in the response of railway slab track systems. Although experimental tests indicate nonlinear behavior of fastening systems, they have been simulated as a linear spring-dashpot element in the available literature. In this paper, the influence of the nonlinear behavior of fastening systems on the slab track response was investigated. In this regard, a nonlinear model of vehicle/slab track interaction, including two commonly used fastening systems (i.e., RFFS and RWFS), was developed. The time history of excitation frequency of the fastening system was derived using the short time Fourier transform. The model was validated, using the results of a comprehensive field test carried out in this study. The frequency response of the track was studied to evaluate the effect of excitation frequency on the railway track response. The results obtained from the model were compared with those of the conventional linear model of vehicle/slab track interaction. The effects of vehicle speed, axle load, pad stiffness, fastening preload on the difference between the outputs obtained from the linear and nonlinear models were investigated through a parametric study. It was shown that the difference between the results obtained from linear and nonlinear models is up to 38 and 18 percent for RWFS and RFFS, respectively. Based on the outcomes obtained, a nonlinear to linear correction factor as a function of vehicle speed, vehicle axle load, pad stiffness and preload was derived. It was shown that consideration of the correction factor compensates the errors caused by the assumption of linear behavior for the fastening systems in the currently used vehicle track interaction models.

Development of non-destructive method of detecting steel bars corrosion in bridge decks

Sadeghi, Javad,Rezvani, Farshad Hashemi Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.5

One of the most common defects in reinforced concrete bridge decks is corrosion of steel reinforcing bars. This invisible defect reduces the deck stiffness and affects the bridge's serviceability. Regular monitoring of the bridge is required to detect and control this type of damage and in turn, minimize repair costs. Because the corrosion is hidden within the deck, this type of damage cannot be easily detected by visual inspection and therefore, an alternative damage detection technique is required. This research develops a non-destructive method for detecting reinforcing bar corrosion. Experimental modal analysis, as a non-destructive testing technique, and finite element (FE) model updating are used in this method. The location and size of corrosion in the reinforcing bars is predicted by creating a finite element model of bridge deck and updating the model characteristics to match the experimental results. The practicality and applicability of the proposed method were evaluated by applying the new technique to a two spans bridge for monitoring steel bar corrosion. It was shown that the proposed method can predict the location and size of reinforcing bars corrosion with reasonable accuracy.

Performance of under foundation shock mat in reduction of railway-induced vibrations

Javad Sadeghi,Ehsan Haghighi,Morteza Esmaeili 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.4

Under foundation shock mats have been used in the current practice in order to reduce/damp vibrations received by buildings through the surrounding environment. Although some investigations have been made on under foundation shock mats performance, their effectiveness in the reduction of railway induced-vibrations has not been fully studied, particularly with the consideration of underneath soil media. In this regard, this research is aimed at investigating performance of shock mat used beneath building foundation for reduction of railway induced-vibrations, taking into account soil-structure interaction. For this purpose, a 2D finite/infinite element model of a building and its surrounding soil media was developed. It includes an elastic soil media, a railway embankment, a shock mat, and the building. The model results were validated using an analytical solution reported in the literature. The performance of shock mats was examined by an extensive parametric analysis on the soil type, bedding modulus of shock mat and dominant excitation frequency. The results obtained indicated that although the shock mat can substantially reduce the building vibrations, its performance is significantly influenced by its underneath soil media. The softer the soil, the lower the shock mat efficiency. Also, as the train excitation frequency increases, a better performance of shock-mats is observed. A simplified model/method was developed for prediction of shock mat effectiveness in reduction of railway-induced vibrations, making use of the results obtained.

Development of optimum modeling approach in prediction of wheelflats effects on railway forces

Javad Sadeghi,Amin Khajehdezfuly,Morteza Esmaeili,Davood Poorveis 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.5

While the wheel flat is an asymmetrical phenomenon in the railway, majority of researches have used two-dimensional models in the investigation of the effect of wheel flat on the wheel rail forces. This is due to the considerably low computational costs of two dimensional (2D) models although their reliability is questionable. This leaves us with the question of “what is the optimum modeling technique?”. It is addressed in this research. For this purpose, two and three dimensional numerical models of railway vehicle/track interaction were developed. The three dimensional (3D) model was validated by comparisons of its results with those obtained from a comprehensive field tests carried out in this research and then, the results obtained from the 2D and 3D models were compared. The results obtained indicate that there are considerable differences between wheel/rail forces obtained from the 2D and 3D models in the conditions of medium to large wheel-flats. On the other hand, it was shown that the results of the 2D models are reliable for particular ranges of vehicle speed, railway track stiffness and wheel-fats lengths and depths. The results were used to draw a diagram, which presents the optimum modeling technique, compromising between the costs and accuracy of the obtained results.

Non-destructive assessment of carbonation in concrete using the ultrasonic test: Influenced parameters

Javad Royaei,Fatemeh Nouban,Kabir Sadeghi 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.3

Concrete carbonation is a continuous and slow process from the outside to the inside, in which its penetration slows down with the increased depth of carbonation. In this paper, the results of the evaluation of the measurement of concrete carbonation depth using a non-destructive ultrasonic testing method are presented. According to the results, the relative nonlinear parameter caused more sensitivity in carbonation changes compared to Rayleigh’s fuzzy velocity. Thus, the acoustic nonlinear parameter is expected to be applied as a quantitative index to recognize carbonation effects. In this research, combo diagrams were developed based on the results of ultrasonic testing and the experiment to determine carbonation depth using a phenolphthalein solution, which could be considered as instructions in the projects involving non-destructive ultrasonic test methods. The minimum and maximum accuracy of this method were 89% and 97%, respectively, which is a reasonable range for operational projects. From the analysis performed, some useful expressions are found by applying the regression analysis for the nonlinearity index and the carbonation penetration depth values as a guideline.

Experimental investigation on the effectiveness of under-foundation isolator against train-induced vibrations considering foundation type

Ehsan Haghighi,Javad Sadeghi,Morteza Esmaeili 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.2

In this paper, the performance of under-foundation isolators against generally annoying train-induced vibrations was examined experimentally. The effect of foundation type on the efficacy of such isolators was investigated for the first time. To this end, laboratory models including a soil container, soil, building with three types of foundation (i.e., single, strip, and mat), and isolator layer were employed. Through various dynamic tests, the effects of foundation type, isolation frequency, and the dominant frequency of train load on the isolator’s performance were studied. The results demonstrated that the vibration level in the unisolated building with the strip and mat foundation was, respectively, 29 and 38% lower than in the building with the single foundation. However, the efficacy of the isolator in the building with the single foundation was, respectively, 21 and 40% higher than in the building with the strip and mat foundation. Furthermore, a lower isolation frequency and a higher excitation frequency resulted in greater isolator efficacy. The best vibration suppression occurred when the excitation frequency was close to the floor’s natural frequency.

Field investigation on load distribution and deflections of railway track sleepers

Jabbar Ali Zakeri,Javad Sadeghi 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.12

Despite the significant role of sleepers in railway track mechanical behavior, no thorough mechanistic approach has been presented for the development of the loading pattern they experience. The current theoretical methods in the analysis of the railway track system need further calibration and verification using field-measured data. In this paper, using specific load-cells between sleepers and the rail and beneath the sleepers, the vertical loading conditions of these main track elements are studied. The lateral resistance of the concrete sleepers in the ballasted tracks is investigated by using full scale sleeper pull-out tests. Moreover, track deflections under the sleeper as the main track analysis parameter are measured and the results are discussed. In this paper, with the results obtained from extensive field measurements, some suggestions are made leading to an improvement in the current understanding of the sleeper loading pattern and the track deflections.