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A new approach for estimating the seismic soil pressure on retaining walls
, Article Scientia Iranica ; Volume 17, Issue 4 A , Aug , 2010 , Pages 273-284 ; 10263098 (ISSN) ; Mahjoubi, S ; Sharif University of Technology
2010
Abstract
In this paper, a simple finite element model for seismic analysis of retaining walls is introduced. The model incorporates nonlinearity in the behavior of near wall soil, wall flexibility and elastic free field soil response. This model can be employed in nonlinear modeling of retaining walls and bridge abutments. The advantages of this model are simplicity and flexibility in addition to acceptable precision. Using this finite element model, an analytical study is conducted on several soil-wall systems using nonlinear time-history analysis by applying real earthquake records. Based on the results of these analyses, new seismic soil pressure distributions are proposed for different soil and...
Effect of boundary conditions on dynamic behaviour of bridges
, Article Proceedings of the Institution of Civil Engineers: Structures and Buildings ; Volume 169, Issue 2 , 2016 , Pages 121-140 ; 09650911 (ISSN) ; Vafai, H ; Sharif University of Technology
Thomas Telford Services Ltd
Abstract
A moving vehicle, owing to its vibration and mass inertia, has significant effects on the dynamic response of structures. Most bridge codes define a factor called the dynamic load allowance, which is applied to the maximum static moment under static loading due to traffic load. This paper presents how to model an actual truck on bridges and how the maximum dynamic stresses of bridges change during the passage of moving vehicles. Furthermore, an algorithm to solve the governing equation of the bridge simultaneous with the equations of motion of an actual European truck is presented. Subsequently, 32 dynamic analyses of different bridges with different spans, road profiles and boundary...
Design and implementation of an FPGA-based real-time simulator for H-bridge converter
, Article 7th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2016, 16 February 2016 through 18 February 2016 ; 2016 , Pages 504-510 ; 9781509003754 (ISBN) ; Zolghadri, M. R ; Shahbazi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
This paper presents a methodology for implementing of the mathematical model of H-Bridge converter in an FPGA-based Real-Time simulator. Furthermore, it introduces a new method for choosing parameters of the Associate Discrete Circuit (ADC) model of semiconductor switches. The ADC-based model allows obtaining a fixed topology irrespective of switches states for the power electronic converters in the digital simulation. Backward-Euler based discretized state space matrix (SSM) of the circuit used for ADC parameter. Choosing appropriate switch parameter is based on 1) reducing the distance of SSM eigenvalues from origin in z-Plane to reduce settling-Time of system response; and 2) reducing the...
Numerical assessment of new compound restrainer for seismic retrofit of bridges
, Article Structure and Infrastructure Engineering ; 2017 , Pages 1-20 ; 15732479 (ISSN) ; Pahlavan Yali, A ; Sharif University of Technology
Abstract
This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one...
Accurate analysis of a single-phase dual active bridge converter for ZVS and deadband conditions
, Article 17th IEEE International Conference on Environment and Electrical Engineering and 2017 1st IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2017, 6 June 2017 through 9 June 2017 ; 2017 ; 9781538639160 (ISBN) ; Haghbin, S ; Zolghadri, M ; Thiringer, T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
Simplified equations are used for the analysis of a dual active bridge converter leading to a conservative estimation of the zero voltage switching (ZVS) region. The ZVS is directly affected by the inserted deadband in each leg of the converter. In this paper the impact of the ZVS capacitor and deadband on soft switching region for this converter is analyzed. Also, the sufficient constraints for ZVS condition in the input and output bridges are determined by analyzing the circuit behavior during the bridges deadband. Simulation results of a 700V-350V, 50-kW DC-DC converter validate the analysis. © 2017 IEEE
Analysis of a three-phase dual active bridge converter during the deadband
, Article 17th IEEE International Conference on Environment and Electrical Engineering and 2017 1st IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2017, 6 June 2017 through 9 June 2017 ; 2017 ; 9781538639160 (ISBN) ; Haghbin, S ; Thiringer, T ; Zolghadri, M ; IEEE EMC Society; IEEE Industry Applications Society (IAS); IEEE Power and Energy Society (PES) ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
A three-phase dual active bridge (DAB) topology has been widely applied in high power DC-DC conversion due to its advantages such as bidirectional power transfer, inherent soft switching capability and small filter size. In this paper, the three-phase DAB dc/dc converter is analyzed during its deadband. Moreover, the influence of the zero-voltage-switching (ZVS) capacitor and deadband on ZVS region are investigated by utilizing an accurate circuit analysis during the deadband. The theoretical results are verified in simulation and in a50 kW experimental setup. © 2017 IEEE
Quick diagnosis of short circuit faults in cascaded H-bridge multilevel inverters using FPGA
, Article Journal of Power Electronics ; Volume 17, Issue 1 , 2017 , Pages 56-66 ; 15982092 (ISSN) ; Zolghadri, M. R ; Rodriguez, J ; Shahbazi, M ; Oraee, H ; Lezana, P ; Schmeisser, A. U ; Sharif University of Technology
Korean Institute of Power Electronics
2017
Abstract
Fast and accurate fault detection is the primary step and one of the most important tasks in fault tolerant converters. In this paper, a fast and simple method is proposed to detect and diagnosis the faulty cell in a cascaded H-bridge multilevel inverter under a short circuit fault. In this method, the reference voltage is calculated using switching control pulses and DC-Link voltages. The comparison result of the output voltage and the reference voltage is used in conjunction with active cell pulses to detect the faulty cell. To achieve this goal, the cell which is active when the Fault signal turns to “0” is detected as the faulty cell. Furthermore, consideration of generating the active...
Numerical assessment of new compound restrainer for seismic retrofit of bridges
, Article Structure and Infrastructure Engineering ; Volume 14, Issue 5 , 2018 , Pages 652-671 ; 15732479 (ISSN) ; Pahlavan Yali, A ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This paper studies through numerical simulation a practical compound restrainer to use for the improvement of seismic performance of bridges. A mechanical model has been introduced for the restrainer and a basic optimisation approach has been conducted to evaluate the performance of the restrainer to changes in the properties of its components. A real 2-span simply supported plate girder bridge has been selected for case study. Using a detailed three-dimensional model, several non-linear time history analyses were performed under seismic excitations in order to assess the performance of the bridge retrofitted by conventional restrainers including linear and non-linear viscous dampers on one...
Post fault vector control of an induction motor fed by a chb inverter
, Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; Pages 149-154 , 2019 ; 9781538692547 (ISBN) ; Zolghadri, M ; Ouni, S ; Babaloo, R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, a new post-fault vector control of an induction motor, fed by a faulty Cascaded H-Bridge (CHB) inverter, is presented. Among fault tolerant control methods, waveform based methods are suitable for closed-loop control and provide higher output voltage. In order to control the speed of the motor, a rotor field oriented control (RFOC) is used. During the fault, the FOC is modified to decrease the fault impact on the motor as low as possible. The proposed method is validated by means of simulation results for different loads and faults. The results show an improvement in both the final operating point and the transient response of the motor
Design and simulation of new soft-switched three-port half bridge converter with extended zvs range
, Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 602-608 ; 9781728115085 (ISBN) ; Jahani, M ; Oraee, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Multi-port converters (MPC), used in multi-input/multi-output power electronic systems have low cost, low weight and low mass integrated control system. Besides these converters offer bidirectional and isolated ports, which are inevitable in some applications. Three-Port Half Bridge Converters (TPHBC) are the ones which have the lowest component count. But these converters suffer from a low Zero Voltage Switching (ZVS) range that is lost in medium to low load powers. Low ZVS range cause low efficiency, especially in low output powers. In this paper a modified Pulse Width Modulation (PWM) technique is introduced to increase the ZVS range of main switches which results higher efficiency and...
Assessing Precision of Commercial Ultrasonic Instrument in Detecting Hole and Imperfection in Concrete Bridge Decks
, M.Sc. Thesis Sharif University of Technology ; Joghataie, Abdolreza (Supervisor)
Abstract
The conventional methods in concrete are usually divided to destructive and nondestructive tests. Among these, nondestructive tests are more preferable because they don’t damage the structure or at least the damage doesn’t significantly affect its performance. According to precision of estimation of concrete conditions, nondestructive tests have different levels. These tests on concrete bridge decks range from chain drag to more developed test like Ground Penetration Radar in concrete The optimum ease of use, cost and the precision of results of Ultrasonic Pulse Velocity (UPV) test compared with other nondestructive methods have made it a most widely used method. The precision of results of...
Hydrodynamic Analysis of “Persian Gulf” Bridge and Feasibility Study of Using Energy Production Systems on the Bridge Structure
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Majid (Supervisor)
Abstract
Nowadays, because high global demand for energy has led to the extensive use of fossil fuels with numerous unintended consequences such as air pollution and greenhouse effect, research and development around optimization of energy infrastructure has become much more important. Consequently, many scientific approaches have been applied to replace fossil fuels with renewable natural energy resources. One of the renewable energy types that fewer papers have been published about it, is the enormous energy of Marine currents. The origin of this energy is mostly tidal effect, or ocean currents that are available in most of oceans and seas around the planet earth. The most important criteria for...
Stability Analysis Rock Mass Abutment Karun 4 by Numerical Method
, M.Sc. Thesis Sharif University of Technology ; Sadaghiani, Mohammad Hossein (Supervisor)
Abstract
Three dimensional analyses have been carried out for predicting the behavior of the jointed rock slope of the abutments of the bridge which is proposed to be constructed across the river Karun4 in Iran using 3DEC. The rock sloping at 500 to 600 are composed of highly jointed rock mass and the joint spacing and orientation are varying at different locations. Since 3DEC is a three-dimensional numerical code, utilizes a Lagrangian calculation scheme to model large movements and deformations of a blocky system, allows for modeling of large movements and rotations, including complete detachment of rigid or deformable discrete blocks has been utilized for the analysis. The analysis has been...
Performance Evaluation of Piezoelectric Based Control System to Mitigate the Vibration of Bridges Caused by Traffic Loads and Seismic Excitation
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
A large number of bridges in Iran are deteriorating under long and heavy traffic loadings, while getting closer to the end of their design life time. Therefore, many of them have been exhibiting various problems such as excessive vibration or large deflection under the normal service loadings. So, mitigating traffic-induced bridge vibration and damages is necessary to extend their efficient period of serviceability. On the other hand, application of active and passive control devices in structural retrofitting have absorbed the attention of many engineers and researchers. In this work, the performance of an active control system made of piezoelectric actuators is investigated in reducing the...
Identification of Damage Type and Location in Reinforced Concrete Piers of Slab– Beam Bridges Using Numerical Methods
, M.Sc. Thesis Sharif University of Technology ; Ahmadizadeh, Mahdi (Supervisor)
Abstract
Bridges are among the crucial elements of transportation networks, and play an important role in facilitating emergency relief efforts following earthquakes. For this reason, it is emparative to monitor their damages to ensure about their performace in earthquakes. The structure of a bridge is divided into two parts, namely the superstructure and substructure. Due to the relatively high rigidity and strength of superstructures, most of structural damage is usually concentrated in substructures, which may ultimately affect the overall stability of the bridge. Therefore, assessing the level of damage in the substructure is of utmost concern. This research attempts to evaluate the damage in the...
Experimental and Numerical Investigation of the Flow Field around Complex Bridge Piers with and without the Scour Hole
, Ph.D. Dissertation Sharif University of Technology ; Ataie Ashtiani, Behzad (Supervisor)
Abstract
Local scour around bridge piers is one of the main causes of bridge failures Application of existing equations to complex flow patterns is problematic and often leads to questionable results in the field applications. A lack of understanding of the complex flow field and erosion mechanisms seems to be at least partly responsible for this state. Despite the rapid expansion of the literature on the flow around cylindrical piers, there are still challenges for flow field comprehension and estimating design scour depths around complex bridge piers. Due to geotechnical and economical reasons, bridge designs often leads to a complex foundation. Laboratory studies of local scour around complex...
Developing a Sustainable Model for Bridge Maintenance in Big Organisations
, M.Sc. Thesis Sharif University of Technology ; Alvanchi, Amin (Supervisor)
Abstract
For increasing longevity of a structure, it is not enough to notice only to designing aspects. In operation phase of a construction, we can increase the level of service and longevity. Asset-based Organizations, in addition to design their new assets, should maintain them. Infrastructures, such as road, bridge, dam, and water network, are important because of social and economic aspects. So they need special attention. There are efficient models for infrastructure maintenance that consider infrastructure element information, such as condition rate, weight, dimensions, deterioration rate, and cost of maintenance as inputs and give planning for maintenance in future. This planning, involves a...
Analysis of the Effects of Parasitic Elements of Pulse Transformer on Output Voltage in High Voltage DC Sources
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
Today, in different industries,as the use of high voltage DC power supplies is increasing, the need of output voltage precision also is increasing. One way to make High DC voltage is to use a multi-output DC-DC converter and makethe output series.Existing problems in measuring high voltages, results in this idea That in these converters, we measure and regulate only one of the outputs and estimate the others by circuit elements. In this estimatin, differences between the transformer parasitic elements are very effectiveon transformer various output voltages. In this thesis after a comprehensive study on the pulse transformer parasitic elements and choose a suitable model for it, the...
Numerical Analyses for Flexural Behavior of Bridge Deck Strengthened with Frp Sheets Using Partially Bonding System
, M.Sc. Thesis Sharif University of Technology ; Vafai, Abolhassan (Supervisor)
Abstract
During times, reinforced concrete sturctures might need to be strengthened due to environmental factors, material properties, design errors or changes indesign guidelines.Fibre-reinforced-polymer (FRP)composites are prominentmaterialsfor this purpose. Externally full bonding systemhas been widely used for flexural strengthening of reinforced concrete sturctures with FRP. However, the drawback of using this strengthening system is the high reduction of structure's deformability.In this research, partially bonding system used in finite element modeling of a bridge’s deck to increase deformability compared to full bonding system. Results showed that not only deformability but also load...
Prediction of Scour Depth Around Complex Piers Using Classification Methods
, M.Sc. Thesis Sharif University of Technology ; Ataie-Ashtiani, Behzad (Supervisor) ; Jamali, Mirmosaddegh (Co-Advisor)
Abstract
In this study, existing prediction methods of maximum scour depth around complex piers are studies using available experimental data and a new relationship for scour prediction is presented. Complex pier consists of a column, pile cap and pile group and is frequently used for foundation of bridge piers in hydraulic and marine structures. The results of 52 clear-water scour experiments on 4 CP models are reported which can be valuable to hydraulic design of a CP. The 4 models had different values of pile cap thickness and number of piles inline with the flow and were tested at different pile cap elevations. The duration of experiments ranged from 24 to 120 hours. Then a database of laboratory...