Babaei, M.,
Shariat mohaymany, A.,
Nikoo, N.,
Ghaffari, A. Publication Date: 2019
Journal of Humanitarian Logistics and Supply Chain Management (20426747)9(2)pp. 250-269
Purpose: One of the problems in post-earthquake disaster management in developing countries, such as Iran, is the prediction of the residual network available for disaster relief operations. Therefore, it is important to use methods that are executable in such countries given the limited amount of accurate data. The purpose of this paper is to present a multi-objective model that seeks to determine the set of roads of a transportation network that should preserve its role in carrying out disaster relief operations (i.e. known as “emergency road network” (ERN)) in the aftermath of earthquakes. Design/methodology/approach: In this paper, the total travel time of emergency trips, the total length of network and the provision of coverage to the emergency demand/supply points have been incorporated as three important metrics of ERN into a multi-objective mixed integer linear programming model. The proposed model has been solved by adopting the e-constraint method. Findings: The results of applying the model to Tehran’s highway network indicated that the least possible length for the emergency transportation network is about half the total length of its major roads (freeways and major arterials). Practical implications: Gathering detailed data about origin-destination pair of emergency trips and network characteristics have a direct effect on designing a suitable emergency network in pre-disaster phase. Originality/value: To become solvable in a reasonable time, especially in large-scale cases, the problem has been modeled based on a decomposing technique. The model has been solved successfully for the emergency roads of Tehran within about 10 min of CPU time. © 2019, Emerald Publishing Limited.
Publication Date: 2023
Electric Power Systems Research (03787796)214
Voltage sags is one of the most important issue of power quality, which can disrupt industrial process and impose huge costs on industrial plants. For improving disturbance ride-through capability of voltage source converter based on high voltage direct current (VSC-HVDC) supplying industrial plant, an auxiliary frequency controller is proposed to control output voltage frequency at inverter station. Since industrial loads are more sensitive to voltage drops compared to frequency deviations, output voltage frequency is slightly deceased based on DC-link voltage changes during disturbances in proposed control scheme in order to prevent voltage collapse and provide desirable voltage quality for industrial plants; hence, the continuity of industrial process will be ensured. The case study is a part of a real industrial plant and variations of DC-link voltage, AC buses voltages, induction motors speed, and performance of adjustable speed drive are investigated when the proposed method is used during faults. In proposed method, voltage drop across industrial plant during a severe fault is less than other methods and dynamic performance of system is improved. The case study is simulated under balanced three-phase fault, double line-to-ground fault, and single line-to-ground fault in PSCAD/EMTDC, and results verify the validity of the proposed control scheme. © 2022
Publication Date: 2022
Electric Power Systems Research (03787796)206
Overcurrent and overvoltage can damage converter valves, DC capacitors and transformers in the VSC-HVDC systems. Therefore, a proper starting-up mechanism is needed to avoid overcurrent and overvoltage. Overcurrent occurs in the second stage of the starting-up procedure due to rapid response of controllers, high dVDC/dt and malfunction of PLL. Traditional methods reduce overcurrent, but they cause an increase in starting-up time duration. In this paper, a new control method is proposed to apply in the second stage of the starting-up procedure. Not only does the proposed method restrain overcurrent and overvoltage, but it also reduces time duration of starting-up. In addition, the proposed method reduces dVDC/dt and can limit the starting-up current to any desired value. Furthermore, the proposed method has a simple control system and does not need any extra elements, leading to a simple manufacturing. The operation and design principles of the proposed method are investigated in detail. Finally, the proposed control method is verified by simulation and experimental results of a bipolar two-level VSC-HVDC. © 2022 Elsevier B.V.
Publication Date: 2020
Transportation (00494488)47(1)pp. 417-443
Due to the interaction among different planning levels and various travel demands during a day, the transit network planning is of great importance. In this paper, a bi-objective multi-period planning model is proposed for the synchronization of timetabling and vehicle scheduling. The main aim of the problem is to minimize the weighted transfer waiting time in the interchange stations along with the operational costs of vehicles. In order to demonstrate the effectiveness of the proposed integrated model, a real case study of Tehran subway is considered. The proposed model is solved by the ε-constraint method and some outstanding results are achieved. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.
Publication Date: 2025
Journal of Materials in Civil Engineering (19435533)37(12)
The rapid expansion of asphalt pavements worldwide has led to increased concerns regarding their deterioration, which incurs significant financial costs and environmental pollution. To mitigate such issues, the application of preventive maintenance treatments like microsurfacing before irreparable damage occurs is crucial. However, designing effective microsurfacing systems presents challenges, particularly in achieving stable asphalt emulsions. The use of suitable stabilizers can address these challenges. This study aims to fill the existing research gap by evaluating the performance of waste engine oil (WEO), waste cooking oil (WCO), and gas oil as stabilizers at three different concentrations. Additionally, to ensure the compatibility of these materials with other additives and to achieve a comprehensive assessment, three different penetration-grade bitumens, including one polymer-modified with polyphosphoric acid (PPA), were utilized. Furthermore, two distinct emulsifiers and two types of fibers - glass and polypropylene - were incorporated into the study. The performance of the microsurfacing mixtures was evaluated through a series of tests, including the cohesion test, wet-track abrasion test (WTAT), loaded wheel test (LWT), mixing time determination test, and consistency test. The results were subsequently analyzed using statistical methods. The findings revealed that gas oil exhibited the best performance as a stabilizer, followed by WCO and WEO. Moreover, the results indicated that the stabilizer type and concentration, as well as the emulsifier type, are critical parameters influencing the performance of microsurfacing systems. © 2025 American Society of Civil Engineers.
Goli, A.,
Sadeghi, P.,
Karimi, A.,
Shojaei, M.,
Kazemi, M. Publication Date: 2025
Journal of Materials in Civil Engineering (19435533)37(7)
The disposal of cigarette filters (CFs), primarily composed of cellulose acetate fibers and containing harmful substances like burned tobacco, tar, and heavy metals, poses a significant environmental threat due to their slow degradation. Thus, finding an effective approach for recycling and disposal is a pressing concern. Repurposing CFs in asphalt mixtures offers a promising recycling solution, particularly for improving asphalt crack resistance, which is crucial for performance but underexplored. This study evaluates the effects of incorporating intact and shredded CFs into stone mastic asphalt (SMA) under different wet and dry conditions on crack resistance. Semicircular bending (SCB) tests at 25°C and-12°C were conducted, examining two fracture modes (Mode I and Mixed Mode I/II). Key performance indicators like crack resistance index (CRI), balanced cracking index (BCI), toughness index (TI), peak load (Fmax), and fracture energy (Gf) were calculated. Results indicate that a 3% inclusion of shredded CFs significantly enhances crack resistance, with wet mixing showing the greatest improvements: Gf, CRI, and BCI increased by up to 46%, 15%, and 75% in Mode I, and 28%, 23%, and 76% in Mixed Mode I/II, respectively. Additionally, this study demonstrates the reliability of non-standard samples for SCB testing in mixed Mode I/II and emphasizes the critical role of CF quantity and the mixing method, with wet mixing proving notably more effective than dry mixing in improving the structural performance of asphalt. © 2025 American Society of Civil Engineers.
Publication Date: 2025
Case Studies in Construction Materials (22145095)22
Microsurfacing has emerged as a favored preventative maintenance solution in pavement engineering due to its economic efficiency, high effectiveness, and environmental benefits. This research, despite the complexity arising from the diversity of additives, conducts a comprehensive evaluation of the effects of various additives on microsurfacing performance. This includes stabilizers—whose significant impact has previously been overlooked—different types of bitumen, and fibers. Utilizing two types of bitumen with varying penetration grades, bitumen modified with polyphosphoric acid (PPA), two distinct emulsifiers, Type I (French) and Type II (Iranian), and four stabilizers (gasoil, petrol, petroleum, and engine oil) in three different percentages. Along with two types of fibers, the study examines their impacts on microsurfacing. The performance of the microsurfacing mixture was then assessed using Cohesion test, Wet-Track Abrasion Test (WTAT), Loaded Wheel Test (LWT), Mixing Time Determination Test, and Schulze–Breuer & Rock (SBRT) test. The findings indicate considerable improvements in microsurfacing performance with the recommended formulations. This study underscores the importance of proper additive selection, identifying gasoil stabilizers and Type I emulsifier as superior choices, though no significant difference was observed between emulsifiers Type I and II. The study suggests using Type II emulsifier for economic efficiency. Microscopic evaluations further confirm the critical role of 2 % gasoil in emulsion stability. Statistical results highlight the stabilizer amount as the most crucial parameter affecting microsurfacing performance. These insights emphasize the criticality of precise additive selection in optimizing microsurfacing efficiency and provide effective guidelines for the optimal design of microsurfacing mixtures. © 2025
Publication Date: 2025
Electrical Engineering (14320487)107pp. 10433-10444
This paper presents a 0.7-MW high-current variable-voltage inductive load that is connected by a 12-pulse thyristor rectifier to the distribution system. In order to compensate at the point of common coupling over the load current range, a parallel hybrid filter (PHF) is used comprising two single-tuned passive filters for 11th and 13th harmonic and a second-order high-pass passive filter for 23th harmonic and DSTATCOM. According to the load reactive power variation, the DSTATCOM is used only to improve the displacement power factor (DPF) while passive filters are incapable of keeping DPF in acceptable values (greater than 0.98). Because of the distribution system voltage variation, it is assumed that voltage varies ± 5% of the network line voltage. A new comprehensive method is presented for the PHF design with simple equations based on accurate equalization of DSTATCOM maximum lead and lag currents (minimum rating and cost) in the fixed and variable network voltage. This equalization not only reduces the rating of DSTATCOM, but also the total power of passive filters. A network current TDD optimization is according to the PSO algorithm carried out with modeling of the system (presenting system equations) and using network harmonics current constraints in PSO loops which puts all network current harmonics in acceptable amounts. What’s more, harnessing PSO algorithm considerably reduces network current TDD in comparison with previous studies. MATLAB simulation results comprising DSTATCOM current and reactive power, network current TDD and harmonics, and other simulation results are presented to verify the better reactive power and harmonic performance of proposed method compared with other method. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Publication Date: 2026
Electric Power Systems Research (03787796)251
An increase in the current of the converter's switching valves beyond their rated value and fluctuations in the DC-link voltage during unbalanced fault conditions are among the most significant challenges in voltage source converter-based high voltage direct current (VSC-HVDC) systems. These issues can significantly reduce the reliability of the system. Existing methods to address these problems tend to increase the complexity of the control system and involve high computational demands. Additionally, their performance may not be suitable for all common transformer configurations in VSC-HVDC systems. In unbalanced fault scenarios, this work proposes a straightforward way to manage the current and minimize DC-link voltage variations. The suggested approach successfully regulates the current across all typical transformer winding connections to the appropriate value. The studied system is simulated under double line-to-ground and single line-to-ground fault conditions in PSCAD/EMTDC. The results confirm the effectiveness of the proposed control method across all common transformer configurations in both two-terminal and multi-terminal VSC-HVDC systems. © 2025 Elsevier B.V.
Publication Date: 2014
Transport (16484142)29(1)pp. 28-35
The evaluation of railway line capacity is an important problem, which effects majority of problems in rail transportation planning. The railway capacity is dependent on infrastructure, traffic, and operating parameters. A key factor affecting railway line capacity is the impact of different train types. As the combination of different train types increases, more interference is generated. In this paper, for evaluation of train type interactions on railway line capacity, an integer-programming model for both line and line section is presented. The problem is formulated as a multicommodity network design model on a space-discrete time network. The railway capacity is calculated using data typically available to planners. The inputs of the model are the characteristic of each train type and railway line attributes. The model determines railway capacity based on train type mixes. In addition, this model considers impact of train types on capacity and waiting time. In order to show the features of the model, a case study is implemented in Iran Railways. The capacity tends to increase non-linearly with small incremental changes in parameters. The mixture of train types reduces the railway line capacity. The proposed model can help railway managers for long-term planning. © 2014 Copyright © 2014 Vilnius Gediminas Technical University (VGTU) Press.
This paper presents a modeling and simulation of two different vehicles topologies (parallel hybrid electric vehicle and series hybrid electric vehicle) using the ADVISOR (ADvanced Vehicle SimulatOR). An accurate analysis of the performance of a hybrid electric vehicle, as well as of its consumption and pollution level, requires a dynamic analysis of its behavior. Two kinds of simulation tools for electric and hybrid electric vehicles exist: steady state and dynamic tools. An accurate analysis of the vehicle performance requires a dynamic model that includes many components such as its electric motor, its batteries and its motor controller. The central controller of this sedan consists of I/O Board, Adapter and Microcontroller of motor drive. In a first step, the vehicle components are sized, using a power flow analysis, to meet the requirements of energy and power of a typical 'Sedan vehicle'. In a second step, simulation results are presented and discussed to analysis complexity and performance. © 2017 IEEE.
Nowadays, to overcome power quality and power factor problems at AC input mains of power systems, various active (Power Factor Correction) PFC techniques are widely employed which utilize switch-mode converters and controller circuits to achieve the aims. Amongst them, in this paper, PFC-based zeta converter and single-phase PWM-rectifier are designated as efficient PFC circuitry to mitigate the Total Harmonic Distortion (THD) and also increase Power Factor (PF). This paper focuses on control and design, analysis, and performance evaluation of each PFC topology separately in the presence of brushless DC motor. The design complexity and number of element required in the PFC circuits are contributing factors to be regarded. Since, the larger these quantities are, the more destructive impact they have on the system reliability and expense. In this regard, this letter, compares the designed PFC-based zeta converter and single-phase PWM-rectifier in terms of their performance, application, design complexity and the number of required elements. The proposed PFC converter topologies are modeled and simulated in Matlab-Simulink environment and then are evaluated through some case studies. © 2019 IEEE.
Publication Date: 2022
IEEE Access (21693536)10pp. 37330-37344
The main purpose of this paper is to analyze a five-phase Voltage Source Inverter (VSI) that is operated with the Pulse Width Modulation (PWM) switching technique. Double Fourier integral (DFI) analysis has been used to extract the harmonics of the line-to-line voltages. Moreover, the harmonic current ripple has been calculated for an effective inductive five-phase load with a regular pentagon connection. Correspondingly, a new closed-form solution for calculating the harmonic losses in five-phase VSIs has been derived. In addition, a new equation for the weighted total harmonic distortion (WTHD) index has been extracted for five-phase VSIs. To validate the suggested analytical solutions (i.e., harmonic losses and WTHD equations), the results are compared with the DFI calculation method and the method of applying the fast Fourier transform (FFT) to a simulated waveform. The results show that the proposed analytical method has high accuracy and requires less mathematical effort, especially at high-frequency ratio values. Finally, the study includes simulation results and the implementation of an experimental setup. © 2013 IEEE.
Publication Date: 2020
International Transactions on Electrical Energy Systems (20507038)30(12)
This paper demonstrates the functionality and control of the gate-controlled series capacitor (GCSC), a new FACTS device composing a pair of antiparallel GTOs in parallel with a fixed capacitor, to mitigate subsynchronous resonance (SSR) in a thermal generation plant connected to a series compensated transmission line. Firstly, by the use of both small-signal stability analysis and time-domain simulation, it is revealed that the studied system compensated by the series fixed capacitor is potentially unstable due to the first torsional mode. Then, in order to take benefits of series compensation without the risk of SSR, the fixed capacitor is replaced by GCSC. The capability and effectiveness of the GCSC to damp SSR are validated using modal analysis and time-domain simulation. Furthermore, GCSC is used in conjunction with a fixed series capacitor to minimize the overall cost of compensation. For this purpose, unlike previous studies, a linear controller is used to stabilize the system. In this study, the IEEE First Benchmark Model is considered as a case study, and MATLAB/Simulink is used as a tool for modeling and design of the control system. Also, time-domain simulations are done using PSCAD/EMTDC. © 2020 John Wiley & Sons Ltd
Publication Date: 2016
Petroleum Science and Technology (15322459)34(6)pp. 505-511
Fatigue is defined as a fracture phenomenon due to a repetitive load or a variable dynamic load that occurs at a lower load than the ultimate static load. Fatigue stability of an asphalt mixture is its ability of enduring the repetitive flexural loads. In this study, the carbon nanotubes are used as the bitumen modifier in the way that the prepared samples contain 0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% carbon nanotubes. Then, the classic and rheological experiments are conducted on these samples. This additive improves the classical properties of bitumen (softening point, penetration degree, and so on) and also the fatigue parameter of bitumen (i.e., G*Sinδ) in comparison to the standard bitumen. Using the rheological graphs, it can be predicted that adding the carbon nanotubes to bitumen might improve the fatigue life of the asphalt mixtures. To evaluate the accuracy of this prediction, the fatigue experiment are performed on the prepared beam samples using a four-point loading in the case of constant strain (600 microstrain) with a semi-sinusoidal wave at 20°C. The end of the samples’ fatigue life is 50% reduction in their initial rigidity. It is observed that with an increase in the percentage of carbon nanotube in fatigue samples, the fatigue life of asphalt mixtures remarkably increases. © 2016 Taylor & Francis Group, LLC.
This study deals with a power factor correction (PFC) based Vienna converter for Switched Reluctance Motor (SRM) drive for medium power applications. Compared with the traditional two-level or three-level unidirectional rectifier, Vienna rectifier is the appropriate choice for its advantage such as only half numbers of the switches, simple structure, high-power efficiency and ability to realize unity power factor with proper control strategy. The PFC-based Vienna converter is designed to operate in continuous inductor current mode and feed two SRM drives from one power supply simultaneously. The proposed drive is designed to operate over a wide range of speed control with improved power quality at ac mains. The performance of the proposed drive is compared with Diode Bridge Rectifier (DBR) and it is validated with simulation results. Simulation of the proposed system for feeding SRM has been done in MATLAB software. The proposed topology provides almost lower input current THD, which is found to be about 0.25% and improved power factor up to 1. © 2018 IEEE.
Publication Date: 2017
Gradevinar (03502465)69(11)pp. 1017-1029
Bridge response to predefined loading schemes is described and recorded by instrumenting the structure with deflectometers and accelerometers. Test results suggest that although vertical deflections of mid-spans are almost constant for all crossing speeds, the root mean square of acceleration values are positively correlated with the crossing speed. Field test results are then used to calibrate and verify the 3D finite element model of the bridge, and the latter is employed to assess behaviour of the structure at the serviceability limit state.
Publication Date: 2017
International Journal of Architectural Heritage (15583066)11(8)pp. 1086-1100
Health monitoring of masonry railway bridges is vital due to their long life in service, an increasing demand for higher axle loads, and the recent trends in sustainability that requires the preservation of aged masonry bridges. Safety assessment of a 70-year-old masonry arch bridge is presented. The bridge is situated in a S-shaped curved section of the track and has long spans of 36 m. Added the deterioration of masonry due to old age of the bridge and complex behavior of masonry arch bridges, dynamic load tests are employed and global structural responses to allowable loading schemes of the bridge are determined. Dynamic amplification factors are determined and compared to those proposed by standards and it is concluded that experimental values are higher than those proposed by standards. Model calibration is carried out using deflection signatures. Experimental and analytical natural frequencies are compared for model verification. Having the model calibrated and verified, safety of bridge in serviceability and ultimate limit states due to application of operational loading schemes and higher axle loads are assessed. It is concluded that the bridge is safe regarding operational loading patterns, and could withstand an increased axle load of 25 tons. © 2017 Taylor & Francis.
Kazemi, M.,
Karimi, A.,
Goli, A.,
Hajikarimi, P.,
Mohammadi, A.,
Doctorsafaei, A.H.,
Fini, E. Publication Date: 2024
Journal of Materials in Civil Engineering (19435533)36(1)
This paper evaluated the effect of a biobased polyurethane modifier on the moisture resistance of asphalt binder. Biomodifiers with high acid values have been implicated in moisture damage to asphalt. Here, castor oil with a relatively high acid value of 190 mg KOH·g-1 was used to produce biobased polyurethane. Biobased polyurethane was produced by combining castor oil, toluene diisocyanate (TDI), and diethylene glycol (DEG) at a molar ratio of 1:2:1. Asphalt binder was modified with 3%, 6%, or 9% of the biobased polyurethane (by weight of asphalt binder), and the moisture susceptibility of the modified asphalt was evaluated with a comprehensive laboratory experiment plan using the boiling water test, the indirect tensile strength test, the bitumen bond strength test, the water contact-angle moisture-susceptibility test, and the moisture-induced shear-thinning index test. Study results showed that the introduction of biobased polyurethane enhanced the bond between the aggregate and asphalt, thereby increasing the asphalt mixture's resistance to moisture damage. Consequently, the resistance of asphalt binders to cohesive failure and adhesive failure was enhanced in biobased polyurethane, as evidenced by respective increases of 19%, 40%, and 49% in tensile strength ratio for dosages of 3%, 6%, and 9% biobased polyurethane. Compared with neat asphalt, the asphalt blend containing 9% polyurethane had the highest bond-strength increases, 55.73% and 37.93%, for dry and wet conditions, respectively. This improvement is attributable to the phenol and amide components in biobased polyurethane, which increase the polarity of asphalt binder and increase the affinity of asphalt binder to siliceous aggregate. In addition, the moisture-induced shear-thinning index and the contact-angle moisture-susceptibility index showed that increased doses of biobased polyurethane resulted in increased resistance of asphalt to moisture damage. The study outcomes promote the sustainability of asphalt construction by introducing biobased polyurethane as a sustainable modifier for asphalt. © 2023 American Society of Civil Engineers.
Yaghini, M.,
Sarmadi, M.,
Nikoo, N.,
Momeni, M. Publication Date: 2014
Networks and Spatial Economics (1566113X)14(3-4)pp. 317-333
In this paper, a compressed timetable is generated to calculate capacity consumption for under construction railway routes using an optimization approach. Since the detailed timetable for under construction routes does not exist, the timetable is not required in the applied model. The model generates a compressed timetable based on UIC 406 method. The capacity consumption problem is formulated as a multicommodity network design model on a space-discrete time network. A local branching heuristic algorithm is proposed to solve the model. The main idea underlining the local branching algorithm is the utilization of a general mixed integer programming solver to explore neighborhoods and locally search around the best-known solution by employing tree search. The parameters of the algorithm are tuned by using design of experiments. The proposed method is implemented in Iran Railways and the results are reported. © 2014, Springer Science+Business Media New York.
Publication Date: 2024
Journal of Composites Science (2504477X)8(3)
This paper presents an innovative bituminous composite containing recycled high-density polyethylene (HDPE) as a means of carbon sequestration. To prepare the composite, rejuvenators and recycled HDPE were introduced to reclaimed asphalt pavement (RAP), separately and in combination. To evaluate efficacy of rejuvenators, this study used the following three rejuvenators: waste engine oil (WEO), oleic acid (OA), and vacuum bottom (VB). The performance of the bituminous composite containing HDPE and rejuvenators was evaluated using the indirect tensile fatigue test, the rutting resistance test, the resilient modulus test, and the semi-circular bending test. Results showed that applying a combination of rejuvenators and recycled HDPE improved the resistance to fatigue, rutting, and cracking. Particularly, in terms of improving resistance to cracking, OA proved to be the most effective rejuvenator, followed by WEO and VB. In all bituminous composites studied here, the hybrid application of HDPE and rejuvenator proved to be more effective than the rejuvenator or HDPE alone. © 2024 by the authors.
Publication Date: 2024
Road Materials and Pavement Design (14680629)25(4)pp. 716-735
This study evaluates the cracking resistance of recycled asphalt pavement (RAP) mixtures including waste engine oil (WEO), crumb rubber (CR), and steel slag aggregates using the Illinois flexibility index test (I-FIT). Performance indices, derived from both this study and another, were predicted by comparing deep neural network (DNN), linear, and polynomial regression models via a k-fold cross-validation process. I-FIT test results demonstrated that WEO, steel slag aggregates, and specific CR proportions enhance cracking resistance while RAP utilisation decreased it. In terms of modelling, it was found that the most appropriate prediction model for the dataset structure of this study is the deep neural network model. The DNN model sensitivity analysis identified WEO as key for high and intermediate temperature (I-FIT) performance. Meanwhile, CR significantly impacted intermediate temperatures (IDEAL-CT), while RAP influenced moisture susceptibility. This model proves reliable and efficient, suggesting its potential for predicting the performance of recycled mixtures. © 2023 Informa UK Limited, trading as Taylor & Francis Group.
Zeinoddin, H.S.,
Abtahi, S.M.,
Hejazi, S.M.,
Babamohammadi, S.,
Goli, A.,
Amuchi, M. Publication Date: 2016
Transportation Infrastructure Geotechnology (21967202)3(3-4)pp. 91-108
In traditional method of hot mix asphalt (HMA) production, large energy consumption and increased environmental awareness have resulted in the innovation of a production technology named warm mix asphalt (WMA). In this technology, various methods are used to reduce the temperature of production and paving. On the other hand, steel slag is the by-product of iron and steel factories, and many researches have been done around the world to use these materials in several fields, such as HMA industry. Various studies show steel slag to be considerably effective in improving the performance of asphalt concrete. One of the properties of steel slag is having high heat capacity value which leads to higher energy consumption during the production of HMA compared to conventional aggregates. The main aim of this study is therefore using WMA technology to reduce the energy consumption and to produce steel slag warm mix asphalt (SSWMA). In order to fabricate SSWMA in lab, an amino-based resin was used as an additive to decrease the viscosity of the bitumen. The amount of resin was ranged from 5 to 15 % by the weight of bitumen. The performance of SSWMA samples was evaluated by several tests, including dynamic shear rheometer, bending beam rheometer, Marshall test, moisture sensitivity, indirect tensile strength, and resilient modulus. Experimental results revealed that amino-based resin additive can decrease the viscosity of the bitumen by producing foam particles. This reduction of viscosity leads to reduction of asphalt production temperature as much as 25 °C in application of 10 % resin by the total weight of the bitumen. It can be also concluded that SSWMA proposed acceptable moisture resistance, and modified bitumen showed a superior performance rather than the neat bitumen in the case of rutting resistance. © 2016, Springer Science+Business Media New York.
Publication Date: 2020
KSCE Journal of Civil Engineering (12267988)24(10)pp. 3050-3063
The disaster response routes play a crucial role in transporting injured people and goods during the 72 golden hours after disaster. These routes connect the major disaster relief centers. Prior identification of the disaster response routes for a city enables the response teams to reach the disaster locations quickly and conduct relief and rescue operations without being obstructed by the outbound flow of evacuees from the city. These routes should not generally be used by the public unlike the evacuation routes. In this paper, a multi-objective stochastic disaster response routes design problem is presented. In this study, with the goal of reducing vulnerability, the disaster response routes network can be protected against disaster scenarios to maintain its connectivity using more independent routes. An exact approach including a bounded objective function method for considering the multi-objective functions, including the network factors (OD connectivity, vulnerability, and management) and an exact method (branch-and-cut) for solving the proposed model are suggested. The results for Sioux-Falls and Tehran networks show the effectiveness of the model. © 2020, Korean Society of Civil Engineers.
Publication Date: 2023
Public Transport (16137159)15(1)pp. 97-128
Dwell time is the amount of time required for performing boarding and alighting activities at stops. Under peak-load conditions, the dwell time can significantly increase due to a higher friction between on-board passengers when alighting and boarding. The influence of on-board crowding on increasing dwell time is indisputable. Herein, we develop a mixed-integer nonlinear programming (MINLP) model to optimize limited-stop patterns for bus services to minimize user and operator costs. The number of non-stop consecutive buses authorized to skip a station and in-vehicle crowding conditions are explicitly considered in our modeling framework. The benefits of limited-stop bus services are mainly overestimated in previous studies that ignore such operating conditions. Moreover, a genetic algorithm is developed to solve the problem in real-world cases. The findings show that the implementation of a limited-stop bus service can reduce in-vehicle travel times for passengers and operating costs for bus agencies in all-demand cases. Nonetheless, it can increase waiting times for users whose origin or destination stations are skipped due to the implementation of limited-stop services. Thus, the desirability of a limited-stop service can decrease with the growth of the demand level. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Publication Date: 2017
Structural Engineering and Mechanics (12254568)64(1)pp. 33-44
In this paper, the dynamic responses of train-bridge system under one-way and two-way high-speed train passing are studied. The 3D finite element modeling is used and the bridge and train are modeled considering their details. The created model is validated by the results of the dynamic field test. To study the effect of train speed, different train passing scenarios are analyzed, including one-way passing, two-way passing in different directions at same speeds, and two-way passing in different directions at different speeds. The results show that the locations of maximum acceleration are different in one-way and two-way passing modes, and the maximum values in two-way passing mode are higher than those in one-way passing mode, while the maximum accelerations in both modes are almost identical. The displacement and acceleration values in different scenarios show peaks at speeds of 260 and 120 km/h, due to the proximity of the natural frequencies of the bridge and loading frequencies of the train at these speeds. Copyright © 2017 Techno-Press, Ltd.
