فصلنامه مهندسی حمل و نقل
سال نهم شماره 2 (پیاپی 34، زمستان 1396)

In this study, the possibility of using sensors to determine the vehicle loads in the pavement simultaneously with the damage detection sensor activity, was investigated. In this research, the possibilities of using damage detection sensor as piezoresistive sensor was investigated simultaneously. With this sensor, in addition to health monitoring and propagation of cracks in their structures over the time, they were also used as a sensor to determine the vehicle load and counter cars. In order to simulate conditions of concrete sensor embedded in concrete pavement, a small concrete sensor was buried in concrete beam as an element of concrete pavement. In order to formulate the traffic load on the pavement, concrete beam was tested under different magnitudes of dynamic loads. The results showed that the maximum external load exerted on the sensor (Fmax) with a maximum response of the sensor (Smax) is related to the proportion of force-time curve slope (tgα) sensor response - time curve slope (tgβ). It also continues to evaluate the behavior of the sensor damage detection concrete sensor by loading in static regime up to failure. The results showed the point of failure, growth of crack propagation and separation of concrete beam were clearly shown by sensor response. Therefore, it can be concluded that use of damage detection sensor for piezoresistive application is possible and the sensor can evaluate the load with of high-precision formulation (R2adj.> 0.99).

Increasing lateral resistance of ballasted track, especially in curves is one of the important issues in Railway. There are several methods in order to receive to this purpose; such as using frictional concrete sleeper, ladder track and winged sleeper. Furthermore using sleeper anchoring is an innovative method that in this study is used. While in the technical literature, the effect of sleeper anchoring on the lateral resistance of track is not evaluated. Evaluation of lateral resistance of track allows the analysis of lateral forces of the track and compares the efficiency of this method with other methods for increasing Lateral resistance. In this research some experiments on concrete sleepers with adding one and two sleeper anchoring is conducted. The results of STPT and TPLT indicated that maximum increasing in first situation will happen when sleeper anchoring is under the inner rail and the amount of that will increase up to 19 percent. If we use two (one sleeper anchoring under each rail), this incensement will be up to 37 percent.

The optimal routing for transferring the wounded and relief assistance is a major problem in the event of a crisis. At this time the importance of two factors, namely time and money, in order to help and rescue the injured is doubled. This paper aims to find the most optimal route from a rescue center to the crisis center. The presented mathematical model aims to minimize the time and cost of accessing a crisis center. We also consider some assumptions, such as multiple storages, multiple paths, multiple scenarios, split delivery, multiple products, heterogeneity of the vehicles and time. Given that the values of some parameters, such as demand and time of the travel are uncertain, in which we state them in respect to the former mentioned assumptions. Considering these parameters uncertain makes them closer to the real problem. Most of the issues raised in this field have not considered all assumptions at the same time and they have considered the mentioned parameters (time and demand) as definitive. Finally, in order to find accurate answers regarding to multiple objectives of the model and different phases of parameters (i.e., time and demand), we use ε-constraint method in small-scale problems. Then because this problem is NP-hard, two meta-heuristic algorithms, namely MOHS and NSGA-II, are used to solve 15 issues large-scale problems. The results numerically show that both algorithms have high potential in producing good solutions at the right time and they are used to solve the largest and most complex issue in less than 480 seconds. This model is very suitable and uncertain with multiple objectives.

Modification of bitumen with different modifiers already has been done in order to modify rheological properties of neat bitumen to ideal bitumen. The point which has to be considered is that asphalt mixture fabricated with this modified bitumen has to show appropriate performance which is expected. Also, environmental consistent with appropriate price materials should be used to modify bitumen. In this research, bitumen modified with crumb rubber and polymer-covered sulfur were prepared using high shear rate mixer. After fabrication of modified and unmodified asphalt mixtures according to Superpave method, dynamic modulus and dynamic creep tests were conducted on them to investigate their performance and mechanical properties. From the results of dynamic modulus test, linear viscoelastic characterization accomplished and dynamic modulus master curves were developed. Comparison of those master curves showed that asphalt mixture with 40 percent polymer-covered sulfur has the highest dynamic modulus in high temperatures (low frequencies). Then, asphalt mixture with 20 percent crumb rubber has higher dynamic modulus compared to control asphalt mixture. Also, dynamic creep test results at 50 ᵒC showed that asphalt mixture modified with polymer-covered sulfur has the most resistance to rutting, and then, asphalt mixture modified with crumb rubber is more resistant to permanent deformation compared to control asphalt mixture.

The rapid development of roadways and the limited budget require establishing an effective pavement management system. The paper aimed to utilize the Life Cycle Cost Analysis (LCCA) and implement HDM-4 Software to determine the most appropriate maintenance and rehabilitation technique in part of a network in South Khorsan Region in Iran. In doing so, initial homogenous segments were assigned based on Pavement Condition Index (PCI), International Roughness Index (IRI) and maximum deflection under the center of the load plate in Falling Weight Deflectmeter (FWD) device. The final homogenous segments were determined based on the selected maintenance and rehabilitation work items. The effects of each rehabilitation alternative on roughness and the attributed costs were analyzed at the network level. Finally, the effects of change in the budget heads and the discount rates were investigated performing sensitivity analysis. Results indicated that all the maintenance and rehabilitation alternatives, except for the base method, decreased the IRI values. Furthermore, the higher amount of road user costs, compared with road agency costs, indicated the importance of considering the user cost in LCCA. With increasing the discount rates, the proposed work program would change. Taking into consideration various maintenance alternatives, the importance of inserting the correct discount rate in LCCA was confirmed. Regarding allocated budget for the analysis period, it was revealed that the allocated 100 billion Rials in the first year of the analysis period, followed by 10 percent annual increase, was enough for implementing the proposed program. With further analysis, it was found that the 700 billion Rials (54 percent of the total allocated budget) was considered a minimum budget required for application of the proposed work program, saving large amounts of national financial sources.

A large portion of the budget of many countries in the world is spent on the transportation projects. Often these projects are capital-intensive in the all of transportation systems, and for this reason, any savings -even small saving- in these projects, could lead to considerable economic benefits. The value engineering is one of the powerful management and cost saving techniques that is capable of significant decreasing in construction cost and time, as well as increasing project performance and value.
In many cases, due to budget limitation, concurrent implementation of multiple projects in the transportation sector is not possible and it is essential that the approved projects prioritized and implemented based on specified criteria. The value engineering focuses on the criteria which could lead to the significant decreasing in the project implementation cost and time, and elimination of unnecessary activities. This research is based on railway transportation expert comments for developing eleven appropriate criteria using value engineering concept for evaluation and prioritizing five projects of the new rail lines construction by applying an ANP model. Based on the results, implementing the “bam-jiroft” project has the highest implementation priority and also the “implementation cost” criterion has the greatest weight compared to other used criteria. In addition based on the results of this study, a framework is proposed for review in the budget allocation management according to the weight of each project which it can be used to reform the current system of budget allocation. In the following, in order to analyze the results, the obtained results of the ANP are confirmed by using four other decision-making models. Also the sensitivity analysis results show that the proposed prioritization model has the highest sensitivity to the “reducing the number of road accidents” criterion and the lowest sensitivity to the “operating cost” criterion.

In order to reduce vibration of structures, Tuned Liquid Dampers (TLDs) have been used widely in recent years. The main purpose of this research is to numerically study the application of TLDs in vibration reduction of airport towers. These structures are among the first systems to which TLDs have been applied. To understand the impact of the damper used in airport tower structure, a simple degree of freedom structure was modeled in Fortran software program with finite element method. This structure was analyzed both without using control devices and implementing five different dampers under three dominant seismic records: the El Centro, Kobe and Tabas earthquakes. The dampers varied in the size of the container and the amount of the water inside. The flow in the container was modeled with shallow water equations. The results show that all TLDs reduce the vibration of structure. Also, for the equal mass of water for different dampers, increasing the size of the tank and in turn reducing the number of TLDs, result in increasing vibration mitigation. The maximum drift of the structure according to the damper type was decreased from 5 to 54 percent of the original amount due to uncontrolled case.

Today, sharing bikes has become one of the growing and significant issues in the field of transportation in more than 800 cities of the world. Many analysts have predicted that the number of injuries and damages will increase after the use and implementation of bike-sharing system, but the empirical research in this area shows that if this system is correctly implemented, the increasing number of injuries and damages resulting from the use of bike-sharing system will decrease. In this paper, by analyzing the data provided by Tehran municipality, we will examine the transaction of Tehran bike-sharing stations and its advantages and disadvantages. We also will examine the lack of people’s interest in some stations and then compare the data obtained from Tehran bike-sharing system with that of London and Paris, two cities which are more experienced in setting up bike-sharing system. Some suggestions are also offered to Tehran municipality regarding the use of electric bikes and the need to use Global Positioning System (GPS) in order to achieve the exact number of trips, the exact location of users, and the number of injuries and damages. In addition, an approach to the efficient use of the special bicycling routes will be presented.

Once pedestrians decide to cross the streets, it is inevitable that they will conflict with motor vehicles. While crossing the streets, pedestrians may get into collisions by inaccurate judgments about the selected time to collision and speed of approaching vehicle. Thus, the aim of the current study is to investigate and identify factors affecting on pedestrians’ risk intensity based on mixed index ranking selected time to collision and speed of approaching vehicle when crossing intersections in urban streets. For this purpose, time to collision and speed of approaching vehicle for 800 pedestrians were collected by using an observational survey of six signalized and un-signalized intersections located in Qazvin city. The critical combination of these two parameters were considered as an indicator of risk. After rating the risk intensity, the ordered logit model was used for modeling. Results of this study showed that the average time to collision selected by male pedestrians (9.5 seconds) is less than women pedestrians (6.6 seconds), but the average speed of approaching vehicle selected by their (25 k/h) is similar for every two gender. The speed of approaching vehicle as the most important criteria in prioritizing pedestrians risk intensity were identified. More than 70 percent of the pedestrians while speed of approaching vehicle was 40 km/h, they taking risk. It is also indicated that factors such as gender, age, pedestrian speed, using mobile, time to collision and speed of approaching vehicles have significantly affect pedestrians risk taking behaviors. Elasticity analysis showed that the speed of approaching vehicle is the most effective variables in risk taking of pedestrians.