JOURNAL OF TRANSPORTATION INFRASTRUCTURE ENGINEERING (JTIE)
Year:2016 | Volume:1 | Issue:4|Papers Count:7

Previous studies have shown that cement production leads to the loss of natural resources such as limestone and fossil fuels and to the environmental pollution by greenhouse gas emissions, such as carbon dioxide. Therefore, durability of concrete structures is of particular importance. Using additives and also replacing conventional materials applied in concrete with new materials, has always been of great consideration. Nanomaterials are one of the new series of materials which have improved the mechanical and durability properties of concrete. In the present research, in order to evaluate the effect of freeze-thaw durability of concrete containing different percentages of nanocarbon cement structures on its flexural strength, weight loss test and three-point bending strength test were conducted. These nanostructures have been grown on Portland cement type II by chemical vapor deposition method. The results indicated that samples with 10% nanocarbon cement structures have led to the best performance of concrete pavement exposed to freeze-thaw cycles. Using of nanocarbon cement structures reduced weight loss and loss of flexural strength in the concrete pavements, and thereby improved the durability of concrete pavements exposed to freeze-thaw cycles.

In order to select the appropriate projects and maintenance strategies for lowest long-term costs, the analysis of road-users costs is very important. This can be considered an essential tool for decision-making on investment for new and existing roads. Consequently, understanding the impact of maintenance and rehabilitation costs on road-users costs is very important and the benefits of regular and periodic maintenance is dependent on this relationship. Therefore, in this research, the economic impact of maintenance and rehabilitation costs on road-users costs with a case study involving a main-road network of Iran has been investigated. On this basis, and with the help of Matlab software, a sensitivity analysis on the effective factors for road-users costs is performed for this selected road network. The results of the analysis indicated that an additional agency investment of one million Rials results in average direct savings to road users of 0.72 Rials per vehicle km. The results obtained for this case study also indicated that the impact of maintenance and rehabilitation costs on road-users costs reduces at a decreasing rate. In other words, great investment expenditures cannot be justified in the field of road maintenance for decreasing the users costs, while the maintenance and rehabilitation costs are too much.

Several criteria have been developed to represent the serviceability conditions of pavement, which international roughness index (IRI) is one of the most important indices. In addition to the application of IRI in case of representing serviceability conditions of the pavement and its application in prioritizing of maintenance and rehabilitation activities, in new mechanistic-empirical methods for design of rigid pavements (e.g MEPDG 2002), it is needed to convert all independent distresses to IRI by utilizing a mathematical model. Thus, determination of IRI on the basis of independent observed distresses is very important. In this research, Adaptive Nero-Fuzzy Inference System (ANFIS) is utilized for modeling of IRI of jointed plane concrete pavements (JPCP) based on long-term pavement performance (LTPP) data. Input data for ANFIS included pavement age in year, initial IRI in m/km, percentage of slabs with transverse cracking, percentage of joints with spalling, pavement surface area with flexible and rigid patching, total joint faulting in mm/km, freezing index in oC and percent subgrade material passing the 0.075-mm sieve and output was considered as IRI in m/km. Results showed that the coefficient of determination (R2) between measured and predicted values of testing set in case of NCHRP equation and ANFIS model are 0.601 and 0.758, respectively. Thus the developed model, based on ANFIS, can be used for accurate predicting of IRI in jointed plane concrete pavements in comparison with NCHRP equation.

Undoubtedly, bridges have substantially effect in metropolitan areas and are usually built to connect between two roads in order to decrease traffic. Pounding, is one of the important parameters to design different bridges as this structures should be controlled during seismic excitation to provide safety conditions in order to organize and support unpredictable situations. During very strong earthquake, bridges may experience large horizontal relative displacement, which may lead to pounding if sufficient gap size is not considered between adjacent slabs of bridge. Insufficient separation distance is naturally caused to collide between two slabs and, subsequently, stiffness of bridge is decreased and finally, collapse is occurred. In order to determine impact force and also absorption energy during collision, many researchers have demonstrated different theories and also suggested various equations by using impact velocity before and after impact. In this study, special element is used between two slabs to determine impact force and a new equation of motion is mathematically presented to calculate impact damping ratio focusing on coefficient of restitution.

Evaluation of the interaction between new and existing underground structures is one of the most important problems in urban tunneling. In this paper, three-dimentional finite difference numerical model of single and twin tunnels in urban areas has been presented. The aim of this research was to evaluate the effects of changing the depth of excavating single tunnel, in constant horizontal distance, on the interaction of single and twin tunnels considering various criteria including forces and moments exerted on twin-tunnels lining and their safety factors, subsidence of ground surface and nearby buildings, excavation stability of single tunnel and stability of pillar lying between single and twin tunnels. The case study is related to single and twin tunnels of Tabriz urban railway, in northwest of Iran. Results indicated that increasing depth of single tunnel causes average safety factor of Sahand tunnel to decrease (6.52 to 6.35) and that of Sabalan to increase (6.78 to 7.02). As the depth of single tunnel increases, excavation stability of single tunnel increases and surface subsidence decreases. The stability of pillar lying between twin and single tunnels increases as the depth of single tunnel increases.

Speed management is an important factor to keep road sections safe, especially at gateway of cities created along the main roads. Perceptual traffic calming is one of the methods to control and reduce the speed of vehicles. Peripheral transverse marking with decreasing intervals was one of the specific perceptual traffic calming method which was implemented in Izadshahr gateway. Effectiveness of the marking on speed reduction was assessed with comparing the mean speeds of vehicles before and after marking implementation by t-test at 95% confidence level. The vehicles’ speed was recorded by radar instrument once before marking implemention as before study and twice after marking implemention as early-after and long-after studies. Speeds were categorized in three general modes of all vehicles, with respect to vehicle classification (light or heavy) and with respect to time (day or night). Results showed that the greatest reduction in vehicles’ mean speed was 5.49 km/h at night mode of early-after study in comparison to before study. Generally, there was decreasing effect of marking in long-after study. But it got reduced with respect to the early-after study.

There are several different approaches for reducing moisture sensitivity in asphalt mixtures, which one of the most one of them is using anti-stripping additives. These anti-stripping additives are added to asphalt binder, aggregates or their mixture. In this study, two types of nano-materials (Fe2O3 and Al2O3) are introduced as anti-stripping additives and asphalt-binder modifiers. Two types of aggregates with different moisture sensitivity potential (limestone and granite), AC 60-70 from Isfahan Refinery and two types of nano-materials (Fe2O3 and Al2O3) as two weights of asphalt binder (2 and 4 percent) were used in this research. The effects of using nano-materials as anti-strip additives on moisture sensitivity of hot-mix asphalt have been assessed by the modified Lottman test (AASHTO T283 test). The results of AASHTO T283 test showed that use of nano-materials increased tensile strength ratio in samples containing modified asphalt-binders. Application of nano Fe2O3 had an obvious effect in decreasing moisture damage potential of asphalt mixtures, as compared to nano Al2O3. Another result that was obtained in this study was that similar to the previous studies, samples made from limestone aggregates performed comparatively better against moisture damage.