مجله مهندسی زیر ساخت های حمل و نقل
سال چهارم شماره 3 (پیاپی 15، پاییز 1397)

Damage in asphalt pavements due to repetitive stresses and strains caused by both traffic loading and environmental factors can manifest itself as fatigue and thermal cracking, respectively. Cracking is considered as a primary distress mechanism in asphalt pavements. Many studies have been carried out on resolving these distresses. One of these ways is the use of polymer modifiers to improve the properties of asphalt binder and asphalt mixtures. Therefore, this research was conducted to study the effects of domestic polymers (with trade names of SBR and PP) in equal proportions on the fatigue properties of asphalt mixtures compared to expensive imported polymer (called SBS). Accordingly, four-point beam fatigue and indirect resilient modulus tests were carried out. It was found that combination of PP and SBR leads to better preservation of fatigue performance of modifed mixes and increases the fatigue life up to 50% compared to SBS-modified mix. Consequently, such polymers combination can be more beneficial than using SBS polymer

In recent years, regarding the insufficiency of new material and significance of environmental conservation, using recycled material such as Recycled asphalt pavement (RAP) has increased due to the decreased production of environmental pollutants resulting from the preparation of asphalt mixtures. Also, to decrease the energy consumption rate, new technologies have been developed to produce and perform warm asphalt mixtures. These asphalt mixtures have lower temperatures than conventional asphalt mixtures. In this research, RAP has been used in building stone matrix asphalt (SMA) mixture to carry out the moisture susceptibility test by adding warm asphalt additives such as zycotherm, sasobit and Topcel fibers to prevent bitumen draindown of this type of asphalt mixture. The purpose of this paper is to develop a model based on adaptive neuro-fuzzy inference system (ANFIS) for prediction of moisture susceptibility of stone matrix asphalt mixtures (SMA) containing various percentages of RAP and warm mix additives. Various percentages of RAP containing warm mix additive are the parameters for input layer and the ratio of saturated specimen’s strength to that of dry specimen’s strength is the model output. Results indicated high accuracy of the model with a coefficient of determination (R2) of 1 and 0.982 for training and testing data sets and 0.774 for evaluation data-set, respectively. Also, the warm mixtures containing 50% RAP have shown more suitable behavior.

Asphalt pavement roads are composed of bitumen, aggregates and filler. Asphalt binder plays an important role in the properties of asphalt mixtures, and it is therefore important to identify its behavior. Asphalt concrete is still the most used material in the construction of roads. Fatigue failure is one of the most common failures in roads, and repairing such failures is very costly. Bitumen correction is one of the important methods to increase the strength of the pavement against failure. In this research, nanosilica and synthesized polyurethane with 3, 5 and 7 asphalt binder percentage were used. Due to the instability of thermoplastic polyurethane in asphalt binder, synthesized polyurethane was used. Polyurethane was synthesized by using a combination of polyol and isocyanate. To test the fatigue, a time sweep test was used. Results showed that synthesized polyurethane and nanosilica have improved the fatigue life. The effect of synthesized polyurethane on fatigue life was much greater than that of nanosilica. The fatigue life was increased 3.7 and 4.5 times for nanosilica and synthesized polyurethane in low strain, respectively. Results of the chemical test of Fourier-Transform Infrared Spectroscopy and physical tests showed that the physical changes which were made in the bitumen are not reliable for prediction of fatigue. In fact, changes in the chemical composition and creation of various bonds are influential on the fatigue behavior.

When a high-speed train enters into a tunnel, a pressure wave will be created. This leads to piston phenomenon in the tunnel, which affects all air currents in the tunnel. This phenomenon may lead to some problems in the long time like destruction of tunnel wall layers, safety of the passengers, ventilation of the subway stations and disturbing train balance. In this research, this phenomenon was investigated for entering of an ICE2 train to a single-line tunnel. Simulation is performed by using numerical solution in ANSYS Fluent CFD software considering sliding mesh, three-dimensional, incompressible and turbulent flow. The numerical method has been validated with an experimental test for the flow speed in the tunnel. Simulations have been done for 60, 80 and 100 m/s train speeds. Overal results showed that with increasing the train speed, the pressure domain and aerial wave speed will increase too. Finally, the strength of train’s front glass against maximum air wave has been studied and permissible train-speed range for entering the tunnel has been obtained.

Beam-column connections are vulnerable areas of reinforced concrete moment frames-shapes of bridge piles and damaging of this area under the earthquake loads results in decreasing of seismic performance of frame and increasing of frame drift and eventually destruction of members and even the entire bridge structure. Due to the importance of connection zones in these frames, correct implementation based on regulations has significant impact on seismic performance of the frame. In this paper, the influence of stirrup of panel zone in a concrete connection of bridge piles with a scale of one-half has been conducted experimentally and numerically under cyclic seismic loading and then another deficient connection without any stirrup in the panel zone has been reinforced by high-performance fiber-reinforced cementitious composites (HPFRCC), and its effect on connection performance and compensation of the lack of stirrup of the panel zone has been studied. Also, to evaluate different states of connection strengthening of bridge piles, seven different analytical samples have been presented and the influence of different panels of HPFRCC on connection improvement and in strengthening the weak concrete connection by prestressed steel angels has been studied and compared. In this study, the hysteresis curves of load-displacement and their envelope curves and also energy dissipation, stiffness and stiffness loss curves of the connections have been studied. Results indicated that increasing the flexural capacity and ductility and rapid decreasing in stiffness-loss of connection in primary cycles of connection retrofitted with HPFRCC were more than those of the connection without stirrup in connection zone of bridge frame-shape piles. Maximum capacity of deficient connection of RC bridge piles was increased by 17-48% using high performance fiber reinforced cementitious composite (HPFRCC) panels.

Clay soils have generally appropriate strength and stiffness in dried conditions. However, their strength parameters such as bearing capacity, unconfined compression strength, and shear strength, are reduced, and compressibility and settlements are increased significantly in the presence of water. In various civil engineering projects, clay soils, especially soft clays, are usually stabilized by using lime. In this research, kaolinite clay samples were stabilized using 0, 10, 15 and 20 percent by weight of lime at temperature of 27 ºC and relative humidity of 98±2 percent. Three series of samples were studied: the first series after 14 days curing, the second series after 28 days curing, and the third series were submerged in water 14 days after curing and then were tested. For macro-structure study, the specimens were tested under unconfined compressive strength test, and for micro-structure studies, and due to cementation of soil-lime-reaction, X-ray Diffraction (XRD) analysis, Scanning Electron Microscope (SEM), and Energy Dispersive X-Ray Spectroscopy (EDS or EDX) were carried out. Results showed that using 10% lime in samples with 14 days curing time and submerged in water for 14 days have 65% lower strengths in comparison with the samples cured for 28 days. This was due to the infiltration of water and breaking and weakening of strength of cementation compounds. Also, for both macro and micro structure studies, optimum lime content is 10% in order to reach the proper soil strength.

Aging and rupture phenomena are important factors which decrease the useful life of asphalt. During the recent decade, by using the images with high spatial accuracy (less than 10 cm) the qualitative monitoring of roads’ surfaces has been achieved. The present study has been performed to evaluate the aging and rupture phenomena on asphalt surface and to evaluate the DSM, extracted from drone images, in asphalt quality control in Alvar-e- Sofla village, Tabriz, Iran. Hyperspectral imaging for three kinds of asphalt (less than 2 years, 4 to 7 years and more than 10 years old) revealed that the 2-year old asphalt has always lower graph than the others because, after a while, the asphalt bitumen losses its quality and gets lighter and thus its surface reflection increases. Calibration of selected learning points for distress shows overall accuracy of 95% and CAPA coefficient of 95, which reveals the high accuracy and correctness of the results. Also, high spatial accuracy (7.5 cm) shows the ability to study type 2 and 3 ruptures, in addition to cracking-depth evaluation and stress via these images at centimeter scale. Results showed that the obtained DSM from overlapping of drone images has the ability to extract lateral slopes of pedestrian and streets, which are applicable in evaluation of asphalt subduction amount during the time. If this problem is fixed and the road slope is standardized, practically the flooding events in cold seasons will be reduced and useful life of asphalt will be increased.