behrooz shirgir

During the last few decades, various types of fibers have been widely used to reinforce concrete. Considering the properties of fiber-reinforced concrete, the production and use of fibers in the industrialized countries of the world have a wide range, and currently all types of fibers with technical specifications and various applications are mass-produced industrial. Considering the need to develop the production and use of fiber concrete technology. In this research, considering the variety of fibers in terms of material, shape, size, etc., to investigate the effect of metal and synthetic fibers (polypropylene) in micro and macro form, to one of the most important fracture parameters of concrete, i.e., fracture toughness, was studied in 100 mm x 100 mm x 500 mm Single-Edge Notched Bending (SENB) beam samples under symmetrical (I), antisymmetric (II) and combined (I/II) loading conditions. Also, considering the favorable performance of micro fibers on increasing the modulus of rupture of concrete and also the desired performance of macro fibers in improving the concrete rupture module and increasing the bearing capacity of concrete in the post-cracking area of concrete, by using these two types of fibers simultaneously, their superposition effect on the characteristics concrete failure was evaluated in different loading modes (tensile mode, shear mode and combined mode). To analyze the failure probability of the samples, we used metal and synthetic fibers in micro and macro form, with volume percentages of 0.2% and 0.5%, respectively. Using two-parameter Weibull statistical distribution, it was observed that the use of fibers in both micro and macro form has a agreeable effect on the probability of failure of the samples based on the fracture toughness of the samples obtained in the laboratory.

It is very common to modify rubber bitumen with warm asphalt waxes such as Sasobit, also the use of cellulose fibers for tensile strength and better strain energy absorption power than other additives has attracted the attention of researchers. This research used cellulose fibers coated with Fishertraps wax (Sasobit) in proportions of 1,3, and 5% as an additive in bitumen with 15% rubber powder. So that modified bitumen can be used to improve strain energy absorption and bitumen shedding in asphalt mixtures with open-graded and low density or to improve the index of resistance against rutting in higher-density mixtures. The results of the investigation of rheological properties indicate that the addition of the mentioned fibers to rubber bitumen, in addition to reducing stiffness, increases its resistance to rutting in both unaged and short-term aged samples. The results show that the upper-performance limit of unaged pure bitumen 22-64, with the presence of 15% rubber powder and improved fibers, for example, adding 5% fibers to bitumen with 15% rubber powder increases the upper limit of bitumen performance up to 94 degrees Celsius. It increases the degree. Also, the performance of short-term aged and non-aged rubber bitumen is similar, but short-term aging of bitumen reduces the effect of fibers. Also, the addition of fibers causes an increase in the modulus of complexity in the middle temperature and better performance in returning from the multi-stress level in the fracture temperature. This better performance makes the rubber powder bitumen-containing fibers perform better against rutting failure at the highest operating temperature.

In order to compute level of service and density in weaving segments, the Highway Capacity Manual (HCM) defined for the first time in 2010 a relationship based on a lane change rate to assess the density of the weaving segment. It is critical to accurately estimate lane changing rate in these situations, but field observations in weaving segments shorter than 250 meters in Tehran, Iran revealed a significant difference between the HCM2016 model estimate and field data. The traffic and geometric data collected at 87 (15-minute) intervals from six weaving segments in Tehran were used to develop models for estimating lane changing rate in weaving segments. These 87 intervals were then divided into 69 (terrain data) for equations and 18 (test data) for model comparisons. Weaving volume and weaving segment area are introduced as two independent variables in the optional lane changing rate model of weaving vehicles in this study, with R2=0.74. Furthermore, for a lane-changing model of non-weaving vehicles with R2=0.95, two new variables of non-weaving volume and traffic solidity were defined. Finally, based on the 18 intervals used to test the results, it showed the improvement of the developed models results compared to HCM2016 models.

Increasing impermeable levels has made water control a great challenge. On the other hand, the increase of impermeable surfaces causes the lack of heat exchange of the underground layers with the air, which will increase global warming. One solution to this challenge is to use porous pavements. Advantages of porous pavement compared to the normal pavement; Only on run-water control, he can easily increase the use of the road, increase the main road and increase the road, and so on. Restrictions on porous concrete include restrictions on use on high-traffic roads or heavy traffic loads; In other words, with the current knowledge about this pavement system, it can be used in fewer traffic routes such as local roads and streets and parking lots. The purpose of this study is to investigate aerated concrete and get acquainted with the standard related to aerated concrete. Also in this research, the advantages and disadvantages of porous concrete, construction, maintenance, and common problems of this system have been required. At the end of this research, only to gain general knowledge about aerated concrete and aerated concrete pavement mix design, common maintenance methods of porous pavement, and common tests in the relevant researches are introduced. In the end, it was concluded that with sufficient knowledge, porous concrete pavement can be used on roads with low traffic or light traffic load.

One of the types of unsignalized intersections is roundabout, which usually has an advantage in terms of efficiency and safety in low to medium traffic conditions. In general, roundabouts are created as a solution to solve traffic problems at intersections, as well as to create ease and safety in weaving movements. As the volume of traffic increases and according to the dimensions and geometric design of the roundabout, its efficiency gradually decreases. Considering the issue of road traffic due to its globalization, it is necessary to develop a transportation network that can be efficient now and in the future. To this aim, proper design and analysis of various infrastructures are performed. One of these infrastructures created in the road network to increase the efficiency of intersections by reducing delay is roundabout. At present, a strong model for Iran's traffic conditions is not available to determine the performance of roundabouts; Therefore, in this research, an attempt has been made to prepare a model to determine the performance of roundabouts based on geometric characteristics. Among the available global models, it has been observed that the geometric characteristics of roundabouts play an important role in roundabout capacity. Therefore, concerning this issue as a basis, a model for roundabout entry capacity has been produced for heterogeneous traffic conditions in Iran. According to the research results, the entry capacity model, which is described by the variables 1- circulating flow, 2- central island diameter, and weaving width, is the best in terms of statistics has been the best model statistically. It was observed that with each meter increase in the diameter of the central island, the entry capacity of the roundabout increased by 6%. Also, with each meter of weaving width, the entry capacity has increased by 35%.

At some intersections, excessive queue lengths may spill out of the left-turn bay and block the through lanes, jeopardizing level of service for the entire intersection. One of the most effective plans recently presented by the researchers is the "Contraflow left-turn lane" (CLL) In this method, left-turn vehicles will use the nearest lane in the opposite direction in addition to the usual left-turn lane. The most important principle in this design is that all vehicles which go into the opposite direction for left-turn movements should be definitely discharged during the left-turning phase. This issue prevents vehicles from a head-on collision when the other traffic signal turns green. Therefore, the number of vehicles entering the lane should be limited by a traffic signal. Accordingly, in this study, while determining the left turning capacity of the intersection with the CLL design based on vehicle traffic with generalized Poisson distribution, optimal CLL length and appropriate timing of the incoming traffic signal were determined. The goal of this study is to examine the effects of the CLL design on intersection performance. Therefore, the simulation of three real intersections in AIMSUN software was performed in two conventional and CLL designs. Comparison of the simulation results of the two designs showed that the CLL design at the intersections while reducing the travel time by 6 to 16 percent, resulted in an 8 to 24 percent reduction in vehicle delay. Also, according to the results of the study, the CLL scheme increased the number of stops for vehicles from 7 to 18%.

In recent decades, increasing population density and economic and industrial activities in metropolitan cities has increased traffic volumes and, consequently, increased levels of air pollution. The major source of air pollution in major developing cities is the massive transport of vehicles that use more than standard fuel and energy, and heavy traffic in the streets of these cities is often rooted in problems such as there is a lack of traffic management and traffic culture. One of the important issues in cities and metropolises that face pollution problems and harmful effects is the issue of informing about the future status of air quality and the amount of urban air pollution to the people. This can be achieved through daily or even hourly forecasts of air pollution and preventing people from being exposed to contaminated areas and their irreversible consequences. Therefore, the need to predict the quality of the air and the quantitative estimates of the concentration of pollutants in the aftermath of the equipment makes it felt that in this study, the problem of the predicted hourly concentration of particulate matter (PM2.5) in the district 11 municipalities of Tehran have exceeded 80% of the contaminated days under the influence of this pollutant. The difficulty and uncertainty associated with estimating and predicting the share of road traffic volume at the general level of air quality is the most important factor that can, if properly diagnosed, be very helpful. In order to take into account the effects of varying the volume of different traffic fleets in the process of changes in the concentration of pollutants and air pollution, it is necessary to pay attention to the effects of other influential variables including hydrological variables, geographical variables, etc. To achieve this, The methods of analytic analysis seem to be able to examine all of these effects together and in an omnipresent manner. The method used to predict this study is one of the methods for analyzing neural networks called Support Vector Machine (SVM). Artificial neural networks are important tools in the field of computational intelligence. Different types of artificial neural networks have been introduced, mainly in applications such as classification, clustering, pattern recognition, modeling and approximation of functions (or regression), control, estimation and optimization of the case Are used. Support Vector Machines (SVM) are a special type of neural network that, unlike other types of neural networks (such as multi-layer perceptron MLP and radial base functions of the RBF), instead of minimizing the error, minimize the operational risk of classification or modeling. Slowly This tool is very powerful and can be used in various fields such as classification, clustering and regression. The results of this study showed that SVM models work well in predicting the contribution and time share of road traffic in propagation of particulate matter, and predictions are well-coordinated with observations. It provides the opportunity to be used as an air quality management tool. Variable significance analysis results for SVM models provide this opportunity to be used as a tool for air quality management, in which the sensitivity of models to variations in emissions can be used to evaluate the effectiveness of a The air quality management scenario will test traffic fleet technology, combine the traffic fleet or its volume.

Pervious concrete is a concrete mixture prepared from cement, aggregates, water, little or no fines, and in some cases admixtures. The hydrological property of pervious concrete is the primary reason for its reappearance in construction. Much research has been conducted on plain concrete, but little attention has been paid to porous concrete, particularly to the analytical prediction modeling of its permeability. In this paper, two important aspects of pervious concrete due to permeability and compressive strength are investigated using artificial neural networks (ANN) based on laboratory data. The proposed network is intended to represent a reliable functional relationship between the input independent variables accounting for the variability of permeability and compressive strength of a porous concrete. Results of the Back Propagation model indicate that the general fit and replication of the data regarding the data points are quite fine. The R-square goodness of fit of predicted versus observed values range between 0.879 and 0.918 for the final model; higher values were observed for the permeability as compared with compressive strength and for the train data set rather than the test data set. The findings can be employed to predict these two important characteristics of pervious concrete when there are no laboratorial data available.

Impact with the interior of the vehicle and being ejected are the most common mechanisms of injury in car accidents. Based on reports, the use of seat belts reduces the probability of being killed by 40–50% for drivers and passengers in the front seat and by about 25% for passengers in the rear seats. Also investigations show that seat belts are most effective in frontal impacts and in running-off-the-road accidents where the probability of being ejected is high if seat belts are not used. We aimed in this paper to model and to compare the accidents both in restrained and unrestrained conditions, based on classic kinetics fundamentals. According to developed models, we can show the higher the speed of vehicle before the accident, the greater the applied impact to passengers. Also the more flexible the body of vehicle, the less the impact to passengers is. In the case of unrestrained passengers, the further the distance of passenger head to windshield, the greater the impact is. Of course arbitrarily getting close to windshield when accidents, is not the natural habit of passengers. For this reason to make passengers safe during crashes, they have to wear seat belts. Seat belts should effectively be able to stretch in accidents to a constant amount of force, F. This force should keep constant by the full stop of vehicle in accident. Modeling shows that the distance of front seat to windshield should be long enough, in the case of using seat belts. In fact seat belts should be designed in a manner that the force applied to passengers during the accident, remains constant.

Transportation management on both the supply and demand sides, due to ever increasing traffic problems is nowadays, considered as a crucial issue by transportation planners and engineers even in developing countries. Ramp metering as a transportation supply management measure with noticeable improvements in performance of the existing infrastructure and more effective use of the limited resources with comparatively little cost, is the focus of this paper. A mathematical programming model is designed to optimize the traffic volume on highways and their ramps via controlling the entrance volume of vehicles through different on-ramps, as decision variables. Flow conservation constraints are the major constraints in this model. A section of Sadr Highway is analyzed as the case for empirical study, for which traffic surveys including traffic counts is administered for the whole section under study. Results show that the flow of vehicles in the selected highway section can increase up to about 6 percent. The adversely high effect of Shariati on-ramp on the whole system under study indicates that its traffic flow can be reduced to 13 percent, with still positive effect on the whole system. Modarres on-ramp is the only ramp that is acting below its boundary limit and needs not any metering in the current circumstances.

This paper investigated the influence of aggregate type on the strength characteristics and abrasion resistance of high strength silica fume concrete. Five different aggregate types (gabbro, basalt, quartzite, limestone and sandstone) were used to produce concrete containing silica fume. Silica fume replacement ratio with cement was 15% on a mass basis. Water-binder ratio was 0.35. The amount of hyper plasticizer was 4% of the binder content by mass. Gabbro concrete showed the highest compressive and flexural tensile strength and abrasion resistance, while sandstone showed the lowest compressive and flexural tensile strength and abrasion resistance. High abrasion resistant aggregate produced a concrete with high abrasion resistance. Three-month compressive strengths of concretes made with basalt, limestone and sandstone were found to be equivalent to the uniaxial compressive strengths of their aggregate rocks. However, the concretes made with quartzite and gabbro aggregate showed lower compressive strength than the uniaxial compressive strength of their aggregate rocks. The results of the current investigation show how aggregate strength limits the compressive and flexural tensile strengths of a concrete, how transition zone strength limits the compressive strength of concrete, and how aggregate types influence abrasion resistance of concrete.