توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Introducing a Fundamental Skid Resistance Asphalt Mix Design
نویسنده(ها): ،
اطلاعات انتشار: اولین همایش بین المللی قیر، سال
تعداد صفحات: ۷
As pavement surface characteristics play an important role in road safety, more agencies are specifying minimum requirements for surface friction. In most cases, these requirements are specified in terms of surface macro and microtexture. Recently a method has been developed and published that uses the International Friction Index (IFI) to determine a design vehicles stopping distance and potential for loss of control. This method relies on the use of the both the IFI and the macro and micro–texture measurements of a pavement surface to calculate a vehicle stopping distance requirements. The advantage of this method is that a lack of macro–texture can be substituted by increasing micro–texture and vice versa giving significantly more options to the maintenance programs. For design of asphalt mixtures, it is proposed to incorporate the macro–texture in terms of the mean profile depth (MPD) that determined from the aggregate gradation and binder content, with the micro–texture determined from the polished aggregate friction value (PV) of the coarse aggregate. An iterative procedure is then used to determine the
combination of macro and micro–texture required for meeting the stopping distance requirements, these values are then used to determine the required aggregate type and gradation and binder content, in the design process. This paper Introduce a method for estimating the macro–texture in terms of the mean profile depth determined from the aggregate gradation and binder content, with the micro–texture determined from the polished aggregate friction value (PV) of the coarse aggregate. At first stage of this method, the required mixtures macro and micro–texture should be determined. There are two steps to determine the required mixtures macro and micro–texture including estimating in–service asphalt micro texture and estimating texture depth from mix gradation and binder content. At last, stopping distance of design vehicle will be calculated. By determining the required mixtures macro and micro–texture, the stopping distance of design vehicle could be calculated. This stage has three steps that include converting values to IFI friction values, determining standard vehicle response from presented charts and complete the design process.<\div>

۲Proposed Recommendations to Minimize Wet Surface Accidents
نویسنده(ها): ،
اطلاعات انتشار: اولین همایش بین المللی قیر، سال
تعداد صفحات: ۸
Road sections with same construction time, material and geometric design can have different skid resistance over time. The frictional properties of pavement surfaces play an important role in highway safety. Analysis of friction information indicates a relationship between variety of conditions including roadway geometry, AADT, polish stone value and Friction Number (formerly referred to as skid number (SN)), climate and economics. Because of these varieties that affect safety aspects, researchers believe that it is best qualified to determine the necessary level of friction in each given situation. According to the statistic reports, approximately 13.5–18% of fatal accidents and 24.3–25% of all accidents occur when pavements are wet. The following factors affect the friction levels of a wet pavement surface: Micro–texture and Macrotexture; Age of the road surface; Seasonal variation; Traffic intensity; Aggregate properties; Road geometry. High demand category surfaces (FN=45–55) will be able to maintain the design frictional characteristics through their service life. Wet Frictional characteristics are easily lost if: Water ponds on the road surface due to rutting, shoving or poor drainage; Pavement flushes and submerges the aggregate; The wrong type of aggregate was used.
To determine surface properties as sufficient for pavement skid resistance, this procedure was suggested: Check if wet weather problem exists; Select target design friction level; predict potential reduction of wet accidents; Calculate Benefit\Cost ratio of design target; Evaluate effectiveness of design; Select surface mix with adequate Polish Value. The following are proposed recommendations to potentially minimize wet surface accidents: Monitoring wet surface accident sites and locations; Identifying sites with low skid resistance and dealt with quickly by a suitable remedial treatment or use "Slippery When Wet" signs; Measuring skid resistance for low FN (FN<40); Testing for PV annually;
Implementing a skid resistance design policy to select a (design FN) and PV for anticipated maximum speeds; Establishing a three–year maintenance program to monitor and eliminate the reduction in skid accidents; Including skid resistance improvement. This paper aims to describe the recommended process in developing a design policy to improve pavement surface friction.<\div>

۳Airport Runway Flexible Pavement Thickness Designing Results Examination by Designing Software
نویسنده(ها): ،
اطلاعات انتشار: نهمین کنگره بین المللی مهندسی عمران، سال
تعداد صفحات: ۶
With today's improving technology, several software are prepared and used to analyze and design the airports runaway pavements which serve the users with better results, especially trustable ones. The most crucial ones presented to design airport runaway pavement are FAARFIELD, PCASE, APSDS. Research aim is to introduce the softwares and their capabilities, and examine the results made in airport runaway thickness with all traffic theories emphasizing huge airplanes. Results show differences in pavement thickness calculation with softwares in sample airports.<\div>

۴analysis of noise pollution due to traffic on pavements
نویسنده(ها): ، ،
اطلاعات انتشار: نهمین کنگره بین المللی مهندسی عمران، سال
تعداد صفحات: ۸
noise pollution due to traffic is an important issue for road users which becomes more important nowadays . The term noise should not be confused with the term sound noise is the generation of sounds that are unwanted with respect to traffic noise would be the generation of sounds that affect the quality of life for persons near roadways one of the most effective and economical methods of reducing this pollutions is to control the source of the noise production. on the other hand it is possible to reduce noise pollution by absorbing them into a pavement there for selection of an appropriate pavement is the best way to reduce noise pollution on roads namely noise due to interation of tire surface and pavement.<\div>

۵An increase in drivers’ awareness by separate tail and brake lamp colors
اطلاعات انتشار: سومین کنفرانس بین المللی حوادث رانندگی و جاده ای، سال
تعداد صفحات: ۱۲
The rare–end accidents, both in number and in severity, are one of the most important concerns which have been investigated for a long time. If a driver does not have the ability (or is not able to) to distinguish advance vehicle brake lights from tail ones, the probability of collisions between these two vehicles will raise intensely. Participants in this study were put in two visual search circumstances; they were asked to detect the time of the braking; first when both of the tail andbrake lamps were red, second when they differed (brake lamps were red and trail ones were yellow).The results confirmed the second assumption, in which the participants reactions increased and rate of diagnostic errors decreased. With respect to this study and previous ones, using proposed ideas to separate the colorsof tail and brake lamps can reduce the rate of rare–end accidents, both in number and in severity<\div>

۶Evaluation of Rumble Strips on Crash Reduction
اطلاعات انتشار: هفتمین کنگره ملی مهندسی عمران، سال
تعداد صفحات: ۷
Every year many people are killed on the roads in Iran. High rate of crashes, which leave financial damages, injuries, or death consequences, made this topic one of the most controversial issues that any country, especially Iran, confronts. A lot of crashes– such as head–on crashes and run–off–the–road (ROR) crashes– in fact, results from fatigue or lack of sleep of drivers. This study has represented effectiveness of shoulder and center rumble strips in reducing of accidents on rural roads. Their main functions are to alert drivers who are encroaching on the opposing lane or leaving the travel lane by producing vibration and noise when crossed by vehicle tires. According to the result of this survey, shoulder line and center line rumble strips, plays a significant role in decreasing the number of head–on crashes and run–off–the–road (ROR) crashes<\div>

۷Overview of warm mix asphalt and it`s performance
نویسنده(ها): ،
اطلاعات انتشار: سومین کنفرانس ملی مصالح و سازه های نوین در مهندسی عمران، سال
تعداد صفحات: ۱۴
Increased environmental awareness and stricter emissions regulations have led to a development of warm mix asphalt (WMA) to reduce the high mixing temperatures of regular hot mix asphalt (HMA). Its benefits are reduction in energy consumption during production and reduced emissions during production and placement. The temperature reduction achieved by WMA comes from the use of various technologies that have been developed in recent years, and which can be classified in the following three groups: asphalt foaming technologies, organic additives, and chemical additives. All three methods reduce the viscosity of the binder at a certain temperature range, allowing the aggregate to be fully coated at lower temperatures than in HMA production. The objective of this paper is to clarify WMA as a new paving technology in the asphalt industry, describing warm mix technologies, evaluating WMA performance compared to traditional HMA and discuss about the benefits of this technology as well as its possible drawbacks and declare the need for further research in this area.<\div>

۸Performance of Geocell base course
اطلاعات انتشار: سومین کنفرانس ملی مصالح و سازه های نوین در مهندسی عمران، سال
تعداد صفحات: ۷
Geocells are a three–dimensional interconnected honeycomb type of Geosynthetics. Many studies have been conducted about different applications of geocell that shoed their appropriate responses was reported. One of the geocell applications in highway construction is for base course reinforcement. Recent researches on the Geocell–reinforced base have shown significant improvement compared to unreinforced one. Geocell has been used to improve performance of base course by providing soil confinement and, consequently, bearing capacity, stiffness increase and permanent deformation reduction. This paper reviews recent studies on use of Geocell to reinforce base course and summarizes the main findings on bearing capacity, stiffness, permanent deformation, creep deformation, and stress distribution.<\div>

۹Development of Asphalt Concrete Stiffness Modulus Prediction Models Using Genetic Programming
نویسنده(ها): ،
اطلاعات انتشار: دومین کنفرانس بین المللی پژوهش های نوین در عمران، معماری و شهرسازی، سال
تعداد صفحات: ۱۳
One of the key parameters to design flexible pavements is the stiffness modulus of asphalt mixtures. This study aimed to develop models for prediction stiffness modulus of asphalt concrete using genetic programming. Due to the viscoelastic nature of asphalt mixes, the stiffness of these materials depends on temperature, loading time duration, rest period, and loading waveform. Therefore, in this paper, the authors use these parameters as independent variables to estimate stiffness of asphalt mixes under two loading waveforms (haversine and square). Stiffness modulus of asphalt mixture samples were determined using resilient modulus indirect tensile test (IDT) under haversine and square waveforms at different temperatures and loading conditions. First, two models were developed using genetic programming (GP) technique with MATLAB® genetic programming toolbox for two loading waveforms. Then, response surface models were developed using STATISTICA® software, and the developed models were evaluated. The predicted stiffness modulus was closely relevant to the measured one and prediction ability of the models was satisfactory that can be prevented from expensive and time–consuming laboratory tests<\div>
نمایش نتایج ۱ تا ۹ از میان ۹ نتیجه