Transportes

Evaluation of resistance to fatigue and rutting of binders with rap and biorejuvenator from soybean oil

2024-10-01T09:03:24-03:00

The high use of RAP (Reclaimed Asphalt Pavement) in asphalt mixtures can affect resistance to defects. To improve the properties of binders, rejuvenating agents are used, which need to be properly dosed to meet specifications. The aim of this study was to investigate the resistance to fatigue damage and rutting of binders containing RAP and a biorejuvenator from soybean oil. Sixteen binders were evaluated, obtained from a mixture of CAP 50/70 binder, binder extracted from RAP and biorejuvenator. The RAP binder was added to the mixture with pure binder in percentages of 15 and 30%, and biorejuvenator in percentages of 5 and 10%, both in relation to the total mass of the sample. A 100% RAP binder sample was also evaluated. Linear Amplitude Sweep (LAS) and Multiple Stress Creep Recovery (MSCR) tests were carried out to assess fatigue and rutting. In parallel, penetration, softening point, viscosity and colloidal instability index (by SARA fractionation) were determined. The results indicate that increasing content of RAP binder compromises fatigue resistance, due to the increase in the amount of aged binder, while resistance to rutting is affected by increasing the rejuvenator content. The biorejuvenator epoxidized from soybean oil proved to be more suitable in terms of resistance to both defects. A good correlation was found between the fatigue and rutting parameters and the physical properties, unlike the colloidal instability index, which showed low relationship with the mechanical parameters.

Critique of statistical inference models to analyze the determinants of accessibility inequalities

2024-10-15T08:49:25-03:00

The strategic diagnosis of socio-spatial inequalities in accessibility commonly uses statistical modeling to analyze causality. However, the formulated linear regression models may not be adequate, generating bias in the estimates and errors in the interpretation of the causal effects. Therefore, the objective of this work is to criticize the statistical models that analyze the cause-effect relationships between land-use and transport subsystems’ restrictions with accessibility levels in the strategic urban planning. For this, data from Fortaleza were used to exemplify the problems that can occur when carrying out a diagnosis without establishing the possible indirect paths between accessibility and its restrictions, in addition to not considering the sources of endogeneity. It was possible to verify that the analysis of complex phenomena through linear regression can benefit from the use of causal diagrams, allowing a better understanding of the causal paths between the variables, with the adequate control of endogeneity.

Reflections on Artificial Intelligence applications: physical models and datadriven models as research paradigms in road infrastructure

2024-12-17T12:17:40-03:00

This paper reflects on applications of Artificial Intelligence in pavement research, whose increasing use represents an epistemological turn in the area, mostly built on top of physical models. In the search for solutions, data-driven models can produce satisfactory results without explaining the underlying physical processes that led to these results. Applications such as automated distress surveying and smart cities are exemplified, and some of the associated risks are recognized, such as ethical issues and data bias. It highlights how innovations should not only improve immediate performance, but contribute to a more complete and sustainable understanding of road infrastructure. AI tools have a transformative potential, as well as the ability to attract students and young researchers, which is essential for the advancement of any area of knowledge. It is hoped that the type of reflection and thinking provided herein will encourage discussions and collaborations necessary to navigating the challenges posed and maximizing the benefits of emerging technologies.

Customization and application of an automated data collection tool of pedestrian crossing at signalized intersections

2024-10-15T08:49:27-03:00

Pedestrian crossing during vehicular green time is a problem that still requires better understanding and investigation given the complexity of the variables involved and their interrelationships. Automated collection tools can be important for observing and for analyzing these variables and interrelationships. The main objective of this study is to customize and apply an automated tool to collect data of important variables in studies of pedestrian crossings at signalized intersections, such as vehicle headways, pedestrian delays, vehicle speeds, vehicle types, and crossing times, per lane. The tool, applied to a video of a signalized intersection in Fortaleza, consisted of the YOLOv7 and StrongSORT algorithms. The tool training mAP was approximately 90%. In total, 9427 vehicles and 723 pedestrians were tracked; the headways showed great amplitude, the average speed of vehicles was 28 km/h, and the average delay for pedestrians was 18 s. Validation with a collection tool (RUBA) showed that there were no significant differences in the two methods regarding the vehicle passage times and headways. For vehicle speeds, the differences were circa ± 6 km/h, and for the pedestrian variables, the mean of differences were up to 0.2 sec.

Fatigue cracking prediction of cobblestone interlayer pavement using non-destructive testing and mechanistic-empirical analyses

2024-10-31T11:45:04-03:00

Several non-destructive testing (NTD) methods have been used to measure surface deflection, which makes to determine the elastic moduli of pavement layers through the back-calculation process and assess the structural capacity of asphalt pavements. In this study was evaluated the back-calculated moduli of the cobblestone interlayer pavements and the load capacity of this type of pavement related to the fatigue cracking criterion based on a mechanistic-empirical analysis. The employed methodology included the performance of on-site trials using non-destructive testing with the Falling Weight Deflectometer (FWD) devices on 84 test points in granular and cobblestone interlayer pavements, determination of deflection basin parameters (DBP), back-calculation layers’ moduli, and estimate of the fatigue cracking performance of the pavements by mechanistic-empirical analyses in MeDiNa software. The pavements with a cobblestone base layer displayed greater deflection measurements on the load application point compared to those measured on pavements with a granular base layer, indicating that conventional pavement displayed more stiffness. Cobblestone interlayer pavement displayed greater amounts of cracked area compared to granular base layer pavements showing lower load capacity based on the fatigue criterion. The DBP-based method by FWD test was able to identify the structural differences between the layers of pavements evaluated and identify the cracking evolution.

Asphalt mixture design related to performance: a literature review

2024-09-27T11:16:42-03:00

Since the first applications of asphalt mixtures as constituent materials for pavement layers in the late 19th century, there has been a need to adopt a methodology to define the appropriate proportions of each component in the mixture, in a process known as mix design. Currently, design methodologies are generally based solely on volumetric parameters, which does not allow for the evaluation of material performance. This paper presents a review of past, present, and future trends in asphalt mixture design, considering different methods developed in the pursuit of generating mixtures that are more resistant to the ever-increasing demands of traffic. Aspects related to current design methodologies and their limitations, the concept and current work on balanced mixtures, as well as a summary of the main performance tests for asphalt mixtures are evaluated. The review results indicate a clear evolution towards design procedures that combine volumetrics and performance, promoting the most suitable selection of materials and their combinations, as well as optimizing the service life of asphalt mixtures in the field. However, the research highlights significant gaps, such as the need for experimental studies to validate new design methods and the integration of more advanced performance tests. These gaps represent important opportunities for future experimental research that can contribute to innovation and efficiency in asphalt mixture design.

Evaluation of the addition of recycled asphalt pavement materials in granular layers for asphalt pavement base

2024-12-02T16:50:32-03:00

Pavement recycling makes it possible to reuse milled materials as inputs for new structures. This practice contributes to sustainable development, reducing waste generation and stone aggregates consumption. Cold recycling methods, without the use of stabilizing additives, as asphalt emulsion or cement, with the incorporation of reclaimed asphalt pavement (RAP) materials into granular layers, are an economically and environmentally attractive possibility. Therefore, in this study, different mixtures produced with the addition of RAPs in unbound granular material with rhyodacite stony aggregates were evaluated, using triaxial tests with repeated loads and prediction models within the National Method for pavement design from Brazil (MeDiNa). The results demonstrated a significant increase in the resilient modulus generated of the mixtures with the addition of RAPs, promoting stress relief and delaying the fatigue cracking of the top layer. In permanent deformation tests, the results varied depending on stress level. However, for structures analyzed, the deformations did not exceed 10mm when only RAP material was used in the base layer. Therefore, under the conditions of this research, the addition of RAPs materials in granular layers promoted a better estimated performance for the pavements, delaying cracking, without presenting excessive deformations. Thus, it is concluded that this practice is capable of producing technical, economic and environmental benefits for pavements constructions. However, each case must be analyzed considering its specificities and available materials.

Synthetic population generation procedure based on Brazilian data

2024-09-09T09:11:40-03:00

This paper presents both a population synthesizer adapted to Brazil and its application to the Metropolitan Area of São Paulo (RMSP). Synthetic populations are used in disaggregate travel demand models; they result from estimating unknown information at a fine geographical level based on available aggregated information and (a sample) of microdata, both made available by the Census. Considering the theoretical approaches and the availability of codes, we selected PopulationSim, synthesizer, belonging to the category of synthetic reconstruction synthesizers. An extension, called PopulationSimBR, was developed to facilitate the use of this synthesizer in different regions of Brazil. OD survey data files were used in addition to Census data for the application to the RMSP. Validation metrics show that results compare favorably to those reported in the literature and suggest that PopulationSim can be used in Brazil, as well as the synthetic population generated for the RMSP.

Development of a spatial multicriteria approach to determine the location of loading/unloading spaces in urban centers

2024-09-27T11:16:40-03:00

This paper proposes an innovative solution approach that combines mathematical programming, multicriteria decision analysis, and a geographic information system (GIS) to determine the optimal number of loading/unloading spaces in urban centers. The proposed methodology was implemented in a case study in the urban center of Fortaleza, a municipality in the Northeast region of Brazil. Employing the hybrid method for selecting optimal loading/ unloading spaces resulted in a 10% increase in the percentage of served clients compared to using solely the mathematical model. On the contrary, as the registered spaces were not determined using a scientific approach, clients located outside the Centro neighborhood experienced notably low service levels, with walking distances exceeding 450 meters.

Efficiency of Brazilian airport cargo terminals considering e-commerce and exogenous variable

2024-12-02T11:25:23-03:00

The study evaluates the operational efficiency of air cargo logistics terminals (TECA) at Brazilian airports, considering the influence of e-commerce and exogenous variables. Since 2011, Brazil has started the concession of airports to private managers to improve infrastructure and efficiency, but there is little evidence of post-concession improvements. The method used is Data Envelopment Analysis (DEA), in two scenarios: one considering all cargo handling and another only e-commerce. The temporal analysis investigated the relationship between efficiency and factors such as industrial GDP, exchange rate, population size, COVID-19 pandemic, and airport concessions. The results indicate that concessions do not necessarily improve the average efficiency of airports. Only some airports showed improvements in efficiency after the concession and before the pandemic. The efficiency of all TECAs was affected during the pandemic due to the reduction of the air network. Tobit regression showed that GDP and concession have a positive effect on efficiency, while the pandemic has a negative impact. Thus, it is concluded that although some concessions and infrastructure investments have led to improvements in the efficiency of terminals, many airports still face challenges, especially amidst the COVID-19 pandemic. The expansion of e-commerce presents unique challenges for TECAs, requiring specific measures to optimize operational efficiency, highlighting the importance of considering internal and external factors in the assessment of TECA efficiency in Brazil.

Contribution to the performance evaluation of reversible lanes

2024-09-26T08:06:22-03:00

Recurrent congestion in urban centers requires traffic managers to adopt temporary or complementary strategies, such as implementing reversible lanes. Its principle comes from the temporary expansion of road capacity by taking advantage of the underutilized capacity of the road in the opposite direction. Despite being historically associated with a simple measure (compared to definitive interventions), there are technical guidelines for its implementation process, from initial stages (planning, previous studies, and design) to later stages (monitoring and performance evaluation), that, if not adequately considered, tend to impair the operation’s benefits. On the other hand, national practice tends to rely on empirical knowledge and personal decisions. Considering the growing popularity of the technique in the country, the evaluation becomes essential not only in terms of measuring the benefits obtained in existing operations but also as a result of benchmarking in new operations. Thus, this research aims to contribute to the practice of reversible lanes, identifying, through a systematic literature review, the primary key information (approaches, indicators, data collection, and methods) used in reversible lane performance evaluation studies. Such information subsidized the development of flowcharts to guide the evaluation process in existing operations.

Laboratory and statistical evaluation of the microstructural characteristics of Sand Asphalt Mortar

2024-12-23T10:40:39-03:00

One of the problems encountered in asphalt pavements is fatigue damage, which is related to the type of aggregate, the rheology of the asphalt binder and its chemical composition, resulting in the emergence of microcracks and, subsequently, macrocracks. Therefore, this phenomenon needs to be studied from the asphalt binder scale to the complete asphalt mixture. In this sense, this paper focuses on the asphalt binder scale with the objective of investigating the microstructural characteristics of cylindrical samples of Sand Asphalt Mortar (SAM). These samples can be made up of standard sand and any type of asphalt binder. The use of SAM can contribute to obtaining laboratory rheological results representing the real binder film thickness that exists in an asphalt mixture. In this study, SAM samples composed of a polymer binder without aging were compacted with a manual press, resulting in cylindrical specimens with 40 mm of height and 12.5 mm of diameter. Its microstructure was investigated by determining the air voids (AV) and the binder film thickness (FT), considering different binder contents: 6%, 8% and 10% by weight. The results indicated that the samples made with 6% binder present homogeneity in terms of microstructural parameters, and represents more realistically the binder film thickness that will exist in a complete asphalt mixture, can be used in oscillatory tests carried out on the dynamic shear rheometer, and contribute to studies on the asphalt binders.