Traffic Axle Research Articles

Fatigue Damage in Asphalt Pavement Based on Axle Load Spectrum and Seasonal Temperature

In asphalt pavement structure design, traffic axle loads and pavement layer temperatures are crucial factors affecting fatigue damage calculations. To investigate the differences in fatigue damage calculations caused by different characterizations of traffic axle loads and temperature, fatigue damage calculations were conducted under equivalent standard axle loads (ESALs), axle load spectra (ALS), constant temperatures, and seasonal temperature variations using the field data from an expressway in Shandong Province, China under seven calculation plans. The results indicated: (1) the annual traffic composition is dominated by vehicle Type 9, with a proportion of about 43% in all the vehicle types, and its load level is also high, with a proportion about of 80% in the heavy load interval at all axle types; (2) The ESALs method underestimates the actual fatigue damage incurred in asphalt pavement by 6.04 times, with an accumulated damage of 2.34 × 10−9 (ESALs), 1.69 × 10−8 (ALS), respectively; (3) The fatigue damage results from a single month with consistent temperature showed similar trends, with an accumulated damage of 1.50 × 10−5, 9.07 × 10−5, respectively; (4) The cumulative fatigue damage calculated using the ALS method across the four seasons, respectively, is 6.51, 5.88, 6.42, and 4.60 times that of the fatigue damage calculated using the ESALs method. Although the ratio of fatigue damage between the two characterizations of traffic axle loads remains consistent, which is 6.04, the fatigue damage calculation that accounts for temperature variations can reveal seasonal trends in fatigue damage development. Based on the axle load spectra and considering temperature variations, fatigue damage calculation will be more closely related to the actual service state of asphalt pavement. These research findings provide insights for estimating asphalt pavement fatigue damage to some extent.

Swelled Mechanism of Crumb Rubber and Technical Properties of Crumb Rubber Modified Bitumen.

Crumb rubber modified bitumen (CRMB) has excellent high-temperature performance and fatigue resistance, and is widely used in asphalt pavement to cope with increasing traffic axle load and changing climate. Under conventional preparation conditions, the swelling degree of CR can directly impact the comprehensive properties of CRMB; however, physical and chemical properties research on swelling crumb rubber (SCR) and crumb rubber recycled bitumen (CRRB) in CRMB is relatively lacking. In this paper, the working performance of CRMB and CRRB in high-temperature and low-temperature conditions were studied through physical and working performance testing of bitumen. The CR and SCR were tested by scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), gel permeation chromatography (GPC), and particle size distribution (PSD) tests to study the physicochemical behavior and microscopic effects before and after CR swelling. The results showed that CR dosage was in the range of 10%, 15%, and 20%, as well as that CR dosages have a positive effect on the high- and low-temperature performance, storage stability, and elastic recovery of bitumen. The high-temperature PG grades of bitumen were directly improved by four grades, and the elastic recovery rate increased by 339.9%. CR improved the ultra-low temperature crack resistance of bitumen. Due to the absorption of lighter components by CR, the relative content of the heavy component of bitumen increased; however, its low-temperature performance decreased significantly. After swelling, the CR particle size increased and the range became wider, the surface complexity of CR became higher, and the specific surface area was larger. At the same time, CR carried out the transformation process from large and medium molecules to small molecules. During the swelling process, a new benzene ring structure appeared in the CR, and the C-C bond and C-S bond of CR broke, forming part of the C=C bond.

Study on the accuracy of axle load spectra used for pavement design

ABSTRACT Weigh-in-Motion (WIM) systems are used in order to reduce the number of overloaded vehicles. Data collected from WIM provide characteristics of vehicle axle loads that are crucial for pavement design as well as for the development of pavement distress prediction models. The inaccuracy of WIM data lead to erroneous estimation of traffic loads and in consequence inaccurate prediction of pavement distress process. The objective of the paper is to present a new methodology of heavy traffic axle load spectra (ALS) correction due to weighing errors (systematic and random) that occur in WIM systems. The theoretical solution which is proposed in the paper was validated successfully. The method enables correction of erroneous data to make traffic load statistics used for pavement design more reliable and precise, with no necessity to remove high number of records, as it is used in other methods. The practical meaning of the newly developed method was emphasised by analysis of the effect of relative and random error of WIM data on pavement fatigue life estimation, as well as on the estimated percentage of overloaded vehicles. Mechanistic-empirical approach (M-EPDG) was used for this purpose.

Evaluation of a current vehicle load model using weigh-in-motion records: a case in China

In order to assess the vehicle load carrying capacity of existing bridges on the national highway G103 in Beijing, the vehicle load model for the practical traffic flow conditions needs to be determined. Based on the traffic axle load data measured by the weigh-in-motion system and the methods proposed by General Code for Design of Highway Bridges and Culverts (JTG D60-2004) and Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTG D62-2004), the vehicle load parameters under practical traffic flow conditions are investigated. A typical 6-axle vehicle model with a 2-1-3 axial pattern is proposed by using the statistical analysis of total weight, axial weight, etc. The live load effects of Daliushu No. 2 Bridge, one highway bridge on the national highway G103, are analyzed using the proposed model and compared to the vehicle load model given in the Chinese code. The results show that there are great differences in the vehicle load parameters and the live load effects from the proposed vehicle load model increased by 20–50% compared with the model given by the code. The overweight vehicles are potential threats to the safety of existing bridges.

Characterisation of heavy traffic axle load spectra for mechanistic-empirical pavement design applications

Heavy traffic axle load spectrum (ALS) is one of the key inputs for mechanistic-empirical analysis and design of pavement structures. Frequently, the entire ALS is aggregated into number of equivalent single axle loads or assumed to have constant contact area (CCA) or constant contact pressure. These characterisations affect the accuracy and computational performance of the pavement analysis. The objective of this study was to evaluate these characterisations based on predicted performances to rutting and fatigue cracking of several pavement structures subjected to ALS data collected from 12 bridge weigh in motion stations. The results indicated that for layers below the top 25 cm, all characterisations produced similar values of predicted rutting. However, for the top 25 cm, the methods differed in the predicted performances to rutting and fatigue cracking. Furthermore, an improvement to the CCA approach was proposed that enhanced the accuracy while maintaining the same level of computational performance.

Study on Load Stress of Lean Concrete Base in Asphalt Pavement

Load stress, which is caused by traffic loading, is important parameter used in the analysis of the new pavement design. In order to study the load stress of lean concrete base in the asphalt pavement, first of all, three–dimension finite element model of the asphalt pavement is established. The main objectives of the paper are investigated. One is calculation for load stress of lean concrete base, and the other is analysis for relationship between load stress of lean concrete base and parameters, such as thickness, modulus. The results show that load stress of lean concrete base decreases, decreases and increases with increase of base’s thickness, surface’s thickness and ratio of base’s modulus to foundation’s modulus respectively. So far as the traffic axle loading is concerned, it has a significant impact on load stress of lean concrete base, and it can be seen from results that when load is taken from 100kN to 220kN, load stress increases quickly with the increase of the traffic axle loading.

Study on the Yangtze River Delta Area Metropolis Circle and Development Strategy of City Groups: an Analysis of Economical Proliferation and Traffic Axle

Based on the analysis of overseas metropolis circle，This paper explains the influence that the traffic have exert economy proliferation. Through the economical distance analysis studies the structure of Yangtze River delta area city circle. Considering the relations of the present traffic axle and economical proliferation circle，the author insists that Yangtze River delta still was in the it font shafting systematic structure. The evolution of the shafting systematic structure will make the future trend towards the structure of the network system. So, this paper finally puts forward concrete measures for the construction of macrozonality traffic system structure of Yangtze River delta area metropolis circle. Key Words: metropolis circle, economy proliferation, traffic axle, shafting, systematic structure Resume L’auteur de cet article expose l’influence et le role de la circulation sur l’extention economique en analysant les cercles de metropoles etrangers, et etude la structure circulaire des villes dans la region du delta de Changjiang en analysant la distance economique. Vu la relation actuelle entre l’axe de circulation et l’extention economique en rond, l’auteur pense que le delta de Changjiang presente encore une structure du systeme de point– axe en zigzag, et que le developpement de cette structure tendra vers la structure du systeme de reseau. Il porpose enfin des mesures concretes pour l’installation du systeme de circulation large du cercle de metropoles dans le delta de Changjiang. Mots-cles: le cercle de metropoles, l’extention economique, l’axe de circulation , la structure du systeme de point –axe 摘 要 本文通過對國外大都市圈的分析，闡述交通對經濟擴散的影響作用；通過對經濟距離的分析研究長江三角洲地區城市圈層結構，基於目前的交通軸與經濟擴散圈層的關係，筆者認為長江三角洲仍處於“之”字型點軸系統結構，點軸系統結構的進化將使未來趨向於網路系統結構，最後由此提出長江三角洲大都市圈的廣域交通體系構造的具體措施。 關鍵詞：大都市圈；經濟擴散；交通軸；點軸系統結構

Using Weigh-in-Motion Data to Calibrate Trade-Derived Estimates of Mexican Trade Truck Volumes in Texas

Weigh-in-motion (WIM) sites are being installed along many highway corridors that carry international trade trucks. Estimating the numbers of trucks carrying international commodities currently relies on manipulating and adjusting trade databases. The variety of vehicle classification data measured at WIM sites provides a rich source of data with which to enhance this adjustment process. Previous WIM border data have focused on port-of-entry truck traffic axle loads, which are heavily influenced by drayage operations. Examined is how WIM data collected at ports of entry and on truck corridors can be used in the determination of standardized truck volumes (termed equivalent trade trucks or ETT) on international highway corridors. Data from the Texas-Mexico border are used to determine ETT North American Free Trade Agreement volumes.

Impact of Changing Traffic Characteristics and Environmental Conditions on Flexible Pavements

Although the trend for the next generation of pavement design methods is shifting to mechanistic design, the use of design methods based on the AASHO road test results is still the current design practice in Texas and some other states. Critical to these design methods are the AASHTO load equivalency factors (LEFs), which are used to convert the mixed traffic axle loads into standard 18-kip (80.1-kN) equivalent single-axle loads. Several studies have been conducted on the subject of load equivalency for pavement design and analysis. However, there remain uncertainties related to various issues of load equivalency. Over the years, the composition and characteristics of traffic using Texas highways have been changing. The North American Free Trade Agreement has accelerated such changes in that more trucks, primarily moving among mid-western states, Texas, and Mexico, are traveling on Texas highways. In addition, the original AASHO road test was conducted at a site with environmental conditions significantly different from the environmental conditions in Texas. It is therefore critical to understand fully the impact of such changing traffic characteristics and environmental conditions on pavements in Texas. Presented is the methodology used to analyze the impact of these factors on the AASHTO LEFs.