Axle Load Limits Research Articles

The Effect of Axle Overloading and High Tire Pressure on Flexible Pavement Structure

Axle overloading and high tire pressures on the highways and motorways in Pakistan are one of the reasons that cause early pavement deterioration. There are numerous sections on the national highway on which trucks are reposted to be operating at 40-80 percent higher tire pressure than the legal limit, and the axle overloading is 30 percent greater than the legal axle load limit. This research aims at determining the effect of axle overloading and high tire pressure on the flexible pavement structure and derive the truck factors for trucks in order to quantify the damage to the pavement due to a single pass of 2-axle, 3-axle, 4-axle, 5-axle, and 6-axle truck using the results reported in the Pilot Axle Load Survey conducted by the National Transport Research Centre. In order to determine the effect of axle overloading and high tire pressure, a theoretical linear elastic mechanistic empirical analysis for different axle configurations was performed using KENLAYER and regression models were developed to find the Equivalent Axle Load Factor (EALFs) for the fatigue cracking, and permanent deformation. It was found that the EALFs were mostly controlled by permanent deformation distress criterion. The EALFs and the truck factors were highly influenced by the axle loads rather than the tire pressure. The 3-axle truck was found to be the most damaging truck followed by 6-axle truck, 5-axle truck, 2- axle truck, and 4-axle truck.

Study on the truck axle load limit for rural roads based on the cost of the concerned entities in China

The axle load limit represents the maximum permissible mass that an axle can carry when a vehicle is operating on a road. This limit is closely associated with the expenses incurred in highway construction, truck transportation, and other related sectors. Consequently, it needs to be determined by carefully weighing the relevant costs. As freight demand continues to rise, many rural roads have failed to meet the requirements for maximizing the social benefits derived from truck transportation in China. To address this issue, this study examines the optimization of the axle load limit for rural roads, taking into consideration advancements in road construction technology, construction funding, and vehicle manufacturing techniques. Initially, the entities affected by the axle load limit, namely, road agencies, truck companies, commodity producers, and consumers, are analyzed. Subsequently, a programming model is developed to optimize the truck axle load limit for rural roads, aiming to maximize the cost gap between the scenarios with the incremental limit and those without the incremental limit. Finally, a case study is conducted to validate the effectiveness of the model, using the rural road network in Guiyang city (China) as an illustrative example. The findings indicate that a limit below 17 tons results in a greater increase in benefits compared to costs. However, if the limit increases to 17 tons, the benefit increment decreases to a smaller value than the cost increment. In conclusion, the optimal axle load limit for the rural road network in Guiyang should be 13 tons, at which point the system cost reduction is maximized, resulting in an annual amount of 17.94 million RMB.

Deformation behavior of flexible pavements by finite element simulation

Flexible pavement is usually designed based on certain axle load limits and climatic conditions. The Iraqi code has specified certain load limits per each axle type that should not be exceeded. However, many trucks violate these limits by carrying additional weights to decrease the transportation cost. These overweight trucks cause severe deterioration to the pavement and thus reduce its life. The Iraqi authorities generally charges the violating trucks a penalty based on their weights. This penalty could be very small compared to the damage occurring to the pavement based on these over weights. Also, some trucks may carry huge weights that the pavement may not support, so unloading such trucks could be a suitable solution rather than paying few amounts of money and deteriorating the pavement. The study aims at studying the effect of axle load increase, and the variation in pavement moduli, on the overall pavement life. It also aims to estimate the overweight truck limits that could be penalized or unloaded. The research uses the ABAQUS software conditions to estimate the tensile strains occurring under the asphalt concrete (AC) layer and the compressive strains above the subgrade surface. These computed strains are incorporated in the fatigue cracking and rutting models to estimate the pavement life for different axle weights. Results showed that violating trucks should be unloaded when their weights exceed certain limits.

Evaluation of the structural response of two in-service thin flexible pavements under heavy vehicle loading during different seasons by built-in sensors

ABSTRACT Long Heavy Vehicles (LHV) are considered more efficient and environmentally friendly transportation of goods compared to conventional trucks. Thus, the maximum allowable gross vehicle weight (GVW) in Sweden was increased on part of the road network from 64 to 74 tons in 2018 by increasing the vehicles’ length and the number of axle groups per vehicle but not the axle load limits. This change in loading conditions is expected to lead to changes in the structural response and degradation rate of thin pavements on the low-volume road network. To improve our understanding of thin pavements behaviour exposed to multiple axle loadings two thin pavement structures located in the north of Sweden were instrumented with road response and climate sensors. Four measurement campaigns were carried out within one year by in-situ stress and strain measurements from the built-in sensors as LHV passes over at normal speed. The recorded response was compared with numerical calculations based on multilayer elastic theory (MLET). Values of stresses and strains showed a generally good agreement with high values of coefficient of determination R 2 during different seasons when the asphalt stiffness values were adjusted based on temperature and granular layer stiffness values based on moisture.

Optimum axle load limit on the trans west African highway – a case study of Ghana’s coastal corridor

The Economic Community of West African States recently reviewed regulations on axle weights. Ghana rolled out its new regulation in January 2014. The allowable axle weights in the new regulation are much stiffer (e.g., the allowable single axle limit is now 11.5 tonnes compared to 13.5 tonnes, previously). Regional freight haulers contend that the new regulations make Ghana’s corridor less attractive to trade. However, the road agency sees it as a way of maintaining and extending road pavement life. The goal of this study is to find the optimum axle limit that is economically feasible to create a balance between road preservation and port competitiveness. Data collected on 47,959 individual trucks from July 2010 to December 2013 were analyzed. A calibrated Highway Development and Maintenance model for Ghana was used to estimate the total transport cost. The analysis showed that 19 % of trucks were overloaded, and footwear was the most frequently overloaded commodity. Overloading was common with all trucks, but 3-axle trucks experienced the highest extent of overloading. It was found that if the road agency maintains a high road maintenance standard (e.g., International Roughness Index = 3 m/km), then the optimum axle limits will be from 12-13 tonnes, 20-22 tonnes, and 28-29 tonnes for single axle, tandem axle, and tridem axle, respectively. However, at a low maintenance target (IRI = 7 m/km), the optimum limits need to be 12.5 tonnes and 18-19 tonnes for single axle and tandem axle, respectively, while the optimum tridem limit remains unchanged.

Damage investigation of thin flexible pavements to Longer Heavier Vehicle loading through instrumented road sections and numerical calculations

Longer Heavier Vehicles provide an improvement in energy efficiency and environmental performance compared to traditional Heavy-Duty Vehicles. In Sweden, the maximum permissible vehicle gross weight has been increased from ∼64 to ∼74 tonnes without increasing the axle load limits. The consequence of this is investigated in this study. Response from two instrumented thin flexible pavements subjected to loading from three types of heavy vehicles (∼64, ∼68 and ∼74 tonnes) has been measured and the recordings were compared with numerical calculations based on 2D multilayer elastic calculations. Pavement damage contribution by the three vehicles was thereafter investigated. As long as the number of axles is increased to compensate for the increased vehicle loading and dual wheels are used, ∼74 tonnes vehicle are not more aggressive to the two thin pavement structures compared to the lighter vehicles with fewer axles but higher average axle loads and tyre pressure.

Influence of Commercial Vehicle Characteristics on the Magnitude of Dynamic Wheel Loads Over Asphalt Pavement Profiles with Different Roughness

The magnitude of commercial vehicle wheel loads applied on the pavement plays a crucial role in pavement performance. To avoid premature failure in the asphalt pavements, an insight into the factors influencing the magnitude of wheel loads is required. The objective of this study is to evaluate the influence of vehicle characteristics such as speed, magnitude of payload, and distribution of payload over the loading platform of a truck on the magnitude of dynamic wheel loads. For this purpose, commercial vehicle models were simulated using TruckMaker software, and the magnitude of wheel loads generated was measured. Three vehicle classes consisting of different axle configurations were considered in this study, and their movement was simulated over the pavement profiles generated according to the guidelines of ISO 8608: 2016. Dynamic wheel loads quantified in terms of dynamic load coefficient are found to be significantly affected by the above three parameters, and the effect of these three parameters is inseparable. Due to the effect of these parameters, the commercial vehicles operating under different conditions can produce dynamic loads, which are 4–60% higher than their static loads. The average load applied by the axles of a truck on the pavement is found to be sensitive to the distribution of payload over the loading platform of the truck. The trucks when loaded to the maximum legal load limit, and only when the load is located between one-third and two-third part of the loading platform, the average load applied by all the axles is found to be within the legal axle load limit.

Comprehensive benefit analysis of reinforced concrete bridge under different axle load limits

Limiting the vehicle load crossing the bridge can improve the safety of the bridge, but the transportation efficiency might be reduced. In order to reasonably evaluate the comprehensive impact of vehicle load limit on bridges, a comprehensive benefit evaluation factor K was defined to analyze the comprehensive benefits of highway bridge transportation under different axle load limits. Firstly, based on WIM data, the random distribution function of total vehicle weight and axle load was fitted, and the loss ratio of transportation benefit before and after limiting the axle load was defined and calculated based on the principle of invariable total vehicle weight. Combined with the random distribution function of the total weight and axle load, Monte-Carlo method was used to simulate the random traffic flow under different load limit levels and calculate the time-varying reliability of typical bridges under different load limit levels. Finally, the evaluation factor K was introduced to evaluate the influence of axle load limit on the comprehensive benefit of highway reinforced cocrete bridges, and reasonable axle load limit suggestions were put forward.

Justification of the Possibility of Changing of a Permissible Axle Load on the Road

This article includes an analysis of the possibility of changing current axle load and total weight limits for vehicles depending on the type of the vehicle and the season of the year during a transport of goods with modern vehicles. The weighing control has shown exceeding an actual weight and the axle load comparing to the maximum values limited by federal regulations. Ineffective use of a modern heavy vehicles in a transport of goods forces the construction organizations to break the rules of transporting or acquire special permissions. The limitations of the maximum values for the axle load and the total weight are established for the whole calendar period which is incorrect, since the road structure turns into “the monolith” due to freezing in the winter period. This gives a prerequisite to believe that it is required to take into account the seasonal features of the behavior of road structures while imposing maximum limitations established by federal law. An important factor that has a destructive influence on the road construction is not the load or the weight of the vehicle, but a pressure arising in a plane of a tread pattern on a road surface. The destructive influence on the road pavement could be insignificant with a large weight of vehicle and a certain diameter of tread pattern.

Determination of Vehicles Load Equivalency Factors for Polish Catalogue of Typical Flexible and Semi-rigid Pavement Structures

The new Polish Catalog of Typical Flexible and Semi-rigid Pavement Structures was introduced to use in practice in 2014. Much of works were focused on actualization of vehicles load equivalency factors. For this purpose data delivered from weigh-in-motion were analyzed. Four methods of determination of load equivalency factors for pavement structure design were compared. The analysis showed that fourth power equation, AASHTO, 1993 and French LCPC methods derived load equivalency factors at similar level and these obtained factors can be underestimated in comparison to results delivered from mechanistic-empirical method. The paper presents a new approach to determine load equivalency factors with consideration of several issues which have a significant impact on traffic load assessment for pavement design. The weigh-in-motion data are available only for a small part of whole road network, thus to determine values valid for roads in whole country, the statistical analysis of load equivalency factor were performed. The dynamic coefficient can have significant impact on load equivalency factor, especially on minor roads with weak roughness of pavement surface. The weigh-in-motion derives archival data and it is known from long-term observations that vehicles weights and axle loads increase while pavement life period. Legal axle load limit and the percentage of overloaded vehicles have significantly impact on load equivalency factors. The final values of vehicle load equivalency factor were adjusted to include the coefficient of vehicle dynamic loads, growth of vehicle weights in the future and impact of overloaded vehicles.

Pavement-Dependent Load Limits

South Dakota statutes limit the weight of nonsteering axles to 500 lb/in. of tire width. The load allowance for single axles or spread tandem axles with wide-base tires is less than the axle load limit for dual tires. The objective of this research is to assess the potential impact of policy change if the load limit on wide-base tires is increased to be the same as the load limit on dual tires. First, a comprehensive literature review was conducted. Results indicated that the impact of wide-base tires on pavement damage varied, depending on pavement structure and damage mechanism. Pavement response and performance data were obtained from previous studies to calculate damage ratios between wide-base tires and dual tires with the same load. Different pavement failure mechanisms (fatigue cracking, top-down cracking, primary rutting, and subgrade rutting) were applied. Cost functions were then developed by relating the life-cycle cost of four typical asphalt pavement structures used in South Dakota to design traffic levels. The impact of the policy change on the cost of pavement damage was estimated by using detailed traffic data for each road segment in the state highway network. It was found that the cost of pavement damage increased because of wide-base tires on thin asphalt pavements commonly used in secondary roads. However, the impact of wide-base tires on Interstate highways was minimal. In addition, the environmental benefits brought about by the use of wide-base tires were equally significant, especially when the reduction in fuel consumption and air pollution was considered.

Controlling Vehicle Overloading in BOT Projects

Commercial Vehicle overloading on highways – a menace; a bane to the exchequer having the onus of maintaining the road infrastructure - it not only increases his expenses but, is also one of the major causes of road accidents. And, over 50% of the commercial vehicles plying on our National/State Highways are overloaded. Although there are legal axle load limit and gross vehicle weight limit of the vehicles plying on roads, they are violated wickedly by the transporters. The damage by over-loaded vehicles to pavements is exponential. It is believed that the damage caused to a pavement by an axle load twice the standard axle is 16 times the damage incurred by the latter.There are standard legal axle load limit and gross vehicle weight limit but neither are followed by transporters nor enforced stringently by the enforcement authority. Overloading vehicles reduce the design pavement life. Controlling overloading not only prevents premature failure of the pavement but, also brings in monetary benefit to the Concessionaire. This paper presents the benefits in term of toll revenue for controlling overloading in a Build Operate and Transfer (BOT) Project with a real case study. From the case study, it is found that maximum revenue has been achieved by allowing vehicle to ply on the road carrying maximum permitted legal load. Other than the beneficial aspects indicated above, controlling overloading reduces accidents, increases speed of vehicles, requires lesser pavement maintenance costs and operating cost. In the end, plausible ways of controlling overloading with strict enforcement are highlighted.

Unbonded Transverse Posttensioning of a Railway Bridge in Haparanda, Sweden

The majority of railway lines in Sweden are designed to support axle loads of up to 250 kN. Because of increased transport needs on some lines, an axle load limit of at least 300 kN would be beneficial. To upgrade the Haparanda line in northern Sweden to 300 kN, the slabs in existing concrete trough bridges require a higher transverse shear resistance. Methods for in situ strengthening of bridge slabs in this way have not been fully developed, and this paper discusses the possibility of increasing the load capacity by horizontal prestressing. Internal, unbonded posttensioning was performed on one bridge on the Haparanda line, and the strengthening effects were investigated. The strengthening was designed according to the European Eurocode design regulations, and testing was conducted before and after the implementation. Strains in the main transverse reinforcement, caused by a train with an axle load of 215 kN, were completely counteracted by eight prestressing bars, stressed with 430 kN/bar. The results indicate that the actual strengthening effect is larger than what is predicted by the design equations. The Haparanda project showed that unbonded posttensioning can be implemented relatively fast and does not obstruct the ongoing railway traffic during installation.

Fatigue and rutting lives in flexible pavement

Flexible pavement is designed based on axle load limits and climatic conditions. The Egyptian code has specified certain load limits that should not be exceeded. The overweight trucks cause severe deterioration to the pavement and thus reduce its life. The study aims at studying the effect of axle load increase, and the variation in pavement modulus, on the overall pavement life. The research uses the BISAR software and the Egyptian environmental and pavement materials conditions to estimate the tensile strains occurring under the asphalt concrete (AC) layer and the compressive strains above the subgrade surface. The results revealed that tensile and compressive strain increased with increasing axle loads and decreased with increasing asphalt layer modulus thus the violating trucks should be unloaded when their weights exceed certain limits. Base thickness and subgrade resilient modulus were the key elements which control the equilibrium between fatigue and rutting lives.

THE HEAVY VECHICLES INTERACTION WITH ROAD PAVEMENT INFLUENCE TO CONSTRUCTION LAYERS ANALYZIS / SUNKIŲJŲ AUTOMOBILIŲ SĄVEIKOS SU KELIO DANGA IR JŲ ĮTAKOS KONSTRUKCIJOS SLUOKSNIAMS ANALIZĖ

Smoothness is the main feature of road exploitation. It particularly affects movement speed, safety and driving comfort. Evenness of the road belongs of three factors: strength of the pavement construction, heavy vehicle traffic and the impact of the axle mass over it’s term of exploitation. The main negative influence on Lithuanian roads has a overloaded heavy vehicle in excess of the permissible axle load limits. Static and dynamic vehicle weighing equipment and technologies were presented in the article. This article explores overloaded heavy vehicle damage done to Lithuanian roads and its intensity increase. Discuss the basic preventive techniques and methods to prevent the rapid wear of pavements. Also analysis of changes in axial load data through the 2009 August is done.

Dynamic Road Load Simulation of Transportable Cranes

This paper develops a general tool for understanding the dynamic road loads generated by mobile cranes that use a boom support dolly. The focal point is the dynamic road loads generated by the vehicle, which is a primary cause of pavement damage. A pitch plane model of the crane is developed and a finite element model is used to characterize the flexible motion of the boom. The simulation can characterize both the traditional and modern styles of mobile cranes. The traditional style uses a walking beam suspension on the carrier and a leaf spring suspension on the dolly. The modern cranes implement a hydropneumatic carrier suspension and an air ride suspension on the dolly. Additionally, other suspension configurations are implemented. The simulation results show that modern cranes generate significantly lower dynamic loads than do traditional cranes. This indicates that there is a need to regulate axle load limits in a manner that compensates for different suspension systems.

Investigation of causes of failures of flexible pavements: a case study of Nairobi-Thika highway

Failures of flexible pavements (bituminous roads) have been prevalent in many developing countries, a trend causing concern to both the road users and the roads authorities. In this regard, it was found necessary that an investigation be initiated to determine the possible causes of such failures, and a case study was carried out on Nairobi-Thika Highway in Kenya. The investigations were conducted in several categories to determine the pavement characteristics such as structural strength by Benkelman Beam Deflection Test (BBDT), skid resistance by British Pendulum Tester (BPT). Traffic loading by Axle load measurements, Traffic volumes by traffic counting and ageing characteristics of the type of the bitumen used by cutting cores and extracting the bitumen for the standard tests, such as penetration, ductility, bitumen content, air voids, softening point and CBR using the Light Drop Weight Tester (LDWT). The visual inspection of the pavement showed that due to the hardening of the bitumen and overloading, cracks and potholes were very common for the whole stretch of the road. Axle load data revealed that, there has been a tendency to exceed the maximum allowed axle load limits, especially until 19th august, 1999, after that the enforcement of axle load limits was tightened. This fact together with the revelation that the road is a very busy one as depicted in the traffic counts, could be one of the major causes of the road's fast deterioration. (Journal of Civil Engineering, JKUAT: 2002 7: 13-26)

Subsoil compaction by vehicles with high axle load—extent, persistence and crop response

Extent and persistence of soil and crop responses to subsoil compaction caused by vehicles with high axle loads are reviewed and methods to protect the subsoil from permanent deterioration are discussed. Traffic by vehicles with high axle loads on soils with high moisture contents generally causes deep subsoil compaction. At an axle load of 10 Mg, compaction typically penetrates to a depth of 50 cm. With still higher loads, compaction to a depth of 1 m has been reported. Subsoil compaction is very persistent. At depths of more than 40 cm it is virtually permanent even in clay soils in regions with annual freezing. Deep subsoil compaction also causes persistent and possibly permanent reductions of crop yields. Complete amelioration by mechanical loosening is usually impossible and definitely expensive. From a soil productivity point of view, limits for mechanical stresses in the subsoil are needed. These may have the form of axle load limits for the vehicles or a combination of limits for the axle load and for some other important factors, such as the ground contact pressure of the running gear or the per cent water saturation of the soil at the time of trafficking. Guidelines for such limits should preferably be worked out in an international joint effort.