Axle Load Research Articles

An innovative rheological approach for predicting the behaviour of critical zones in a railway track

The poor performance of critical zones along a railway line has long been a subject of concern for rail infrastructure managers. The rapid deterioration of track geometry in these zones is primarily ascribed to limited understanding of the underlying mechanism and scarcity of adequate tools to assess the severity of the potential issue. Therefore, a comprehensive evaluation of their behaviour is paramount to improve the design and ensure adequate service quality. With this objective, a novel methodology is introduced, which can predict the differential plastic deformations at the critical zones and assess the suitability of different countermeasures in improving the track performance. The proposed technique employs a three-dimensional geotechnical rheological track model that considers varied support conditions of the critical zone. The approach is successfully validated with published field data and predictions from finite element analysis. This methodology is then applied to a bridge-open track transition zone, where it is observed that an increase in axle load exacerbates the track geometry degradation problem. The results show that the performance of critical zones with weak subgrade can be improved by increasing the granular layer thickness. Interpretation of the predicted differential settlement for different countermeasures exemplifies the practical significance of the proposed methodology.

An integrated 3D dynamic FE vehicle-track model in elasto-plasticity to investigate short pitch corrugation under cyclic wheel loads

The mechanism of rail short pitch corrugation has remained elusive in the past. The damage mechanisms of the corrugation are reported to be differential wear or plastic deformation. The former has been extensively studied, while the plastic deformation, especially under multiple wheel passages has been seldom studied. To uncover the facts behind it, an integrated dynamic vehicle-track model with the rail material treated in elasto-plasticity is developed. Further, a novel method which can simulate the material deformation under cyclical axle loads is proposed. This method is used to study the rail material response at corrugation. Our research found that for the cases studied, the rail material undergoes cyclic plastic deformation at corrugation peaks only for a limited number of cycles (2–4 cycles) before reaching the elastic shakedown limit. After that, no further residual stresses and strains accumulate. The plastic deformation at corrugation peaks weakens the corrugation amplitude, serving as an early corrugation attenuation mechanism. Conversely, work-hardening at corrugation peaks increases wear resistance at those peaks, promoting corrugation in the long term. The explanation of the corrugation development process under the interplays of the plastic deformation and wear has been validated by field corrugation data. Additionally, we propose a wear coefficient in the wear model to account for the work-hardening and change in the wear resistance. Experimental results of the hardness distribution show the similar characteristics to the numerical results.

Fatigue of Cold Recycled Cement-Treated Pavement Layers: Experimental and Modeling Study

Fatigue is the main design criterion for cold recycled cement-treated mixtures (CRCTMs). However, the literature shows that the fatigue behavior of such mixtures is still not well known. For example, the effect of increasing reclaimed asphalt pavement (RAP) contents is yet a topic of discussion. This experimental and modeling study helps fill knowledge gaps on CRCTM fatigue behavior using long-term curing fatigue tests and three design methods currently being used in different countries. The objectives of this study were: (1) to characterize the mechanical and fatigue behavior of mixtures of RAP, aggregates and cement; (2) to evaluate the fatigue life of pavements with base and subbase layers of such mixtures using the novel Brazilian design method (MeDiNa); and (3) to compare the results with those obtained using the South African Pavement Engineering Manual (SAPEM) transfer functions and the American Association of State Highway and Transportation Officials AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software. The mixtures were tested in the laboratory using flexural static and cyclic tests, and the required parameters to use the methods were obtained. Experimental results and modeling demonstrated a superior fatigue behavior of recycled layers with higher RAP contents. On the other side, layers with lower RAP contents abruptly lost stiffness in short periods, making thicker structures necessary. Therefore, using high RAP contents is not only a sustainable practice, but also a technical benefit. The equivalent single axle loads obtained using the SAPEM were higher than those obtained using MeDiNa, while the PMED ones were higher than both previous methods. Despite the inherent differences, this suggests that MeDiNa is more conservative. It also highlights the importance of calibration based on long-term pavement performance data.

Multiscale analysis of wheel-rail rolling contact wear and damage mechanisms using molecular dynamics and explicit finite elements

As traffic density and axle loads increase, the macroscopic wheel-rail contact can lead to severe rail wear. This paper constructs a multi-scale analysis framework from macroscopic force characteristics to microscopic wear mechanisms based on explicit finite element methods and molecular dynamics models. The study shows that the mutual proximity and annihilation of reverse dislocations in the rail material under the action of wheel-rail forces is an important cause of grain boundary fragmentation, while the proliferation of dislocations on the Subsurface leads to work hardening of the rail. The analytical framework proposed in this paper achieves a multiscale correlation between wheel-rail macroscopic contact and material microscopic response, and the conclusions obtained reveal the microscopic wear mechanism of rail materials.

Probabilistic fatigue life assessment of steel rail-bridge in dual response surface framework

A new probabilistic fatigue life assessment (PFLA) procedure is proposed considering dynamic effects of train loading, possible enhancement of axle load, and uncertainty there-in. In conventional PFLA, Monte Carlo simulation (MCS) is used to simulate stochastic load. Thereafter, rainflow counting method is used to obtain mean stress ranges. However, it is well-established now that only mean stress range may not depict the detailed stochastic nature of train axle load time-histories. Moreover, such MCS-based PFLA is computationally demanding for real-life complex structures, and routine implementation of it is quite troublesome due to dearth of skilled engineers in advanced fatigue analysis and interface software. To circumvent this, the proposed PFLA procedure resorts to dual response surface method (DRSM), which yields explicit equations for mean as well as standard deviation of stress range. Using these equations, the proposed approach directly relates fatigue life with the input factors (train speed, axle load, etc.) through an excel spreadsheet without requiring MCS. The effectiveness of the proposed procedure is elucidated through an existing steel railway bridge in India. The accuracy of the approach is also validated with four other steel bridges practically failed in fatigue. The results show that the proposed PFLA is in excellent agreement with the most accurate direct MCS-based PFLA, and the practical data obtained from failed steel bridges; whereas, the conventional moving load analysis-based deterministic fatigue life assessment approach yields significantly deviated results. Also, the proposed DRSM-based PFLA approach is observed to be computationally more efficient than the conventional direct MCS-based PFLA.

Novel Soft-Computing Approach to Better Predict Flexible Pavement Roughness

Road infrastructures are fundamental parts of peoples’ lives, allowing them to access various destinations and activities. Accordingly, infrastructure should be in an appropriate condition. A pavement maintenance plan should be optimized, and pavement condition should be predicted accurately to obtain optimal pavement maintenance solutions. Therefore, the prediction of pavement conditions with high accuracy has been an immense concern. This study aims to introduce a new approach to accurately predict pavement international roughness index (IRI) over the long term. To this end, all the vital parameters, including initial IRI, pavement age, lane width, traffic loadings, structural characteristics, climatic features, and pavement distresses, are considered. With all the vital parameters, the prediction problem includes 58 variables. Thus, the application of a proper feature-selection technique is vital. To this end, a novel hybrid feature-selection method is introduced by a combination of arithmetic optimization algorithm and stochastic gradient descent regression (AOA-SGDR). Moreover, the performance of the proposed feature-selection method is compared with Lasso and all features. Five machine-learning algorithms, including random forest regression (RFR), support vector machine, multi-layer perceptron, decision-tree regression, and multiple linear regression, are employed for the prediction process. By employing AOA-SGDR, the average testing-data mean absolute error (MAE) reduces by at least 7.92%. Meanwhile, RFR provides the highest accuracy, with average testing-data MAE of 0.095 m/km. Moreover, analyzing the parameters indicates that initial IRI, pavement age, equivalent single axle load (ESAL), and structural number (SN) have the most significant relative influence on IRI.

Efficient model‐correction based reliability analysis of uncertain dynamical systems

AbstractIn this contribution, a model‐correction‐based strategy is applied for efficient reliability analysis of uncertain dynamical systems based on a low‐fidelity (LF) model whose outcomes are corrected in a probabilistic sense to represent the more realistic outcomes of the high‐fidelity (HF) model. In the model‐correction approach utilized, the LF model is calibrated to the HF model close to the so‐called most probable point (MPP) in standard normal space, which allows a more realistic assessment of the considered complex dynamical system. Since only few expensive limit state function evaluations of the HF model are required, an efficient reliability analysis is enabled. In an application example, the LF model describes an existing single span railway bridge modelled as simply supported Euler‐Bernoulli beam subjected to moving single forces representing the axle loads of a moving train. The HF modelling approach accounts for the bridge‐train interaction by modelling the passing train as mass‐spring‐damper (MSD) system, however increasing the computational effort of the limit state function evaluations. The failure probabilities evaluated with the model‐correction approach are contrasted and discussed with the failure probabilities of the sophisticated bridge‐train interaction model. It is shown that the model‐correction‐based approach provides reliable failure probability prediction of the HF model while leading to a significant reduction in computational effort.

SIMPLIFIED MECHANISTIC – EMPIRICAL ANALYSIS OF FLEXIBLE PAVEMENT

Pavement stress-strain analysis is an ideal tool for analytical modelling of pavement behaviour and thus, constitutes an integral part of pavement design and performance evaluation. It is the fundamental basis for the mechanistic design theory. Predicting pavement response by simplified procedure analysis by relying on equivalency factors using axle load spectrum which is obtained from Weigh-In-Motion (WIM) data is aimed for this study. The framework for computing the structural response of the standard axle group loads on a pavement structure by using a layered elastic computer program and calculation of pavement responses for axle load distribution for different axle groups and axle types by using the theoretical analysis. From the study, the summary of the obtained results are as follows: (1) axle load distribution was developed for the four considered axle configurations; (2) Single axle with single tyre has the greatest destructive impact followed by the tridem axle with dual tyres (TRDT) and next by TADT. The least destructive axle group type is the Single Axle with Dual tyre SADT.The predicted pavement response by theoretical analysis indicates that the critical tensile strains obtained results are all greater than the critical vertical strains. At the heaviest axle load, from 70KN, for both SAST and SADT; from 140KN for TADT; and from 210KN, the critical strains have the greatest magnitude by SAST and followed by SADT and next by TADT. The least critical tensile strain is from the TRDT.

EFFECTS OF WASTE CROSSED-LINKED POLYETHYLENE ELECTRICAL WASTE COATING ON THE PROPERTIES OF BITUMEN

The high cost of construction materials and increased axle loads has motivated researchers to seek alternative cost-effective materials for road construction. Studies on the use of waste thermoplastic polyethylene material to improve bitumen properties have been investigated. However, few studies on the use of thermoset polyethylene (cross-linked polyethylene) to modify bitumen have been carried out. This research investigated the use of waste cross-linked polyethylene (XLPE) cable coating on bitumen properties. An FTIR analysis carried out on waste XLPE cable coating revealed that it is predominantly composed of XLPE material. A comparative study carried out on the bitumen properties revealed that the modifier had a decreasing effect on its penetration and ductility but, had an increasing effect on softening point and specific gravity; Hence, a considerable improvement in the temperature susceptibility and stability of the bitumen. The short-term ageing analysis carried out revealed that the modified bitumen can withstand short-term ageing requirements at 2% and 4% by weight of pure bitumen. FTIR analysis carried out on the pure and modified bitumen revealed that changes observed in bitumen properties with increasing modifier content were a result of physical changes and not chemical changes. A one-way ANOVA carried out on the properties of various bitumen content revealed that the modifier had a significant effect on the properties of pure bitumen with increasing bitumen content. The regression models developed properly described the relationship between the modifier content and the bitumen properties as they expressed very good R2 values.

A computer vision-assisted method for identifying wheel loads of moving vehicles from dynamic bridge responses

Bridge weigh-in-motion (BWIM) technology, which identifies traffic information such as the axle weights, wheelbases, and velocities of vehicles passing over a bridge from bridge responses, can be beneficial for bridge design, management, and maintenance. However, conventional BWIM methods simplified the coaxial wheel loads of a vehicle using one concentrated force, commonly known as the axle load. Such simplification would lead to two problems. Firstly, it fails to calculate the wheel weights of moving vehicles, which are essential for evaluating the service status of roads and is required to be measured by national weigh-in-motion specifications, such as ASTM E1318-09. Secondly, the transverse distance between the coaxial wheels (track width), and unequal load distributions between left and right coaxial wheels (unbalance) were ignored in the conventional BWIM methods. However, these two factors represented the actual characteristics of the vehicle load applied on the bridge. Hence, ignoring these two factors could lead to significant errors in estimating the vehicle weight when the track width or the unbalance ratio of the test vehicle was different from that of the calibration vehicle. To address the above two problems, this study proposed a new BWIM method, where two concentrated loads with fixed transverse distance were used to represent the coaxial wheel loads of the truck in analyzing the interactions between the truck and the bridge. By doing so, the wheel weights of moving vehicles can be calculated, and both the effects of the unbalance and the track width can be considered in estimating the axle weights of the vehicle. Both experiment results and simulation results demonstrated that the proposed method can effectively identify the wheel weights of moving vehicles, and provide more accurate axle weights than conventional BWIM methods under complex traffic scenarios.

ЕФЕКТИВНІСТЬ ЗАСТОСУВАННЯ СИСТЕМ WIM НА АВТОМОБІЛЬНИХ ДОРОГАХ

Introduction. The introduction to the paper highlights the general role of the weight control of motor vehicles on roads by WiM – methods (Wegh-in-Motion) in the assurance of the traffic safety and in the transportation infrastructure preservation. Problem statement. The issues of the paper concern the problems of implementation of contemporary technologies of the High-Speed WiM (HS-WiM) where the conditions of the measurements of the loads from the vehicle generate high measurement error. Purpose. The main goal of the paper is to perform an analytical review of methods of the weight control of vehicles and of competitive aspects of existing WiM technologies and also the analysis of the practice of WiM application. Results. The analytical reviewing led to the following results: it was revealed that the basic principle of WiM systems operation consists in determining the dynamic wheel/axle loading of a vehicle transmitted to the pavement; data thus obtained shall be used to reveal the overloading. Modern WiM systems give possibilities to obtain data concerning axle number, axle spaces, vehicle length and speed, axle (or wheel) dynamic loading, number of equivalents of standard axle loading, and also data regarding the traffic flow characteristics; it was concluded that WiM systems can be divided into two main types: the systems operating at low speed of a vehicle (up to 15 km/h, LS WiM) and those operating at steady speed of the traffic flow (up to 130 km/h, or high speed, HS WiM). LS WiM ensure the accuracy of the measurement in a range from 3 % to 5 % and belong to the methods of weight control of motor vehicles approved by the legal metrology as well as the static weighing does. HS WiM control is more sensitive to the external factors due to the effect of a vehicle dynamic and thus cannot assure the above stated accuracy of measurements, moreover, cannot assure the appropriate accuracy for the satisfactory number of trucks. HS WiM systems are not approved by the legal metrology; factors affecting the accuracy of measurements in HS WiM systems were analyzed. It was revealed that the effect of a vehicle dynamic on the measurement error can be mitigated assuring the compliance of the road pavement surface condition with the standard requirements mainly with those concerning pavement surface roughness.

ДОСЛІДЖЕННЯ СТІЙКОСТІ ДО УТВОРЕННЯ КОЛІЇ ТЕПЛИХ АСФАЛЬТОБЕТОННИХ СУМІШЕЙ НА ОСНОВІ БІТУМУ З ВИКОРИСТАННЯМ ЕНЕРГОЗБЕРІГАЮЧИХ ДОБАВОК ТА СПІНЕНОГО БІТУМУ З ДОДАВАННЯМ РЕГЕНЕРОВАНОГО АСФАЛЬТОБЕТОНУ

Introduction. The article investigates asphalt mixtures produced by standard technology according to [1, 2] and the so-called warm asphalt mixtures produced at reduced process temperatures based on bitumen with the addition of energy-saving additives and foamed bitumen. Problems. The resistance of asphalt mixtures to rutting is a key parameter in the design of the mixture, as the load on the pavement structure is increasing under current conditions due to the increased transport capacity of new vehicles that can carry loads with higher than standard axle loads. Objective. The aim of the study was to investigate asphalt mixtures made using standard technology according to [1, 2] and the so-called warm asphalt mixtures made at reduced process temperatures based on bitumen with the addition of energy-saving additives and foamed bitumen. Materials and methods. Experimental comparative tests of traditional hot asphalt concrete ASG.Sh.N.I.A.BND 70/100, asphalt concrete using foamed and bitumen, and asphalt concrete based on bitumen with the addition of energy-saving additives were carried out. Results. Graphical dependences of rut formation after more than

Development of a New Test-Rig for Wheel–Rail Contact Experiments under Large Slip Conditions

In order to further theoretical and experimental research on adhesion recovery, an innovative new test-rig for wheel–rail contact experiments under large slip conditions was developed. The wheel-on-ring category of test-rig was determined to preserve surface conditions on rail. A scale factor of 1/4 and a circling diameter of 2 m were adopted considering the power limit in the laboratory and wheel–rail contact similarity. The test-rig consisting of wheel assemblies, ring track, gearbox, motors and sprinkler system was specially designed for motor decoupling and precise slip control. Then, the accuracy of slip under PID control was verified by simulation and experimental validation. Thereafter, experimental observations with different speeds, axle loads and surface contaminants showed the potential of the new test-rig for exploring adhesion recovery under various surface conditions.

Truck platoon analysis for autonomous trucks

Selection of optimum platoon pattern based on types of trucks inside the platoon, the number of trucks in the platoon, headway distance, interplatoon distance as well as the use of different lateral wander modes for autonomous trucks has been analyzed. The objective of this research is to study the impacts of axle configurations, truck grouping, headway distance and lateral wander options on the performance of truck platoons. Four different headway distances from 2 to 5 m are compared. The first platoon PT-1 only consists of semi trailers, the second platoon PT-2 only consists of rigid body trucks and the third platoon PT-3 consists of equally distributed random traffic mix. Analysis has been conducted using the dload subroutine for projecting zero wander and uniform wander movements for each truck in the platoon on a three layered pavement crossection at vehicle speeds of 90 km/h for a total of 15 years of pavement lifetime consisting of 1.4 million equivalent single axle loads in finite element software ABAQUS. Results show that PT-3 platoon yields the minimum accumulation of damaging strains when compared against other platoon types. A headway distance of 5 m is suggested when using a zero wander mode and 3 m when using a uniform wander mode. In case of zero wander mode, fatigue life of the pavement decreases by 1.2 years and the use of uniform wander mode delays the rutting by 1.6 years, thereby increasing lifetime of the pavement.

Analysis of Dynamic Load Characteristics of Accelerated Pavement Testing Equipment Based on Virtual Prototype Model

The purpose of this paper is to study the actual dynamic load characteristics of a full-scale Accelerated Pavement Test (APT) device called Natural Environment-Automatically Loaded Track (NE-ALT) during its operation. The NEALT uses hydraulic and support reaction forces to apply axle loads, which are somewhat different from real trucks. Therefore, in order to ensure the accuracy of the loading parameters of the device, it is necessary to analyze the dynamic load characteristics of the device during operation. In this paper, a virtual prototype model of the device was established, and the important parameters, including vehicle speed and axle load, were set. The dynamic axle load, dynamic load coefficient, and influential factors of the NE-ALT were analyzed using the model at different speeds, hydraulic pressures, and road roughness. The results have shown that the dynamic axle load accuracy was most affected by speed, followed by road roughness, and then hydraulic cylinder pressure. Compared with the real truck, its dynamic load stability was better than the real truck due to the restriction of the guide rail in the acceleration loading system and the method of hydraulic loading, and the larger the load, the more stable the load, which was different from the real truck. Therefore, in the design of accelerated pavement loading experiments, the dynamic axle load characteristics of equipment need to be considered. The results of this study can provide guidance for the further improvement and application of the NE-ALT.

ANALISIS FAKTOR KEAMANAN PADA JEMBATAN KERETA API BH NOMOR 105 KM 49+093 ANTARA STASIUN LUBUKALUNG DAN STASIUN SICINCIN DI DIVRE 2 SUMATERA BARAT

One of the structures on various railroads, of which is a bridge. On the railway bridge, there are calculated loads. The load is divided into three, namely the girder self-load, additional dead load, and live load. Locomotives and wain have different axle loads and axle distances, so there is a change in the forces acting on the rail structure. Currently, the planned train loading is based on the 1921 Load Plan (RM) scheme. On the bridge BH No. 105 which connects Lubukalung Station with Sicincin is passed by BB 303 locomotive and closed wain, loading analysis is carried out by making axle loads and axle distances on a span of 50 m. Then we can compare the calculation of the load with the RM 1921 and RM Sumbar scheme, it is necessary to check the capacity of the entire bridge structure against the applicable loading. Obtained the value of the calculation of the safety factor of the existing loading with the RM 1921 scheme for a maximum reaction is 2,353 and a maximum moment is 2,32. With the RM Sumbar scheme, a maximum reaction is 0.8365 and a maximum moment is 0.74125. This shows the achievement of a safety factor of more than 1.5 for the calculation of the safety factor of the existing loading with the RM 1921 scheme. While the maximum displacement safety factor value for the RM 1921 scheme is 0.005, West Sumatra RM 0.005, and the existing charge is 0.0667. Based on the calculation results, it is smaller than the maximum safety factor value that meets the requirements.

PERENCANAAN PERKUATAN PERLINTASAN KERETA API SEBIDANG DENGAN MENGGUNAKAN PLAT BETON BERTULANG

lroad track and a motorized highway. Based on data and field reports at railroad crossings with highways, it is often found that damage to the asphalt layer (Surface Coarse). The cause of asphalt damage occurs due to a shift between the ballast gravel under the asphalt surface. Where the asphalt layer should be on a solid pavement or foundation, so that the life of the asphalt surface will be more durable. So to overcome these problems, a comparative study was conducted on the planning of retrofitting of the crossing using reinforced concrete slabs and using used railroad tracks. In the design of the reinforced concrete slab, a plate measuring 3x0.6 meters thick 7 cm with a concrete quality of K-225 (18.68 Mpa) is used which can withstand a train axle load of 18 tons. The load on the used railroad tracks is used by large-loaded vehicles, namely truck loads of 10 tons

Research on simulation method and equipment of axle load transfer of motorcycle brake performance bench test

In order to eliminate the influence of axle load transfer on the bench test of motorcycle braking performance, a method of simulating axial load transfer on the bench was developed and testing equipment was constructed.The comparison tests of road condition, bench without axle load transfer condition and bench with axle load transfer condition were carried out under three braking modes respectively. After simulating axle load transfer, the results of bench test are closer to the road test.In front braking mode,the average deceleration deviation rate, braking distance deviation rate and braking time deviation rate of bench test with simulating axial load decreased by 6.8%, 6.4% and 4.7%. In back braking mode,the average deceleration deviation rate, braking distance deviation rate and braking time deviation rate of bench test with simulating axial load decreased by 8.9%, 7.9% and 10.2%.In front-back braking mode,the average deceleration deviation rate, braking distance deviation rate and braking time deviation rate of bench test with simulating axial load decreased by 7.3%, 6.1% and 6.5%The accuracy of the bench test of motorcycle braking performance were effectively improved.

Effect of track flexibility on fatigue life of railway concrete slab track

Although reduction of fastening system stiffness and interlayer stiffness are two main approaches to increase the track flexibility, it is not obvious which one has a greater effect on decreasing the fatigue life of the concrete slab in different conditions. This research was carried to eliminate this limitation. In this regard, a numerical model of vehicle/slab track interaction was developed in the FORTRAN environment and a code was written in MATLAB to calculate the fatigue life of concrete slab based on the compressive and tensile stresses, Miner’s rule and a proper concrete fatigue life model. Through a parametric study, the effects of different parameters such as concrete slab thickness, concrete compressive strength, vehicle speed and vehicle axle load on the influences of rail-pad and interlayer stiffness on the fatigue life of concrete slab were investigated. The results obtained from the parametric study were summarized in contour figures to find a proper strategy to simultaneous increase in the railway track flexibility and the fatigue life. It was shown that decreasing the rail-pad stiffness and increasing the interlayer stiffness leads to simultaneous increase in the flexibility and fatigue life of railway concrete slab track. It was found that the track flexibility and fatigue life reach an acceptable level when the rail-pad and interlayer stiffness is lower and greater than 60 and 2500 MN/m, respectively.

Paving of concrete carriageway Case study Tauern motorway at the Wengen-Pongau junction

Passenger and freight traffic on our roads continues to increase in number and severity. High axle loads, high tyre pressures and greater dynamic loads require load-bearing and stable road pavements. Concrete road pavements are highly suitable for meeting these demands over long periods of time. Therefore, they are well suited for the new construction and renewal of motorways, federal and country roads, local bypasses, bus traffic areas, intersections and roundabouts, and cycle paths. Concrete road pavements have a long service life even under heavy use. Nevertheless, the production costs are competitive and the maintenance costs are low. This makes concrete pavements particularly economical by comparison.