Axle Weight Research Articles

Semi-probabilistic method for residual lifetime of aluminothermic welded rails with foot cracks

One of the most frequent and dangerous failure modes in continuous welded rails is fatigue crack propagation terminated by brittle fracture. Due to the brittleness of the weld material and HAZ and the scatter in its mechanical properties, a statistical approach is necessary. The paper deals with surface cracks at the foot base of aluminothermic welded rails, developing a probabilistic methodology for determining the day by day prospective failure probability. The investigations presented here comprise weld material characterization, simulation of fatigue crack propagation and finally the determination of the failure probability using the Monte Carlo method. The effect of various parameters, such as axle weight, initial crack size, residual stresses, fatigue crack propagation threshold and date of inspection were analyzed. The results show that, independent of the date of the last inspection, almost any failure event happens in wintertime. This is in accordance with practical experience. However, from the proposed analysis it is evident that the main parameter controlling rail fracture is not only the minimum local temperature, but the temperature range over the whole year. Finally, the results are compared to the standard rail classification method.

Traffic volume and load data measurement using a portable weigh in motion system: A case study

Traditionally, traffic loading characteristics are collected for pavement design and performance prediction purposes using permanent roadside weigh-in-motion (WIM) stations. However, high installation and maintenance costs associated with these permanent WIM stations dictate that their deployment be mostly limited to major highways, such as the interstate network. Quite often however, pavement damage on high volume rural highways with heavy truck proportions is more severe than anticipated, and there is no effective way of quantifying the traffic loading on these highways. Therefore, this study was conducted to evaluate the potential application of portable WIM systems as a means for bringing the WIM technology to these high volume rural highways. A portable WIM unit was deployed in the Texas overweight corridor in Hidalgo County (Pharr District) near the USA-Mexico border on highway FM 1016 for collecting traffic data for a minimum of three weeks in each direction. The collected traffic data were analyzed to generate traffic parameters such as volume, load spectra, and overloading information both in terms of the gross vehicle weight (GVW) and axle weight. The computed traffic parameters were successful in partially explaining some of the existing pavement conditions on this highway. Overall, the study findings indicated that the portable WIM unit can be used as a convenient and cost-effective means for collecting reliable traffic information for design, analysis, and monitoring purposes. However, proper in-situ calibration of the portable WIM unit at each site is imperative prior to any real-time traffic data collection.

Probabilistic structural integrity evaluation of a highway steel bridge under unknown trucks

This paper presents fragility curves derived from a best-fit regression model that enable to quantify probabilistic structural integrity of an in-service highway steel bridge under multiple truck passages with uncertain characteristics. The regression model is able to be identified via analytical modelling techniques incorporating the bridge response quantities resulting from unknown five-axle trucks through structural health monitoring system. These quantities coupled with weigh-in-motion (WIM) data obtained from two weigh stations closest to the bridge are used (1) to identify which unknown trucks are presumably to travel over the bridge and (2) to quantify the plausible characteristics of the trucks and the corresponding load ratings determined following the AASHTO Manual. With this information, the regression models can be made to demonstrate load ratings as the truck characteristics change. Based on the best-fitted load ratings, nine significant truck characteristics were looked at in their role in causing a below satisfactory bridge capacity. Key findings reveal that the all axle weights affect the fragility curves though the axle weights are not significantly different, and the most significant axle spacing is the first spacing.

Integration of Weigh-in-Motion (WIM) and inductive signature data for truck body classification

Transportation agencies tasked with forecasting freight movements, creating and evaluating policy to mitigate transportation impacts on infrastructure and air quality, and furnishing the data necessary for performance driven investment depend on quality, detailed, and ubiquitous vehicle data. Unfortunately in the US, currently available commercial vehicle data contain critical gaps when it comes to linking vehicle and operational characteristics. Leveraging existing traffic sensor infrastructure, we developed a novel, readily implementable approach of integrating two complementary data collection devices, Weigh-in-Motion (WIM) systems and advanced inductive loop detectors (ILD), to produce high resolution truck data. For each vehicle traversing a WIM site, an inductive signature was collected along with WIM measurements such as axle spacing and weight which were then used as inputs to a series of truck body classification models that encompass all truck classes in the most common axle-based Federal Highway Administration (FHWA) classification scheme in the US. Since body configuration can be linked to commodity carried, drive and duty cycle, and other distinct operating characteristics, body class data is undeniably useful for freight planning and air quality monitoring. A multiple classifier systems (MCS) method was adopted to increase the classification accuracy for minority body classes. In all, eight separate body classifications models were developed from an extensive data set of 18,967 truck records distinguishing an unprecedented total of 23 single unit truck and 31 single and semi-trailer body configurations, each with over 80% correct classification rates (CCR). Remarkably, the body class model for five axle semi-tractor trailers – the most diverse truck category – achieved MCS CCRs above 85% for several industry specific classes including refrigerated and non-refrigerated intermodal containers, livestock, and logging trailers.

Recommended Procedure to Adjust Inaccurate Weigh-in-Motion Data

Weigh-in-motion (WIM) stations are used to monitor traffic volumes and loadings on roads and bridges. When a station is installed, a vehicle of known axle weights is typically used to calibrate the sensors. Because of environmental changes, pavement changes, sensor fatigue, and repeated loadings, the initial calibration doesn’t always maintain its validity. Therefore, the WIM station output must be monitored so that potential problems can be identified and corrected. It is common for analysts to discover that WIM data are inaccurate when they are attempting to use the data for design or planning. An analyst must then decide whether to conduct the analysis with inaccurate data or to not conduct the analysis at all. There is a need to develop a procedure that allows inaccurate WIM data to be adjusted and remain usable. Adjustment of WIM data after they have been collected may not be an acceptable practice to all agencies or for certain applications. A new accuracy metric was developed that relates Class 9 front axle weight with gross vehicle weight with data from the Long-Term Pavement Performance (LTPP) program. This new metric and other existing accuracy metrics in the literature will serve as baselines for adjusting the data. The adjustment procedure involves time series analysis, which eliminates temperature-induced variations in weight measurements that are known to occur with certain WIM sensors. The adjustment procedure is applied to an LTPP WIM station to illustrate the data before and after adjustment.

Understanding and Estimating In-Service Axle Weights of Transit Buses

Despite evidence that certain transit buses exceed axle weight limits (sometimes without any passengers on board) and mostly anecdotal indications of the concomitant pavement impacts, relatively little empirical evidence substantiates these impacts. The number of transit buses exceeding weight limits has been exacerbated by regulatory changes directed at improving emissions and accessibility. These changes have required manufacturers to include heavy auxiliary equipment, such as emissions reduction components and hydraulic systems, on transit buses and have been introduced without commensurate increases in the weight limits of transit buses. Public agencies have limited knowledge about transit bus weights and their pavement impacts. Further, estimating in-service weights of transit buses is difficult. To help improve knowledge about issues of transit bus weights, this paper describes the legal and regulatory factors surrounding transit bus weight, basic estimates of in-service bus weights, contributing factors to transit bus weights, challenges for reducing bus weights, pavement impacts of transit buses, and challenges for estimating in-service weights of transit buses. The paper also develops and applies a methodology for estimating in-service weights of transit buses by using Winnipeg, Manitoba, Canada, as a case study. Application of this methodology ( a) demonstrates the need for reliable local data when in-service weights of transit buses are estimated and ( b) empirically corroborates regulatory compliance and pavement-related concerns by using data collected from in-service transit buses.

The Influence of Weight Distribution on the Handling Characteristics of Intercity Bus under Steady State Vehicle Cornering Condition

The vehicle cornering behavior is an important performance in handling stability especially for the intercity bus. Accordingly, one of the significant parameters concerns the weight distribution which is affected by the center of gravity (CG). In this paper, the effect of weight distribution while varying the turning radius is compared and it should be expressed, and interpreted by understeer gradient which is influenced by the location of CG. The characteristic of intercity bus was modeled and evaluated using the multi-body dynamic analysis software. The analysis has been conducted under steady state cornering based on a total of three configurations, with front/rear axle weight in percent, as 40/60, 45/55, and 50/50.The results stated that the magnitude of weight distribution on front axle of bus in a range of 40% to 50% caused the incremental value of understeer gradient and it was also increased as three times in each turning radius since the difference lateral slip angles between front and rear are expanded.

Truck loading with weight balancing considerations

In order to ensure transportation safety, one main factor in the truck loading problem (TLP) that must be addressed is stability. This paper presents two models of the TLP with weight balancing considerations: 1) balancing the axle weight; 2) balancing the total weight. In the first model, a set of stock keeping units (SKUs) with different weights are loaded on to a pallet, and then the pallets are loaded on to available trucks to minimise the total number of used trucks under the constraints of truck weight limit and axle weight balancing. In the second model, a set of cargoes with different weights are loaded on to a fixed number of trucks with the purpose to balance the loaded weights for all the trucks under the constraints of weight limit. Both models are mixed integer programmes (MIPs). Efficient heuristics are designed to solve these models. Computational results show that the proposed approach can be used to solve the real world TLPs with balancing considerations.

Truck loading with weight balancing considerations

In order to ensure transportation safety, one main factor in the truck loading problem (TLP) that must be addressed is stability. This paper presents two models of the TLP with weight balancing considerations: 1) balancing the axle weight; 2) balancing the total weight. In the first model, a set of stock keeping units (SKUs) with different weights are loaded on to a pallet, and then the pallets are loaded on to available trucks to minimise the total number of used trucks under the constraints of truck weight limit and axle weight balancing. In the second model, a set of cargoes with different weights are loaded on to a fixed number of trucks with the purpose to balance the loaded weights for all the trucks under the constraints of weight limit. Both models are mixed integer programmes (MIPs). Efficient heuristics are designed to solve these models. Computational results show that the proposed approach can be used to solve the real world TLPs with balancing considerations.

Extreme Vehicle Loads on Bridges: Evaluating and Regulating Farm Equipment in Wisconsin

In May 2014, the Wisconsin legislature passed Act 377. Among other things, the act creates an increased weight allowance for vehicles classified as implements of husbandry (IoH), known to most simply as farm vehicles. These vehicles, which are both large and heavy, were designed for use in the field, but in today’s modern infrastructure, they must sometimes navigate roads and bridges as well. The increased weight allowance is a modification of the federal bridge formula (FBF). It allows IoH to operate at 15% above FBF limitations for both axle and gross weights. The act includes partial exemptions for certain implements and creates a permitting structure for implements that exceed the stated limits. The act attempts to strike a balance between the needs of the farming community in Wisconsin and the effects of heavy vehicles on the inventory bridges in the state. In this paper, the work done by the Wisconsin Department of Transportation’s Bureau of Structures to render a structural recommendation concerning operation of IoH on the Wisconsin bridge inventory is documented. Both analysis work to assess risk to the inventory as a whole and permitting processes and procedures to address IoH on a more local level are included. The intent is that other state departments of transportation and infrastructure owners benefit from Wisconsin’s experiences.

601 走行車両の軸重値推定法を改善するための小型実験装置の開発と実験(機械力学・計測制御IV)

601 走行車両の軸重値推定法を改善するための小型実験装置の開発と実験(機械力学・計測制御IV)

Assessment of Pavement Damage from Bus Rapid Transit: Case Study for Nevada

This study presents the determination of rutting and fatigue-based load equivalency factors (LEFs) for the bus rapid transit (BRT) buses operating in northern and southern Nevada. The methodology presented in this study was based on performance models calibrated to local material, traffic, and environmental conditions. The objectives of this study were accomplished by obtaining pavement responses corresponding to all cases of bus loading and climatic conditions by using the three-dimensional Move software, Version 2.1. The critical pavement responses were then used to estimate the LEFs for the various BRT vehicles. In the assessment of pavement damage, simplified and extended methodologies were developed. The interaction between pavement temperature and axle loading for both northern and southern Nevada BRT buses was considered in the extended method, which considered seasonal distributions of pavement temperature and bus passenger ridership to determine LEFs. In the simplified method, pavement responses from a single combination of the analysis temperature with either the average ridership loading or gross axle weight rating were considered. Results showed that pavement damage from BRT buses in Nevada was significantly influenced by variability in climatic conditions and passenger ridership. Of the two distress types evaluated in this case study, fatigue-based LEFs occurred at a significantly higher rate than rutting-based LEFs. Thus, for a given pavement structure, more fatigue damage is anticipated under the passage of a BRT bus.

Highway-user fees for overweight trucks: Consequences of deviations from the fourth-power law

ABSTRACTIn updating road-user fees, highway agencies are motivated by the twin objectives of equity and efficiency. The concepts of marginal pavement consumption cost (MPCC) and the fourth-power law have been used in past research in a bid to establish efficient and equitable user fees. Over the past few decades, the use of the fourth-power law has faced some criticism that the actual power of the relationship between loading and pavement deterioration deviates significantly from 4.0. In addressing this issue, this article presents a methodology that investigates the consequences of the power variations to the estimated MPCC and the distributional (equity) impacts of road-user fees for overweight (OW) trucks. The methodology incorporates practical schedules of highway maintenance, rehabilitation, and reconstruction. The analysis suggests that there are extremely small differences between the MPCC values that result from using different values of the exponent in the power law. However, different values of the exponent in the power law result in significantly different equity impacts. This article demonstrates that the equity impacts are moderate in the case of OW trucks whose individual axles are loaded close to standard axle weights. For OW trucks that are loaded within 10% of the maximum permissible weight, this article estimates that variation of the power value from 3.0 to 5.0 results in a 1%–10% surplus or deficit of their road-user charges.

Integrated structural health monitoring system and multi-regression models for determining load ratings for complex steel bridges

This paper presents a multi-regression-based framework to efficiently and accurately determine load ratings of complex steel bridges. To validate the efficiency and accuracy of the proposed framework, the framework was applied to an in-service steel bridge located in Iowa. A network of strain sensors was placed on critical regions of the bridge to capture its behaviors resulting from actual ambient five-axle trucks. To approximate the trucks, relevant Weigh-In-Motion (WIM) data were secured from two weigh stations nearest the bridge. As part of the load rating calculation process, strain sensors were tested for significance and compared to the WIM data to explore which trucks significantly affect the sensors. Four different regression methods were used with the significant WIM data that were condensed to match the size of conventional rating data obtained from a series of structural analyses of the bridge based upon the AASHTO Manual. The four different truck data sets obtained from the regression methods were then each combined with the conventional data to create the corresponding regression models to predict load ratings. The predicted data were compared to the conventional data to determine the best fit regression model. Using the best fit model, a sensitivity analysis was performed to test which truck characteristic parameters affect the predicted ratings the most. Findings indicated that the framework can build the best fit regression model capable of accurately and rapidly predicting load ratings given unknown truck data. It was also found that each axle weight and the largest axle spacing have a great influence on the predicted ratings, implying that these variables may be holistically considered to ensure structural safety of steel bridges subjected to unknown trucks.

Maximum Dynamic-Load Allowance of Bridge with GFRP-Reinforced Concrete Deck

AbstractThe 26.87-m, single-span Beaver Creek Bridge on U.S. Highway 6 in Utah was built in 2009. Elements of the bridge included AASHTO Type IV prestressed concrete girders and posttensioned, full-depth, precast concrete deck panels reinforced with glass fiber reinforced polymer (GFRP) bars. The bridge was given three static and five dynamic truck load–controlled tests before it was opened to traffic. Vertical acceleration data was also collected from random truck traffic. Dynamic truck load data was used to verify a finite element model and obtain dynamic load allowance (DLA) values. DLA was determined to be a function of the number of axles, axle group weight, and axle spacing. The maximum DLA for the bridge with a GFRP-reinforced concrete deck was found to be less than the value specified in the AASHTP LRFD Bridge Design Specifications.

Generalized Method and Monitoring Technique for Shear-Strain-Based Bridge Weigh-in-Motion

AbstractDevelopment and testing of a new type of bridge weigh-in-motion system (BWIM) based on the measurement of shear forces near the supports of the bridges is described. The proposed system is applicable to both determinate as well as indeterminate bridges. Fiber-optic Bragg grating rosette sensors were used in this approach. Formulations are based on the establishment of shear influence lines in terms of axle weights and spacings. The system further involves calibration for the estimation of a bridge parameter α, which is a function of the cross-sectional and material properties of the bridge. Three different bridges, one box-girder prestressed concrete bridge and two concrete-slab-on-steel-girder bridges with different span lengths, were instrumented for the evaluation of the proposed BWIM system. Field implementation involved a series of truck runs for calibration and evaluation of the BWIM system. Measured and actual truck-axle weights, spacings, and axle speeds as well as the gross vehicle weight...

Comparison of Pavement Response Analysis between a 18-Axles Truck and Standard Thai Truck

This article intends to present the pavement response analysis due to the 18-axles special truck used to transport a 400 tons generator parts. According to the DOH Declarations issued in 2005, DOH had issued the additional declarations containing special trucks or vehicles for overloaded transportation, proper axle and gross weights of each type of vehicles. However, the strain of the special truck must be less than the standard Thai truck (Truck25). The typical asphalt pavement is modeled and performed based on layered elastic analysis theory. The pavement is loaded with 18-axle truck. The maximum tensile strains under asphaltic concrete layer and compression strains on base, subbase, selected material and subgrade for special truck load are 234.4 ,618.1, 494.4, 422.9, and 772.3 με, respectively. However, the maximum compressive strains on selected material and subgrade of the special 18-axle truck was exceeded the standard Thai truck.

Overcoming vertical obstacles and ditches by car and wheeled tractor

Functional dependencies between all relevant parameters of wheeled vehicles of different drive types and driving conditions with maximum height of obstacle and width of ditch are obtained for the first time. The dependencies allow to ensure at the design stage the optimum axle weight distribution of machine for specified operating conditions, and thus maximum possible traction force and cross-country ability. The influence of resistance of motion on cross-country ability of wheeled vehicle is shown by specific example.

The Virtual Axle concept for detection of localised damage using Bridge Weigh-in-Motion data

This paper proposes a new level I damage identification method for short span statically indeterminate bridges using the information provided by a Bridge Weigh-in-Motion system. Bridge Weigh-in-Motion systems measure the bridge deformation due to the crossing of traffic to estimate traffic attributes, namely axle weights and distances between axles for each vehicle. It is theoretically shown that it is convenient to introduce a fictitious weightless axle, which has been termed ‘Virtual Axle’, in the Bridge Weigh-in-Motion calculations to derive a damage indicator. The latter can be used both as a new robust output-only model-free level I Structural Health Monitoring technique and as a new self-calibration method for Bridge Weigh-in-Motion systems. The response of a fixed-fixed beam traversed by a 2-axle vehicle travelling over an irregular profile is used to validate the proposed method. By means of Monte Carlo simulation the influence of the key parameters such as the degree and location of damage, noise levels, span lengths and profile irregularities on the accuracy of the method are investigated. The results show that the ‘Virtual Axle’ method is able to detect small local damages in statically indeterminate structures.

Practical Approach for Determining Permit Fees for Overweight Trucks

A practical approach is presented for determining permit fees for overweight (OW) trucks based on consumption of service life of highways. A mechanistic–empirical design philosophy is used to estimate deterioration of the pavement structure. The methodology uses permanent deformation, load-related fatigue damage, and roughness scores as descriptors to estimate service life consumption for flexible pavements and punchouts and roughness measures for rigid pavements. The experiment included flexible and rigid pavement sections with varying structural numbers and slab thicknesses from sections across Texas to account for climatic and geographical differences. Each pavement section was simulated under different loading conditions reflecting the full spectrum of axle weights characteristic of single, tandem, tridem, and quad axles. The exercise provided the basis for developing group equivalency factors and axle load factors for individual axle groups. Axle-specific parameters enabled a modular approach toward determining gross load equivalencies for any truck category without restriction on axle weights or configuration. Consumption of service life was calculated as the additional pavement structure required to accommodate OW traffic in excess of the design truck volume while ensuring the same terminal distress condition. The cost incurred in providing the additional structure to offset the accelerated consumption was assigned to the responsible truck fleet in proportion to the marginal load equivalency over the legal gross vehicle weight and axle weight tolerances. Permit fees of 3.7¢/mi per equivalent single-axle load for flexible pavements and 2.9¢/mi per equivalent single-axle load for rigid pavements were found to be practical.