Superheavy Load Research Articles

A probabilistic approach to assess slope stability of roadway shoulders under superheavy traffic operations

Non-conventional Super Heavy Load (SHL) units generally transport heavy loads weighing significantly higher than conventional trucks. Movements of such SHL trailer units with overweight tires and non-generic axle assemblies are detrimental to the structural integrity of sloped roadway shoulders. This research proposes an approach to realistically evaluate stability of roadway shoulders under subjected to SHL units. The developed methodology upgrades conventional Limit Equilibrium Method to a probabilistic approach to consider uncertainties attributed to orthogonal stiffness characteristics of aggregate materials in pavement structures. The proposed novel approach is also capable of assessing complex traffic loads imparted under SHLs. To achieve these objectives, the researchers first developed a field-testing scheme to obtain prominent features associated with the SHL trailer units and their loading configurations, as well as pavement material and road shoulder characteristics for ten overweight corridors in Texas. The field-derived information was then used as inputs in a series of 3D finite element model to characterize SHL-induced forces. Monte-Carlo methods was also deployed to establish a distribution of shear strength factors, within the bounds of laboratory-derived data for base and subbase layers as well as subgrade soils. Eventually, the resisting forces were contrasted with mobilizing forces along failure surfaces to assess stability of pavement shoulders. Results underscored the importance of tire load magnitude, shoulder slope inclination, surface treatment, and moisture management mechanisms in stability studies of roadway shoulders under demanding stress paths in overweight routes. The permutations pertaining to extreme weather events such as flooding, heavy rainfall, and prolonged inundation events also showed the detrimental effect of SHL operations on the stability of sloped shoulders. The proposed approach and synthesized results for Texas SHL corridors provided in this research facilitate realistic evaluation of the potential failure risk of sloped shoulders under SHL operations, considering non-typical nature of SHLs, environmental factors, and unique features of roadway shoulders in such regions.

Mechanistic Basis for Permit Fee Decision of Superloads Traveling on Low-Volume Roads Using Structural Damage Evaluation

Superloads, including “Implements of Husbandry” and “Superheavy Loads” transporting significant amounts of heavy agricultural and industrial products, frequently travel on county or municipal roads designed for low-volume traffic to avoid interrupting highway traffic flow by their slow-moving behavior and wide vehicle widths. The non-standardized loading configurations and high gross vehicle and axle weights of superloads have significant potential for causing unexpectedly greater distress on low-volume roads than the general vehicle classes categorized for U.S. roads by the Federal Highway Administration. To evaluate the impact of superloads on paved and granular roads designed for low-volume traffic, a mechanistic road structural and damage-associated cost analysis is needed for predicting unexpected damage induced by various types of superloads, and to provide a logical basis for superload permit fee decisions. In this study, a layered elastic theory-based road and pavement analysis was performed to quantify damage to flexible pavements and granular roads caused by superloads. Costs associated with damage to flexible pavements and granular roads subjected to a single pass of various superload types were also derived and compared through multivariate life cycle cost analysis. The potential permit fees for each type of superload traveling under different road conditions were then suggested by calculating damage-associated costs related to traffic, road structure, material, and treatment types.

Shear failure investigation of unbound pavement layers under accelerated heavy aircraft loading: case study

ABSTRACT Airport pavements are designed to sustain aircraft-induced stresses while maintaining adequate serviceability. To enhance pavement design procedures, the Federal Aviation Administration (FAA) utilises the National Airport Pavement Test Facility (NAPTF) to perform full-scale tests of airfield pavements under representative tire loads. Due to higher tire loads and pressures, unbound layers may experience shear failure and excessive permanent deformation. In this study, a new methodology is proposed to estimate the shear strength parameters of unbound materials by extrapolating resilient modulus test data until failure by adopting the hyperbolic stress–strain constitutive soil model. Using those shear strength parameters of unbound pavement layers of the NAPTF Construction Cycle 3 (CC3), a comprehensive simulation was performed using a modified version of SuperPACK (Super Heavy Load Pavement Analysis PACKage), developed based on the Federal Highway Administration (FHWA) Analysis Methodology for superheavy load (SHL). Pavement behaviour and performance were investigated for four FAA flexible pavement configurations tested mainly to study the role of different subbase thicknesses. It was found that modified SuperPACK was able to reasonably predict the shear failure mechanism in the different unbound layers existing in CC3.

Phase field approach to damage and fracture in asphalt concrete using multiscale finite element modeling of an instrumented pavement section

This study presents a Multiscale Finite Element Model (MsFEM) and Phase Field Fracture (PFF) based approach to study the responses and damage behavior of the viscoelastic Asphalt Concrete (AC) based on the actual traffic loadings. AC is a multiphase heterogeneous material. Understanding the mechanical responses and damage accumulation in different phases of AC has been a challenge for the pavement research community. This study proposes a methodology to overcome this challenge by combining a two-way linked multiscale finite element model with phase-field fracture. A modified PFF degradation function is formulated to quantify the damage and fracture in the AC microstructure. Combining MsFEM with PFF, it is possible to take the material heterogeneity, anisotropic and viscoelastic damage accumulation in the AC microstructure into consideration to identify the overall performance of the macroscale pavement. The developed MsFEM with PFF is validated based on the responses from an instrumented pavement section under Falling Weight Deflectometer (FWD) test load. Model responses are in agreement with field sensor responses, demonstrating that MsFEM with PFF can be used to accurately and efficiently predict AC microstructure performances. The model is also used to perform parametric studies to determine the extent of damage in the microscale AC due to the movement of Super Heavy Loads (SHLs) which is computationally very expensive in a traditional single scale model. The results from the parametric study show that weaker and thinner unbound layers have the highest potential of initiating fatigue damage in the AC microstructure.

Plastic strain rate in granular materials as a function of stress history: a probabilistic approach for the PBD model

ABSTRACT The permanent deformation of granular materials is an important indicator in making decisions associated with the traffic of superheavy vehicles on pavements. The PBD model, a recently developed mechanistic-empirical model, analyzes the effect of superheavy load vehicles using the plastic strain rate as an indicator. The plastic strain rates of materials subjected to repeated cyclic stresses are defined by two states: (1) the post-compaction phase and (2) the shakedown state, with a probable range of permanent deformation being defined from each of these states. This paper explores the limits of applicability of the PBD model at different times in the stress history of granular materials. An accelerated pavement test with typical pavement structures from Quebec (Canada) is used as a reference. The changes in the plastic strain rate to variables related to the stress history in the granular material were studied, and a probabilistic relationship is proposed to improve the analytical predictions of the PBD model.

Structural and Fatigue Analysis of Jointed Plain Concrete Pavement Top-Down and Bottom-Up Transverse Cracking Subjected to Superloads

Superheavy vehicles, also called superloads, have non-standardized loading configurations as well as high gross vehicle weights (GVW) and axle loadings, all of which may cause unexpectedly greater distresses on jointed plain concrete pavements (JPCP) than those caused by conventional vehicle class types categorized by the Federal Highway Administration (FHWA). In general, superloads include “Implements of Husbandry” and “Superheavy Loads”, both known to be the main types of heavy transport vehicles in the Midwestern region of the United States. To characterize non-standardized loading configurations of superloads, a mechanistic analysis approach is needed for predicting potential damage to JPCPs. In this paper, critical loading locations are determined and categorized according to the superload loading configuration for each superload generating critical pavement responses for both bottom-up transverse cracking and top-down transverse cracking. Critical pavement responses of JPCPs under critical loading conditions for each superload are calculated by performing finite element analysis and are then converted to damage ratios by comparing them with critical pavement responses resulting from FHWA class 9 truck loading using various available transfer functions based on concrete fatigue test results. The resulting critical loading location for each superload category can then be derived easily and the potential for damage to the JPCP pavement systems by each superload can be determined by comparing fatigue damage ratios.

Critical Responses of Flexible Pavements Under Superheavy Loads and Data-Driven Surrogate Model

Critical Responses of Flexible Pavements Under Superheavy Loads and Data-Driven Surrogate Model

A criterion to quantify the effect of superheavy vehicles on asphalt pavements based on layers deformation

ABSTRACT The transit of superheavy vehicles on the road network requires a specific authorisation, which results from a critical analysis of the vehicle's effect on the pavement and other road infrastructure. The assessment of the damage caused by these atypical loading conditions is based on the mechanistic-empirical approach to pavement analysis. In practice, two critical behaviours are taken as reference: (1) fatigue failure and (2) structural rutting of the pavement. However, damage assessment is carried out based on partial stresses, making it an incomplete approach to the conditions described by superheavy loads. This article compares different analysis criteria to quantify the damage caused by superheavy trucks and identifies common interest elements. Additionally, a novel approach is used to study the partial contribution of pavement layers to the structure's performance under atypical loading conditions.

Analysis of the effect of superheavy load vehicles: a review of current criteria

The analysis of damage caused by vehicles with atypical load magnitudes and axle conditions on flexible pavements is challenging for engineers. This analysis determines whether the road network’s use by this type of vehicle is authorized or denied. Consequently, it is a fundamental part of the planning and final cost estimation associated with transporting specific loads. In the literature available, different approaches are presented to address this problem. In this paper, the background in these approaches is presented, and their advantages and limitations are discussed. A compilation of different criteria can cover the aspects relevant to this type of analysis more broadly. However, some conceptual weaknesses can be identified in some currently available standards, leaving room for future research to improve how the effect of superheavy vehicles is analyzed.

Use of the permanent strain rate to analyze the effect of superheavy vehicles on pavements: Field validation

In the development and maintenance of hydroelectric, mining, or oil industries, it is necessary to transport elements with non-conventional load magnitudes. The approval or rejection of the road network's use by vehicles carrying this type of load is conditioned on the pavement's capacity to withstand these special loading conditions without suffering considerable damage. The quantification of permanent deformation in granular materials is one of the critical parameters to consider. The authors have recently proposed a model for analyzing the effect of superheavy loads based on the rate of permanent deformation in granular materials. The model has been developed from laboratory tests, and its applicability has been demonstrated with numerical model results. In this paper, field measurements were used to validate the proposed model. Field stress measurements were used to predict the probable ranges for plastic strains using the model, and these results were compared with the plastic strains measured in the field. Consistency between predicted ranges and field measurements was observed in five cases of superheavy vehicles, evaluated at different speeds and climatic conditions. An adjustment factor for the field stresses is introduced to improve the model prediction, and typical values for the parameters of the deformation rate model are given in the paper.

Impact of super heavy load vehicles on transportation infrastructure: economic aspects

Sometimes, there is a need to transport very heavy equipment, so heavy that the resulting load is several times larger than the maximal load that the corresponding road segment was designed to withstand. Such super heavy load vehicles decrease the remaining service life of the road segment, and sometimes even make the segment unusable and needing repairs. In both cases, the need for earlier-than-expected repairs means additional costs. It is therefore desirable to estimate the expected value of this additional cost. In locations where the owner of the super heavy load vehicle pays for the vehicle passage, this is necessary to decide how much to charge the owner. In other locations, where the agreement is that the cost of additional repairs comes from the additional taxes that the vehicle owners pay, such an estimate is needed to the road owners—e.g., to the county or to the state—so as to select the route for which the expected additional cost of repairs is the smallest.

Substantiation of the necessity and method of upgrading the software of the measuring complex for assessing the load capacity of girder spans of road bridges

The article notes that the software of the complex used in the Russian troops to solve in a short time the actual problem of determining the possibility of safe passage of super heavy loads on girder road bridges has the following disadvantages: 1) it can only be used for split concrete bridges; 2) the decision to pass a large load through the bridge is made only by the value of the deflection in the center of the span, without taking into account the resulting stresses in the bridge span structure structures, and without taking into account the bearing capacity of the supports. In the article, in order to eliminate these shortcomings: 1) a strict formula is obtained for calculating the deflection in the middle of beam spans made of any structural materials from the angle of rotation of their support sections; 2) based on the use of the fundamental relationship between the relative heights of girder spans, the relative deformations of the edges of their cross sections and their relative deflections, it is proved that the maximum stresses in the edges of the cross sections of girder spans from any structural materials can be calculated by the maximum deflection value in the middle of their spans; 3) a method is established for determining the ability of beam bridge supports to ensure safe passage of a heavy vehicle by the nature of changing the rotation angles of the supporting cross sections of the span structures under the influence of the movement of the heavy vehicle layout. Taking these three results into account, when upgrading the software of the measurement system, ensures that the goal of the work is achieved.

Experience of application of the measuring complex «Measurement System for testing permanent bridges» to determine the possibility of passing on permanent bridges of superheavy loads

The article presents the experience of using the measuring complex SI-PPM 15N1955 to determine the possibility of passing on permanent bridges of superheavy loads used by military engineers. The first part of the article substantiates the need to examine a large number of bridges of various designs on the routes of exit and maneuver of the troops, which in turn puts before the engineering service of associations and connections serious tasks to determine the load capacity of artificial structures on roads. In the 2000s, specialists of the Military engineering Academy and the Moscow Institute of heat engineering developed a unified method for determining the bearing capacity of reinforced concrete beam bridges, which was implemented by STC «Technical diagnostics and precision measurements» in a portable measurement system to check the permanent bridges SI-PPM 15N1955. The basis for the creation of SI-PPM is the calculation and experimental method of operational (on-site testing) determination of the state of the load-bearing structures of permanent bridges, using multi-channel measurements of angular and corresponding vertical movements of various sections of the main beams of superstructures from the impact of mobile test load. Unlike traditional methods of measuring deflections unacceptable in complexity and time of the survey of permanent bridges for the passage of modern missile systems. The main part of the article describes the measurement system. The bearing capacity of a particular bridge span is determined in the calculation program «Bridge» (the structure is presented in the article), which is part of the system. To determine the possibility of skipping the unit for a specific span of the bridge, the calculation program uses the angles of rotation of the main beams of the bridge near the supports from the impact of the mobile test load on the span, the arrangement of the wheels and the weight on the axes for the test load and the unit as the initial data. To learn how to operate the measuring system SI-MRP developed program simulator.

Evaluation of Texas Superheavy-Load Criteria for Bridges

AbstractThe number of permits for superheavy loads crossing Texas bridges has steadily increased over the years, and compared with several other states, the criteria that establish superheavy-load status are generous. The result is that many Texas bridges experience high-stress loads that cause accelerated deterioration. In this study, bridge load and rating factors and the validity of the criteria for establishing superheavy-load status are evaluated. The primary objective of this study was to evaluate Texas superheavy-load criteria for bridges. To accomplish this, field tests for the response behavior of a bridge subjected to overweight vehicles and a parametric study using finite element analysis were utilized to extract bridge criteria triggers. The field-verified solid model and related parametric study show that the Texas superheavy-load criteria are valid for the study bridge type. Load ratings computed using the distribution factors determined in this study show that the evaluated bridge has much ...

Evaluation of superheavy load movement on flexible pavements

Due to industrial plant expansion, superheavy load moves have increased drastically in Louisiana within the past decade. This paper presents a case study of a superheavy load movement with over 1.8-million kg loads on a flexible pavement. The study included pavement structural analysis under superheavy load and the estimation of cost attributable to the movement. The structural evaluation was performed by both three-dimensional (3D) finite element and the layered elastic analysis with the 3D Mohr–Coulomb yield criterion. Three wheel load configurations were analysed. The comparison of the two methods showed comparable results for the single-line load configuration. In addition, a simple and rational cost allocation process was proposed to estimate the cost attributable to a superheavy load move. The proposed process was based on the predicted damage caused by a superheavy load move and on the estimated cost for repairing the deteriorated pavement.

Mitigating seal coat damage due to superheavy load moves in Texas low volume roads

Over the past few years, the number of Super Heavy Load (SHL) moves on the Texas highways has drastically increased, resulting in severe damage, particularly on low volume roads. One of the major failure modes on these low volume roads is peeling the fresh seal coats that have been employed as a primary maintenance option by the Texas Department of Transportation (TxDOT). In this paper, a mechanistic-empirical (M-E) guideline that incorporates a Microsoft Excel spreadsheet program was developed to aid in the evaluation and characterization of the damage (peel-off) potential of seal coats when subjected to SHL vehicle loading. Field validations were conducted to validate and calibrate the guideline. It was observed that the pavement surface temperature is the most critical factor along with pavement slope in travel direction, combination of aggregate and binder types, and curing period. Additionally, the texture depth that was measured using the sand patch test method was found to play a significant role in characterizing and controlling seal coat damage. Overall, the developed M-E guideline exhibits great promising potential to serve as an aid for evaluating and mitigating seal coat damage due to SHL vehicle loading on low volume roads in Texas.

A review of the superheavy load permitting programme in Texas

Regulating and permitting superheavy loads is a part of the Department of Transportation's operation. Since the size and weight of the superheavy loads greatly exceeds that of ordinary trucks, pavement engineers face a challenge if they do not have an appropriate analysis procedure. This paper covers the general superheavy load programme in Texas as well as some analysis and field monitoring done between November 2001 and November 2002. The results presented here are those related to gross vehicle weight (GVWs) greater than 227,000 kg where pavement analysis is required. There have been 63 superheavy load moves evaluated during the year monitored. There were three superheavy load moves of over 454,000 kg on load-zoned roads (with a GVW restriction of 26,520 kg). No structure-related damages or rapid shear failure have been observed during the monitoring period. Only three cases of minor pavement damage were reported by the districts as a result of superheavy moves. Two cases were related to a fresh seal coat overlay. Thus, superheavy load moves on such newly overlaid pavements should be curtailed in the future. Because of this observation, a policy was adopted to re-route superheavy load moves to 5 weeks or older pavements. Currently, it is thought that the structure is adequate to support the moves when the remaining life prediction from the Asphalt Institute equation is 585 repetitions or greater. Although there are imperfections in the analysis procedure adopted, Texas Department of Transportation (TxDOT) is committed to continuously improve the superheavy load analysis procedure with more on-site monitoring.

Application of Falling Weight Deflectometer Data for Analysis of Superheavy Loads

Permitting superheavy loads may increase the rate of pavement damage and the cost of maintenance. An analysis of a proposed superheavy load route (FM519) to evaluate the potential pavement damage caused by a planned superheavy load move is presented. Falling weight deflection (FWD) tests and backcalculations of layer moduli were performed on the FM519. FWD tests and backcalculation of layer moduli were performed on the pavement before and after the superheavy load was moved. ELSYM5 and BISAR were used to evaluate the pavement responses using the backcalculated layer moduli from FWD data. The predictions of surface deflections from ELSYM5 and BISAR were close to (within 10 percent of) the measured deflections from FWD tests. The FWD data and analyses show that the existing pavement structure is adequate for the planned superheavy load move. Finally, the permit was issued with the condition that the transport vehicle should be kept within the travel lanes and away from the shoulder whenever possible. FWD tests were conducted after the superheavy load move and comparisons with before superheavy load move were made. T-tests were performed to check for significant difference at the 95 percent confidence level. T-tests showed that there is no significant difference between before and after superheavy load move. Also, no significant distresses due to this superheavy load were observed after the move, and the pavement condition is consistent with the analysis performed to issue the permit.

Application of Falling Weight Deflectometer Data for Analysis of Superheavy Loads

Permitting superheavy loads may increase the rate of pavement damage and the cost of maintenance. An analysis of a proposed superheavy load route (FM519) to evaluate the potential pavement damage caused by a planned superheavy load move is presented. Falling weight deflection (FWD) tests and backcalculations of layer moduli were performed on the FM519. FWD tests and backcalculation of layer moduli were performed on the pavement before and after the superheavy load was moved. ELSYM5 and BISAR were used to evaluate the pavement responses using the backcalculated layer moduli from FWD data. The predictions of surface deflections from ELSYM5 and BISAR were close to (within 10 percent of) the measured deflections from FWD tests. The FWD data and analyses show that the existing pavement structure is adequate for the planned superheavy load move. Finally, the permit was issued with the condition that the transport vehicle should be kept within the travel lanes and away from the shoulder whenever possible. FWD te...