The Impact of Hurricane Harvey on Pavement Structures in the South East Texas and South West Louisiana

This study developed a methodology to estimate the damage caused by flooding, such that caused by Hurricane Harvey, on a road or street network. The flooded street or pavement sections are identified using GIS flood maps with street GIS maps used for pavement management systems (PMS) by cities or state authorities. Then the damage caused by flooding directly through the increase moisture in foundation layers or indirectly due to the increase heavy traffic during the relief effort is estimated. An example Excel macro was created to illustrate the estimation process. The methodology estimates the increase in rehabilitation costs since the flooding imposes that many rehabilitation works must be done earlier than anticipated before the flooding. The methodology also estimated the increase in fuel consumption caused by the increased in pavement roughness if the rehabilitation works are done when anticipated before the flooding. The methodology and the Excel macro can also be used to identify the pavement structures with better resilience to the flooding by grouping sections based on the flooding duration (no flooding, single and multiple day flooding) and on design features such as pavement type, functional class, age or time from the most recent resurfacing or reconstruction, subgrade soil type, traffic volume, layer thickness

Characterization of Pavement Layer Interfaces.

The two primary objectives of the research were to derive constitutive models for the interfaces of flexible pavement layers, and to determine the effects of the mechanical properties of interfaces on pavement performance. A simple constitutive model was derived for the asphalt-to-asphalt interfaces using data provided by laboratory direct shear tests at several normal load levels. In the model, the shear displacement and stress are proportional until the shear strength of the interface is reached. After failure, a friction model represents realistically the interface condition. The test results proved that, if a tack-coat is not applied between layers, the shear strength at the interface and the shear stress-displacement relationship depend on the magnitude of the normal stress acting on interface with tack-coat. Fatigue tests at constant normal to shear stress ratio indicated a longer life for the interfaces with tack-coat. Field shear tests at several levels of normal load indicated that asphalt surface layers bond well to soil-cement bases. Failure at these interfaces appears due to shear in the cement stabilized material. The field tests proved that, due to their very high resistance to movement, asphalt surface layers can be considered to be fully bonded to granular base layers. The interface constitutive models were integrated into the ABAQUS finite element model in order to determine the effects of interface condition and the horizontal loads on the stress-strain field in a road structure. The study proved a significant impact of the interface condition on pavement life

A Mechanistic-Empirical Impact Analysis of Different Truck Configurations on a Jointed Plain Concrete Pavement (JPCP)

Until the last decade, the 1993 American Association of State Highway and Transportation Officials (AASHTO) design guide has been traditionally used for the design of flexible and rigid pavements in the USA and some parts of the world. However, because of its inability to meet the new traffic and material challenges, a Mechanistic Empirical Pavement Design Guide (MEPDG) was introduced based on an NCHRP 1-37 A study conducted in 2004. This study used the MEPDG software and associated models to determine, through comparative truck damage analysis, the effects of nine different truck configurations on a 12 inch-jointed plain concrete pavement (JPCP). The study recorded truck damages at the end of each analysis period (40 years) and comparatively analyzed the relative pavement damage in terms of fatigue cracking, faulting, and surface roughness. The results indicated that the most critical damage to the concrete pavement was caused by truck cases with high and uneven load distribution and relatively smaller size axles group (e.g. tandem). Other key findings included the following; (1) increase in damage when the truckloads were shifted between the same size axles, (2) decrease in truck damage when the truckloads were shifted from tandem axle to quad axles, and (3) no change in truck damage when the axle spacing was increased between wheels of a quad axle

Evaluation of Strains at the Bottom of the Asphalt Base Layer of a Semi-Rigid Pavement Under a Class 6 Vehicle

A newly constructed pavement on US-287 near Mansfield, TX was instrumented with gauges installed at the bottom of the asphalt concrete base layer to measure the longitudinal and transverse strains developed under a test vehicle. The finite element program Abaqus was used to compute the strains at the location of the gauges; they were found in good agreement with the measured strains. The research showed that the strains under the steering axle were of similar magnitude as the strains under the rear tandem axle. The measured transverse strains were in general slightly bigger than the corresponding longitudinal strains, while the finite element model computed higher strains in the longitudinal direction. These findings suggest the need to account for the strain responses from the steering axle of trucks and to account for both the longitudinal and the transverse strains when computing the fatigue damage induced by trucks

Development of Deflection Parameters to Evaluate the Structural Capacity of Flexible Pavements at the Network Level: Case Study for the State of Texas

Pavement deflection has been used widely as a nondestructive technique to evaluate the structural capacity of pavements at both network and project levels. Various transportation agencies use several evaluation methods to evaluate the integrity of the pavement layers. Most of these up-to-date developed indices are exclusively based on either central deflections or one deflection point along FWD deflection bowl. However, no standardized method that utilizes the full FWD deflection bowl is available. This study aims to introduce new comprehensive pavement layer deflection and deflection bowl area parameters that are based on the entire FWD deflection bowl rather than one single deflection point and to relate the developed parameters to the field measured distress data. Thirty-five different pavement sections in the State of Texas were utilized in the study. Two comprehensive deflection parameters and a ranking scale were developed that may be utilized for the overall pavement structural condition evaluation

Evaluation of Comparative Damaging Effects of Multiple Truck Axles for Flexible Pavements

Corresponding data set for Tran-SET Project No. 17PUTA01. Abstract of the final report is stated below for reference: This study aims at evaluating the effect of overlapping flexible pavement strain responses from truck axles that are not part of multiple axle configurations (i.e., tandem, triple and quad). For this purpose, a newly constructed pavement was instrumented with strain gauges installed at the bottom of the asphalt concrete base layer on US-287 south of Mansfield, TX. This pavement structure is typically used for medium- to high-volume roads in the South-Central region of the United States. The strain gauges were used to measure longitudinal and transverse strains under several passes of a test vehicle. This was a class 6 truck with a steering axle load of 56.9 kN (12.8 kips) and a tandem drive axle load of 161.9 kN (36.4 kips). The speed and the lateral position of the vehicle were recorded for each test vehicle pass. Sufficient quantities of the top two layers of asphalt concrete were obtained during construction to allow dynamic modulus testing in the laboratory. The general-purpose finite element program Abaqus was used to model the instrumented pavement section and compute the longitudinal and transverse strains at the location of the strain gauges. In the analysis, the asphalt concrete layers were modeled as visco-elastic materials. The Abaqus estimated strains were found in good agreement with the measured strains. Both the field measurements and the finite element analysis showed that the strains under the passing of the steering axle were of similar magnitude as the strains under the passing of the rear tandem axle. The measured transverse strains were in general slightly larger than the corresponding longitudinal strains. This can be attributed to the accumulation of strain from the front axle and the rear axle that takes place only in the transverse direction. However, the finite element model computed higher strains in the longitudinal direction than in the transverse direction. These findings suggest the need to account for the overlap in strain responses from the steering and the following axles of trucks. Furthermore, findings suggest that both the longitudinal and the transverse strain responses need to be considered in evaluating the fatigue damage impacted from trucks

Simplified Approach for Structural Evaluation of Flexible Pavements at the Network Level

Currently, there are few available simple procedures to identify structurally weak pavement sections utilizing Falling Weight Deflectometer (FWD) data at the network level (e.g., city, state or province). A simple method is required to determine the structural condition of pavement sections that can be directly implemented and automated in current pavement databases. The objective of this research study is to develop a simple analysis method to determine the structural condition of pavement sections utilizing the currently available non-destructive testing (NDT) deflection measurement devices at the network level that can be directly implemented and automated in the database of a typical transportation agency. In addition, the study had conducted an advanced mechanistic analysis to mimic the FWD deflection bowl obtained from the field. The developed structural condition parameters can be easily implemented in pavement management systems (PMS). This will aid Departments of Transportation (DOTs) and local highway agencies to make more informed decisions about the most suitable maintenance and rehabilitation strategies. Those parameters were also utilized to predict the remaining fatigue lives of the studied pavement sections

Evaluation of Strains at the Bottom of the Asphalt Base Layer of a Semi-Rigid Pavement Under a Class 6 Vehicle

A newly constructed pavement on US-287 near Mansfield, TX was instrumented with gauges installed at the bottom of the asphalt concrete base layer to measure the longitudinal and transverse strains developed under a test vehicle. The finite element program Abaqus was used to compute the strains at the location of the gauges; they were found in good agreement with the measured strains. The research showed that the strains under the steering axle were of similar magnitude as the strains under the rear tandem axle. The measured transverse strains were in general slightly bigger than the corresponding longitudinal strains, while the finite element model computed higher strains in the longitudinal direction. These findings suggest the need to account for the strain responses from the steering axle of trucks and to account for both the longitudinal and the transverse strains when computing the fatigue damage induced by trucks