Determination of Sample Size and Influencing Factors to Characterize Faulting in Jointed Concrete Pavements

The objective of this study is to evaluate the field variability of jointed concrete pavement (JCP) faulting and its effects on pavement performance. The standard deviation of faulting along both the longitudinal and transverse directions are calculated. Based on these, the overall variability is determined, and the required sample sizes needed for a given precision at a certain confidence level are calculated and presented. This calculation is very important as state departments of transportation are required to report faulting every 0.1 mi to the Federal Highway Administration as required by the 2015 FAST Act. On average, twice the number of measurements are needed on jointed reinforced concrete pavements (JRCP) to achieve the same confidence and precision as on jointed plain concrete pavements (JPCP). For example, a sample size of 13 is needed to achieve a 95% confidence interval with a precision of 1.0 mm for average faulting of JPCP, while 26 measurements are required for JRCP ones. Average faulting was found to correlate with several climatic, structural, and traffic variables, while no significant difference was found between edge and outer wheelpath measurements. The application of Portland cement concrete overlay and the use of dowel bars (rather than aggregate interlock) are found to significantly reduce faulting. Older sections located on higher functional classes, and in regions of high precipitation or where the daily temperature change is larger, tend to have higher faulting, and might require larger samples sizes as compared with the rest when faulting surveys are to be conducted.

Mechanistic-Based Parametric Model for Predicting Rolling Resistance of Concrete Pavements

The structural rolling resistance (SRR) is the component of rolling resistance that occurs because of the viscoelastic deformation of the pavement structure. In this paper, a simple model to calculate the energy dissipation as a result of the SRR on rigid pavements is developed for use in applications such as life cycle cost analysis and life cycle assessment. First, the energy dissipated by different vehicles was calculated on 12 concrete pavement sections using a fully mechanistic approach. Using the program DYNASLAB to simulate the vehicles moving along the pavement sections, the energy dissipation was calculated as the work done by the vehicle to overcome the slope seen by the wheels because of the pavement deformation. The results were then used to develop a simple and rapid-to-use model to predict the energy dissipation on any jointed concrete pavement. The model consists of a simple predictive function that can provide the value of the SRR energy dissipation given the mechanical properties of the pavement section (slab thickness and stiffness, modulus of subgrade reaction, subgrade damping coefficient, pavement geometry, and load transfer efficiency) and the loading conditions (speed and loads). The model was based on a sensitivity analysis that was used to select the optimal set of structural and environmental factors.

Development of a New Faulting Model in Jointed Concrete Pavement using LTPP Data

Faulting is a major and commonplace distress in jointed concrete pavement (JCP) that can directly cause pavement roughness and adversely influence the ride quality of a vehicle. Faulting also plays an essential role in concrete pavement design. Notwithstanding the importance of faulting, the accuracy and reasonability of the faulting prediction models that have been developed to date remain controversial. Furthermore, the process of faulting over time is still not fully understood. This paper proposes a novel mechanistic-empirical model to estimate faulting depth at joints in the wheel path in JCP. Two stages within the process of faulting were revealed by the model and are introduced in this study. To distinguish the two stages of faulting, an inflection point, as a critical faulting depth, was directly determined by this model and suggested to be an indicator of the initiation of erosion for concrete pavement design. The proposed model was proven accurate and reliable by using long-term pavement performance data. The parameters in the model were statistically calibrated with performance-related factors by Akaike’s Information Criterion for variable selection and performing stepwise regression.

Statistical Model to Detect Voids for Curled or Warped Concrete Pavements

A statistical classifier was developed to interpret falling weight deflectometer data for the detection of voids under jointed concrete pavement slabs. The classifier was trained with the Seasonal Monitoring Program sections in the Long-Term Pavement Performance (LTPP) database and data from the Minnesota Road Research Facility. A two-level cross-validation process was used to assess the performance of existing void detection methods, according to a threshold of a single variable, and the least absolute shrinkage and selection operator (LASSO) classifier, which is based on several variables. Simple void detection methods based on the normalized 9,000-lb deflection were found to perform better than void detection methods based on variable deflection analysis. The LASSO classifier outperformed any of the existing void detection techniques. The LASSO classifier was validated through two field trials in Pennsylvania and an LTPP general pavement section in which significant faulting had developed.

Modeling of Dowel Jointed Rigid Airfield Pavement under Thermal Gradients and Dynamic Loads

Concrete pavements have been widely used for constructing runways, taxiways, and apron areas at airports. The aviation industry has responded to increased demand for air travel by developing longer, wider, and heavier aircraft with increasing numbers of wheels to support the aircraft while in ground operation. Many researchers developed their models based on the finite element method (FEM) for the analysis of jointed concrete pavement. Despite the notable improvement, important considerations were overlooked. These simplifications may affect the results of the developed models and make them unrealistic. Sensitivity studies were conducted in this study to investigate the effect of the loading parameters on the load transfer efficiency (LTE) indictors where concept of LTE is fundamental in airfield design procedures. The effect of main gear loading magnitudes in different wheel configurations combined with positive and negative thermal gradients was investigated. The verification process was presented to increases the confidence in the model results. Understanding the response of rigid airfield pavement under such circumstances is important developing a new pavement design procedure, as well as implementing a suitable remedial measure for existing pavements. The results obtained that utilizing a dynamic load allows studying the fatigue cycles that pavement can be subjected under different wheel configurations. Moreover, the change in the thermal gradient from positive to negative significantly changed the slab curvature shape.

Estimation of Joint and Interface Parameters for the Finite Element Analysis of Jointed Concrete Pavement Using Structural Evaluation Results

In the analysis of jointed concrete pavement, it is necessary to appropriately model certain aspects of the pavement for accurate estimation of its structural responses. These include load transfer at joints (doweled and aggregate interlocked) and interface condition between slab and foundation. This paper presents a backcalculation method for estimating the joint parameters, both transverse and longitudinal, and the interface parameter along with the pavement layer moduli by using the results of structural evaluation of an in-service concrete pavement. The details of the structural evaluation using Falling Weight Deflectometer (FWD) and the two-stage backcalculation procedure using a three-dimensional finite element (FE) model for jointed concrete pavement are discussed. Modulus of dowel support and modulus of interlocking joints are the transverse and longitudinal joint parameters respectively and the coefficient of friction between concrete slab and foundation is the interface parameter considered for the analysis. These parameters are the useful inputs in modeling jointed concrete pavement using finite element method.