Dowel bars in jointed plain concrete pavement (JPCP) have the important function of transferring wheel loads from one slab to the other, hence ensuring that the deflections on each side of the joint are kept almost equal. As well, the dowels should not impede the concrete pavement movements due to environmental effects (temperature and moisture). Dowel bar misalignment, attributed to deficient construction practice, is a major cause of joint distress or faulting by inhibiting the free movement of the slab at the joint. To prevent these issues, tolerance guidelines on misalignment levels are implemented by transportation agencies. Review of previous studies indicate that many researchers analysed the effects of dowel bar misalignment on pavement behaviour using a pull-out test, that is a forcebased opening of the joint. These approaches neglect that joints movements in the field are strain-governed by non-linear temperature and shrinkage actions, leading to combined axial movements and curling of the slab. In this study, the fundamental dowel bar behaviour under shrinkage and thermal loading was determined through detailed 3D finite element modelling (3D-FEM). To that end, models of dowel jointed concrete slabs were developed and subjected to realistic non-linear profiles of shrinkage and thermal strains. Studies were carried out on a single-bar model, taking into account bar-concrete friction and plastic concrete behaviour. The parameters that were investigated included different configurations and levels of bar misalignment and different friction coefficients between the steel and the concrete, simulating the use of bond-breakers. To interpret the results from the numerical analysis, criteria for concrete damage were developed and used in parallel with measures of joint load transfer efficiency; these were obtained by examining the response of the slab under a Falling Weight Deflectometer (FWD) drop at the joint. The results were verified by comparing the outputs of a model consisting of one half of a slab to published data. The analysis of the models revealead that none of the models showed signs of significant damage after the application of shrinkage and two thermal cycles. Analyses with up to ten thermal cycles did not indicate progressive accumulation of damage, suggesting that for the chosen parameters there is no the concrete around the dowel bar will not fail. Models with bars placed higher in the slab and bars with angular misalignment exhibited more damage than the non-misaligned models without reaching the damage criteria used in this study. The models did not exhibit the amount of damage reported in the studies on dowel bar misalignment having used pull-out tests. It was found that no significant difference existed between uncoated and coated dowel bars models results with regards to concrete damage at the joint. However, a high coefficient of friction between the dowel and the concrete, simulating dowel bar corrosion, proved to be the most detrimental to joint integrity. All of the models performed very well with respect to joint load transfer efficiency, suggesting that the plastic strains in the concrete around the dowel did not have a significant impact on joint performance for the realistic range of parameters investigated.

Dowel bars in jointed plain concrete pavement (JPCP) have the important function of transferring wheel loads from one slab to the other, hence ensuring that the deflections on each side of the joint are kept almost equal. As well, the dowels should not impede the concrete pavement movements due to environmental effects (temperature and moisture). Dowel bar misalignment, attributed to deficient construction practice, is a major cause of joint distress or faulting by inhibiting the free movement of the slab at the joint. To prevent these issues, tolerance guidelines on misalignment levels are implemented by transportation agencies. Review of previous studies indicate that many researchers analysed the effects of dowel bar misalignment on pavement behaviour using a pull-out test, that is a forcebased opening of the joint. These approaches neglect that joints movements in the field are strain-governed by non-linear temperature and shrinkage actions, leading to combined axial movements and curling of the slab. In this study, the fundamental dowel bar behaviour under shrinkage and thermal loading was determined through detailed 3D finite element modelling (3D-FEM). To that end, models of dowel jointed concrete slabs were developed and subjected to realistic non-linear profiles of shrinkage and thermal strains. Studies were carried out on a single-bar model, taking into account bar-concrete friction and plastic concrete behaviour. The parameters that were investigated included different configurations and levels of bar misalignment and different friction coefficients between the steel and the concrete, simulating the use of bond-breakers. To interpret the results from the numerical analysis, criteria for concrete damage were developed and used in parallel with measures of joint load transfer efficiency; these were obtained by examining the response of the slab under a Falling Weight Deflectometer (FWD) drop at the joint. The results were verified by comparing the outputs of a model consisting of one half of a slab to published data. The analysis of the models revealead that none of the models showed signs of significant damage after the application of shrinkage and two thermal cycles. Analyses with up to ten thermal cycles did not indicate progressive accumulation of damage, suggesting that for the chosen parameters there is no the concrete around the dowel bar will not fail. Models with bars placed higher in the slab and bars with angular misalignment exhibited more damage than the non-misaligned models without reaching the damage criteria used in this study. The models did not exhibit the amount of damage reported in the studies on dowel bar misalignment having used pull-out tests. It was found that no significant difference existed between uncoated and coated dowel bars models results with regards to concrete damage at the joint. However, a high coefficient of friction between the dowel and the concrete, simulating dowel bar corrosion, proved to be the most detrimental to joint integrity. All of the models performed very well with respect to joint load transfer efficiency, suggesting that the plastic strains in the concrete around the dowel did not have a significant impact on joint performance for the realistic range of parameters investigated.

A Rolling Dynamic Deflectometer (RDD) is a nondestructive testing device for determining continuous deflection profiles of pavements. Theses deflection profiles can be used more effectively when combined with other data such as pavement thickness, variability in moisture and other subsurface conditions, void detection and pavement right-of-way conditions. Therefore, a new, multi-function pavement testing device has been developed by a joint effort between the Texas Department of Transportation (TxDOT), the Center for Transportation Research (CTR) at the University of Texas at Austin (UT) and the Texas A&M Transportation Institute (TTI) at Texas A&M University. This new device is called the Total Pavement Acceptance Device (TPAD). The objective of TPAD testing is to nondestructively and nonintrusively investigate the structural adequacy of the total pavement system. The multiple functions of the TPAD presently include the following measurement capabilities: (1) rolling dynamic deflectometer (RDD), (2) ground penetrating radar (GPR), (3) global positioning (GPS), (4) pavement surface temperature, (5) digital video imaging of pavement and right-of-way conditions and (6) longitudinal survey offsets from known points through distance measurement (DMI). The TPAD is currently designed to perform continuous measurements at speeds around 2 to 3 mph. The effort in this dissertation is directed at: (1) developing the fourth-generation rolling sensors for faster testing speeds with the TPAD, (2) developing the Jointed Concrete Pavement (JCP) testbed with known and well-documented conditions (3) developing and evaluating the TPAD mobile platform, (4) evaluating the performance of the fourth-generation rolling sensors and refining a field calibration procedure and (5) studying the influence of the longitudinal and transverse joints in Jointed Concrete Pavement on TPAD deflection profile measurements. The first part involved the study of previous research and preliminary testing using the second-generation rolling sensor. Key benefits of the fourth-generation rolling sensor are: (1) reduced rolling noise during the testing, (2) higher signal-to-noise ratio (SNR), and (3) better tracking of the sensor. The second part of this work involved the development of the JCP testbed at the Texas Department of Transportation (TxDOT), Flight Services Facility (FSF) adjacent to the Austin-Bergstrom International Airport (ABIA). The JCP testbed was developed to establish a pavement facility with known and well-documented conditions for use in future research dealing with rigid pavement testing. The third part of this work involved the acceptance testing of the TPAD mobile platform for the RDD deflection measurements. The mobile platform was the one of the key components to develop the new moving pavement testing device. The TPAD mobile platform was developed by modifying a small, off-road vibroseies built by Industrial Vehicle International, Inc. (IVI). Acceptance testing of each of the following components was performed: (1) automated speed control, (2) static loading system and (3) dynamic loading system. The fourth part of this work involved the TPAD deflection measurements at the testbed at the TxDOT FSF. The deflection profiles using the fourth-generation rolling sensors and TPAD were performed at the established testbed. During the performance evaluation testing, the new sensor positioning, towing and raising/lowering system was developed and installed in the TPAD. The fifth part of this study involved the deflection measurement using the TPAD-RDD system on the jointed concrete pavement. This study includes the repeatability of the TPAD deflection measurements, the influence of the proximity to the longitudinal and transverse joints in JCP on TPAD deflection measurements, deflection measurements under different pavement surface temperature, the characteristic of the TPAD-RDD deflections and the comparison between the Falling Weight Deflectometer and TPAD deflection measurement testing. / text