This paper discusses the analytical simulation of crack propagation using the Fictitious Crack Model for notched and unnotched Portland Cement Concrete beam specimens. Parameters such as those controlling the loading conditions, mesh fineness, aspect ratio in the vertical or horizontal directions, and notch to beam thickness ratio are considered. The commercial program ABAQUS is used, and simulations are compared to previous analytical and experimental results. A linear elastic investigation is first conducted to test the agreement of the results with the Timoshenko beam theory. Subsequently, an investigation is conducted to test the built-in fracture mechanics capabilities of ABAQUS for tracking crack propagation. Since these built-in capabilities are found to be inadequate, the creation of a model from basic elements is pursued. This is accomplished by introducing JOINTC elements along the crack plane to model joint interactions. Several series of tabulated results are used to illustrate the advantage of using finite element simulation over conducting laboratory experiments, reflected in the time, effort, and money saved. The application of fracture mechanics to understanding concrete pavement cracking is found to be desirable, practical and feasible. It is argued that the development of a truly mechanistic design procedure hinges on the elimination of long-held empirical concepts, including statistical transfer functions.

The Finite Element Method has been a very powerful tool for the analysis of slab-on­ grade type pavements in the last two decades. A number of programs have been developed which treat the slab as an elastic plate and characterize foundation support either as a dense liquid or as an elastic solid. This paper describes the development of an expanded and revised version of ILLI-SLAB, which now incorporates four subgrade idealizations: the Winkler dense liquid, the Boussinesq elastic solid, the stress dependent resilient subgrade and the Vlasov two-parameter foundation. Comparative studies are greatly facilitated and results from numerous runs are presented to illustrate the scope of the program's applicability. The efficient utilization of ILLI­ SLAB is ensured by adherence to guidelines established during several convergence studies described.

Critical aspects related to the design, construction, maintenance, and performance of permeable bases are examined, and a case study is presented to put such considerations in a more practical perspective. While the popularity of carefully designed subsurface drainage systems is justified by sound engineering considerations, and their performance has been generally satisfactory, their general use is not free of problems. Disappointing local experiences sometimes discourage agencies from specifying permeable bases. One such example is offered by the United States Route 50 test road near Athens, Ohio, for which the performance of the permeable base in the context of the overall subsurface drainage system is investigated. It is found that almost one-third of the outlets at the site could not be located, and that due to little or no maintenance many of the remainder had been silted in. Software DRIP 2.0 calculations affirm that outlet spacing is adequate, yet a considerably higher permeable base thickness is required, and that the permeability of one of the gradations used is too low. Moreover, the absence of a compatible separator layer between the permeable base and subgrade exposes the system to the danger of clogging.

This paper challenges the popular narrative whereby the contribution of a base layer under a concrete pavement slab can be accommodated by augmenting the subgrade modulus, k . Following a close reading of the primary sources, it is demonstrated that the roots of this concept hail to a tentative suggestion in 1955 by Yoder, whose idea was catapulted to prominence by its immediate adoption by the Portland Cement Association. Subsequent implementations by the American Association of State Highway Officials, the Federal Aviation Administration, and agencies in the U.S. Department of Defense have resulted in the widespread and uncritical proliferation of Yoder’s proposal, even though Yoder himself never acknowledged it again. It is submitted in this paper that generating “bump-the- k -value” charts is a misguided violation of the immiscibility principle that proscribes mingling the dense liquid subgrade idealization by Westergaard with that of the elastic solid analog by Burmister. Mathematical relationships are derived and used to prove the interdependence of all available charts of this type, despite any differences in appearance. It is concluded that pavement engineers are well advised to abandon this methodology for accommodating base layers and to pursue alternatives grounded on fundamental principles, thereby exploiting computational tools that are currently available.

This historical review by Anastasios M. Ioannides traces and evaluates the evolution of pavement fatigue concepts, with a focus on the application of Miner's linear cumulative fatigue hypothesis in the design of Portland cement concrete (PCC) and hot mix asphalt (HMA) pavements. The study reviews various fatigue transfer functions and their discrepancies, reflecting the lack of consensus among researchers on the factors controlling pavement fatigue behavior. The review includes early experiments on PCC pavements dating back to the late 19th century and discusses the significant influence of fatigue testing for PCC pavements on modern design concepts. The adoption of Miner's hypothesis, especially after the AASHO Road Test, and its implications for pavement design are critically examined. Alternatives to current fatigue concepts, such as sophisticated fracture mechanics, are recommended to enhance pavement design accuracy. This paper highlights the ongoing USACE study expected to develop an improved methodology for accounting for pavement fatigue, reflecting a comprehensive understanding of fatigue phenomena in pavement materials and the necessity for more accurate design methodologies. (Abstract generated by AI tool ChatGPT 4)

This study presents a mechanistic approach for designing and evaluating doweled joints in concrete pavements, offering a significant advancement over traditional empirical methods. The analysis centers on the role of dowels as load transfer devices in jointed concrete pavements. Utilizing principles from previous studies and new analytical developments, the research introduces a rational, easily implemented methodology for determining dowel size and spacing to achieve desired load transfer efficiencies. This mechanistic design procedure incorporates the dimensionless joint stiffness and the effects of variables such as dowel support modulus and joint opening on load transfer. By integrating the work of pioneers like Friberg, Skarlatos, Ioannides, and Hammons, the paper synthesizes a comprehensive design and evaluation framework. Implementation through a user-friendly spreadsheet model allows for interactive modification of dowel parameters, facilitating optimization of joint performance. Additionally, the study outlines a procedure for assessing in-service joints using nondestructive testing, enabling back-calculation of joint properties. Despite its focus on mechanistic aspects, the paper acknowledges the influence of environmental factors like temperature and moisture on pavement behavior, suggesting areas for future research. Overall, this work lays the groundwork for more precise, efficient pavement joint design and evaluation, contributing to the durability and performance of concrete pavements. (Abstract generated by AI tool ChatGPT 4)

This study conducts a comprehensive numerical analysis of crack propagation in concrete pavement slabs with doweled joints, utilizing the finite element software ABAQUS (R) 6.9-2. The investigation employs traction-separation cohesive elements to model the fracture process, adhering to the principles of the fictitious crack model. The analysis encompasses both wheel loading and thermal curling effects to understand their influence on pavement behavior. Key parameters under scrutiny include joint width, idealization of dowel-concrete interaction, and dowel slip. Results show that increasing the initial joint opening (from 5 mm to 20 mm) slightly reduces system stiffness, evidenced by a decrease in the slope of the load-displacement curve, but has minimal impact on peak load capacity (similar to 200 kN). Dowel-concrete interaction is a critical factor, with dowel slip reducing peak load capacity by up to 20% and load transfer efficiency (LTE) dropping from 0.705 (fully bonded) to 0.696 (friction coefficient = 0.01). Thermal gradients significantly affect performance, with daytime temperature conditions reducing peak load resistance to similar to 80 kN, compared to similar to 423 kN at nighttime. The findings highlight the suitability of cohesive elements for fracture analysis and suggest improvements for rational failure criteria in mechanistic-empirical pavement design frameworks.

An efficient and effective methodology is proposed for assessing the inherent reliability in an airfield concrete pavement design process, such as the one employed by the US Department of Defense (DOD). Combination of Monte Carlo Simulation with an application of dimensional analysis results in an easy-to-use, stand-alone computer spreadsheet for this purpose. A surrogate procedure is used to reproduce the results of DOD's pavement design software (PCASE), in a manner that eliminates the need for the software in each of the thousands of simulation cycles. Results obtained show that the PCASE design reliability varies only slightly with aircraft type, ranging from 0.58 to 0.60 for the assumed value of the safety factor of 1.75. Moreover, it appears practically impossible to increase PCASE reliability above 90%, since safety factor values of more than 25 are required. This observation suggests that the PCASE design transfer function is in need of reconsideration.

The 1982 Consultant Board review of the US Army Corps of Engineers (USACE) overlay procedure is re-examined in the light of more recent analytical developments that provide a pathway to implementing the recommendations formulated at that time. The history of the existing USACE equations is traced, and new equations proposed in the aftermath of the 1982 Review are re-evaluated. These equations were not recommended at the time as substitutes to the prevailing USACE approach, since these could not be verified by the limited field data available. This study shows that selection of the thickness of a notional slab, h(N), is tantamount to fixing a threshold stress level for the calculation of the required overlay slab thickness, h(O). Once verification becomes reduced to an exercise of matching stresses, excellent agreement may be restored between the assumed values of h(N) and the backcalculated h(O)-values, using mechanistic analytical tools.

In contemporary pavement engineering parlance, a "transfer function" is a statisticalempirical formula that is used to determine the number of cycles or repetitions of a specified loading condition to which a pavement system may be subjected before it develops a particular distress of a specified extent. The significance of the transfer function in modern pavement engineering is unmatched by any other aspect of the design process. At the same time, it is generally recognized that the transfer function is the weakest component in a pavement design, reflecting the shortcomings of the current state-of-the-art and being fraught with statistical uncertainty. This paper will demonstrate that this has not always been so. In earlier times, transfer functions served the purpose of providing a safety factor, an indispensable tool for engineering design. How from such relatively humble beginnings, grounded in time-honored engineering practices, the transfer function has evolved to its current widely questioned but hardly ever challenged crucial role in pavement design is a topic that is explored in depth in this paper, through the critical review of the pertinent published literature. It is concluded that the transfer function has always been a tool for implementing policy, rather than a data driven algorithm. Consequently, it is suggested that reliance on transfer function use in pavement design must be supplemented by a careful assessment of the rational foundation of pavement design policies.

Monte Carlo simulation is used to elucidate the relationship between reliability and safety factor in the AASHTO 86/93 flexible pavement design procedure, for any given level of variability in material properties and traffic. This relationship is found to be much more sensitive to variability in material properties, than to traffic variability. The methodology developed is simple to implement and leads to practical values of the elusive overall standard deviation, So, required in AASHTO 86/93 designs, in a manner responsive to prevailing variability levels. The success or failure of a flexible pavement is found to depend more on the accuracy of the predictions of the Office of Engineering, which is responsible for materials-related aspects of flexible pavement design, than to those pertaining to traffic, as provided by the Bureau of Statistics. Additional insights are extracted with respect to the recommended range of So, the effect of quality control, and the remaining life of a pavement beyond its design period.

The so-called 72-in. rule, employed in U.S. Department of Defense rigid pavement design for establishing the number of strain cycles arising under a pass of any aircraft on a particular pavement system, is re-examined using mechanistic tools, particularly layer elastic theory and dimensional analysis. Field data collected at Denver International Airport are reproduced using analytical simulations, which permit the generation of analogous synthetic results pertaining to different pavement systems and aircraft gear configurations. The analysis affirms the expectation that the criterion for establishing the number of strain cycles cannot be simply a fixed value, defined exclusively by the tandem wheel spacing. Rather, the dual wheel spacing and the radius of each tire-print must also be taken into consideration. In addition, the radius of relative stiffness of the pavement system needs to be accounted for. In this study, these variables are accommodated in the form of three dimensionless independent input parameters. The single dependent variable is the ratio (trough strain / maximum strain), denoted herein as υ. A process is formulated to ascertain whether υ is positive or negative: if υ> 0, then one strain cycle may be expected; if υ<0, then two strain cycles may be expected. Comparisons of the process outcomes to those from the 72-in. rule show excellent agreement for the Denver conditions, testifying to the admirable simplicity and laudable wisdom of the latter. The process may be further refined for application to more complex gear configurations, e.g., tridems.

This paper discusses the effects of temperature curling on post-crack responses of concrete slabs-on-grade. The fracture process is idealized using traction–separation cohesive elements recently incorporated in ABAQUS based on the Fictitious Crack Model. Effects of curling alone as well as curling-plus-wheel load are investigated; the latter is carried out by considering two loading scenario: fixed temperature followed by increasing wheel load, and fixed wheel load followed by increasing temperature. In both loading cases, the effects of parameters, such as concrete age, notch size, slab size, slab self-weight, day time and night time temperature variation, concrete tensile strength and fracture energy have been conducted. When the slab is under curling-plus-load, it is observed that daytime curling significantly reduces the peak load capacity results in sudden failure of the slab whereas nighttime curling causes stable cracks and increases the peak load resisted by the slab. It is hoped that the application of fracture mechanics outlined in this study through a step-by-step approach may be extended to in situ pavement systems, thereby addressing the limitations in current pavement design procedures that exclusively rely on statistical algorithms for the prediction of pavement distresses.

This paper discusses finite element analysis of crack propagation in pavement slabs-on-grade with aggregate interlock joints, using the finite element package ABAQUS®6.9-2. The fracture process is idealized using nonlinear fracture mechanics approach implemented through cohesive elements. Load transfer at the joint is achieved by aggregate interlock mechanism simulated in accordance with Walraven’s nonlinear constitutive relations. The proposed discretization is first verified by comparing the pre-crack responses with experimental and numerical results published by independent researchers. Then the discretization is extended to post-crack analysis of slab responses. Parametric studies are conducted concerning the effects of joint opening and aggregate size on post-crack pavement responses. It is observed that load transfer efficiency with respect to load, vertical and crack mouth opening displacements decreases almost linearly with increasing joint opening. Aggregate size is found to have a negligible effect when the initial joint opening is small. On the other hand, as initial joint opening increases, larger aggregate particles result in stiffer joint behavior. A daytime temperature profile is observed to reduce both the peak load supported by the slab system and the load transfer efficiency of the joint, while a nighttime temperature distribution results in modest increases in these metrics. It is concluded that the proposed approach lays a computational basis for further exploration of fracture analysis in jointed slab-on-grade systems. The step-by-step methodology implemented in this study may contribute to the ongoing development of rational failure criteria that can replace the statistical/empirical algorithms currently used in pavement design procedures.

This study reviews methods for the development of performance prediction expressions for flexible and rigid pavements, and the application of performance estimation routines for planning and maintenance. Using Pavespec 3.0, 200 simulations are completed, using as-constructed pavement system data from the Ohio Route 50 project as inputs. Observed distress data trends are used for calibration, and simulations for the service life of the test pavement are generated. It is found that determining the long-term performance of a pavement using observations spanning over a small fraction of its design life and a set of purely statistical/empirical algorithms poses significant engineering interpretation challenges. Nonetheless, it is found that the test pavement may be expected to fail due to transverse cracking long before it exhibits objectionable extents of spalling, or even before it becomes too rough. Neither the existence nor the type of sealant treatment used is likely to influence the progression of cracking.

This paper presents a numerical analysis of the fracture behavior of pavement slabs, using special purpose cohesive finite elements. Hilleborg's fictitious crack model is employed in sensitivity studies exploring the effect of a number of modeling parameters on edge loading responses. Moreover, the case of interior loading is investigated, anticipating a future thermal stress analysis. Results are compared with previous experimental as well as numerical investigations conducted by other independent researchers. It is shown that cohesive elements are suitable for modeling crack propagation as required in pavement engineering. It is envisaged that the approach presented in this study can be extended to more realistic in situ pavement systems, thereby addressing the limitations of current mechanistic-empirical pavement design procedures.

Material specification C1240 of the American Society for Testing and Materials (ASTM) requires wet-sieved microsilica to pass the #325 sieve with no more than 10% retained and advises that care be exercised 'to avoid retaining agglomerations of extremely fine material'. The Ohio Department of Transportation (ODOT) has found that densified microsilica samples that are submitted sometimes do not meet this specification when subjected to test method ASTM C430, apparently because wet-sieving is not capable of breaking the agglomerations. In this study, the possible repercussions of densification of microsilica into larger particle sizes on the mechanical and other engineering properties of the resulting concrete mix are examined. Results of microsilica tests conducted suggest that ASTM C430 is not an appropriate test for assessing the suitability of microsilica for use in concrete. Tests conducted on concrete specimens indicate that those made with undensified microsilica show higher flexural and compressive strengths than concrete made with densified microsilica and with microsilica abused by prolonged exposure to moisture, for both natural and crushed aggregates. Trends observed in almost all mixes with respect to increase in strength with age, microsilica type, aggregate type and specimen size were as expected. The strength increased with age and strength increase was more rapid in the initial ages than during later ages. Both large and small cylinders attained compressive strengths of more than 34.5 MPa after 28 days of curing. Therefore, densified microsilica concrete can be used in the construction of pavements and bridges by ODOT.

The Indiana Harbor Canal (IHC) is a waterway extensively polluted with heavy metals and petroleum. Since there are limited disposal options for the petroleum-contaminated sediments (PCSs) of the canal, the environmental impact of IHC dewatered sediment when used as partial replacement of the aggregate used in hot mix asphalt (HMA) for road construction was investigated. In order to assess the long term migration of the target contaminants into the environment, the TCLP, SPLP, and a Constant pH leaching test were applied to a HMA mixture containing 10% of dewatered PCS, a conventional HMA, and the dewatered PCS. None of the heavy metals significantly leached from any of the tested materials in any of the conducted tests. Despite the presence of PAHs in the PCS, these were not found in any of the leachate samples. Finally, among the measured VOCs, only acetone and 2-butanone were found to leach from the asphalt mixtures and the sediment in the Constant pH experiment. It was concluded that it may be environmentally safe to replace the aggregates of the HMA used in road construction in the studied proportions with dewatered PCS based upon leaching levels as compared to TCLP regulated levels. This could be a viable, beneficial use option for the PCS, and therefore, for the canal remediation.

This paper discusses the simulation of crack propagation in concrete beam specimens with a finite element package, ABAQUS, version 6.7-1. Special-purpose cohesive elements are used to model the fracture process by means of the fictitious crack model. Two- as well as three-dimensional finite element discretizations are carried out. Parameters influencing the responses, such as mesh fineness, cohesive zone width, type of softening curve, and analysis technique, are studied. The responses are then compared with previous experimental and numerical investigations conducted by various independent researchers, and it is shown that cohesive elements can be used in modeling crack propagation as required in pavement engineering.