Anastasios M. Ioannides

ABAQUS model for PCC slab cracking

To contribute towards the development of improved failure criteria for pavement systems that could potentially replace Miners hypothesis in future pavement design guides, Hillerborgs Fictitious Crack Model can be used to simulate crack propagation in concrete pavement slabs, thereby dispensing with the need to conduct time consuming and expensive physical experiments in the laboratory and the field. Commercial finite element program ABAQUS is used for slabs assumed to rest on a dense liquid foundation, and to be loaded by an edge load. Both notched and unnotched slabs are considered, and the effects of various loading parameters, notch size, size of the loaded area, slab thickness and slab size are examined. A comparison is made between displacement and loading-controlled testing of the slabs.

Application of Artificial Neural Networks to Concrete Pavement Joint Evaluation

Application of the principles of dimensional analysis has recently led to the development of a robust method for assessing the deflection and stress load transfer efficiencies of concrete pavement joints and for backcalculating joint parameters. The new method eliminates the need to make a priori assumptions since pertinent inputs can now be experimentally determined using the falling weight deflectometer. A data base has been generated using numerical integration of Westergaard-type integrals and has been used to train a backpropagation neural network algorithm for joint evaluation. The resulting computer program is simple, efficient, and precise and can be used on site for immediate results. Its predictions are verified by comparisons with closed-form and finite-element solutions pertaining to data collected at three major civilian airports in the United States, including the new Denver International Airport. Also discussed is the role of dimensional analysis in the generation of the training set for a ...

Environmental impact of the use of contaminated sediments as partial replacement of the aggregate used in road construction

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.

Concrete pavement analysis: the first eighty years

This paper traces the evolution of analytical methods for concrete pavements over the period from the publication of Westergaards early work in the 1920s until today. It is demonstrated that this development was accomplished in parallel with the birth and coming of age of geotechnical engineering, and was likewise pioneered by a number of colorful and distinguished personalities. Westergaards analysis had been based on a series of limiting assumptions, which have defined the task for generations of pavement engineers. The eventual elimination of these shortcomings has been possible only through a combination of road tests and laboratory studies, jerry-rigged equipment and sophisticated electronic tools. As a new era of mechanistic-empirical pavement design is ushered in, it behooves the profession to undertake a concerted and serious effort to eliminate the most crucial remaining stumbling block to their efforts: Miners fatigue hypothesis. Fracture mechanics, similitude concepts and the principles of dimensional analysis hold the brightest promise of a future worthy of the pioneers celebrated herein.

Simulation of Crack Propagation in Concrete Beams with Cohesive Elements in ABAQUS

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.

Stress Prediction for Cracking of Jointed Plain Concrete Pavements, 1925-2000: An Overview

The evolution of analytical methods for the prediction of cracking in jointed plain concrete pavements was traced over the period from the publication of Westergaards early work until the year 2000. This development was accomplished in parallel with the birth and coming of age of geotechnical engineering and was likewise pioneered by a number of colorful and distinguished personalities. Westergaards limiting assumptions have defined the task for generations of pavement engineers who, with road tests and laboratory studies, jerry-rigged equipment, and sophisticated electronic tools, have eventually managed to eliminate each one of them. As a new era of mechanistic-empirical pavement design is ushered in, it behooves the profession to undertake a concerted and serious effort to eliminate the most crucial remaining stumbling block to their efforts: Miners fatigue hypothesis. Fracture mechanics, similitude concepts, and the principles of dimensional analysis hold the brightest promise of a future worthy of...

An overview and a case study of pavement performance prediction

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.

Laboratory study of larger sized aggregate in Portland cement concrete

A laboratory examination of the effects of coarse aggregate type and size on the mechanical properties of concrete is presented, in an effort to develop more cost-efficient mixes for pavements and other highway structures. Aggregate blending is used to generate the required coarse aggregate gradations. Six different concrete mixes are prepared, using three different coarse aggregate gradations, along with two different aggregate types, natural and crushed. Test results show that coarse aggregate properties often do not have a significant effect on the mechanical properties of concrete. When significant differences are observed, these are confounded by variability issues related to the testing protocols themselves, and by mineralogical distinctions among the various aggregate blends.

Modeling Capacity Reliability of Minor Roads at At-Grade Un-Signalized Intersections for Potential Performance Evaluation

Abstractn Given stochastic features of the demands on both the major road and the minor road at an at-grade un-signalized intersection, the capacity of the minor road is viewed as the vulnerable and critical part impacting on the overall capacity of the intersection. To facilitate the analysis of intersection performance reliability, the capacity reliability of the minor road is defined as the probability that the capacity of the minor road can accommodate a certain traffic demand at a certain degree of saturation. The headway distribution of traffic stream on major road is reflected by three types of distributions, namely, exponential distribution, shifted exponential distribution, and Cowans M3 distribution. Based on field observations, the volumes on both major roads and minor roads are treated as correlated normal random variables. This paper presents the methods for modeling capacity reliability of the minor road at an at-grade un-signalized priority intersection. A method based on first-order reliability method is used to model the capacity reliability index. As important associated factors of capacity reliability analysis, the methods for modeling and analyzing capacity sensitivity of the minor road and reserve capacity of the priority intersection are also presented. A procedure for evaluating the intersection potential performance using capacity reliability, sensitivity and reserve capacity is developed and demonstrated with a numerical example. Finally, some new findings from the case studies are summarized.

Undispersed agglomerates and the strength of microsilica concrete

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.