Regis Carvalho | University of Maryland, College Park (original) (raw)

Papers by Regis Carvalho

ASTM International eBooks, Nov 19, 2012

Transportation Research Record, 2012

Structural models in pavement management systems range from the simple to the relatively complex.... more Structural models in pavement management systems range from the simple to the relatively complex. The simplest models use deflections or deflection basin parameters to characterize subgrade and pavement structural properties, while the more complex ones use pavement layer moduli (derived from deflections) and pavement layer thicknesses and material types to calculate pavement response, which is then used to predict failure, much like project-level pavement design analysis. Any pavement management system using the latter, more complex approach would undoubtedly need more defection information. In any case, deflection data collection is expensive and time-consuming. Most states and local agencies have few falling weight deflectometers, which are used mainly to collect project-level deflection data for scoping maintenance and rehabilitation work at the project level and for research purposes. This study explores the use of models to estimate the error associated with the choice of different deflection test spacings that can be used to optimize data collection for more efficient and economical applications in pavement management systems.

Transportation Research Board eBooks, Jan 15, 2012

Airfield and Highway Pavement 2013, 2013

The permanent deformations in the asphalt concrete layer in flexible pavement structures are anal... more The permanent deformations in the asphalt concrete layer in flexible pavement structures are analyzed using a fully mechanistic three-dimensional finite element (FE) model based on Perzyna’s viscoplasticity theory. The importance of modeling traffic as a moving wheel load as opposed to the more usual and less computationally demanding “bouncing” repeated wheel load is investigated. The effect of the induced stress reversals in the moving wheel simulation is clearly observed: The total rutting observed at the surface is about 1.6 times greater for the moving than the bouncing wheel loading after 500 cycles. Field data from MnRoad trench studies confirm the good qualitative agreement between permanent strain distributions measured in the field and those predicted by the moving wheel simulations. The moving wheel simulation is used to investigate the empirical rutting model in the mechanisticempirical pavement design guide (MEPDG). New pavement-specific depth correction functions are derived from the permanent strain distributions calculated in the moving wheel FE simulations. This approach could provide a basis for future enhancements of the MEPDG.

The primary focus of this research was to determine the effects of design and construction featur... more The primary focus of this research was to determine the effects of design and construction features, such as overlay thickness and mix type, presence of milling, and type of restoration, on pavement response and performance and to establish their importance in the prediction of future performances of rehabilitated pavements. Long-Term Pavement Performance program Specific Pavement Study (SPS)-5 and SPS-6 experiments provided information to obtain a better understanding of the effects of design and construction features on pavement response and performance of rehabilitated flexible and rigid pavements. The research findings provided guidance to identify appropriate features and rehabilitation alternatives for different pavement types and recommendations for improving data collection activities. The analyses results obtained in this study helped determine the causes of distress and helped formulate models for predicting performance of rehabilitated pavements. In addition, data from SP...

Asphalt Paving Technology, 2020

This study evaluated the cracking characteristics of asphalt materials containing RAP/RAS and pre... more This study evaluated the cracking characteristics of asphalt materials containing RAP/RAS and prepared with WMA technology. Tests were performed in the laboratory and at a full-scale testing facility. Ten test lanes were built at FHWA’s Accelerated Loading Facility (ALF). The experimental design included three RAP percentages up to 44% by weight (40% recycled binder ratio, RBR), two WMA technologies (water foaming and chemical additive), one RAS percentage with 20% RBR, and two different virgin binders (PG 58-28 and PG 64- 22). Specimens prepared from loose mixes sampled from the construction and field cores sampled at different times were evaluated using the direct tension monotonic test. Performance grade and cracking resistance of asphalt binders recovered from tested loose mix and field cores were determined. The laboratory monotonic testing results were compared to and statistically correlated to the ALF field cracking performance. Experimental results from both laboratory mix and binder tests capture the oxidative aging that occurs with time in the top lift. Aging observed in the bottom lift of the asphalt pavement was considerably less. One of the mechanical parameters developed from the mix monotonic test closely correlated with the binder tolerance strain obtained from the binder DENT test. Long- term oven aging aged the mix significantly more severely than was observed in threeyear old ALF sections. Testing of ALF materials shows that the mixtures with 40% RAP RBR or 20% RAS RBR and stiff binder exhibited the worst cracking performance. A softer PG grade was found to be effective at improving the performance for 40% RAP RBR mixes but ineffective at improving the performance of 20% RAS RBR mix. No difference in field performance was observed between the HMA and WMA mixtures having the same mix design. Statistical analysis indicated a strong correlation between the direct tension monotonic mix test and ALF field testing in terms of evaluating the cracking

International Journal of Pavement Engineering, 2018

Cracking in asphalt concrete (AC) layers is among the driving modes of flexible pavement deterior... more Cracking in asphalt concrete (AC) layers is among the driving modes of flexible pavement deterioration. Material properties, along with structural layer characteristics and external factors such as vehicular and environmental loading, govern cracking mechanisms in flexible pavements. Current practice of AC and pavement structural design methods does not allow for direct characterisation of AC impact on crack damage initiation and propagation. Asphalt concrete performance tests are the essential components of performance-related and performance-based specifications, for which they can be used either for screening AC to minimise deterioration risks or to directly predict specific modes of pavement deterioration. This paper evaluates commonly used performance tests intended to characterise AC fracture resistance. A multistep evaluation protocol was applied using various statistical techniques to determine the discrimination ability of each test method outcome criterion as well as strength of correlation to field performance. The results from full-scale accelerated pavement test (APT) sections were used to correlate with the results obtained from various laboratory performance tests. Mixes used in the study contained various levels of reclaimed asphalt pavement and recycled asphalt shingles with a recycled binder ratio up to 40%. It was shown that the flexibility index parameter obtained from the Illinois semi-circular bending (IL-SCB) test, also referred to as the Illinois Flexibility Index Test (I-FIT), resulted in the highest number of subsets and consistent ranking with APT field performance, indicating a high discrimination potential. Even though two of the overlay test's criteria resulted in fewer subsets, they also provided a consistent ranking with APT field performance. Composite scores indicate that the overlay test criteria and flexibility index from the I-FIT had the highest strength of correlation to field performance.

Transportation Research Record: Journal of the Transportation Research Board, 2006

Flexible pavement designs and performance predictions derived from the empirical 1993 AASHTO pave... more Flexible pavement designs and performance predictions derived from the empirical 1993 AASHTO pavement design methodology and the mechanistic–empirical NCHRP Project 1–37A approach are compared for a range of locations within the United States, each with its own climate, subgrade, and other material properties and local design preferences. Particular emphasis is devoted to the influence of traffic and reliability levels. The results suggest that relative to the NCHRP Project 1–37A predicted performance, the 1993 AASHTO guide overestimates performance (i.e., underestimates distress) for pavements in warm locations and at high traffic levels. Trends of pavement performance with reliability level were similar for both methodologies. The results suggest that the default design criteria incorporated in the NCHRP Project 1–37A software are broadly consistent with what would be observed historically from pavements designed with the 1993 AASHTO guide.

Stavební obzor - Civil Engineering Journal, 2017

The pavement surface condition assessment is a critical component for a proper pavement managemen... more The pavement surface condition assessment is a critical component for a proper pavement management system as well as for pavement rehabilitation design. A number of devices were developed to automatically record surface distresses in a continuous survey mode, but the software required for automatic distress identification remains a big challenge. In this study, a new method named PICture Unsupervised Classification with Human Analysis (PICUCHA) is proposed to circumvent many of the limitations of existing approaches, based on a combination of human and artificial intelligence. It was designed from scratch to be capable to identify sealed and unsealed cracks, potholes, patches, different types of pavements and others. The self-learning algorithms do not use any distresses predefinition and can process images taken by cameras with different brands, technologies and resolution. This study describes some key aspects of the new method and provides examples in which PICUCHA was tested in ...

This report proposes revisions to the "Mechanistic-Empirical Pavement Design Guide" (ME... more This report proposes revisions to the "Mechanistic-Empirical Pavement Design Guide" (MEPDG) and software to (1) incorporate three alternative rut-depth prediction models that rely on repeated load (triaxial) permanent deformation or constant height testing to provide the requisite input data, and (2) provide revised coefficients for the original and alternative rut-depth transfer functions or prediction models derived from material properties measured in the laboratory and pavement performance data. Thus, the report will be of immediate interest to engineers in public- and private-sector organizations with responsibility for the structural design and analysis of asphalt concrete pavements.

This report provides airports and their stakeholders with a method to assess the risk of lateral ... more This report provides airports and their stakeholders with a method to assess the risk of lateral runway excursions, also known as veer-offs, and suggests ways to improve veer-off incident/accident reporting. The culmination of the research is the development of the Lateral Runway Safety Area Risk Analysis (LRSARA) tool that practitioners can use to determine the probability of runway veer-offs in specific areas at their particular airport. This report contains eight chapters. Chapter 1 provides a background for the study. Chapter 2 describes the research approach. Chapters 3 and 4 discuss veer-off reporting and data collection, availability, and limitations. Chapters 5 through 7 outline the approach taken to model veer-off risk and to develop and validate the analysis software. Conclusions and suggestions for improved veer-off reporting are provided in Chapter 8. A series of appendices complement the report and software tool, including a template for veer-off reporting, a summary of the data used in the study, and a user guide for the tool. The LRSARA tool can be downloaded from the CD (CRP-CD-145) included with this report or from the Transportation Research Board website (www.trb.org). Two types of analyses are possible with the tool: simplified and full. The simplified analysis uses default or user-defined values. The full analysis allows users to perform risk assessments based on runway dimensions, obstacles, fleet mix, weather data, field elevation, air temperature, and runway surface condition.

Pavement Performance: Current Trends, Advances, and Challenges, 2012

This paper describes the evaluation of preventive treatments in mitigating the rate of distress p... more This paper describes the evaluation of preventive treatments in mitigating the rate of distress propagation in flexible pavements. The analysis was based on data from preventive maintenance treatments data collected in the Long Term Pavement Performance (LTPP) program. Data were obtained from 81 sites across the United States and Canada which were part of the specific pavement experiments (SPS-3). SPS-3 was designed to monitor the performance of four treatments: thin overlay, chip seal, crack seal and slurry seal under different design conditions. Design conditions considered were precipitation, temperature, traffic, subgrade materials and pavement condition prior to applying preventive treatment. Fatigue cracking, rutting and longitudinal roughness data collected during the LTPP program were used to compare the overall performance of different treatments. A weighted average index was defined to represent the overall performance of the sections over the years. Statistical techniques were used to compare the effectiveness of each treatment in relation to others and the control section, which did not receive any treatment. Conclusions from the analyses indicated that thin overlay and chip seal are effective treatment options for most design conditions with respect to fatigue cracking. Thin overlay outperforms other treatments in most design conditions with respect to rutting and in some cases with respect to roughness. The difference between the performance of crack seal, slurry seal and control section was not found to be statistically significant with respect to any distress type and design factor.

Transportation Research E Circular, 2012

... Page 3. AIRPORT COOPERATIVE RESEARCH PROGRAM ACRP REPORT 50 Improved Models for Risk Assessme... more ... Page 3. AIRPORT COOPERATIVE RESEARCH PROGRAM ACRP REPORT 50 Improved Models for Risk Assessment of Runway Safety Areas Manuel Ayres Jr. Hamid Shirazi Regis Carvalho Jim Hall Richard Speir Edith Arambula APPLIED RESEARCH ASSOCIATES, INC. ...