Education

Research Description

Dr. Underwood's research and education program focuses on materials and their interaction with society and the natural and built environments. This program pursues research, education, and service activities that evaluate, inform, and shape the science of these interactions, particularly how material decisions influence the use, function, and impact of civil infrastructure. As he and his students pursue these questions both broadly (by expanding the scope or significance of impact assessment) and deeply (by building the methods and models to better explain the physical behaviors that occur) new findings are integrated into his teaching. He and his students pursue this research in two ways. First, they use experimental mechanics and constitutive models to evaluate and understand the behavior of infrastructure materials, principally asphalt concrete. This knowledge is then exploited to better engineer the materials and/or structures to achieve sustainability and resiliency. Second, they use emerging perspectives and analytical tools to assess the role of social constructs in governing the impact of technological advances on infrastructure. Specific attention is given to pavements and with a focus on resilience due to a recognition that pavement engineering and indeed engineering of infrastructure in the built environment is facing great uncertainty.

Publications

Alternate interpretation of stress sensitivity in AASHTO T350

Stempihar, J., Gundla, A., & Underwood, B. S. (2017),

Autonomous vehicles: Assessment of the implications of truck positioning on flexible pavement performance and design

Noorvand, H., Sai, G., & Underwood, B. S. (2017), Transportation Research Record, 21–28.

Correlating field performance to laboratory dynamic modulus from torsion bar and indirect tension

Yang, S., Braham, A., Underwood, B. S., Hanz, A., & Reinke, G. (2017), Road Materials and Pavement Design, 18(1), 104–127.

Development of modulus and fatigue test protocol for fine aggregate matrix for axial direction of loading

Gudipudi, P., & Underwood, B. S. (2017), Journal of Testing and Evaluation, 45(2), 497–508.

Evaluation of in situ RAP interaction in asphalt mastics using micromechanical models

Gundla, A., & Underwood, B. S. (2017), International Journal of Pavement Engineering, 18(9), 798–810.

Evaluation of the sensitivity of asphalt concrete modulus to binder oxidation with a multiple length scale study

Gundla, A., Gudipudi, P., & Underwood, B. S. (2017), Construction and Building Materials, 954–963.

Impact of alternative project deliver systems on the International Roughness Index (IRI) ? case studies of transportation projects in the Western U.S.

Abkarian, H., Asmar, M., & Underwood, B. S. (2017), Transportation Research Record, 2630, 76–84.

Impact of climate change on pavement structural performance in the United States

Gudipudi, P. P., Underwood, B. S., & Zalghout, A. (2017), Transportation Research. Part D, Transport and Environment, 57, 172–184.

Impact of climate change on the pavement performance and its sensitivity to various climate prediction models

Gudipudi, P., Underwood, B. S., & Zalghout, A. (2017),

Implications of autonomous truck use on flexible pavement performance and design

Noorvand, H., Sai, G., & Underwood, B. S. (2017),

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Grants

Calibration of Structural Layer Coefficients for North Carolina Asphalt Pavements

NC Department of Transportation(8/01/18 - 7/31/20)

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Calibration of Structural Layer Coefficients for North Carolina Asphalt Pavements

Sponsor: NC Department of Transportation

Start Date: 8/01/18

End Date: 7/31/20

Abstract

The North Carolina Department of Transportation (NCDOT) uses the AASHTO Guide for Design of Pavement Structures 1993 to determine the minimum pavement stiffness that ensures pavement longevity. During design, this stiffness is first determined using an iterative design process, charts, or software. Then, the engineer selects materials and layer thicknesses that provide the required stiffness by summing the contributions of individual layers. The contribution from any given layer is calculated by the product of that layer’s thickness and a structural layer coefficient that captures the overall quality and structural benefit of the material. In the NCDOT procedure, the structural layer coefficient for asphalt concrete (AC) is 0.44 (surface and intermediate mixtures) or 0.30 (base mixtures), while other material types are lower, e.g., the structural layer coefficient for unbound aggregate base materials is 0.14. While the NCDOT has had success with these structural layer coefficient values, they are based on a test road constructed and evaluated in one climate zone and with one set of materials. Modern material selection and design have resulted in substantial changes in AC and aggregate base since this time. These improvements have likely resulted in different structural contributions from these materials, which means the structural layer coefficients should be reviewed and possibly changed. Proper characterization of these layer coefficients could result in substantial cost savings to the NCDOT by reducing the required pavement thickness and/or leading to pavements that require less frequent rehabilitation and reconstruction.

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Ruggedness and Interlaboratory Studies for Asphalt Mixture Performance Tester (AMPT) Cylcic Fatigue test

Federal Highway Administration (FHWA)(9/28/17 - 3/27/20)

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Ruggedness and Interlaboratory Studies for Asphalt Mixture Performance Tester (AMPT) Cylcic Fatigue test

Sponsor: Federal Highway Administration (FHWA)

Start Date: 9/28/17

End Date: 3/27/20

Abstract

AASHTO TP 107 enables the practical, mechanistic performance characterization of asphalt concrete using cyclic fatigue testing in the Asphalt Mixture Performance Tester (AMPT). AASHTO TP 107 was initially developed for the use of 100-mm diameter specimens, which yield a single test specimen per gyratory sample. Recently, a modified version of AASHTO TP 107 was proposed for the testing of 38-mm diameter small specimens that improves the efficiency of specimen fabrication and enables the testing of field cores extracted from as-built pavement layers. The objective of the proposed research is to improve AASHTO TP 107 by conducting ruggedness and interlaboratory studies using both small and large specimens. The ruggedness evaluation will identify controllable experimental factors that significantly affect the test results and to establish limits for their control. The interlaboratory study will lead to precision statements that define the repeatability and reproducibility of small and large cyclic fatigue the test results.

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SAFETY OF EARTHEN STORMWATER INFILTRATION BEST MANAGEMENT PRACTICES (BMP) ADJACENT TO HIGHWAYS

California Department of Transportation(2/01/18 - 1/31/20)

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SAFETY OF EARTHEN STORMWATER INFILTRATION BEST MANAGEMENT PRACTICES (BMP) ADJACENT TO HIGHWAYS

Sponsor: California Department of Transportation

Start Date: 2/01/18

End Date: 1/31/20

Abstract

Stormwater best management practices (BMP) are in place to prevent pollution in stormwater runoff from the Caltrans properties and also to facilitate the stormwater discharge from road infrastructure. Caltrans is required to comply with the National Pollution Discharge Elimination (NPDES) permit, including the infiltration of stormwater runoff from the highway and implementing soil based BMPs. As per the new permit, Caltrans needs to install soil based BMPs that are capable of allowing infiltration of the 85th percentile of a 24-hour stormwater event. The area available for this purpose is typically the clear recovery zone (CRZ), including embankments and slopes that must be traversable and recoverable to meet traffic safety requirements. Thus, compliance with the NPDES must also come with adherence to traffic safety design requirements. Determining the hydraulic conductivity of the soil and then measuring this value for different soil amendment and BMP strategies is a fairly straightforward process. However, correcting low infiltration conditions adjacent to the roadway environment and maintaining a safe, stable, CRZ adjacent to the roadway is a much more complex issue. According to Section 19-5.03 of the current Caltrans construction specifications, soils should be compacted to at least 90 percent of relative compaction. Soil based BMPs with amended soils may also be compacted to 90 percent of relative compaction, with the soil amendments help in ensuring that a 90 percent compaction value results in sufficient permeability for stormwater infiltration. However, some slopes may not be built according to this standard as Section 21-2.03J indicates incorporate material compaction between 82 and 90 percent. These differences suggest that new specifications for Section 19 or other may be warranted. Modifying the specifications is not straightforward as there are concerns that reduced compaction may compromise traffic safety due to soft shoulder and soil rutting in the roadside and a subsequently higher likelihood of rollover incidents. This problem necessitates the importance of the research in this area. Engineers currently lack a scientifically supported assessment of the impact of stormwater BMP designs on traffic safety thus limiting the effective use of these strategies and/or potentially having negative effects on the safety of travelers. Likewise they lack documentation on best practices for construction of BMP roadsides. In addition the information available in the literature, from the Federal Highway Administration, and from neighboring states is inconclusive. The objective of the proposed study is to develop a set of scientific based parameters, protocols, and/or tool(s) that can be applied to design or analyze different scenarios for the clear recovery zone in order to meet stormwater BMPs and provide for acceptable traffic safety. The design methodology will be applicable to the range of cross-sections employed by Caltrans as well as the soils that exist in California. The resulting guide will allow engineers to determine if the BMPs currently cause soft shoulders, CRZ issues, traversability issues, or rutting to a degree that there exist traffic safety issues and then develop an appropriate BMP design that does not compromise traffic safety. For example, as part of the effort, it will be determined if there is an acceptable setback from the edge of pavement to which this type of soil modification can be implemented. This study is part of a greater goal for Caltrans to update its design guidance, tools, and specifications for the stormwater BMPs to comply with both the new NPDES permit and highway design manual goals of traffic safety.

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MEPDG Inputs for Warm Mix Asphalts

NC Department of Transportation(8/16/11 - 11/15/14)

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MEPDG Inputs for Warm Mix Asphalts

Sponsor: NC Department of Transportation

Start Date: 8/16/11

End Date: 11/15/14

Abstract

The objectives of the proposed research project are: (1) to determine the dynamic moduli, fatigue characteristics, and rutting characteristics of WMA mixtures that are currently used in North Carolina as a function of moisture conditioning and aging levels; (2) to compare the material properties of WMA mixtures with their HMA counterparts; and (3) to develop recommendations for MEPDG input parameters for the various WMA mixtures. These objectives will be accomplished by performing dynamic modulus tests for stiffness characterization, direct tension cyclic tests for fatigue performance characterization, and triaxial repeated load permanent deformation (TRLPD) tests for rutting characterization. These tests will be performed on various WMA and HMA mixtures subjected to varying moisture conditioning and aging levels in order to address these two major sources for the different behaviors between the HMA and WMA mixtures. All the test methods and analyses will be the same as those performed under previous NCDOT projects (HWY-2003-09 Typical Dynamic Moduli for North Carolina Asphalt Concrete Mixes and HWY-2007-07 Local Calibration of the MEPDG for Flexible Pavement Design) for HMA characterization so that consistency can be ensured between the existing HMA database and the WMA database to be developed from this study.

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Performance-Related Specifications for Asphaltic Binders Used in Preservation Surface Treatments

US Dept. of Transportation (DOT)(8/01/11 - 11/30/15)

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Performance-Related Specifications for Asphaltic Binders Used in Preservation Surface Treatments

Sponsor: US Dept. of Transportation (DOT)

Start Date: 8/01/11

End Date: 11/30/15

Abstract

Abstract Pavement preservation treatments (PPTs) are effective means of improving surface quality and extending service life of pavements. They become increasingly more important tools for highway agencies as the national road network ages and deteriorates. One of the most commonly used PPTs is surface treatments of various types. The NCHRP 09-50 Request for Proposal (RFP) defines preservation surface treatments (PSTs) as: treatments that are applied to a large surface area of an existing roadway to slow future deterioration and maintain or improve its functional condition (without increasing structural capacity), such as chip seals, microsurfacing, and slurry seals. The properties of asphaltic binders used in PSTs are very important to the performance of the treatment in which they are used. However, asphaltic binders used in such treatments are often selected based on availability and other factors that are not necessarily related to the performance of the final product. Performance-related specifications (PRS) that specify quality in terms related to long-term performance will help in the selection of the proper binder for a specific application. Although such PRS have been developed for the constituents of hot-mix asphalt mixture used in pavements, PRS are not readily available for binders used in PSTs. Therefore, the NCHRP 09-50 RFP sets out the following two objectives: (1) evaluate existing binder tests and, if necessary, identify new tests that related to performance and (2) develop PRS for PSTs that provide a direct relationship between key quality characteristics of asphaltic binders and performance. The proposal describes the joint research effort among NC State University, University of Wisconsin-Madison, and Asphalt Institute to accomplish the project objectives.

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Development of Fatigue Failure Criteria for RAP and Non-RAP Mixtures

US Dept. of Transportation (DOT)(8/11/10 - 12/31/15)

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Development of Fatigue Failure Criteria for RAP and Non-RAP Mixtures

Sponsor: US Dept. of Transportation (DOT)

Start Date: 8/11/10

End Date: 12/31/15

Abstract

The primary objective of the proposed research is to develop fatigue failure criteria for RAP and non?]RAP mixtures that can be used in the Simplified Viscoelastic Continuum Damage (S?]VECD) model. Previous research at North Carolina State University (NCSU) funded by the North Carolina Department of Transportation (NCDOT) has established a preliminary form of the failure criteria. This previous research indicates poor fatigue cracking performance with RAP mixtures compared to the performance of corresponding non?]RAP mixtures. The proposed study will attempt to refine the failure criteria and develop relationships between the failure criteria and mixture characteristics using the mixtures to be collected in the New England RAP Pooled Fund study (hereinafter called NE RAP study).

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Development of SMART Pavement Design Methodology

Korea Expressway Corp. (fka. Korea Highway Corp.)(6/24/09 - 6/10/12)

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Development of SMART Pavement Design Methodology

Sponsor: Korea Expressway Corp. (fka. Korea Highway Corp.)

Start Date: 6/24/09

End Date: 6/10/12

Abstract

The primary objectives of this research are: (1) to develop low-noise, low-splash, warm-mix asphalt (WMA) mixtures to be used in SMART Highway in Korea using the viscoelastoplastic continuum damage (VEPCD) model and (2) to develop a SMART pavement design methodology and its associated manuals.

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