The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

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The Environmental Protection Agency

Artificial neural networks (ANNs) constitute a class of flexible nonlinear models designed to mimic biological neural systems. In this entry, we introduce ANN using familiar econometric terminology and provide an overview of ANN modeling approach and its implementation methods. † Correspondence: Chung-Ming Kuan, Institute of Economics, Academia Sinica, 128 Academia Road, Sec. 2, Taipei 115, Taiwan; ckuan@econ.sinica.edu.tw. †† I would like to express my sincere gratitude to the editor, Professor Steven Durlauf, for his patience and constructive comments on early drafts of this entry. I also thank Shih-Hsun Hsu and Yu-Lieh Huang for very helpful suggestions. The remaining errors are all mine.

Artificial neural networks

Highway Capacity Manual改訂の動向--テイラ-教授の講演より

Dynamics of structures

Development of a proposed overweight vehicle permit fee structure in Illinois.

Truck platoons have many benefits over traditional truck mobility. Truck platoons have the potential to improve safety and reduce fuel consumption between 5% and 15%, based on platoon configuration. In Illinois, trucks carry more than 50% of freight tonnage and constitute 25% of the traffic on interstates. Therefore, expected fuel savings would be significant for trucks. Deployment of truck platoons within interstate highways may have a direct effect on flexible pavement performance, as the time between consecutive axle loads (i.e., resting time) is expected to decrease significantly. Moreover, platoons could potentially accelerate pavement damage accumulation due to trucks’ channelized position, decreasing pavement service life and increasing maintenance and rehabilitation costs. The main objective of this project was to quantify the effects of truck platoons on pavements and to provide guidelines to control corresponding potential pavement damage. Finite-element models were utilized to quantify the impact of rest period on pavement damage. Recovered and accumulated strains were predicted by fitting exponential functions to the calculated strain profiles. The results suggested that strain accumulation was negligible at a truck spacing greater that 10 ft. A new methodology to control pavement damage due to truck platoons was introduced. The method optimizes trucks’ lateral positions on the pavements, and an increase in pavement service life could be achieved if all platoons follow this optimization method. Life cycle assessment and life cycle cost analysis were conducted for fully autonomous, human-driven, and mixed-traffic regimes. For example, for an analysis period of 45 years, channelized truck platoons could save life cycle costs and environmental impacts by 28% and 21% compared with human-driven trucks, respectively. Furthermore, optimum truck platoon configuration could reduce life cycle costs and environmental impacts by 48% and 36%, respectively, compared with human-driven trucks. In contrast, channelized traffic could increase pavement roughness, increasing fuel consumption by 15%, even though platooning vehicles still benefit from reduction in air drag forces. Given that truck platoons are expected to be connected only in the first phase, no actions are required by the agency. However, in the second phase when truck platoons are also expected to be autonomous, a protocol for driving trends should be established per the recommendation of this study.

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Truck Platooning on Flexible Pavements in Illinois

Unbound crushed concrete in high volume roads—evaluation of field behavior and structural performance

The behavior of asphalt concrete (AC) is highly dependent on the temperature and frequency of loading. Traditionally, the modulus of AC materials is characterized by performing creep recovery or complex modulus tests without considering the impact of the lateral confinement level. Because traffic-induced loading generates a multi-axial stress state within the pavement structure, quantifying the effect of the lateral confinement on the global AC behavior becomes a necessity. Studies have shown that the responses of dense-graded AC mixtures are highly dependent on confinement levels, especially at low frequencies and high temperatures. In this study, a constitutive model was developed for confinement-dependent linear viscoelastic (LVE) behavior. The model was then incorporated into finite element pavement models using a user material subroutine. The numerical pavement models were used to quantify the impact of lateral confinement on pavement critical responses under various temperature profiles and tire loadings. Multiple loading levels were selected to consider the effect of road roughness on tire loading amplification. Results show that the effect of confinement depends on the relative position of the moving load. Vertical strains under the tire are significantly reduced by confinement. Finally, the maximum percentage decreases in the compressive and vertical shear strains from incorporating the confinement-dependent LVE model were found to be 31% and 17.5%, respectively, for the highest load–temperature combination.

Impact of Dynamic Loading on Confined Asphalt Concrete Surface

Three full-depth flexible pavement sections having 152, 254, and 420mm of HMA placed on 300mm of lime-stabilized subgrade were constructed and exposed to APT using the Advanced Transportation Loading ASsembly (ATLAS), housed at the University of Illinois at Urbana-Champaign. Transverse tensile strain histories at the bottom of HMA under various loading conditions (load, tire pressure, and speed) were measured through embedded strain gauges at the HMAstabilized subgrade interface. Indirect tensile complex modulus tests for three HMA materials were conducted using an Instron Universal Test Machine (UTM). The elastic modulus of subgrade was backcalculated from FWD testing conducted on the test sections. The pavement responses of test sections were calculated using the NCHRP 1-37A Mechanistic-Empirical Pavement Design Guide (MEPDG) procedure as well as a finite element model.

Imad L. Al-Qadi

Papers

Development of a proposed overweight vehicle permit fee structure in Illinois.

Truck Platooning on Flexible Pavements in Illinois

Unbound crushed concrete in high volume roads—evaluation of field behavior and structural performance

Impact of Dynamic Loading on Confined Asphalt Concrete Surface

Comparison between mechanistic analysis and in-situ response of full-depth flexible pavements