This document constitutes the user manual for tBeam, standalone software for the analysis of energy dissipation in pavements under moving vehicles. tBeam was developed as part of the improvement of modeling capabilities for environmental life cycle assessment of pavements being conducted by the University of California Pavement Research Center for the California Department of Transportation. tBeam is finite element based, employing multi-layered three-node Timoshenko beam elements resting on a viscoelastic Winkler foundation. It provides an approximation of the deflection bowl of pavements and the energy dissipated in pavement structures when subjected to loads moving at constant velocities. tBeam supports two loading options: a uniform pressure (per unit length) applied to a segment at the center of the beam, and a rolling rigid wheel. To achieve numerical efficiency the load-beam-foundation system is represented relative to a moving coordinate system attached to the moving load. The higher efficiency is made possible because, in this framework, an observer attached to the moving coordinate system perceives a “static” state (i.e., independent of time). The standalone tBeam software serves two purposes. First, to provide developers of pavement LCA tools a “guide” as to how to integrate tBeam technology into their program. To this end, the “main” of tBeam can be used as “guide” for integrating tBeam capabilities within the LCA tool. Second, tBeam capabilities are relevant to pavement research in general. Thus, it could represent a useful addition to the toolset for pavement viscoelastic mechanics.
One of the most important contributors to the environmental impacts from use of highways is the energy exerted by vehicles, particularly routes that carry higher volumes of traffic. Part of this energy is consumed by response of the vehicle’s tires and suspension to pavement surface roughness and macrotexture. Another part of the energy consumed is by energy dissipation due to the structural response of the pavement itself under the moving load. This document is the theoretical and validation manual tor tBeam, standalone software for the analysis of energy dissipation in pavements under moving vehicles. tBeam was developed as part of the improvement of modeling capabilities for environmental life cycle assessment of pavements being conducted the University of California Pavement Research Center for the California Department of Transportation. The energy consumed due to structural response are controlled by the structural properties of the pavement which are dependent on the time of day, the season, and the condition (damage) of the pavement. The energy dissipation also depends on the speed and weight of each moving wheel load. As a result, estimating the lifetime energy dissipated in a pavement structure requires multiple analyses considering the thousands of permutations of these variables for a given segment of the highway network. Therefore, models for pavement-vehicle energy dissipation must balance two opposing needs: obtaining a reasonably accurate estimate of the dissipated energy, and high numerical efficiency. For numerical efficiency, the tBeam software employs a one-dimensional finite-element based solution of a wheel traveling at a constant velocity on a viscoelastic beam-foundation system, and a further reduction of numerical effort is obtained by formulating the model relative to a moving coordinate system attached to the wheel. The one-dimensional solution is, by nature, an approximation to the three-dimensional world. This approximation can be improved by incorporating a “correction factor,” which is based on comparisons with pavement simulations accounting for the double curvature observed in loaded pavements. In this report prediction disparity for a single structure is studied. The results show a clear trend where the correction factor decreases with rising temperature, and increases with higher velocity. The present study was insufficient to establish a law for the correction factor even for the single case studied. The correction factor ranged from about 1.25 at low temperature and high velocity to about 0.6 for high temperature and low velocity. The first part of this report presents the underlying theory for tBeam and implementation details. The second part presents closed form solutions for specialized pavement-foundation systems. The third component of the report presents some of the validation simulations undertaken to demonstrate the performance of tBeam, including comparisons with closed form solutions provided in this report, and recommendations for further development of tBeam.
The work described in this report is adjunct to a five-year study of tire/pavement noise undertaken by the University of California Pavement Research Center for the California Department of Transportation under the Partnered Pavement Research Center program (PPRC). This part of the study was performed in cooperation with the Danish Road Institute/Road Directorate, and it examined the influence of air temperature on tire/pavement noise measurements performed on two types of tires (Aquatred and Standard Reference Test Tire [SRTT]) on different asphalt pavement surfaces using the On-board Sound Intensity (OBSI) method. Field noise measurement testing was carried out in two series: one in the Southern California desert on State Route 138 using the SRTT, and the other with data collected on a statewide selection of pavements tested with the Goodyear Aquatred tire in an earlier part of the PPRC noise study. The field measurements yielded data for deriving air temperature coefficients for the two types of tires, and a comparison of them is made. A worldwide survey of the available literature accompanies the field work and analysis, and a summary of it is used to compare the air temperature coefficients of the SRTT with a combination of tire types used in European testing. In addition, findings in the literature serve as the basis for a series of predicted temperature coefficients for passenger cars on various cement concrete and asphalt pavements. Finally, the report presents ten general conclusions drawn regarding the relationship between air temperature correction and tire/road noise on asphalt and concrete pavements.
This report presents a series of methods implemented in Denmark and other European countries for the assessment and control of the impacts of highway noise on the neighboring public. It introduces Danish guidelines for the assessment of noise impact. Also described are examples of noise abatement planning for three different cases: planning of new highways, planning of highway widening projects, and noise abatement on existing highways. Experience shows that there is no single approach that can remove all noise problems along highways. It will be necessary for more effective noise abatement to take different approaches together, including noise-reducing pavements, noise barriers, facade insulation, and proper land use strategies. Harmonized public-private partnership is also critical for successful implementation of public policy and regulations related to noise abatement.
The level of noise generated by tire/pavement interaction of a pavement section changes over time. While the general consensus is that the noise level tends to increase as the pavement ages, more scientific investigation is necessary to better understand the process of acoustic aging of pavements. For more than a decade, independent studies by Caltrans and the Danish Road Institute (DRI-DK) have included monitoring of tire/pavement noise levels on selected pavements. Using data sets collected as part of those studies, a comprehensive analysis was conducted in this study to characterize the acoustic aging properties of different types of asphalt pavements. Pavement types considered in the analysis include dense-graded asphalt concrete (DGAC), open-graded asphalt concrete (OGAC), thin open-graded asphalt layer, and porous asphalt concrete (PAC). This report presents the results of the data analysis in terms of the relative changes of tire/pavement noise over time for the respective pavements. It also describes the development of an acoustic aging model for asphalt pavements. The model predicts the increase in noise level as a function of pavement age, traffic volume, and pavement type, primarily for highways with speeds over 50 mph. Further study is recommended to improve the prediction model and to integrate the noise model in a Pavement Management System.
Noise barriers are widely used as an effective means to abate highway traffic noise. With public interest in eco-friendly and aesthetic designs for noise barriers growing, highway agencies are exerting greater efforts to provide the public with “green” noise barriers that are functionally sound as well as adaptive to the surrounding environment. This report presents a summary of green noise barrier design practices experienced by the Danish Road Institute (DRI-DK) and other European countries for the last two decades. Some example noise barrier designs are described with recommendations for more effective and innovative ones. The report contains a recommendation to use varied approaches in green noise barrier designs that are adapted to urban and rural settings.
