Environmental Effects in Pavement Mix and Structural Design Systems
Author: Houston, William N | Size: 2.26 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2005 | pages: 298 | ISBN: -
It is well documented that environmental effects play a significant role in characterizing the material properties, which in turn affect the pavement performance. Studies under the Strategic Highway Research Program (SHRP) were carried out to study the age hardening characteristics of asphalt binders and mixes. As a result of this study, laboratory procedures American Association of State Highway and Transportation Officials, provisional protocols (AASHTO PP1-98 and PP2-99) were developed to study the hardening potential of asphalt binders and mixes. The approaches followed in these procedures are of great value for the ongoing research on pavement aging; however, due to the limited resources and time constraints under the SHRP program, these provisional procedures have certain limitations associated with them. Research study, National Cooperative Highway Research Program (NCHRP) 9-23 was initiated to assess these limitations and if possible, enhance the predictive capabilities of these protocols. Binders and field cores were obtained from LTPP sections and other sites across the United States. Original, laboratory-aged, and field-aged binders were characterized. Based on the findings, an alternate procedure to the AASHTO PP1-98 protocol is suggested and presented. The alternate procedure includes field aging conditions and volumetric properties of the mix. The model developed was calibrated and validated using the data obtained from the field cores. Parametric analysis was performed on the final model to ascertain the practicality of the output. The assessment of the existing PP2-99 test protocol is also presented. Asphalt mix cores aged in the laboratory were tested for complex modulus. These modulus values were then compared to the modulus values of the field cores, the ages of which were known from the construction records. Due to the limited amount of data available, the PP2-99 protocol could not be improved.
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This document explores a methodology designed to predict the safety performance of various elements considered in the planning, design, and operation of nonlimited-access rural multilane highways. Chapter I provides an introduction, covering the background and the research objectives and scope of this project. Chapter II documents the literature review on existing statistical models, Accident Modification Factors (AMFs), and other predictive methodologies relevant to this study. Chapter III summarizes the results of a survey conducted in this study. Chapter IV describes the characteristics of the data collected in this project. Chapter V describes the model development and accident prediction methodology. Chapter VI summarizes the modeling results for estimating the safety performance of rural multilane highways. Chapter VII provides a summary of the work accomplished in this project and proposes recommendations for further work. The appendices document additional models from related research for consideration, Highway Safety Manual Chapter 9, the survey instrument, Cumulative Residuals (CURE plots), crash severity models, a methodology for estimating the variance of the product between baseline models and AMFs, and the Joint NCHRP 17-25/17-29 Expert Panel assessment.
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Multimodal Level of Service Analysis for Urban Streets: Users Guide
Author: Dowling, Richard G | Size: 1.82 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2008 | pages: 60 | ISBN: -
This document explores a set of procedures for predicting traveler perceptions of quality of service and performance measures for urban streets. Quality of service and performance are considered in terms of the needs of auto drivers, bus passengers, bicyclists, and pedestrians.
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A Guide to Emergency Quarantine and Isolation Controls of Roads in Rural Areas
Author: Graham, Jerry L | Size: 2.26 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2008 | pages: 113 | ISBN: -
This document contains an annotated bibliography that reviews several state emergency response plans associated with traffic control of rural roads in an agricultural emergency; a summary of the information gathered from interviews with state and local officials involved in agricultural emergency response; lessons learned from the case studies, the literature review, and phone interviews with state and local officials; a discussion of the development of the guide along with a taxonomy of the existing general procedures for handling an agricultural emergency; and a review of this guide by state and local officials, including the one-day workshops in four rural counties. The material contained in this document was used to help produce NCHRP Report 525, Volume 13: A Guide to Traffic Control of Rural Roads in an Agricultural Emergency, which explores recommended practices and procedures associated with traffic control on local and state roads during agricultural emergencies.
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Right of Way Methods and Tools to Control Project Cost Escalation
Author: Anderson, Stuart D Texas A&M University, College Station Molenaar, Keith R University of Colorado, Boulder Schexnayder, Clifford J Arizona State University, Tempe | Size: 2.40 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2008 | pages: 115 | ISBN: -
The ability of state highway agency management to control project cost escalation is dependent on strategic and structured project development processes. Right-of-way costs are among the most difficult to control and, therefore, necessitate disciplined estimating and management procedures. Yet in many agencies there exist “stove pipe” divisional structures that lead to failures in communicating important project information affecting scope, design, and cost. NCHRP Project 8-49 “Guidance on Cost Estimation and Management for Highway Projects During Planning, Programming, and Preconstruction,” and other estimating studies identified right-of-way cost estimating and management of right-of-way estimates and actual costs as critical to achieving estimate consistency and accuracy. The original NCHRP Project 8-49 addressed right-of-way cost estimating to a limited extent but the project’s scope did not allow for an in-depth treatment of this specialized area. This report describes the research process for additional NCHRP 8-49 work addressing right-of-way cost estimating and cost management. It provides an overview of the data gathering and analysis processes used to create a Procedures Guide specifically for right-of-way cost estimating.
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Transportation project management, for all modes of transportation, is under extreme budgetary, political, and community pressure to contain costs and improve efficiency in the delivery of projects “on time and on budget.” In order to meet these twin goals, transportation agencies must employ dynamic project management tools. The successful planning, design and implementation of transportation projects needs to meet various performance metrics depending on each stakeholder’s perspective. Thus, the general terms of “on time” and “on budget” can mean different things to the users and to their clients—whether public or private. (For example, a change order might be viewed by the designer as within the timeframe and an acceptable extension of costs; a client might view the same change order as outside both time and budget). It is essential that project management take these different perspectives into account. The purpose of this guidebook is to provide a toolbox that offers detailed project management subject areas and innovative practices that can be applied to achieve a higher level of project success. This guidebook has been developed to assist project managers who work for Department of Transportation (DOT) agencies or other public transportation agencies, whether they are DOT/agency employees or consultants working for the DOT/agency. Most DOT agencies have a project manual for each of the following phases of a project: planning, design, and construction. The guidebook has been developed to complement the agencies’ project manuals, not replace them. After researching numerous DOT websites and project manuals, the common milestones for the planning, design, and construction phases for transportation projects were compiled and made into a generic outline for each of the phases. The outline concentrates on those steps that are essential to a public agency project within the three phases of planning, design, and construction. The guidebook offers tools to better improve the agency’s process or to offer some suggestions to those that may be looking for a more innovative way to manage a project.
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Recommended Practice for Stabilization of Subgrade Soils and Base Materials
Author: Little, Dallas N Texas Transportation Institute Nair, Syam Texas Transportation Institute | Size: 1.02 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2009 | pages: 67 | ISBN: -
Long-term performance of pavement structures is significantly impacted by the stability of the underlying soils. In situ subgrades often do not provide the support required to achieve acceptable performance under traffic loading and environmental demands. Although stabilization is an effective alternative for improving soil properties, the engineering properties derived from stabilization vary widely due to heterogeneity in soil composition, differences in micro and macro structure among soils, heterogeneity of geologic deposits, and differences in physical and chemical interactions between the soil and candidate stabilizers. These variations necessitate the consideration of site-specific treatment options which must be validated through testing of soil-stabilizer mixtures. This report addresses soil treatment with the traditional calcium-based stabilizers: Portland cement, lime, and fly ash. The report describes and compares the basic reactions that occur between these stabilizers and soil and the mechanisms that result in stabilization. The report presents a straightforward methodology to determine which stabilizers should be considered as candidates for stabilization for a specific soil, pavement, and environment. The report then presents a protocol for each stabilizer through which the selection of the stabilizer is validated based on mixture testing and mixture design. The mixture design process defines an acceptable amount of stabilizer for the soil in question based on consistency testing, strength testing, and in some cases (resilient) modulus testing. Within each additive validation and mixture design protocol, an assessment of the potential for deleterious soil-additive reactions is made.
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Recommended Practice for Stabilization of Sulfate-Rich Subgrade Soils
Author: Little, Dallas N Texas A&M University, College Station Nair, Syam Texas A&M University, College Station | Size: 1.08 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2009 | pages: 66 | ISBN: -
Calcium-based stabilizers (CaO-based stabilizers) develop a high pH environment when mixed with water during construction. This high pH condition and the presence of lime (CaO) introduce an environment favorable to the formation of two expansive minerals, ettringite and possibly thaumasite, when sulfate-bearing salts are present in soil. The success of a lime stabilization project depends heavily on the accuracy of predictions regarding the potential of the native soils to form these disruptive minerals. This report describes the nature of these minerals and the mechanism of their formation in soils stabilized with lime, cement, or fly ash. The key issue for the engineer in deciding how to properly stabilize sulfate-bearing soils is to quickly and efficiently determine: (1) the sulfate content of the soils and (2) the threshold quantity of sulfates likely to cause damage. This report addresses both issues but focuses on the methods used to quantify sulfate content. Quick and effective field techniques and more precise laboratory tests are compared and evaluated. Recommendations are presented regarding the appropriate testing protocol to use. Specific recommendations for changes to the American Association of State Highway and Transportation Officials (AASHTO) test method T-290-95 (methods A and B) are made. The report also outlines techniques for effective risk assessment including reconnaissance, topographical assessment, pedological and geological assessment, climatic assessment, and soil sampling plans. The report also outlines construction tests that can reduce risks for various levels of sulfate determined using a method such as AASHTO T-290-95 (revised) or equivalent.
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This report documents and presents the results of a study of minimum reinforcement requirements for the design of concrete bridge structures. This study included a review of U.S. and international practice, test data and research findings related to minimum reinforcement requirements and flexural cracking of concrete structures. A total of 4 representative methods of specifying minimum reinforcement were evaluated and compared by performing design calculations on a wide range of concrete bridge members. The findings of this study suggest that in nearly all cases lightly reinforced concrete members can develop the nominal flexural strength and have significant strength and ductility reserves after cracking has occurred. Also, the modulus of rupture over estimates the flexural cracking stress of concrete bridge members. A rational approach to the specification of minimum reinforcement is proposed, where variables are appropriately factored and includes the maximum rather than nominal strength of the section as a true measure of ductile versus brittle response.
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