U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: Date: January/February 2004|
Issue No: Vol. 67 No. 4
Date: January/February 2004
Below are brief descriptions of products recently published online by the Federal Highway Administration's (FHWA) Office of Research, Development, and Technology. Some of the publications also may be available from the National Technical Information Service (NTIS). In some cases, limited copies are available from the Research and Technology (R&T) Product Distribution Center.
When ordering from NTIS, include the NTIS publication number (PB number) and the publication title. You also may visit the NTIS Web site at www.ntis.gov to order publications online. Call NTIS for current prices. For customers outside the United States, Canada, and Mexico, the cost is usually double the listed price. Address requests to:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Toll-free number: 800-553-NTIS (6847)
Address requests for items available from the R&T Product Distribution Center to:
R&T Product Distribution Center, HRTS-03
Federal Highway Administration
9701 Philadelphia Court, Unit Q
Lanham, MD 20706
For more information on research and technology publications from FHWA, visit the Turner-Fairbank Highway Research Center's (TFHRC) Web site at www.fhwa.dot.gov/research/tfhrc/, FHWA's Web site at www.fhwa.dot.gov, the National Transportation Library's Web site at http://ntl.bts.gov, or the OneDOT information network at http://dotlibrary.dot.gov.
Infrastructure Research and Technology Stakeholder Workshop Summary Report: Workshop Proceedings
Publication No. FHWA-RD-03-071
To meet the challenges for highway infrastructure that lie ahead, FHWA is refocusing and revitalizing its program for research and technology (R&T) to raise the bar in research, technology, and deployment activities. The program represents a new way of doing business for FHWA, with increased emphasis on stakeholder involvement and partnerships. The overall goals are to enhance mobility and productivity, extend the life of pavements and bridges, and improve safety and performance. These goals require investing in four essential elements: information, people, technology, and deployment.
To share its vision with stakeholders, FHWA held a workshop for infrastructure R&T stakeholders in Chicago, IL, on October 31 and November 1, 2002. The workshop drew more than 60 representatives from highway agencies, academia, associations, and industry. The meeting was designed to give FHWA an opportunity to hear feedback from stakeholders, refine its vision, and build stakeholder commitment in achieving infrastructure innovations. This report documents the discussions and stakeholder recommendations. FHWA is using the feedback to revise and sharpen the infrastructure R&T vision and help define stakeholder involvement.
Concrete Mixture Optimization Using Statistical Methods: Final Report
Publication No. FHWA-RD-03-060
This report presents the results of a research project that investigated the feasibility of using statistical experiment design and analysis methods to optimize concrete mixture proportions. As part of the project, the researchers developed an Internet-based software program that optimizes concrete mixtures using those methods. The researchers investigated two approaches to experiment design (classical mixture and factorial-based central composite design) in the laboratory. In each case, they used six component materials and optimized the mixtures for four performance criteria (properties) and cost. Based on the experimental results, the factorial-based approach was selected as the basis for the Internet-based system, the Concrete Optimization Software Tool (COST). The tool employs a six-step interactive procedure starting with materials selection and working through trial batches, testing, and analysis of results. The end result is recommended mixture proportions to achieve the desired performance levels. COST was developed as a tool to introduce the industry to the potential benefits of using statistical methods in proportioning concrete mixtures and to give interested parties an opportunity to try the methods for themselves.
Effects of Geosynthetic Reinforcement
Spacing on the Performance of Mechanically Stabilized Earth Walls
Publication No. FHWA-RD-03-048
Researchers investigated the performance of mechanically stabilized earth walls (MSEW) with modular block facing and geosynthetic reinforcement, using numerical models that simulate construction of the wall, layer by layer, until it fails under gravity loading. The two-dimensional finite difference program Fast Lagrangian Analysis of Continua (FLAC), version 3.4, Itasca 1998, carried out the numerical analysis. The material properties were based on data reported in the literature, representing typical values used in design practice. Failure mechanisms of MSEWs were identified as a function of geosynthetic spacing considering the effects of soil strength, reinforcement stiffness, connection strength, secondary reinforcement layers, and foundation stiffness. The effects of reinforcement length on stresses and wall stability also were investigated. The researchers compared the FLAC predictions with the design method used by the American Association of State Highway and Transportation Officials (AASHTO). Additional numerical experiments were carried out to investigate the effects of certain modeling parameters on wall response.
Four failure modes were identified: external, deep-seated, compound, and connection. The reinforcement spacing proved to be a major factor controlling the behavior of the walls. Small and large spacing was considered in the study: less than or equal to 0.4 meter (1.3 feet) and larger than 0.4 meter (1.3 feet). Increasing reinforcement spacing decreased the wall stability and changed the predominant failure mode from external or deep-seated to compound and connection modes. Similar effects were identified upon decreasing the soil strength, reinforcement stiffness, or foundation stiffness. Connection strength appeared to affect only the behavior of walls with large reinforcement spacing, that is, increased connection strength, decreased wall displacements, improved wall stability, and changed failure mode. Similar effects were identified when secondary reinforcement layers were introduced in a model with large reinforcement spacing. Increased reinforcement length improved wall stability and decreased displacements and reinforcement forces.
Comparing FLAC predictions and AASHTO calculations showed agreement. The comparisons indicated that the existing design method could distinguish the modes of failure identified by FLAC analysis, especially those due to external stability.
Long-Term Performance of Corrosion Inhibitors Used in Repair of Reinforced Concrete Bridge Components
Publication No. FHWA-RD-01-097
In 1987 the Strategic Highway Research Program (SHRP) launched multiple research efforts to study all aspects of the deterioration of reinforced concrete. One of the projects, (SHRP C-103) under the structures portion of SHRP, evaluated the effectiveness of using corrosion inhibitors as a means for mitigating corrosion in reinforced components of concrete bridges. That project, completed in 1993, involved a laboratory study and field validation and concluded that corrosion inhibitors could be applied successfully using repair and rehabilitation techniques in the field.
FHWA initiated a follow-on study in August 1994, which ended in July 1999. The primary objective of this multitask project was to determine the effectiveness of cathodic protection, electrochemical chloride extraction, and corrosion-inhibitor treatment systems installed during the SHRP effort through the long-term evaluation of 32 test sites in the field and several concrete slab specimens in the laboratory.
One task involved monitoring the long-term performance of corrosion-inhibitor treatments on selected components of four bridges that were treated and evaluated under SHRP C-103. Over a period of 5 years, researchers conducted three evaluations on structures located in Minnesota, New York, and Pennsylvania, and two evaluations were conducted on a structure in Washington State. An analysis of the results concluded that neither of the corrosion inhibitors evaluated during the study using the specified repairs and exposed to the specific environments provided any corrosion-inhibiting benefit.
With the exception of the test site in Washington State, shrinkage cracking plagued repairs at all other sites. The concrete surrounding the patched areas was contaminated with chloride ions to varying degrees. At some test sites, shrinkage cracking allowed faster ingress of chloride ions into the repair patches. At all four sites, the results of the visual and delamination surveys and corrosion-rate measurements did not show any difference between patches containing corrosion inhibitors and those without.