Communication Product Updates
Below are brief descriptions of reports recently published by the Federal Highway Administration's (FHWA) Office of Research, Development, and
Technology. All of the publications are available from the National Technical Information Service (NTIS). In some cases, limited copies are available from the Research and Technology (R&T) Report Center.
When ordering from NTIS, include the NTIS publication 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)
Expanded Sales Desk Hours: 8 a.m. to 8 p.m. EST, Mon.-Fri.
Address requests for items available from the R&T Report Center to:
R&T Report 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://isweb.tasc.dot.gov/library/library.htm.
Electrochemical Chloride Extraction: Influence of Concrete Surface on Treatment
Publication No. FHWA-RD-02-107
One bridge restoration technique available for reducing corrosion-induced concrete deterioration, which removes chloride ions while simultaneously re-alkalizing the concrete adjacent to the steel, is electrochemical chloride extraction (ECE). Studies have shown that ECE is capable of removing, in a single application, a significant portion of the chloride ions from a reinforced concrete structure. Prior research also has shown that the quantity of chloride ions removed is dependent on numerous factors, including quantity and spacing of reinforcing steel, applied voltage, initial chloride concentration, etc. In addition, investigations into chloride binding and competition between other ions as current carriers have helped clarify the probable mechanisms responsible for decreases in current efficiency with time during chloride removal.
This portion of the investigation has focused on the influence of the water-to-cement (w/c) ratio. In addition, an investigation was conducted to identify the cause of the decrease in efficiency during chloride removal. A clear relationship between the w/c ratio and the chloride extraction rate was not evident. However, the investigation revealed that the resistance of the concrete surface layer increases considerably during ECE, which effectively restricts the current flow, while the resistance of the underlying layer of concrete either decreases or remains constant. It appears that the increased resistance of the surface layer concrete is accompanied by the formation of a tightly adhering residue on the concrete surface. Preliminary analysis of the surface formation indicates it contains carbonate and calcium chloride.
IHSDM Intersection Diagnostic Review Model Knowledge Base Report
Publication No. FHWA-RD-02-045
This report documents the results of a study on the "Development of an Expert System for the Interactive Highway Safety Design Model (IHSDM)." The objective was to develop software to perform a diagnostic review of intersections on rural two-lane highways, referred to as the Intersection Diagnostic Review Model (IDRM). The report focuses on documenting the knowledge base developed for the IDRM software. It also documents the software in that it identifies the knowledge structure, problem definitions, models, decision algorithms, formulas, and parameter values implemented in the software.
Modifications of Highway Air Pollution Models for Complex Site Geometries, Volume I: Data Analysis And Model Development
Publication No. FHWA-RD-02-036
This is volume I of a two-volume report on a study to improve air pollution dispersion models for depressed highway sites. The study assesses limitations of flat terrain and other street-canyon air pollution models. Experimental results from other documented field and atmospheric wind tunnel tests, supplemented by those tests conducted during this study, led to improved concepts and quantification of airflow dynamics for depressed sites. A comprehensive set of highway cross-sections and pertinent physical relationships were examined for resultant wind flows, turbulence, concentration fields, and visual tracer paths.
Modifications of Highway Air Pollution Models for Complex Site Geometries, Volume II: Wind Tunnel Test Program
Publication No. FHWA-RD-02-037
This is volume II of a two-volume report on a study to increase the scope and clarity of air pollution models for depressed highway and street canyon sites. The report presents the atmospheric wind tunnel program conducted to increase the database and improve physical concepts of pertinent movements and mixing of air and its contaminants. Wind tunnel measurements are less costly than field measurements and are sensitive to controlled input variables.
The first wind tunnel operations assured geometric, vortex structure, and upstream flow similarity and correct building wake and moving vehicle effects. Tracer gases from point, line, and moving vehicle sources were used appropriately. For wind tunnel models of depressed roads or street canyons, hot-wire anemometer velocity and turbulence, pressure distribution, and receptor point concentration measurements were made. Using a selected standard road model which had two dimensions and a width/height (W/H) ratio of one, effects of wind angle, local source location, added upwind cuts, vehicle speed, ambient wind speed, and the presence of upwind wall canopy were observed. Other two-dimensional tests involved changing the W/H ratios from 0.25 to 6.0, sloping the walls, slotted walls, walls of unequal heights, and curved roads. Three-dimensional tests included end effects, intersections, and an added taller structure along one side of the road. Test results gave qualitative evaluations, concise tables, graphic illustrations, and qualitative concepts of wind flows and dispersion.