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Project Highlights
Study on SCC Bridge Girders Underway at SDSU
Researchers at South Dakota State University (SDSU) have attained a major milestone in their latest MPC-sponsored research study on bridge girders.
The study began in July and by early November the experimental part of the study was complete. The project, identified as MPC-285: "Structural Performance of Prestressed Self-Consolidating Concrete (SCC) Bridge Girders Made with Limestone Aggregates" seeks the development of SCC mix designs made with limestone coarse aggregates for use in prestressed bridge girders and investigates the structural performance of such girders. SCC is a highly flowable concrete that flows into the form work and consolidates without the need for mechanical vibration. The use of SCC may lead to better finished products, reduced labor, and increased safety during construction.
Experimental work was performed in the summer of 2007 at the Materials Laboratory at SDSU to measure the fresh and hardened properties of the SCC mix designs. Three girders were instrumented and fabricated in August 2007 at Cretex West fabrication facility in Rapid City. The girders were transported more than 330 miles to the Lohr Structures Laboratory at SDSU where they were tested until failure.
Analysis of the data is currently being conducted to evaluate the behavior of SCC girders and compare their performance to that of conventional concrete girders. The study is cosponsored by the South Dakota DOT and Cretex West of Rapid City, SD. The research team consists of Nadim Wehbe, associate professor of civil and environmental engineering and Arden Sigl, professor of civil and environmental engineering, and graduate research assistants Chad Stripling and Zachary Gutzmer.
RAP, Dust, Heavy Trucks, and Gravel Roads: Is It a Good Mix?
With the recent influx of oil and gas drilling in the Rocky Mountains region, local jurisdictions are seeing substantial increases in traffic, particularly trucks, on their road networks. Often this results in increased maintenance costs that are out of reach of many local jurisdiction budgets.
The University of Wyoming secured funding for a study to address both structural and surfacing issues associated with unpaved roads subjected to heavier traffic applications. Funding for this study will be provided by the Wyoming Department of Transportation and the MPC. Different gravel types with various dust suppressants including recycled asphalt pavement (RAP) and soil stabilizers will be evaluated in an attempt to provide the best road surface at the least total cost.
Gravel loss, primarily in the form of dust, is a common problem on Wyoming's gravel roads. This loss both degrades the road surface and creates environmental problems. For both engineering and environmental reasons, it is in the best interests of the road owners and users to minimize dust loss and provide a good road surface. As vehicles kick up dust and it blows away, the gravel surfacing loses the binding effects of fine particles. Then, washboards – rhythmic corrugations – develop on the road surface; when the loss of fine material makes the surface more permeable, more water is trapped on the surface, leading to more potholes.
When dust enters the air, it increases the risk of violating federal air quality standards. Sheridan County, Wyoming, is a non-attainment area for PM-10 particulates as designated by the U.S. Environmental Protection Agency. "As more traffic travels Wyoming's gravel roads, the risk posed by fugitive dust will only increase unless steps are taken to reduce this air quality problem," says Khaled Ksaibati, MPC director at University of Wyoming.
He notes that many unpaved county roads throughout Wyoming carry more than 1,000 vehicles per day (vpd), yet typical recommendations for when to pave an unpaved road range from 150 to 400 vpd. "For financial reasons, many counties are unable to pave roads even though, in the long run, paving is the most economical solution. Further complicating the issue is the knowledge that on many of these roads, traffic volumes will drop when drilling activities slow," Ksaibati says. "Unfortunately, no one has a crystal ball that tells them just how much drilling activity will take place over the next few decades. Considering these factors, it is important to know the most cost effective ways of managing unpaved roads, even at higher traffic volumes."
In general, unpaved roads have lower initial construction costs but higher maintenance costs than paved roads. Balancing construction costs, maintenance costs, vehicle wear and tear, rider comfort, and safety should be the objective of any organization responsible for unpaved roads. The University of Wyoming study seeks to provide information that will allow organizations to minimize the total costs on their unpaved roads. In addition, this study will provide counties in Wyoming and across the region with specific information on the cost effectiveness of using recycled asphalt pavement in gravel roads. WYDOT has committed to provide $1 million of RAP to counties which makes it important to make sure that the RAP is used effectively.
As part of the study, test sections on Schoonover and Dead Horse roads in Johnson County, Wyoming, will be reconstructed during the 2007 and 2008 construction seasons. These roads carry in excess of 1,200 vpd; the predominant traffic type is trucks serving drilling activities. Construction will be administered by Johnson County and monitored by the University of Wyoming.
Gravel samples will be tested by the Wyoming Department of Transportation's materials program. Sections will be monitored for two years to track maintenance activities and expenses. Traffic and dust loss also will be monitored by University of Wyoming. In addition, weather data will be collected.
The goal of the analysis will be to determine the most cost effective approach to constructing and maintaining unpaved roads. In addition, specific recommendations will be made on the effectiveness of using RAP on gravel roads.
UGPTI Conducts Focus Groups on Risky Driving Among Young Men
If you want to know what prompts young male drivers to skip using seatbelts and drive while under the influence of alcohol, the best way to find out may be to just ask them.
That's what NDSU researcher Tamara VanWechel did with 14 focus group meetings across North Dakota in October, November and December. In each meeting she met with 8 to 12 men ages 21 to 34 and asked them a series of questions about seatbelt use and driving while under the influence. She encouraged discussion among the participants. As the participants talked, the discussion was audio recorded while assistant Laurel Benson took notes.
VanWechel and Benson are poring through the notes and transcripts now to identify common themes, issues, and concerns. A final report will be prepared and presented to the North Dakota Department of Transportation. "Ultimately, the information will be used to develop intervention strategies to improve highway safety and reduce fatalities and injuries," she says. VanWechel is an associate research fellow with the Upper Great Plains Transportation Institute (UGPTI) at NDSU.
The project originated with a request from North Dakota Department of Transportation's Office of Traffic Safety which wanted help identifying some of the root causes for risky driving behavior by young drivers. Based on North Dakota crash data, the researchers decided to focus on seat belt use and driving under the influence using the target group male drivers aged 21 to 34. The project is funded by the NDDOT, the MPC, and the UGPTI's Rural Transportation Safety and Security Center.
The focus groups were held around the state, with meetings held in each of the eight regions designated by the North Dakota Department of Human Services. There is at least one local Safe Communities program coordinator in each of the regions. The safe communities program uses statewide, community, and individual partnerships to identify and reduce injuries in North Dakota. The local coordinator helped identify sites and participants for the meetings.
"Driving under the influence and failing to use seatbelts are large contributors to crashes and fatalities in North Dakota," VanWechel said. "We anticipate that our findings from these focus groups will help the DOT make the most effective investment it can in an effort to reduce those crash numbers and improve safety."
