ROADS REPORT

Article December 28, 2000
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Bridge work boom anticipated

A recent survey by Finley McNary Engineers indicated the degree of change anticipated by many contractors, owners and designers of bridges due to the Transportation Equity Act for the 21st Century (TEA-21). The Survey on the Effects of TEA-21 on Bridge Construction found that 44% of participants said their company, department or agency has made or plans to make organizational changes to pursue TEA-21 related work, half hired new personnel and 29% formed a new group or division.

Most responding bridge owners, contractors and designers said they expect the law to affect their organization—with 82% of respondents anticipating the effect to be positive and 5% expecting it to have a negative effect. Forty-nine percent indicated that they had already felt an impact from the new law. Examples of the type of impact included, “States are increasing programs”; “Additional funding—including seismic retrofit”; “South Carolina has experienced a surge of projects”; “Several bridge projects are in the design-build competitive phase”; “Significant increase in interstate bridge widening jobs”; “Less federal bridge money coming into the state”; and “The DOTs haven’t yet pushed the extra work through.”

Concrete getting smarter

Truck-weighing stations on highways could become a thing of the past as a result of a new application for “smart concrete” developed by University of Buffalo engineers. A paper on the research authored by Deborah D.L. Chung, Ph.D., UB Niagara Mohawk Chair of Materials Research and professor of mechanical and aerospace engineering, and Zeng-Qiang Shi, a graduate student in the UB Department of Mechanical and Aerospace Engineering, was recently published in Cement and Concrete Research.

Developed and patented by Chung, smart concrete is concrete that has been reinforced with short carbon fibers. She demonstrated that the electrical resistance of concrete that has been modified with a very small amount of fibers changes in response to strain or stress. The concrete acts as a sensor because the carbon fibers are much more electrically conductive than the concrete mix. By calibrating the smart concrete prior to the testing, the researchers were able to determine the relationship between resistance and weight.

Other applications for smart concrete include using it to sense real-time vibrations of bridges, other highway structures or buildings for use in dampening vibrations, or for earthquake mitigation.

Chung said the cost of adding short carbon fibers to concrete would increase the materials cost by about 30%, still significantly cheaper than attaching or embedding sensors into roads, a method already in use by some highway authorities.

Bald eagles making a comeback in New England

The Connecticut River is home to six active bald eagle nests reported in the spring from northern Connecticut to southern New Hampshire. The eagles had disappeared from the area by the turn of the century, but are appearing in rural areas as well as edging into the cities. The state has counted 11 active eagle nests, up from nine last year.

Three chicks are being raised in a three-year-old nest behind and auto transmission shop. They are the second generation to be hatched along the river since a state reintroduction effort produced the first chick in 1986. Eagles usually add to the same nest each year, however sometimes they seem to like change.

Drug violations down 41%

The latest federally conducted survey of trucking companies shows the industry's estimated drug violation rate has been cut from 2.2% to 1.3% of drivers tested—a 41% reduction from 1996 to 1997. The new rate includes data from 1,294 randomly selected motor carriers comprising an estimated 112,730 drivers.

For the second year in a row, the study also showed that the alcohol use violation rate remained at a low rate of 0.2% of drivers tested randomly. Citing this low violation rate, the U.S. Department of Transportation's Office of Motor Carrier & Highway Safety last year lowered the trucking industry's minimum annual random alcohol testing rate from 25% to 10% of its drivers.

Recycled rubber in the road

How much space would it take to bury 7,750 tons of shredded tires or 229 tons of crushed glass? None if you’re in Texas—Texas DOT (TxDOT) is taking mountainous volumes of these and other materials once destined for landfills and using them to build roads.

To alleviate the disposal and public health problems associated with stockpiled tires, TxDOT utilized 6,000 tons of tires as fill in a Loop 375 bridge embankment in El Paso. The shredded tires are lightweight, low-pressure, durable, free draining and inexpensive, making them well suited for use in road and bridge construction. Crushed glass was installed as a bedding around two pipe sections near an intersection that was widened.

More than 100 million tons of construction demolition debris is deposited in landfills each year. By reclassifying this material, TxDOT has saved up to $250,000. The project utilizes reclassified sandblasting material and crushed concrete as feedstocks.

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