|
|
K-State civil engineering keeps Kansans moving By Kira Everhart
There is a growing problem with the bridges in Kansas. Many were built before 1970 and are now being subjected to loads heavier than what they were meant to bear. This means quicker degradation and the need for either repair or replacement. With current economic conditions, there is less money to be spent on reconstruction and more necessity for cost-effective repairs. That is what the researchers at the Civil infrastructure Systems Laboratory at Kansas State University are working to find. Their past projects have been instrumental in developing techniques for bridge construction and repair and through their current research they continue to provide new and better methods.
"In terms of Kansas, we have a lot of bridges that need to be upgraded," said Bob Peterman, associate professor of civil engineering at K-State and researcher in the laboratory. "We have to figure out how can we take a bridge and keep it out there for another 10-20 years." Kansas has approximately 25,000 bridges. Five thousand of those are state-funded. Because bridge upkeep is a priority for the state, these bridges are in good condition, Peterman said. However, the 20,000 county roads are another matter. There is little money to put into their maintenance and they are therefore suffering from the most deterioration. The problem of aging and deteriorating bridges is particularly severe in western Kansas, where the majority of the bridges are found on county roads. The deterioration is due to the high number of oil fields and the agricultural industry, Peterman said. In transporting oil rigs from field to field, the mandatory method is to use a crane to lift and secure the rigs on a semi trailer. However, many individuals instead simply winch the rig up on the back of the truck. This method, cheaper but also against regulation, creates a lever effect that concentrates a high percentage of the weight on the back wheels. When the trucks carrying the rigs drive across the bridges, the overload accelerates damage to the structure. Overloaded grain trucks are another problem, Peterman said. They often avoid driving on highways where they are forced to stop at weigh stations, and instead spend more time on county roads, driving over bridges not designed to bear their weight. To combat this problem, innovative and effective bridge repair techniques are needed as total replacement is simply too expensive. The K-State team has developed such techniques. "We are working to develop easy-to-use repair techniques for a variety of strengthening and rehabilitation needs," Peterman said. Fiber reinforced polymers seem to be the answer. According to Peterman, this process involves the application of a sheet of carbon fibers to the underside of the bridge in need of repair. One inch-wide strip of this material can support a load of up to 5,000 pounds. It is then bonded to the bridge with epoxy and a paint roller. An additional advantage of the polymers is there is no need to block off access to the bridge during repairs, allowing traffic to flow normally. This leaves many drivers unaware that any maintenance has been performed. "When I'm doing my job, the average Kansan won't be aware of it," Peterman said. "We're finding ways to strengthen without it being noticeable. It kind of goes on behind the scenes." The technique is currently being proposed for implementation to the Kansas Department of Transportation. Another current project is research on self-consolidating concrete. Funded by the Kansas Department of Transportation, the project studies this easy-to-pour concrete: its liquid-like consistency eliminates the need for shoveling or vibrating while providing better quality and appearance. Also known for its architectural features, self-consolidating concrete can be just as strong or stronger than conventional concrete and allows for better durability. Its implementation would save costs both in money and time, Peterman said, and would also reduce many on-the-job injuries caused by shoveling, vibrating or noise. K-State civil engineering's past projects have also been instrumental in the safety of Kansas bridges. The development of what Peterman calls an inverted T-system has made bridge reconstruction quicker and easier. The system allows a new bridge to be pre-cast ahead of time and then simply dropped into place. It is a quick alternative that significantly reduces the amount of time the bridge will be closed to traffic. Another area of the laboratory's work may soon be applied to one of Kansas's longest bridges. The Randolph Lake Bridge, located north of Manhattan, is coming due for renovation. According to Peterman, the concrete deck is deteriorating and in need of replacement. The special lightweight concrete used for the deck of the mile-long bridge has proven to be less durable than originally hoped. Unfortunately, the steel beams and support system of the bridge were only designed to withstand the load of lightweight concrete. Replacing the current deck with a more durable conventional concrete deck would be too heavy for the bridge's supports and would require reconstructing the entire bridge, an extremely long and expensive process. The solution to this problem may be found in past research. Fiberglass bridge decks, developed in Russell by Kansas Structural Composites, Inc., and tested in the K-State laboratory, are both lightweight and durable. Completely made of fiberglass in a honeycomb structure, they are an economical, efficient and safe alternative to a complete reconstruction of the Randolph Lake Bridge.
"It's increasingly critical that we explore new techniques that can be safer, faster, cheaper and stronger," he said. "What we're doing is developing the tools that the Kansas Department of Transportation and other bridge owners can use in their processes." What they continue to focus on is developing techniques that are safe and effective so that Kansans can get on down the road, Peterman said. "When you drive over a bridge, you don't want to be made aware of the fact that you are crossing one," he said. "You just want to go about your normal business."
Photo: The civil infrastructure systems lab tests the deflection of a fiberglass bridge deck. This relatively new material is both lightweight and durable and is being considered for the replacement deck on the Randolph State Bridge north of Manhattan. Photo courtesy Bob Peterman. Winter 2003 |
With
the third highest number of bridges in the nation, Kansas has to keep
bridge condition a priority. Together with the Kansas Department of Transportation,
the civil engineering team at K-State works hard to create the best possible
techniques for their construction, Peterman said.