Glass fiber composites build a bridge of the future

American architects built a bridge with 23 carbon and fiberglass fabrics. About 160,000 of the 600,000 highway bridges in the United States need to be repaired or replaced. If this hybrid design approach is popular, fiber-reinforced composites A major breakthrough will be achieved when applied to highways.

Neil Bridge is located in the southern part of Maine, USA. The bridge has two lanes and is about 34 feet long (about 10.4 meters) across a small stream.

What is new is that the bridge has its unique structure. The bridge is not made of steel or concrete, but consists of an arched structure of 23 carbon and fiberglass fabrics. These 12-inch (about 30 cm) diameter tubes are expanded and bent into a suitable shape and then hardened with a plastic resin. After being installed, they are filled with concrete, just like Italian pasta. Finally, the bridge and compacted soil are laid, and the arched structure can support the standard sand and asphalt pavement.

The bridge is the designer's first work, located 50 miles (80 km) from the University of Maine at Oron, using a combination of composite materials and traditional concrete. About 160,000 of the 600,000 highway bridges in the United States need to be repaired or replaced. If this hybrid design approach is popular, fiber-reinforced plastics will make a major breakthrough in the road.

“This was just an experiment for us, but it’s time to practice and see if it’s really feasible,” said Habib Dagher, director of the Advanced Structures and Composites Center. .

From the beginning to the successful construction of Neil Bridge, it cost about $600,000 and was monitored using deflection sensors and other instruments. Currently, it is undergoing daily high-intensity traffic tests. "It works great," Dr. Dagai said. "And it's $170,000 cheaper than pre-cast bridges."

This has attracted the attention of the Obama administration. Transport Minister Lahoud went to the experimental center to visit the relevant achievements of the bridge.

The fiber arch design is the lowest of the seven bids. In the 1980s, fiber reinforced plastics were first used in the construction of bridges. Civil engineers are attracted by their good characteristics - high strength, light weight and corrosion resistance.

Experts say that one of the reasons why fiber-reinforced composites are not widely used is that engineers and contractors do not have much knowledge of the raw materials. The standard system for how fiber-reinforced composites are used in highway construction has not yet been established. John Busel, director of composite materials promoted by the American Composites Manufacturers Association, said: "Engineers are very concerned about safety. They want to fully understand how the raw materials are developed and how they can be used."

This material is also not always integrated with other substances. One of the problems with fiber reinforced composite decks is that asphalt or concrete covering the road surface is quickly crushed. Professor Zheng Lijuan, an engineering assistant at the University of California, Davis, said. However, the main argument for the use of fiber reinforced composites is its economic benefits. “The first is the cost of the previous period,” said Paul Ziehl, an associate professor at the University of South Carolina.

Dr. Zil helped design and test a small bridge bridge in Texas with fiber-reinforced composites. He said: "If you want to design things, from the perspective of optimal engineering, they are unique at first, until was able to achieve economies of promotion. "bridge to Texas, for example, is specially designed and customized using labor-intensive methods of construction.

“The construction industry is very cost-conscious,” Mr. Busel said. “Fiber-reinforced composites are more expensive and sometimes more expensive than traditional materials.” Contractors need to know that using lightweight materials can save on transportation. Labor, equipment costs and potential maintenance costs.

These savings are also one of the goals of the University of Maine design, Dr. Dagai said. Use expensive fiber reinforced composites - the main role is to form the frame structure of the concrete. Pipes protect concrete from erosion by deicing chemicals, reducing maintenance costs.

Tubular bridge arches are not the only hybrid design. John Hillman, engineer and president of HC Bridges in Wilmette, Ill., developed straight beams using a mixture of polymers, concrete and steel. The bridge is formed by a rectangular fiber reinforced composite tube and an arched tube. The pipe is filled with concrete – which increases the compressive strength. The bridge has been tested on the Colorado Railroad Bridge and some road bridges in Illinois and New Jersey.

“The design of the bridge is consistent with the traditional construction method. Mr. Hillman, who has been engaged in design work for 14 years, said: “In terms of installation cost, the cost of installing bridges between fiber reinforced composites and concrete and steel is very high. Close. ”

The bridges designed by Mr. Hillman must still be transported by truck, although they are light. However, the bridge designed by the University of Maine can be built on site – the fiberglass fabric is expanded and bent into a simple structure and the resin is filled with a vacuum pump. They are so light that they can be installed quickly and then poured into concrete. This eliminates the need for assistance from large cranes or other heavy equipment.